Chunghwa Telecom (CHT) 20-F19 Apr 212020 FY Annual report (foreign)Financial data

Company Profile

Document and Entity Information

Document and Entity Information	12 Months Ended
Document and Entity Information	Dec. 31, 2020shares
Document Information [Line Items]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Registrant Name	Chunghwa Telecom Co Ltd.
Entity Central Index Key	0001132924
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
ICFR Auditor Attestation Flag	true
Entity Common Stock, Shares Outstanding	7,757,446,545
Entity File Number	001-31731
Entity Incorporation, State or Country Code	F5
Entity Address, Address Line One	21-3 Hsinyi Road
Entity Address, Address Line Two	Section 1
Entity Address, City or Town	Taipei
Entity Address, Country	TW
Document Annual Report	true
Document Transition Report	false
Document Shell Company Report	false
Document Accounting Standard	International Financial Reporting Standards
Document Registration Statement	false
Common Shares, Par Value NT$10 Per Share [Member]
Document Information [Line Items]
No Trading Symbol Flag	true
Title of 12(b) Security	Common Shares, par value NT$10 per share
Security Exchange Name	NYSE
American Depositary Shares [Member]
Document Information [Line Items]
Trading Symbol	CHT
Title of 12(b) Security	American Depositary Shares, as evidenced by American Depositary Receipts, each representing 10 Common Shares
Security Exchange Name	NYSE
Business Contact [Member]
Document Information [Line Items]
Entity Address, Address Line One	21-3 Hsinyi Road
Entity Address, Address Line Two	Section 1
Entity Address, City or Town	Taipei
Entity Address, Country	TW
Contact Personnel Name	Fufu Shen
City Area Code	+886 2
Local Phone Number	2344-5488
Contact Personnel Email Address	chtir@cht.com.tw

Consolidated Balance Sheet

Consolidated Balance Sheet $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
CURRENT ASSETS
Cash and cash equivalents	$ 30,420,000,000	$ 1,083	$ 34,050,000,000
Financial assets at fair value through profit or loss	10,000,000	0	1,000,000
Hedging financial assets	2,000,000	0	0
Contract assets	5,331,000,000	190	4,441,000,000
Trade notes and accounts receivable, net	22,622,000,000	806	26,408,000,000
Receivables from related parties	230,000,000	8	17,000,000
Inventories	12,409,000,000	442	17,344,000,000
Prepayments	2,306,000,000	82	1,883,000,000
Other current monetary assets	6,124,000,000	218	7,498,000,000
Other current assets	2,349,000,000	84	2,430,000,000
Total current assets	81,803,000,000	2,913	94,072,000,000
NONCURRENT ASSETS
Financial assets at fair value through profit or loss	677,000,000	24	778,000,000
Financial assets at fair value through other comprehensive income	7,193,000,000	256	7,154,000,000
Investments accounted for using equity method	6,695,000,000	238	7,139,000,000
Contract assets	2,495,000,000	89	2,601,000,000
Property, plant and equipment	281,416,000,000	10,022	283,694,000,000
Right-of-use assets	11,009,000,000	392	11,364,000,000
Investment properties	9,621,000,000	343	8,169,000,000
Intangible assets	90,285,000,000	3,214	47,047,000,000
Deferred income tax assets	3,133,000,000	112	3,259,000,000
Incremental costs of obtaining a contract	1,000,000,000	36	943,000,000
Net defined benefit assets	3,373,000,000	120	2,128,000,000
Prepayments	2,214,000,000	79	2,679,000,000
Other noncurrent assets	5,266,000,000	188	6,101,000,000
Total noncurrent assets	424,377,000,000	15,113	383,056,000,000
TOTAL	506,180,000,000	18,026	477,128,000,000
CURRENT LIABILITIES
Short-term loans	67,000,000	2	90,000,000
Short-term bills payable	6,999,000,000	249	0
Financial liabilities at fair value through profit or loss	0	0	0
Contract liabilities	13,437,000,000	479	16,840,000,000
Trade notes and accounts payable	15,591,000,000	555	15,312,000,000
Payables to related parties	646,000,000	24	654,000,000
Current tax liabilities	6,157,000,000	219	5,812,000,000
Lease liabilities	3,382,000,000	120	3,291,000,000
Other payables	23,988,000,000	854	22,953,000,000
Provisions	314,000,000	11	207,000,000
Current portion of long-term loans	1,600,000,000	57	0
Other current liabilities	1,042,000,000	38	984,000,000
Total current liabilities	73,223,000,000	2,608	66,143,000,000
NONCURRENT LIABILITIES
Long-term loans	0	0	1,600,000,000
Bonds payable	19,980,000,000	712	0
Contract liabilities	7,289,000,000	260	6,841,000,000
Deferred income tax liabilities	1,967,000,000	70	1,912,000,000
Provisions	101,000,000	4	97,000,000
Lease liabilities	6,215,000,000	221	6,467,000,000
Customers’ deposits	4,827,000,000	172	4,748,000,000
Net defined benefit liabilities	3,415,000,000	122	3,505,000,000
Other noncurrent liabilities	1,890,000,000	66	1,543,000,000
Total noncurrent liabilities	45,684,000,000	1,627	26,713,000,000
Total liabilities	118,907,000,000	4,235	92,856,000,000
EQUITY ATTRIBUTABLE TO STOCKHOLDERS OF THE PARENT
Common stocks	77,574,000,000	2,763	77,574,000,000
Additional paid-in capital	149,790,000,000	5,334	149,762,000,000
Retained earnings
Legal reserve	77,574,000,000	2,763	77,574,000,000
Special reserve	2,676,000,000	95	2,676,000,000
Unappropriated earnings	67,574,000,000	2,406	65,984,000,000
Total retained earnings	147,824,000,000	5,264	146,234,000,000
Others	927,000,000	33	587,000,000
Total equity attributable to stockholders of the parent	376,115,000,000	13,394	374,157,000,000
NONCONTROLLING INTERESTS	11,158,000,000	397	10,115,000,000
Total equity	387,273,000,000	13,791	384,272,000,000
TOTAL	$ 506,180,000,000	$ 18,026	$ 477,128,000,000

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)$ / shares	Dec. 31, 2020USD ($)$ / shares	Dec. 31, 2019TWD ($)$ / shares	Dec. 31, 2018TWD ($)$ / shares
Statement [LineItems]
REVENUES	$ 207,609	$ 7,393	$ 207,520	$ 215,483
OPERATING COSTS	137,029	4,880	135,953	139,545
GROSS PROFIT	70,580	2,513	71,567	75,938
OPERATING EXPENSES
Marketing	20,913	745	22,220	23,170
General and administrative	5,006	178	4,758	4,589
Research and development	3,850	137	3,941	3,725
Expected credit loss (reversal of credit loss)	45	2	(125)	920
Total operating expenses	29,814	1,062	30,794	32,404
OTHER INCOME AND EXPENSES	1,595	57	(127)	110
INCOME FROM OPERATIONS	42,361	1,508	40,646	43,644
NON-OPERATING INCOME AND EXPENSES
Interest income	116	4	251	197
Other income	470	17	531	700
Other gains and losses	(159)	(6)	84	(46)
Interest expenses	(206)	(7)	(104)	(18)
Share of profits of associates and joint ventures accounted for using equity method	244	9	459	509
Total non-operating income and expenses	465	17	1,221	1,342
INCOME BEFORE INCOME TAX	42,826	1,525	41,867	44,986
INCOME TAX EXPENSE	8,122	289	7,946	6,405
NET INCOME	34,704	1,236	33,921	38,581
Items that will not be reclassified to profit or loss:
Remeasurements of defined benefit pension plans	1,193	43	1,527	(1,215)
Unrealized gain or loss on investments in equity instruments at fair value through other comprehensive income	519	18	171	(346)
Gain or loss on hedging instruments subject to basis adjustment	2	0	(1)	2
Share of remeasurements of defined benefit pension plans of associates and joint ventures	(4)	0	(2)	2
Income tax relating to items that will not be reclassified to profit or loss	(239)	(9)	(305)	450
Items that will not be reclassified to profit or loss	1,471	52	1,390	(1,107)
Items that may be reclassified subsequently to profit or loss:
Exchange differences arising from the translation of the foreign operations	(177)	(6)	(61)	90
Share of exchange differences arising from the translation of the foreign operations of associates and joint ventures	(4)	0	(1)	3
Income tax relating to items that may be reclassified subsequently	0	0	0	0
Items that may be reclassified subsequently to profit or loss	(181)	(6)	(62)	93
Total other comprehensive income (loss), net of income tax	1,290	46	1,328	(1,014)
TOTAL COMPREHENSIVE INCOME	35,994	1,282	35,249	37,567
NET INCOME ATTRIBUTABLE TO
Stockholders of the parent	33,419	1,190	32,947	37,557
Noncontrolling interests	1,285	46	974	1,024
NET INCOME	34,704	1,236	33,921	38,581
COMPREHENSIVE INCOME ATTRIBUTABLE TO
Stockholders of the parent	34,713	1,236	34,282	36,552
Noncontrolling interests	1,281	46	967	1,015
TOTAL COMPREHENSIVE INCOME	$ 35,994	$ 1,282	$ 35,249	$ 37,567
EARNINGS PER SHARE
Basic \| (per share)	$ 4.31	$ 0.15	$ 4.25	$ 4.84
Diluted \| (per share)	4.30	0.15	4.24	4.83
American Depositary Shares [Member]
EARNINGS PER SHARE
Basic \| (per share)	43.08	1.53	42.47	48.41
Diluted \| (per share)	$ 43.03	$ 1.53	$ 42.42	$ 48.35

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity $ in Millions, $ in Millions	TWD ($)	USD ($)	Common stocks [Member]TWD ($)	Common stocks [Member]USD ($)	Additional paid-in capital [Member]TWD ($)	Additional paid-in capital [Member]USD ($)	Legal reserve [Member]TWD ($)	Legal reserve [Member]USD ($)	Special reserve [Member]TWD ($)	Special reserve [Member]USD ($)	Unappropriated earnings [Member]TWD ($)	Unappropriated earnings [Member]USD ($)	Total retained earnings [Member]TWD ($)	Total retained earnings [Member]USD ($)	Exchange differences arising from the translation of the foreign operations [Member]TWD ($)	Exchange differences arising from the translation of the foreign operations [Member]USD ($)	Unrealized gain or loss on financial assets at fair value through other comprehensive income [Member]TWD ($)	Unrealized gain or loss on financial assets at fair value through other comprehensive income [Member]USD ($)	Gain or Loss on hedging instruments [Member]TWD ($)	Gain or Loss on hedging instruments [Member]USD ($)	Total Others [member]TWD ($)	Total Others [member]USD ($)	Total equity attributable to stockholders of the parent [Member]TWD ($)	Total equity attributable to stockholders of the parent [Member]USD ($)	Noncontrolling interests [Member]TWD ($)	Noncontrolling interests [Member]USD ($)
Beginning balance at Dec. 31, 2017	$ 382,124		$ 77,574		$ 148,091		$ 77,574		$ 2,681		$ 67,026		$ 147,281		$ (174)		$ 883		$ (1)		$ 708		$ 373,654		$ 8,470
Reversal of special reserve	0		0		0		0		(5)		5		0		0		0		0		0		0		0
Cash dividends paid or distributed by Chunghwa	(37,205)		0		0		0		0		(37,205)		(37,205)		0		0		0		0		(37,205)		0
Cash dividends distributed by subsidiaries	(958)		0		0		0		0		0		0		0		0		0		0		0		(958)
Unclaimed dividend	2		0		2		0		0		0		0		0		0		0		0		2		0
Change in additional paid-in capital from investments in associates and joint ventures accounted for using equity method																									0
Partial disposal of interests in subsidiaries	1,175		0		826		0		0		0		0		0		0		0		0		826		349
Change in additional paid-in capital for not participating proportionately in the capital increase of subsidiaries	1,477		0		777		0		0		0		0		0		0		0		0		777		700
Net income	38,581		0		0		0		0		37,557		37,557		0		0		0		0		37,557		1,024
Total other comprehensive income (loss), net of income tax	(1,014)		0		0		0		0		(757)		(757)		95		(345)		2		(248)		(1,005)		(9)
TOTAL COMPREHENSIVE INCOME	37,567		0		0		0		0		36,800		36,800		95		(345)		2		(248)		36,552		1,015
Share-based payment transactions of subsidiaries	53		0		11		0		0		0		0		0		0		0		0		11		42
Net increase (decrease) in noncontrolling interests	294		0		55		0		0		0		0		0		0		0		0		55		239
Ending balance at Dec. 31, 2018	384,529		77,574		149,762		77,574		2,676		66,626		146,876		(79)		538		1		460		374,672		9,857
Effect of retrospective application (IFRS16 [Member]) at Dec. 31, 2018	(71)		0		0		0		0		(51)		(51)		0		0		0		0		(51)		(20)
BALANCE, AS ADJUSTED at Dec. 31, 2018	384,458		77,574		149,762		77,574		2,676		66,575		146,825		(79)		538		1		460		374,621		9,837
Cash dividends paid or distributed by Chunghwa	(34,746)		0		0		0		0		(34,746)		(34,746)		0		0		0		0		(34,746)		0
Cash dividends distributed by subsidiaries	(710)		0		0		0		0		0		0		0		0		0		0		0		(710)
Unclaimed dividend	1		0		1		0		0		0		0		0		0		0		0		1		0
Change in additional paid-in capital from investments in associates and joint ventures accounted for using equity method																									0
Partial disposal of interests in subsidiaries																									0
Net income	33,921		0		0		0		0		32,947		32,947		0		0		0		0		32,947		974
Total other comprehensive income (loss), net of income tax	1,328		0		0		0		0		1,208		1,208		(69)		197		(1)		127		1,335		(7)
TOTAL COMPREHENSIVE INCOME	35,249		0		0		0		0		34,155		34,155		(69)		197		(1)		127		34,282		967
Share-based payment transactions of subsidiaries	21		0		(1)		0		0		0		0		0		0		0		0		(1)		22
Net increase (decrease) in noncontrolling interests	(1)		0		0		0		0		0		0		0		0		0		0		0		(1)
Ending balance at Dec. 31, 2019	384,272		77,574		149,762		77,574		2,676		65,984		146,234		(148)		735		0		587		374,157		10,115
Cash dividends paid or distributed by Chunghwa	(32,783)		0		0		0		0		(32,783)		(32,783)		0		0		0		0		(32,783)		0
Cash dividends distributed by subsidiaries	(775)		0		0		0		0		0		0		0		0		0		0		0		(775)
Unclaimed dividend	2		0		2		0		0		0		0		0		0		0		0		2		0
Change in additional paid-in capital from investments in associates and joint ventures accounted for using equity method	(2)		0		0		0		0		0		0		0		0		0		0		0		(2)
Partial disposal of interests in subsidiaries																									0
Change in additional paid-in capital for not participating proportionately in the capital increase of subsidiaries	0		0		0		0		0		0		0		0		0		0		0		0		0
Net income	34,704	$ 1,236	0		0		0		0		33,419		33,419		0		0		0		0		33,419		1,285
Total other comprehensive income (loss), net of income tax	1,290	46	0		0		0		0		937		937		(167)		522		2		357		1,294		(4)
TOTAL COMPREHENSIVE INCOME	35,994	1,282	0		0		0		0		34,356		34,356		(167)		522		2		357		34,713		1,281
Disposal of investments in equity instruments at fair value through other comprehensive income	0		0		0		0		0		17		17		0		(17)		0		(17)		0		0
Share-based payment transactions of subsidiaries	89		0		26		0		0		0		0		0		0		0		0		26		63
Net increase (decrease) in noncontrolling interests	476		0		0		0		0		0		0		0		0		0		0		0		476
Ending balance at Dec. 31, 2020	$ 387,273	$ 13,791	$ 77,574	$ 2,763	$ 149,790	$ 5,334	$ 77,574	$ 2,763	$ 2,676	$ 95	$ 67,574	$ 2,406	$ 147,824	$ 5,264	$ (315)	$ (11)	$ 1,240	$ 44	$ 2	$ 0	$ 927	$ 33	$ 376,115	$ 13,394	$ 11,158	$ 397

Consolidated Statements of Cash

Consolidated Statements of Cash Flows $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
CASH FLOWS FROM OPERATING ACTIVITIES
Income before income tax	$ 42,826	$ 1,525	$ 41,867	$ 44,986
Adjustments for:
Depreciation	30,942	1,102	30,923	27,482
Amortization	5,424	193	4,253	4,386
Amortization of incremental costs of obtaining contracts	772	27	1,173	1,941
Expected credit loss (reversal of credit loss)	45	2	(125)	920
Interest expenses	206	7	104	18
Interest income	(116)	(4)	(251)	(197)
Dividend income	(246)	(9)	(296)	(396)
Compensation cost of share-based payment transactions	8	0	2	17
Share of profits of associates and joint ventures accounted for using equity method	(244)	(9)	(459)	(509)
Loss (gain) on disposal of property, plant and equipment	(1,428)	(51)	38	(142)
Gain on disposal of investment properties	(151)	(5)	0	0
Loss on disposal of intangible assets	2	0	0	0
Loss (gain) on disposal of financial instruments	2	0	(4)	(6)
Gain on disposal of investments accounted for using equity method	(10)	0	(151)	0
Provision for impairment loss and obsolescence of inventory	1,161	41	475	365
Impairment loss on property, plant and equipment	0	0	93	0
Reversal of impairment loss on investment properties	(27)	(1)	(57)	(19)
Impairment loss on intangible assets	9	0	9	51
Impairment loss on other assets	0	0	44	0
Valuation loss on financial assets and liabilities at fair value through profit or loss, net	99	4	38	21
Others	4	0	(26)	(17)
Changes in operating assets and liabilities:
Financial assets mandatorily measured at fair value through profit or loss	0	0	0	63
Contract assets	(203)	(7)	173	2,751
Trade notes and accounts receivable	4,071	145	4,039	1,354
Receivables from related parties	(214)	(8)	7	25
Inventories	3,915	139	(2,698)	(6,778)
Prepayments	173	6	115	418
Other current monetary assets	355	13	(155)	(173)
Other current assets	156	6	146	(261)
Incremental cost of obtaining contracts	(829)	(30)	(781)	(802)
Contract liabilities	(3,289)	(117)	6,701	2,653
Trade notes and accounts payable	21	1	(5,152)	1,065
Payables to related parties	(8)	0	(264)	234
Other payables	(924)	(33)	697	(1,089)
Provisions	95	4	97	27
Other current liabilities	46	2	(159)	422
Net defined benefit plans	(174)	(6)	534	(1,535)
Cash generated from operations	82,469	2,937	80,950	77,275
Interest paid	(161)	(5)	(104)	(18)
Income tax paid	(7,852)	(280)	(8,419)	(10,891)
Net cash provided by operating activities	74,456	2,652	72,427	66,366
CASH FLOWS FROM INVESTING ACTIVITIES
Acquisition of financial assets at fair value through other comprehensive income	(85)	(3)	(60)	(290)
Proceeds from disposal of financial assets at fair value through other comprehensive income	297	11	0	0
Proceeds from return of financial assets at fair value through other comprehensive income	0	0	9	7
Acquisition of financial assets at fair value through profit or loss	(39)	(1)	(443)	0
Proceeds from disposal of financial assets at fair value through profit or loss	30	1	146	0
Acquisition of time deposits and negotiable certificates of deposit with maturities of more than three months	(5,216)	(186)	(14,381)	(9,720)
Acquisition of repurchase agreements collateralized by bonds with maturities of more than three months	0	0	(15)	0
Proceeds from disposal of time deposits and negotiable certificates of deposit with maturities of more than three months	6,630	236	16,520	5,655
Proceeds from disposal of repurchase agreements collateralized by bonds with maturities of more than three months	15	1	0	0
Acquisition of investments accounted for using equity method	(10)	0	(4,190)	(205)
Proceeds from disposal of investments accounted for using equity method	0	0	32	3
Proceeds from capital reduction of investments accounted for using equity method	0	0	0	19
Acquisition of property, plant and equipment	(23,511)	(838)	(24,166)	(28,550)
Proceeds from disposal of property, plant and equipment	319	11	48	264
Acquisition of intangible assets	(47,605)	(1,695)	(363)	(498)
Acquisition of investment properties	(54)	(2)	(1)	(6)
Proceeds from disposal of investment properties	188	7	0	0
Increase in other noncurrent assets	(208)	(7)	(1,122)	(80)
Interest received	125	4	257	187
Dividends received	516	17	602	600
Net cash inflow on acquisition of subsidiaries	354	13	0	0
Net cash used in investing activities	(68,254)	(2,431)	(27,127)	(32,614)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from short-term loans	115	4	575	360
Repayment of short-term loans	(142)	(5)	(585)	(330)
Proceeds from short-term bills payable	41,000	1,460	0	0
Repayment of short-term bills payable	(34,000)	(1,211)	0	0
Proceeds from issuance of bonds	20,000	712	0	0
Payments for transaction costs attributable to the issuance of bonds	(21)	(1)	0	0
Increase in customers’ deposits	62	2	8	31
Payments for the principal of lease liabilities	(3,683)	(131)	(3,728)	0
Increase in other noncurrent liabilities	342	13	233	84
Cash dividends paid	(32,783)	(1,167)	(34,746)	(37,205)
Partial disposal of interests in subsidiaries without losing control	0	0	0	1,175
Cash dividends distributed to noncontrolling interests	(775)	(28)	(710)	(958)
Change in other noncontrolling interests	81	3	18	1,806
Unclaimed dividend	2	0	1	2
Net cash used in financing activities	(9,802)	(349)	(38,934)	(35,035)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	(30)	(1)	39	103
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(3,630)	(129)	6,405	(1,180)
CASH AND CASH EQUIVALENTS, BEGINNING OF THE YEAR	34,050	1,212	27,645	28,825
CASH AND CASH EQUIVALENTS, END OF THE YEAR	$ 30,420	$ 1,083	$ 34,050	$ 27,645

General

General	12 Months Ended
General	Dec. 31, 2020
General Information [Abstract]
General	1. GENERAL Chunghwa Telecom Co., Ltd. (“Chunghwa”) was incorporated on July 1, 1996 in the Republic of China (“ROC”). Chunghwa is a company limited by shares and, prior to August 2000, was wholly owned by the Ministry of Transportation and Communications (“MOTC”). Prior to July 1, 1996, the current operations of Chunghwa were carried out under the Directorate General of Telecommunications (“DGT”). The DGT was established by the MOTC in June 1943 to take primary responsibility in the development of telecommunications infrastructure and to formulate policies related to telecommunications. On July 1, 1996, the telecom operations of the DGT were spun-off as Chunghwa which continues to carry out the business and the DGT continues to be the industry regulator. Effective August 12, 2005, the MOTC completed the process of privatizing Chunghwa by reducing the government ownership to below 50% in various stages. In July 2000, Chunghwa received approval from the Securities and Futures Commission (the “SFC”) for a domestic initial public offering and its common stocks were listed and traded on the Taiwan Stock Exchange (the “TWSE”) on October 27, 2000. Certain of Chunghwa’s common stocks were sold, in connection with the foregoing privatization plan, in domestic public offerings at various dates from August 2000 to July 2003. Certain of Chunghwa’s common stocks were also sold in an international offering of securities in the form of American Depository Shares (“ADS”) on July 17, 2003 and were listed and traded on the New York Stock Exchange (the “NYSE”). The MOTC sold common stocks of Chunghwa by auction in the ROC on August 9, 2005 and completed the second international offering on August 10, 2005. Upon completion of the share transfers associated with these offerings on August 12, 2005, the MOTC owned less than 50% of the outstanding shares of Chunghwa and completed the privatization plan. Chunghwa together with its subsidiaries are hereinafter referred to collectively as the “Company”.

Approval of Financial Statement

Approval of Financial Statements	12 Months Ended
Approval of Financial Statements	Dec. 31, 2020
Disclosure Of Approval Of Financial Statement [Abstract]
Approval of Financial Statements	2. APPROVAL OF FINANCIAL STATEMENTS The consolidated financial statements were authorized for issue by the management on March 31, 2021.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2020
Disclosure Of Summary Of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies	3. The Company initially applied IFRS 16 “Leases” on January 1, 2019 and elected not to reflect the figures on a retrospective basis in comparative periods. Different accounting policies for each accounting period as a result of the application of new accounting standards are listed by year separately. Statement of Compliance The accompanying consolidated financial statements have been prepared in conformity with International Financial Reporting Standards as issued by the International Accounting Standards Board (collectively, “IFRSs”). Basis of Preparation The consolidated financial statements have been prepared on the historical cost basis except for certain financial instruments that are measured at fair values and net defined benefit liabilities (assets) which are measured at the present value of the defined benefit obligations less the fair value of plan assets. Current and Noncurrent Assets and Liabilities Current assets include: a. Assets held primarily for the purpose of trading; b. Assets expected to be realized within twelve months after the reporting period; and c. Cash and cash equivalents unless the asset is restricted from being exchanged or used to settle a liability for at least twelve months after the reporting period. Current liabilities include: a. Liabilities held primarily for the purpose of trading; b. Liabilities due to be settled within twelve months after the reporting period; and c. Liabilities for which the Company does not have an unconditional right to defer settlement for at least twelve months after the reporting period. Assets and liabilities that are not classified as current are classified as noncurrent. Light Era Development Co., Ltd. (LED) engages mainly in development of property for rent and sale. The assets and liabilities of LED related to property development within its operating cycle, which is over one year, are classified as current items. Basis of Consolidation a. Principles for preparing consolidated financial statements The consolidated financial statements incorporate the financial statements of Chunghwa and entities controlled by Chunghwa (its subsidiaries). Income and expenses of subsidiaries acquired are included in the consolidated statements of comprehensive income from the acquisition date. When necessary, adjustments are made to the financial statements of subsidiaries to bring their accounting policies in line with those used by the Company. All inter-company transactions, balances, income and expenses are eliminated in full upon consolidation. Attribution of total comprehensive income to noncontrolling interests Total comprehensive income of subsidiaries is attributed to the stockholders of the parent and to the noncontrolling interests even if it results in the noncontrolling interests having a deficit balance. Changes in the Company’s ownership interests in subsidiaries Changes in the Company’s ownership interests in subsidiaries that do not result in the Company losing control over the subsidiaries are accounted for as equity transactions. The carrying amounts of the Company’s interests and the noncontrolling interests are adjusted to reflect the changes in their relative interests in the subsidiaries. Any difference between the amount by which the noncontrolling interests are adjusted and the fair value of the consideration paid or received is recognized directly in equity and attributed to stockholders of the parent. b. The subsidiaries in the consolidated financial statements The detail information of the subsidiaries at the end of reporting period was as follows: Percentage of Ownership interests December 31 Name of Investor Name of Investee Main Businesses and Products 2019 2020 Note Chunghwa Telecom Co., Ltd. Senao International Co., Ltd. (“SENAO”) Handset and peripherals retailer, sales of CHT mobile phone plans as an agent 28 28 a) Light Era Development Co., Ltd. (“LED”) Planning and development of real estate and intelligent buildings, and property management 100 100 Donghwa Telecom Co., Ltd. (“DHT”) International private leased circuit, IP VPN service, and IP transit services 100 100 Chunghwa Telecom Singapore Pte., Ltd. (“CHTS”) International private leased circuit, IP VPN service, and IP transit services 100 100 Chunghwa System Integration Co., Ltd. (“CHSI”) Providing system integration services and telecommunications equipment 100 100 Chunghwa Investment Co., Ltd. (“CHI”) Investment 89 89 CHIEF Telecom Inc. (“CHIEF”) Network integration, internet data center (“IDC”), communications integration and cloud application services 57 56 b) CHYP Multimedia Marketing & Communications Co., Ltd. (“CHYP”) Digital information supply services and advertisement services 100 100 Prime Asia Investments Group Ltd. (B.V.I.) (“Prime Asia”) Investment 100 100 Spring House Entertainment Tech. Inc. (“SHE”) Software design services, internet contents production and play, and motion picture production and distribution 56 56 c) Chunghwa Telecom Global, Inc. (“CHTG”) International private leased circuit, internet services, and transit services 100 100 Chunghwa Telecom Vietnam Co., Ltd. (“CHTV”) Intelligent energy saving solutions, international circuit, and information and communication technology (“ICT”) services 100 100 Smartfun Digital Co., Ltd. (“SFD”) Providing diversified family education digital services 65 65 Chunghwa Telecom Japan Co., Ltd. (“CHTJ”) International private leased circuit, IP VPN service, and IP transit services 100 100 Chunghwa Sochamp Technology Inc. (“CHST”) Design, development and production of Automatic License Plate Recognition software and hardware 51 51 Honghwa International Co., Ltd. (“HHI”) Telecommunications engineering, sales agent of mobile phone plan application and other business services, etc. 100 100 Chunghwa Leading Photonics Tech Co., Ltd. (“CLPT”) Production and sale of electronic components and finished products 75 75 Chunghwa Telecom (Thailand) Co., Ltd. (“CHTT”) International private leased circuit, IP VPN service, ICT and cloud VAS services 100 100 d) (Continued) Percentage of Ownership interests December 31 Name of Investor Name of Investee Main Businesses and Products 2019 2020 Note CHT Security Co., Ltd. (“CHTSC”) Computing equipment installation, wholesale of computing and business machinery equipment and software, management consulting services, data processing services, digital information supply services and internet identify services 80 80 International Integrated Systems, Inc. (“IISI”) IT solution provider, IT application consultation, system integration and package solution — 51 e) Senao International Co., Ltd. Senao International (Samoa) Holding Ltd. (“SIS”) International investment 100 100 f) Youth Co., Ltd. (“Youth”) Sale of information and communication technologies products 93 96 g) Aval Technologies Co., Ltd. (“Aval”) Sale of information and communication technologies products 100 100 Senyoung Insurance Agent Co., Ltd. (“SENYOUNG”) Property and liability insurance agency 100 100 Youth Co., Ltd. ISPOT Co., Ltd. (“ISPOT”) Sale of information and communication technologies products 100 100 Youyi Co., Ltd. (“Youyi”) Maintenance of information and communication technologies products 100 100 Aval Technologies Co., Ltd. Wiin Technology Co., Ltd. (“Wiin”) Sale of information and communication technologies products 100 100 h) Senyoung Insurance Agent Co., Ltd. Senaolife Insurance Agent Co., Ltd. (“Senaolife”) Life insurance services 100 100 i) Light Era Development Co., Ltd. Taoyuan Asia Silicon Valley Innovation Co., Ltd. (“TASVI”) Development of real estate — — j) CHIEF Telecom Inc. Unigate Telecom Inc. (“Unigate”) Telecommunications and internet service 100 100 Chief International Corp. (“CIC”) Telecommunications and internet service 100 100 Shanghai Chief Telecom Co., Ltd. (“SCT”) Telecommunications and internet service 49 49 k) Chunghwa Investment Co., Ltd. Chunghwa Precision Test Tech. Co., Ltd. (“CHPT”) Production and sale of semiconductor testing components and printed circuit board 34 34 l) Chunghwa Precision Test Tech. Co., Ltd. Chunghwa Precision Test Tech. USA Corporation (“CHPT (US)”) Design and after-sale services of semiconductor testing components and printed circuit board 100 100 CHPT Japan Co., Ltd. (“CHPT (JP)”) Related services of electronic parts, machinery processed products and printed circuit board 100 100 Chunghwa Precision Test Tech. International, Ltd. (“CHPT (International)”) Wholesale and retail of electronic materials, and investment 100 100 Senao International (Samoa) Holding Ltd. Senao International HK Limited (“SIHK”) International investment 100 100 m) (Continued) Percentage of Ownership interests December 31 Name of Investor Name of Investee Main Businesses and Products 2019 2020 Note Senao International HK Limited Senao Trading (Fujian) Co., Ltd. (“STF”) Sale of information and communication technologies products — — n) Senao International Trading (Shanghai) Co., Ltd. (“SITS”) Sale of information and communication technologies products 100 100 o) Senao International Trading (Jiangsu) Co., Ltd. (“SITJ”) Sale of information and communication technologies products — — p) Prime Asia Investments Group Ltd. (B.V.I.) Chunghwa Hsingta Co., Ltd. (“CHC”) Investment 100 100 Chunghwa Hsingta Co., Ltd. Chunghwa Telecom (China) Co., Ltd. (“CTC”) Integrated information and communication solution services for enterprise clients, and intelligent energy network service 100 100 q) Chunghwa Precision Test Tech. International, Ltd. Shanghai Taihua Electronic Technology Limited (“STET”) Design of printed circuit board and related consultation service 100 100 Su Zhou Precision Test Tech. Ltd. (“SZPT”) Assembly processed of circuit board, design of printed circuit board and related consultation service 100 100 r) International Integrated Systems, Inc. Infoexplorer International Co., Ltd.(“IESA”) Investment — 100 s) IISI Investment Co., Ltd. (“IICL”) Investment — 100 s) Unitronics Technology Corp. (“UTC”) Development and maintenance of information system — 99.96 s) Infoexplorer International Co., Ltd. International Integrated Systems (Hong Kong) Limited (“IEHK”) Investment and technical consulting service — 100 s) IISI Investment Co., Ltd. Leading Tech Co., Ltd. (“LTCL”) Investment — 100 s) Leading Tech Co., Ltd. Leading Systems Co., Ltd. (“LSCL”) Investment — 100 s) Leading Systems Co., Ltd. International Integrated Systems Inc. (Shanghai) (“IISS”) Development and maintenance of information system — 100 s) International Integrated Systems Inc. (Shanghai) Huiyu Shanghai Management Consultancy Co., Ltd. (“HSMC”) Development and maintenance of information system — — s) t) (Concluded) a ) Chunghwa continues to control six out of eleven seats of the Board of Directors of SENAO through the support of large beneficial stockholders. As a result, the Company treated SENAO as a subsidiary. b ) CHIEF issued new shares in March 2019, November 2019, March 2020 and December 2020 as its employees exercised options. Therefore, the Company’s ownership interest in CHIEF decreased to 59.75% and 59.08% as of December 31, 2019 and 2020, respectively. c ) SHE reduced 19.72% of its capital to offset accumulated deficits in December 2019 and the Company’s ownership interest in SHE remained the same. d ) The Company increased its investment in CHTT proportionally in October 2019 and the Company’s ownership interest in CHTT remained the same. e ) Chunghwa obtained 20.38% ownership interest in IISI in July 2020 and Chunghwa’s ownership interest in IISI increased to 51.54% by considering the previously held ownership interest in IISI. Chunghwa obtained over half of the seats of the Board of Directors of IISI; therefore, Chunghwa gained control over IISI and treated it as a subsidiary. IISI issued new shares in September 2020 as its employees exercised options; therefore, the Company’s ownership interest in IISI decreased to 51.20% as of December 31, 2020. f ) SIS reduced and returned its capital to its stakeholders in November 2020. The Company’s ownership interest in SIS remained the same. g ) SENAO subscribed for all the shares in the capital increase of Youth in April 2020. Therefore, the Company’s ownership interest in Youth increased from 92.89% to 95.79%. h ) Aval invested 100% equity shares of Wiin Technology Co., Ltd. (“Wiin”) in September 2019. i ) SENYOUNG invested 100% equity shares of Senaolife Insurance Agent Co., Ltd. (“Senaolife”) in November 2019. j ) TASVI completed its liquidation in September 2019. k ) CHIEF has two out of three seats of the Board of Directors of SCT according to the mutual agreements among stockholders and gained control over SCT; hence, SCT is deemed as a subsidiary of the Company. l ) Though the Company’s ownership interest in CHPT is less than 50%, the management considered the absolute and relative size of ownership interest, and the dispersion of shares owned by the other stockholders and concluded that the Company has a sufficiently dominant voting interest to direct the relevant activities; hence, CHPT is deemed as a subsidiary of the Company. m ) SIHK reduced and returned its capital to its stakeholders in November 2020. The Company’s ownership interest in SIHK remained the same. n ) STF completed its liquidation in May 2019. o ) SITS was approved to end and dissolve its business in December 2020. The liquidation of SITS is still in process. p ) SITJ completed its liquidation in March 2019. q ) CTC was approved to end and dissolve its business in August 2020. The liquidation of CTC is still in process. r ) s ) It is a subsidiary of IISI. t) HSMC completed its liquidation in December 2020. The following diagram presented information regarding the relationship and percentages of ownership interests between Chunghwa and its subsidiaries as of December 31, 2020. Business Combinations Acquisitions of businesses are accounted for using the acquisition method. Acquisition-related costs are generally recognized in profit or loss as they are incurred. Goodwill is measured as the excess of the sum of the consideration transferred and the fair value of the acquirer’s previously held equity interests in the acquiree over the net of the acquisition-date amounts of the identifiable assets acquired and the liabilities assumed. Noncontrolling interests that are present ownership interests and entitle their holders to a proportionate share of the entity’s net assets in the event of liquidation are measured at the noncontrolling interests’ proportionate share of the recognized amounts of the acquiree’s identifiable net assets. When a business combination is achieved in stages, the Company’s previously held equity interest in an acquiree is remeasured to fair value at the acquisition date and the resulting gain or loss is recognized in profit or loss. Amounts arising from interests in the acquiree prior to the acquisition date that have previously been recognized in other comprehensive income are recognized on the same basis as would be required had those interests been directly disposed of by the Company. Foreign Currencies In preparing the financial statements of each individual entity, transactions in currencies other than the entity’s functional currency (foreign currencies) are recognized at the rates of exchange prevailing at the dates of the transactions. At the end of each reporting period, monetary items denominated in foreign currencies are retranslated at the rates prevailing at that date. Exchange differences on monetary items arising from settlement or translation are recognized in profit or loss in the period in which they arise. Non-monetary items carried at fair value that are denominated in foreign currencies are retranslated at the rates prevailing at the date when the fair value was determined and related exchange differences are recognized in profit or loss. Conversely, when the fair value changes were recognized in other comprehensive income, related exchange difference shall be recognized in other comprehensive income. Non-monetary items that are measured at historical cost in a foreign currency are not retranslated. Chunghwa uses New Taiwan dollars (NT$) as the functional currency. For the purposes of presenting consolidated financial statements, the assets and liabilities of the Company’s foreign operations (including of the subsidiaries, associates and joint ventures in other countries or currencies used different with Chunghwa) are translated into New Taiwan dollars using exchange rates prevailing at the end of each reporting period. Income and expense items are translated at the average exchange rates for the period. Exchange differences arising, if any, are recognized in other comprehensive income and attributed to stockholders of the parent and noncontrolling interests as appropriate. Cash Equivalents Cash equivalents include commercial paper, negotiable certificates of deposit, time deposits, repurchase agreements collateralized by bonds with original maturities within three months from the date of acquisition and government stimulus vouchers, highly liquid, readily convertible to a known amount of cash and are subject to an insignificant risk of changes in value. These cash equivalents are held for the purpose of meeting short-term cash commitments. Inventories Inventories are stated at the lower of cost or net realizable value item by item, except for those that may be appropriate to group items of similar or related inventories. Net realizable value is the estimated selling price of inventories less all estimated costs of completion and costs necessary to make the sale. The calculation of the cost of inventory is derived using the weighted-average method. Buildings and Land Consigned to Construction Contractors Inventories of LED are stated at the lower of cost or net realizable value item by item, except for those that may be appropriate to group as similar items or related inventories. Land acquired before construction is classified as land held for development, and then reclassified as land held under development after LED begins its construction project. Upon the completion of the construction project, LED recognizes revenues in the amount of proceeds from customers for land and buildings and related costs when ownership is transferred to the customers. The unsold portion of the completed construction project is transferred to land and building held for sale. Investments in Associates and Joint Ventures An associate is an entity over which the Company has significant influence and that is neither a subsidiary nor an interest in a joint venture. A joint venture is a joint arrangement whereby the Company and other parties that have joint control of the arrangement have rights to the net assets of the arrangement. Investments accounted for using the equity method include investments in associates and interests in joint ventures. Under the equity method, an investment in an associate or a joint venture is initially recognized at cost and adjusted thereafter to recognize the Company’s share of profit or loss and other comprehensive income of the associate and joint venture as well as the distribution received. The Company also recognizes its share in changes in the associates and joint ventures. When the Company subscribes for new shares of an associate and a joint venture at a percentage different from its existing ownership percentage, the resulting carrying amount of the investment differs from the amount of the Company’s proportionate interest in the associate and joint venture. The Company records such a difference as an adjustment to investments with the corresponding amount charged or credited to additional paid-in capital. When the adjustment should be debited to additional paid-in capital but the additional paid-in capital recognized from investments accounted for using equity method is insufficient, the shortage is debited to retained earnings. Any excess of the cost of acquisition over the Company’s share of the fair value of the identifiable net assets and liabilities of an associate and a joint venture at the date of acquisition is recognized as goodwill, which is included within the carrying amount of the investment and shall not be amortized. Any excess of the Company’s share of the net fair value of the identifiable assets and liabilities over the cost of acquisition is recognized immediately in profit or loss. The entire carrying amount of an investment (including goodwill) is tested for impairment as a single asset by comparing its recoverable amount with its carrying amount. Any impairment loss recognized is not allocated to any asset, including goodwill, that forms part of the carrying amount of the investment. Any reversal of that impairment loss is recognized to the extent that the recoverable amount of the investment subsequently increases. The Company discontinues the use of the equity method from the date on which its investment ceases to be an associate and a joint venture. Any retained investment is measured at fair value at that date, and the fair value is regarded as the investment’s fair value on initial recognition as a financial asset. The difference between the previous carrying amount of the associate and joint venture attributable to the retained interest and its fair value is included in the determination of the gain or loss on disposal of the associate and joint venture. The Company accounts for all amounts previously recognized in other comprehensive income in relation to that associate and joint venture on the same basis as would be required had that associate and joint venture directly disposed of the related assets or liabilities. When the Company transacts with its associate and joint venture, profits and losses resulting from the transactions with the associate and joint venture are recognized in the Company’s consolidated financial statements only to the extent of interests in the associate and joint venture that are not related to the Company. Property, Plant and Equipment Property, plant and equipment are initially measured at cost and subsequently measured at cost less accumulated depreciation and accumulated impairment loss. Property, plant and equipment in the course of construction are depreciated and classified to the appropriate categories of property, plant and equipment when completed and ready for their intended use. Depreciation on property, plant and equipment is recognized using the straight-line method. Each significant part is depreciated separately. Freehold land is not depreciated. The estimated useful lives, residual values and depreciation method are reviewed at the end of each year, with the effect of any changes in estimate accounted for on a prospective basis. On derecognition of an item of property, plant and equipment, the difference between the net disposal proceeds and the carrying amount of the asset is recognized in profit or loss in the period in which the property is derecognized. Investment Properties Investment properties are properties held to earn rentals and/or for capital appreciation. Investment properties also include land held for a currently undetermined future use. Investment properties are measured initially at cost, including transaction costs. Subsequent to initial recognition, investment properties are measured at cost less accumulated depreciation and accumulated impairment loss. Depreciation is recognized using the straight-line method. For a transfer from the investment properties to property, plant and equipment, the deemed cost of the property, plant and equipment for subsequent accounting is its carrying amount at the commencement of owner-occupation. For a transfer from the property, plant and equipment to investment properties, the deemed cost of the investment properties for subsequent accounting is its carrying amount at the end of owner-occupation. For a contract where a land owner provides land for the construction of buildings by a property developer in exchange for a certain percentage of the buildings, any exchange gain or loss is recognized when the exchange transaction occurs if the exchange transaction has commercial substance. On derecognition of the investment properties, the difference between the net disposal proceeds and the carrying amount of the asset is recognized in profit or loss in the period in which the property is derecognized. Goodwill Goodwill arising from the acquisition of a business is carried at cost as established at the date of acquisition of the business less accumulated impairment loss. For the purpose of impairment testing, goodwill is allocated to each of the Company’s cash-generating units or groups of cash-generating units (referred to as “cash-generating unit”) that are expected to benefit from the synergies of the business combination. A cash-generating unit to which goodwill has been allocated is tested for impairment annually, or more frequently when there is an indication that the unit may be impaired, by comparing its carrying amount, including the attributable goodwill, with its recoverable amount. However, if the goodwill allocated to a cash-generating unit was acquired in a business combination during the current annual period, that unit shall be tested for impairment before the end of the current annual period. If the recoverable amount of the cash-generating unit is less than its carrying amount, the impairment loss is allocated first to reduce the carrying amount of any goodwill allocated to the unit and then to the other assets of the unit pro rata based on the carrying amount of each asset in the unit. Any impairment loss is recognized directly in profit or loss. An impairment loss recognized for goodwill is not reversed in subsequent periods. Intangible Assets Other Than Goodwill Intangible assets with finite useful lives that are acquired separately are initially measured at cost and subsequently measured at cost less accumulated amortization and accumulated impairment loss. Amortization is recognized on a straight-line basis. The estimated useful life, residual value, and amortization method are reviewed at the end of each reporting period, with the effect of any changes in estimate being accounted for on a prospective basis. The residual value of an intangible asset with a finite useful life shall be assumed to be zero unless the Company expects to dispose of the intangible asset before the end of its economic life. Intangible assets acquired in a business combination and recognized separately from goodwill are initially recognized at their fair value at the acquisition date (which is regarded as their cost). Subsequent to initial recognition, they are measured on the same basis as intangible assets that are acquired separately. Gains or losses arising from derecognition of an intangible asset, measured as the difference between the net disposal proceeds and the carrying amount of the asset, are recognized in profit or loss in the period in which the asset is derecognized. Impairment of Property, Plant and Equipment, Right-of-use Assets, Intangible Assets Other Than Goodwill and Incremental Costs of Obtaining Contracts At the end of each reporting period, the Company reviews the carrying amounts of its property, plant and equipment, right-of-use assets and intangible assets, excluding goodwill, to determine whether there is any indication that those assets have suffered an impairment loss. If any such indication exists, the recoverable amount of the asset is estimated in order to determine the extent of the impairment loss. When it is not possible to estimate the recoverable amount of an individual asset, the Company estimates the recoverable amount of the cash-generating unit to which the asset belongs. Intangible assets not yet available for use are tested for impairment at least annually, and whenever there is an indication that the asset may be impaired. Recoverable amount is the higher of fair value less costs to sell and value in use. If the recoverable amount of an asset or cash-generating unit is estimated to be less than its carrying amount, the carrying amount of the asset or cash-generating unit is reduced to its recoverable amount, with the resulting impairment loss recognized in profit or loss. Impairment loss from the assets related to incremental cost of obtaining contracts is recognized to the extent that the carrying amount of the assets exceeds the remaining amount of consideration that the Company expects to receive in exchange for related goods or services less the costs which relate directly to providing those goods or services. When an impairment loss is subsequently reversed, the carrying amount of the asset or cash-generating unit is increased to the revised estimate of its recoverable amount, but only to the extent of the carrying amount that would have been determined had no impairment loss been recognized for the asset or cash-generating unit in prior years. A reversal of an impairment loss is recognized in profit or loss. Financial Instruments Financial assets and financial liabilities are recognized when the Company becomes a party to the contractual provisions of the instruments. Financial assets and financial liabilities are initially measured at fair value. Transaction costs that are directly attributable to the acquisition of financial assets and financial liabilities (other than financial assets and financial liabilities at fair value through profit or loss) are added to the fair value of the financial assets or financial liabilities, as appropriate, on initial recognition. Transaction costs directly attributable to the acquisition of financial assets or financial liabilities at fair value through profit or loss are recognized immediately in profit or loss. a. Financial assets All regular way purchases or sales of financial assets are recognized and derecognized on a trade date basis. The regular way of transaction means the purchase or sale of financial assets delivered within the time frame established by regulation or convention in the marketplace. 1) Measurement category a) Financial assets at fair value through profit or loss (FVTPL) Financial asset is classified as at FVTPL when the financial asset is mandatorily classified as at FVTPL. Financial assets mandatorily classified as at FVTPL include investments in equity instruments which are not designated as at fair value through other comprehensive income (FVOCI). Financial assets at FVTPL are stated at fair value, with any gains or losses arising on remeasurement recognized in profit or loss. The net gain or loss recognized in profit or loss does not incorporate any dividend earned on the financial asset. Fair value is determined in the manner described in Note 38. b) Financial assets at amortized cost Financial assets that meet the following conditions are subsequently measured at amortized cost: i. The financial asset is held within a business model whose objective is to hold financial assets in order to collect contractual cash flows; and ii. The contractual terms of the financial asset give rise on specified dates to cash flows that are solely payments of principal and interest on the principal amount outstanding. Subsequent to initial recognition, financial assets at amortized cost are measured at amortized cost, which equals to gross carrying amount determined by the effective interest method less any impairment loss, except for short-term receivables as the effect of discounting is immaterial. Exchange differences are recognized in profit or loss. Interest income is calculated by applying the effective interest rate to the gross carrying amount of such financial assets. c) Investments in equity instruments at FVOCI On initial recognition, the Company may make an irrevocable election to designate investments in equity instruments as at FVOCI. Designation at FVOCI is not permitted if the equity investment is held for trading or if it is contingent consideration recognized by an acquirer in a business combination. Investments in equity instruments at FVOCI are subsequently measured at fair value with gains and losses arising from changes in fair value recognized in other comprehensive income and accumulated in other equity. The cumulative gain or loss will not be reclassified to profit or loss on disposal of the equity investments. Instead, it will be transferred to retained earnings. Dividends on these investments in equity instruments are recognized in profit or loss when the Company’s right to receive the dividends is established, unless the dividends clearly represent a recovery of part of the cost of the investment. 2) Impairment of financi

Critical Accounting Judgments a

Critical Accounting Judgments and Key Sources of Estimation, Uncertainty and Assumption	12 Months Ended
	Dec. 31, 2020
Disclosure Of Accounting Judgements And Estimates [Abstract]
Critical Accounting Judgments and Key Sources of Estimation, Uncertainty and Assumption	4. CRITICAL ACCOUNTING JUDGMENTS AND KEY SOURCES OF ESTIMATION, UNCERTAINTY AND ASSUMPTION In the application of the Company’s accounting policies, the management is required to make judgments, estimates and assumptions which are based on historical experience and other factors that are not readily apparent from other sources. Actual results may differ from these estimates. The estimates and underlying assumptions are reviewed by the management on an ongoing basis. Revisions to accounting estimates are recognized in the period in which the estimate is revised if the revision affects only that period or in the period of the revision and future periods if the revision affects both current and future periods. a. Critical accounting judgments 1)Revenue recognition The Company’s project agreements are mainly to provide one or more customized equipment or services to customers. In order to fulfill the agreements, another party may be involved in some agreements. The Company considers the following factors to determine whether the Company is a principal of the transaction: whether the Company is the primary obligation provider of the agreements, its exposures to inventory risks and the discretion in establishing prices, etc. The determination of whether the Company is a principal or an agent will affect the amount of revenue recognized by the Company. Only when the Company is acting as a principal, gross inflows of economic benefits arising from transactions is recognized as revenue. 2)Control over subsidiaries As discussed in Note 3, “Summary of Significant Accounting Policies - Basis of Consolidation”, some entities are subsidiaries of the Company although the Company only owns less than 50% ownership interests in these entities. After considering the Company’s absolute size of holding in the entity and the relative size of and the dispersion of shares owned by the other stockholders, and the contractual arrangements between the Company and other investors, potential voting interests and the written agreement between stockholders, the management concluded that the Company has a sufficiently dominant voting interest to direct the relevant activities of the entity and to have control over the governance of the entity and therefore the Company has control over these entities. b . Key sources of estimation uncertainty and assumption The following are the key assumptions concerning the future, and other key sources of estimation uncertainty at the end of the reporting period. Actual results may differ from these estimates. 1) Impairment of trade notes and accounts receivable The provision for impairment of trade notes and accounts receivable is based on assumptions about risk of default and expected loss rates. The Company uses judgment in making these assumptions and in selecting the inputs to the impairment calculation, based on the Company’s past experience, current market conditions as well as forward looking information at the end of each reporting period. For details of the key assumptions and inputs used, see Note 10. Where the actual future cash flows are less than expected, a material impairment loss may arise. 2) Fair value measurements and valuation processes For the assets and liabilities measured at fair value without quoted prices in active markets, the Company’s management determines the appropriate valuation techniques for the fair value measurements and whether to engage third party qualified appraisers based on the related regulations and professional judgments. Information about the valuation techniques and inputs used in determining the fair value of various assets and liabilities was disclosed in Note 38. If the actual changes of inputs in the future differ from expectation, the fair value may vary accordingly. The Company updates inputs periodically to monitor the appropriateness of the fair value measurement. 3) Provision for inventory valuation and obsolescence Inventories are stated at the lower of cost or net realizable value. Estimates of net realizable value are based on the most reliable evidence available at the time the estimates are made at the end of reporting period. These estimates take into consideration fluctuations of price or cost directly relating to events occurring after the end of the period to the extent that such events confirm conditions existing at the end of the period. Inventory write-downs are determined on an item by item basis, except for those similar items which could be categorized into the same groups. The Company uses the inventory holding period and turnover as the evaluation basis for inventory obsolescence losses. 4) Impairment of property, plant and equipment, right-of-use assets and intangible assets In the process of evaluating the potential impairment of tangible and intangible assets, the Company is required to consider internal and external indicators of impairment and make subjective judgments in determining the independent cash flows, useful lives, expected future revenue and expenses related to the specific asset groups within the context of the telecommunication industry. Any changes in these estimates based on changed economic conditions or business strategies could result in significant impairment charges in future periods. 5) Useful lives of property, plant and equipment As discussed in Note 3, “Summary of Significant Accounting Policies - Property, Plant and Equipment”, the Company reviews estimated useful lives of property, plant and equipment at the end of each year. 6) Recognition and measurement of defined benefit plans Net defined benefit liabilities (assets) and the resulting pension expense under defined benefit pension plans are calculated using the Projected Unit Credit Method. Actuarial assumptions comprise the discount rate, employee turnover rate, average future salary increase and etc. Changes in economic circumstances and market conditions will affect these assumptions and may have a material impact on the amount of the expense and the liability. 7) Lessees’ incremental borrowing rates Starting from 2019 In determining a lessee’s incremental borrowing rate used in discounting lease payments, a risk-free rate for relevant duration and the same currency is selected as a reference rate. The lessee’s credit spread adjustments and lease specific adjustments are also taken into account.

Application of New and Amended

Application of New and Amended International Financial Reporting Standards	12 Months Ended
	Dec. 31, 2020
Description Of Expected Impact Of Initial Application Of New Standards Or Interpretations [Abstract]
Application of New and Amended International Financial Reporting Standards	5. APPLICATION OF NEW AND AMENDED INTERNATIONAL FINANCIAL REPORTING STANDARDS Amendments to IFRSs and the New Interpretation That Are Mandatorily Effective for the Current Year The Company has applied Amendments to IFRS 3: Definition of a Business, Amendments to IAS 9 and IAS 39 and IFRS 7: Interest Rate Benchmark Reform, Amendments to IAS 1 and IAS 8: Definition of Material. The application of these new standards and amendments has had no impact on the disclosures or amounts recognized in the Company’s consolidated financial statements. New and Amended IFRSs in Issue But Not Yet Effective The Company has not applied the following new and amended IFRSs that have been issued but are not yet effective. New or Amended Standards and Interpretations Effective Date Issued by IASB (Note 1) Amendments to IFRS 9, IAS 39, IFRS 7, IFRS 4 and IFRS 16 Interest Rate Benchmark Reform-Phase 2 January 1, 2021 Amendments to IFRSs Annual Improvements to IFRS Standards 2018-2020 January 1, 2022 (Note 2) Amendments to IFRS 3 Reference to the Conceptual Framework January 1, 2022 (Note 3) Amendments to IFRS 10 and IAS 28 Sale or Contribution of Assets between An Investor and Its Associate or Joint Venture To be determined by IASB Amendments to IAS 1 Classification of liabilities as current or noncurrent January 1, 2023 Amendments to IAS 1 Disclosure of Accounting Policies January 1, 2023 (Note 4) Amendments to IAS 8 Definition of Accounting Estimates January 1, 2023 (Note 5) Amendments to IAS 16 Property, Plant and Equipment - Proceeds before Intended Use January 1, 2022 (Note 6) Amendments to IAS 37 Onerous Contracts - Cost of Fulfilling a Contract January 1, 2022 (Note 7) Note 1: The aforementioned new or amended standards or interpretations are effective after fiscal year beginning on or after the effective dates, unless specified otherwise. Note 2 ： The amendments to IFRS 9 are applied prospectively to financial liabilities that are exchanged or modified on or after the annual reporting periods beginning on or after January 1, 2022. Note 3 ： The amendments are applicable to business combinations for which the acquisition date is on or after the annual reporting period beginning on or after January 1, 2022. Note 4 ： The amendments will be applied prospectively for annual reporting periods beginning on or after January 1, 2023. Note 5 ： The amendments are applicable to changes in accounting estimates and changes in accounting policies that occur on or after the beginning of the annual reporting period beginning on or after January 1, 2023. Note 6 ： The amendments are applicable to property, plant and equipment that are brought to the location and condition necessary for them to be capable of operating in the manner intended by management on or after January 1, 2021. Note 7 ： The application of “Amendments to IFRS 9, IAS 39, IFRS 7, IFRS 4 and IFRS 16: Interest Rate Benchmark Reform-phase 2” will not have material impact on the Company’s consolidated financial statements. As of the date the consolidated financial statements were authorized for issue, the Company is continuously assessing whether the application of “Amendments to IFRSs: Annual Improvements to IFRS Standards 2018-2020”, “Amendments to IFRS 3: Reference to the Conceptual Framework”, “Amendments to IFRS 10 and IAS 28: Sale or Contribution of Assets between An Investor and Its Associate or Joint Venture”, “Amendments to IAS 1: Classification of liabilities as current or noncurrent”, “Amendments to IAS 1: Definition of Accounting Estimates”, “Amendments to IAS 8: Disclosure Initiative - Accounting Policies”, “Amendments to IAS 16: Property, Plant and Equipment - Proceeds before Intended Use” and “Amendments to IAS 37: Onerous Contracts - Cost of Fulfilling a Contract” will have the impact on the Company’s financial position and operating result. The Company will disclose the relevant impact when the assessment is completed.

U.S. Dollar Amounts

U.S. Dollar Amounts	12 Months Ended
U.S. Dollar Amounts	Dec. 31, 2020
Foreign Exchange Rates [Abstract]
U.S. Dollar Amounts	6 . U.S. DOLLAR AMOUNTS The Company maintains its accounts and expresses its consolidated financial statements in New Taiwan dollars. For readers’ convenience only, U.S. dollar amounts presented in the accompanying consolidated financial statements have been translated from New Taiwan dollars as set forth in the statistical release of the Federal Reserve Board of the United States as of December 31, 2020, which was NT$28.08 to US$1.00. The convenience translations should not be construed as representations that the New Taiwan dollar amounts have been, could have been, or could in the future be, converted into U.S. dollars at this or any other rate of exchange.

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
Cash and Cash Equivalents	Dec. 31, 2020
Cash And Cash Equivalents [Abstract]
Cash and Cash Equivalents	7. CASH AND CASH EQUIVALENTS December 31 2019 2020 NT$ NT$ (In Millions) Cash Cash on hand $ 353 $ 487 Bank deposits 9,433 10,961 9,786 11,448 Cash equivalents (investments with maturities of less than three months) Commercial paper $ 20,110 $ 14,061 Negotiable certificates of deposit 1,700 2,600 Time deposits 2,451 2,308 Repurchase agreements collateralized by bonds 3 — Government stimulus vouchers — 3 24,264 18,972 $ 34,050 $ 30,420 The annual yield rates of bank deposits, commercial paper, negotiable certificates of deposit, time deposits and repurchase agreements collateralized by bonds as of balance sheet dates were as follows: December 31 2019 2020 Bank deposits 0.00%-0.74% 0.00%-0.40% Commercial paper 0.47%-0.54% 0.14%-0.26% Negotiable certificates of deposit 0.58%-0.60% 0.24%-0.30% Time deposits 0.09%-4.40% 0.10%-3.60% Repurchase agreements collateralized by bonds 1.90% —

Financial Instruments at Fair V

Financial Instruments at Fair Value Through Profit or Loss	12 Months Ended
Financial Instruments at Fair Value Through Profit or Loss	Dec. 31, 2020
Disclosure Of Financial Instruments At Fair Value Through Profit Or Loss [Abstract]
Financial Instruments at Fair Value Through Profit or Loss	8. FINANCIAL INSTRUMENTS AT FAIR VALUE THROUGH PROFIT OR LOSS December 31 2019 2020 NT$ NT$ (In Millions) Financial assets-current Mandatorily measured at FVTPL Derivatives (not designated for hedge) Forward exchange contracts $ — $ 2 Non-derivatives Listed stocks - domestic 1 8 $ 1 $ 10 Financial assets-noncurrent Mandatorily measured at FVTPL Non-derivatives Non-listed stocks - domestic $ 511 $ 441 Non-listed stocks - foreign 267 236 $ 778 $ 677 Financial liabilities-current Held for trading Derivatives (not designated for hedge) Forward exchange contracts $ — $ — The Company increased its investment in Taiwania Capital Buffalo Fund Co., Ltd. proportionally for $300 million in October 2019 and the Company’s ownership interest in Taiwania Capital Buffalo Fund Co., Ltd. remained at 12.9%. Outstanding forward exchange contracts not designated for hedge as of balance sheet dates were as follows: Maturity Contract Amount Currency Period (In Millions) December 31, 2019 Forward exchange contracts - buy NT$/EUR 2020.03 NT$51/EUR2 Forward exchange contracts - buy NT$/US$ 2020.01 NT$26/US$1 December 31, 2020 Forward exchange contracts - buy NT$/EUR 2021.03 NT$50/EUR2 Forward exchange contracts - sell US$/NT$ 2021.02-03 US$14/NT379 The Company entered into the above forward exchange contracts to manage its exposure to foreign currency risk due to fluctuations in exchange rates. However, the aforementioned derivatives did not meet the criteria for hedge accounting.

Financial Assets at Fair Value

Financial Assets at Fair Value through Other Comprehensive Income Noncurrent	12 Months Ended
	Dec. 31, 2020
Noncurrent Financial Assets At Fair Value Through Other Comprehensive Income [Abstract]
Financial Assets at Fair Value through Other Comprehensive Income Noncurrent	9. FINANCIAL ASSETS AT FAIR VALUE THROUGH OTHER COMPREHENSIVE INCOME - NONCURRENT December 31 2019 2020 NT$ NT$ (In Millions) Domestic investments Listed stocks $ 2,454 $ 2,754 Non-listed stocks 4,566 4,325 Foreign investments Non-listed stocks 134 114 $ 7,154 $ 7,193 The Company holds the above foreign and domestic stocks for medium to long-term strategic purposes and expects to profit from long-term investment. Accordingly, the management elected to designate these investments in equity instruments at FVOCI as they believe that recognizing short-term fair value fluctuations of these investments in profit or loss is not consistent with the Company’s strategy of holding these investments for long-term purposes. The Company holds Powtec Electro Chemical Corporation (“Powtec”) as financial assets at FVOCI. The Board of Directors of Powtec resolved in February 2020 to file a petition with court for the declaration of its bankruptcy which was adjudged by the court in April 2020. The Company evaluated and determined the fair value of such investment was nil after its declaration of bankruptcy and recognized related loss in the consolidated statements of comprehensive income for the year ended December 31, 2019. The Company disposed a portion of its investment in China Airlines, Ltd. at fair value of $568 million in December 2020. As of December 31, 2020, the settlement of funds/securities amounting to $270 million had not been completed. The related unrealized gain on investments in equity instruments at fair value through other comprehensive income of $17 million was transferred from other equity to retained earnings upon the aforementioned disposal. The Company recognized dividend income of $396 million, $296 million and $246 million for the years ended December 31, 2018, 2019 and 2020, respectively, from the investments still held on December 31, 2018, 2019 and 2020.

Trade Notes and Accounts Receiv

Trade Notes and Accounts Receivable, Net	12 Months Ended
Trade Notes and Accounts Receivable, Net	Dec. 31, 2020
Trade notes and accounts receivable [Member]
Disclosure Of Financial Assets [Line Items]
Trade Notes and Accounts Receivable, Net	1 0 . TRADE NOTES AND ACCOUNTS RECEIVABLE, NET December 31 2019 2020 NT$ NT$ (In Millions) Trade notes and accounts receivable $ 28,768 $ 24,776 Less: Loss allowance (2,360 ) (2,154 ) $ 26,408 $ 22,622 The main credit terms range from 30 to 90 days. The Company serves a large consumer base for telecommunications business; therefore, the concentration of credit risk is limited. When having transactions with customers, the Company considers the record of arrears in the past. In addition, the Company may also collect some telecommunication charges in advance to reduce the payment arrears in subsequent periods. The Company adopted a policy of dealing with counterparties with certain credit ratings for project business and to obtain collateral where necessary to mitigate the risk of loss arising from defaults. Credit rating information is provided by independent rating agencies where available and, if such credit rating information is not available, the Company uses other publicly available financial information and its own historical transaction experience to rate its major customers. The Company continues to monitor the credit exposure and credit ratings of its counterparties and spread the credit risk amongst qualified counterparties. In order to mitigate credit risk, the management of the Company has delegated a team responsible for determining credit limits, credit approvals and other monitoring procedures to ensure the recoverability of receivables. In addition, the Company reviews the recoverable amount of receivables at balance sheet dates to ensure that adequate allowance is provided for possible irrecoverable amounts. In this regard, the management believes the Company’s credit risk could be reasonably reduced. The Company applies the simplified approach to providing for expected credit losses prescribed by IFRS 9, which permits the use of lifetime expected loss provision for receivables. The expected credit losses on receivables are estimated using a provision matrix by reference to past default experience of the customers and an analysis of the customers’ current financial positions, as well as the forward-looking indicators such as macroeconomic business indicators. When there is evidence indicating that the counterparty is in evasion, bankruptcy, deregistration of its company or the accounts receivable are over two years past due and the recoverable amount cannot be reasonable estimated, the Company writes off the trade notes and accounts receivable. For accounts receivable that have been written off, the Company continues to engage in enforcement activity to attempt to recover the receivables due. Where recoveries are made, these are recognized in profit or loss. Except for receivables arising from telecommunications business and project business, the Company’s remaining accounts receivable are limited. Therefore, only Chunghwa’s provision matrix arising from telecommunications business and project business is disclosed below: December 31, 2019 Not Past Due Past Due Less than 30 Days Pass Due 31 to 60 Days Pass Due 61 to 90 Days Pass Due 91 to 120 Days Pass Due 121 to 180 Days Pass Due over 180 Days Total NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Telecommunications business Expected credit loss rate (Note a) 0%-2% 0%-25% 0%-68% 0%-83% 11%-90% 17%-96% 100% Gross carrying amount $ 19,020 $ 268 $ 75 $ 47 $ 41 $ 28 $ 601 $ 20,080 Loss allowance (Lifetime ECL) (56 ) (26 ) (28 ) (35 ) (26 ) (27 ) (601 ) (799 ) Amortized cost $ 18,964 $ 242 $ 47 $ 12 $ 15 $ 1 $ — $ 19,281 Project business Expected credit loss rate (Note b) 0%-5% 5% 10% 30% 50% 80% 100% Gross carrying amount $ 4,054 $ 78 $ 52 $ 30 $ 12 $ 1 $ 1,472 $ 5,699 Loss allowance (Lifetime ECL) (3 ) (5 ) (5 ) (11 ) (5 ) (1 ) (1,472 ) (1,502 ) Amortized cost $ 4,051 $ 73 $ 47 $ 19 $ 7 $ — $ — $ 4,197 December 31, 2020 Not Past Due Past Due Less than 30 Days Pass Due 31 to 60 Days Pass Due 61 to 90 Days Pass Due 91 to 120 Days Pass Due 121 to 180 Days Pass Due over 180 Days Total NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Telecommunications business Expected credit loss rate (Note a) 0%-2% 2%-24% 3%-68% 11%-83% 28%-90% 52%-96% 100% Gross carrying amount $ 15,839 $ 204 $ 51 $ 31 $ 30 $ 25 $ 626 $ 16,806 Loss allowance (Lifetime ECL) (56 ) (21 ) (24 ) (25 ) (24 ) (21 ) (626 ) (797 ) Amortized cost $ 15,783 $ 183 $ 27 $ 6 $ 6 $ 4 $ — $ 16,009 Project business Expected credit loss rate (Note b) 0%-5% 5% 10% 30% 50% 80% 100% Gross carrying amount $ 3,473 $ 64 $ 27 $ 9 $ 2 $ 3 $ 1,288 $ 4,866 Loss allowance (Lifetime ECL) (20 ) (3 ) (3 ) (3 ) (1 ) (2 ) (1,288 ) (1,320 ) Amortized cost $ 3,453 $ 61 $ 24 $ 6 $ 1 $ 1 $ — $ 3,546 Note a: Please refer to Notes 31 and 45 for the information of disaggregation of telecommunications service revenue. The expected credit loss rate applicable to different business revenue varies so as to reflect the risk level indicating by factors like historical experience. Note b : The project business has different loss types according to the customer types. The expected credit loss rate listed above is for general customers. When the customer is a government-affiliated entity, it is anticipated that there will not be an instance of credit loss. Customers with past history of bounced checks or accounts receivable exceeding six months overdue are classified as high-risk customers, with an expected credit loss rate of 50%, increasing by period as the days overdue increase. Movements of loss allowance for trade notes and accounts receivable were as follows: Year Ended December 31 2019 2020 NT$ NT$ (In Millions) Beginning balance $ 2,602 $ 2,360 Add: Provision for (reversal of) credit loss (54 ) 49 Add: Acquired by business combinations (Note 14) — 2 Less: Amounts written off (188 ) (257 ) Ending balance $ 2,360 $ 2,154

Inventories

Inventories	12 Months Ended
Inventories	Dec. 31, 2020
Classes Of Inventories [Abstract]
Inventories	1 1 . INVENTORIES December 31 2019 2020 NT$ NT$ (In Millions) Merchandise $ 3,858 $ 3,903 Project in process 11,113 6,167 Work in process 141 126 Raw materials 156 137 15,268 10,333 Land held under development 1,999 1,999 Construction in progress 77 77 $ 17,344 $ 12,409 The operating costs related to inventories were $48,649 million, $49,258 million and $53,847 million for the years ended December 31, 2018, 2019 and 2020, respectively. For the years ended December 31, 2018, 2019 and 2020, valuation loss on inventories recognized as operating costs included the amounts of $365 million, $475 million and $1,161 million, respectively. As of December 31, 2019 and 2020, inventories of $2,076 million and $2,076 million, respectively, were expected to be recovered for a time period longer than twelve months. The aforementioned amount of inventories is related to property development owned by LED. Land held under development and construction in progress was developed by LED for Qingshan Sec., Dayuan Dist., Taoyuan City project.

Prepayments

Prepayments	12 Months Ended
Prepayments	Dec. 31, 2020
Prepayments And Accrued Income [Abstract]
Prepayments	1 2 . PREPAYMENTS December 31 2019 2020 NT$ NT$ (In Millions) Prepaid rents $ 3,382 $ 2,864 Others 1,180 1,656 $ 4,562 $ 4,520 Current Prepaid rents $ 704 $ 652 Others 1,179 1,654 $ 1,883 $ 2,306 Noncurrent Prepaid rents $ 2,678 $ 2,212 Others 1 2 $ 2,679 $ 2,214 Prepaid rents comprised the prepayments from the lease agreements applying the recognition exemption and the prepayments for leases that do not meet the definition of leases under IFRS 16.

Other Current Monetary Assets

Other Current Monetary Assets	12 Months Ended
Other Current Monetary Assets	Dec. 31, 2020
Disclosure Of Other Current Monetary Assets [Abstract]
Other Current Monetary Assets	1 3 . OTHER CURRENT MONETARY ASSETS December 31 2019 2020 NT$ NT$ (In Millions) Time deposits and negotiable certificates of deposit with maturities of more than three months $ 5,959 $ 4,596 Repurchase agreements collateralized by bonds with maturities of more than three months 15 — Others 1,524 1,528 $ 7,498 $ 6,124 The annual yield rates of time deposits, negotiable certificates of deposit and repurchase agreements collateralized by bonds with maturities of more than three months at the balance sheet dates were as follows: December 31 2019 2020 Time deposits and negotiable certificates of deposit with maturities of more than three months 0.03%-2.73% 0.07%-2.25% Repurchase agreements collateralized by bonds with maturities of more than three months 2.50% —

Subsidiaries

Subsidiaries	12 Months Ended
Subsidiaries	Dec. 31, 2020
Disclosure Of Significant Investments In Subsidiaries [Abstract]
Subsidiaries	1 4 . a. Information on subsidiaries with material noncontrolling interests The table below shows details of less than wholly owned subsidiaries of the Company that have material noncontrolling interests: Place of Incorporation Proportion of Ownership Interests and Voting Rights Held by Noncontrolling Interests and Principal December 31 Subsidiaries Place of Business 2019 2020 SENAO Taiwan 72% 72% CHPT Taiwan 66% 66% Profit Allocated to Noncontrolling Interests Accumulated Noncontrolling Interests Year Ended December 31 December 31 2018 2019 2020 2019 2020 NT$ NT$ NT$ NT$ NT$ (In Millions) SENAO $ 326 $ 291 $ 312 $ 4,146 $ 4,189 CHPT $ 477 $ 414 $ 604 4,217 4,606 Individually immaterial subsidiaries with noncontrolling interests 1,752 2,363 $ 10,115 $ 11,158 Summarized financial information in respect of SENAO and its subsidiaries that has material noncontrolling interests is set out below. The summarized financial information below represented amounts before intercompany eliminations. December 31 2019 2020 NT$ NT$ (In Millions) Current assets $ 6,751 $ 6,834 Noncurrent assets $ 3,173 $ 3,194 Current liabilities $ 3,637 $ 3,854 Noncurrent liabilities $ 590 $ 416 Equity attributable to the parent $ 1,551 $ 1,569 Equity attributable to noncontrolling interests $ 4,146 $ 4,189 Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Revenues and income $ 31,540 $ 29,131 $ 27,232 Costs and expenses 31,081 28,725 26,797 Profit for the year $ 459 $ 406 $ 435 Profit attributable to the parent $ 133 $ 115 $ 123 Profit attributable to noncontrolling interests 326 291 312 Profit for the year $ 459 $ 406 $ 435 Other comprehensive income (loss) attributable to the parent $ (2 ) $ (7 ) $ 1 Other comprehensive income (loss) attributable to noncontrolling interests (10 ) 22 2 Other comprehensive income (loss) for the year $ (12 ) $ 15 $ 3 Total comprehensive income attributable to the parent $ 131 $ 108 $ 124 Total comprehensive income attributable to noncontrolling interests 316 313 314 Total comprehensive income for the year $ 447 $ 421 $ 438 Net cash flow from operating activities $ 696 $ 538 $ 862 Net cash flow from investing activities (13 ) 235 54 Net cash flow from financing activities (491 ) (718 ) (687 ) Effect of exchange rate changes on cash and cash equivalents 1 — — Net cash inflow $ 193 $ 55 $ 229 Dividends paid to noncontrolling interests $ 587 $ 269 $ 269 Summarized financial information in respect of CHPT and its subsidiaries that has material noncontrolling interests is set out below. The summarized financial information below represented amounts before intercompany eliminations. December 31 2019 2020 NT$ NT$ (In Millions) Current assets $ 3,710 $ 4,122 Noncurrent assets $ 4,044 $ 4,013 Current liabilities $ 1,316 $ 1,115 Noncurrent liabilities $ 22 $ 12 Equity attributable to CHI $ 2,199 $ 2,402 Equity attributable to noncontrolling interests $ 4,217 $ 4,606 Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Revenues and income $ 3,299 $ 3,404 $ 4,221 Costs and expenses 2,549 2,775 3,301 Profit for the year $ 750 $ 629 $ 920 Profit attributable to CHI $ 273 $ 215 $ 316 Profit attributable to noncontrolling interests 477 414 604 Profit for the year $ 750 $ 629 $ 920 Other comprehensive loss attributable to CHI $ — $ (1 ) $ — Other comprehensive loss attributable to noncontrolling interests — (2 ) — Other comprehensive loss for the year $ — $ (3 ) $ — Total comprehensive income attributable to CHI $ 273 $ 214 $ 316 Total comprehensive income attributable to noncontrolling interests 477 412 604 Total comprehensive income for the year $ 750 $ 626 $ 920 Net cash flow from operating activities $ 862 $ 507 $ 1,483 Net cash flow from investing activities (733 ) (1,426 ) (533 ) Net cash flow from financing activities (328 ) (349 ) (349 ) Effect of exchange rate changes on cash and cash equivalents 1 (5 ) 1 Net cash inflow (outflow) $ (198 ) $ (1,273 ) $ 602 Dividends paid to noncontrolling interests $ 210 $ 216 $ 216 b. Equity transactions with noncontrolling interests CHI disposed some shares of CHPT from April to August 2018. Therefore, the Company’s ownership interest in CHPT decreased to 34.25% as of December 31, 2019 and 2020. Chunghwa and CHI disposed some shares of CHIEF in May 2018 before CHIEF traded its shares on the emerging stock market and the General Stock Market of the Taipei Exchange according to the local requirements. In addition, Chunghwa and CHI did not participate in the capital increase of CHIEF in June 2018. Furthermore, CHIEF issued new shares in March 2018, November 2018, March 2019, November 2019, March 2020 and December 2020, as its employees exercised options. Therefore, the Company’s ownership interest in CHIEF decreased to 59.75% and 59.08% as of December 31, 2019 and 2020. See Note 35(c)(d) for details. SENAO transferred its treasury stock to employees in June 2018; therefore, the Company’s ownership interest in SENAO decreased to 28.18% as of December 31, 2019 and 2020. See Note 35(b) for details. SENAO subscribed for all the shares in the capital increase of Youth in December 2018 and April 2020; therefore, the Company’s ownership interest in Youth increased to 93% and 96% as of December 31, 2019 and 2020, respectively. IISI issued new shares in September 2020 as its employees exercised options; therefore, the Company’s ownership interest in IISI decreased. See Note 35(f) for details. The above transactions were accounted for as equity transactions since the Company did not cease to have control over these subsidiaries. The detailed information of the equity transactions for the years ended December 31, 2018, 2019 and 2020 was as follows: Year Ended December 31, 2018 SENAO not Proportionately participating in the Capital Increase of Youth SENAO Transferred its Treasury Stock CHI Disposed Some Shares of CHPT Chunghwa and CHI Did Not Participate in the Capital Increase of CHIEF Chunghwa and CHI Disposed Some Shares of CHIEF Share-Based Payment of CHIEF NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Cash consideration received from noncontrolling interests $ — $ 327 $ 1,042 $ 1,477 $ 133 $ 35 The proportionate share of the carrying amount of the net assets of the subsidiary transferred to noncontrolling interests — (272 ) (330 ) (700 ) (19 ) (24 ) Differences arising from equity transactions $ — $ 55 $ 712 $ 777 $ 114 $ 11 Line items for equity transaction adjustments Additional paid-in capital - difference between consideration received or paid and the carrying amount of the subsidiaries’ net assets upon actual disposal or acquisition $ — $ — $ 712 $ — $ 114 $ — Additional paid-in capital - arising from changes in equities of subsidiaries $ — $ 55 $ — $ 777 $ — $ 11 Year Ended December 31, 2019 CHIEF Share-Based Payment NT$ (In Millions) Cash consideration received from noncontrolling interests $ 19 The proportionate share of the carrying amount of the net assets of the subsidiary transferred to noncontrolling interests (20 ) Differences arising from equity transactions $ (1 ) Line items for equity transaction adjustments Additional paid-in capital - arising from changes in equities of subsidiaries $ (1 ) Year Ended December 31, 2020 CHIEF Share-Based Payment SENAO Not Proportionately Participating in the Capital Increase of Youth IISI Share-Based Payment NT$ NT$ NT$ (In Millions) Cash consideration received from noncontrolling interests $ 75 $ — $ 7 The proportionate share of the carrying amount of the net assets of the subsidiary transferred to noncontrolling interests (49 ) — (7 ) Differences arising from equity transactions $ 26 $ — $ — Line items for equity transaction adjustments Additional paid-in capital - arising from changes in equities of subsidiaries $ 26 $ — $ — c . Business combinations 1 ) Subsidiary acquired In order to develop and cultivate the enterprise customer market, Chunghwa obtained 20.38% ownership interest in IISI by cash on July 1, 2020, the acquisition date. (Note) Chunghwa’s ownership interest in IISI increased to 51.54% by considering the previously held ownership interest in IISI. Chunghwa obtained over half of the seats of the Board of Directors of IISI; therefore, Chunghwa gained control over IISI and included IISI and its subsidiaries in the consolidated financial statements starting from the acquisition date. IISI mainly engages in information system development and maintenance service business, etc. Note: IISI issued new shares in April 2020 as its employees exercised options; therefore, the percentage of ownership interest in IISI obtained on the acquisition date is lower than that approved by Chunghwa’s Board of Directors in January 2020. 2 ) Assets acquired and liabilities assumed at acquisition date IISI and Its Subsidiaries Current assets Cash and cash equivalents $ 588 Contract assets 583 Trade notes and accounts receivable 165 Inventories 141 Prepayments 114 Other current monetary assets 114 Other current assets 75 Noncurrent assets Property, plant and equipment 48 Right-of-use assets 70 Intangible assets 12 Deferred income tax assets 6 Other noncurrent assets 102 Current liabilities Short-term loans (4 ) Contract liabilities (334 ) Trade notes and accounts payable (257 ) Current tax liabilities (19 ) Lease liabilities (26 ) Other payables (266 ) Provisions (15 ) Other current liabilities (30 ) Noncurrent liabilities Deferred income tax liabilities (3 ) Lease liabilities (45 ) Net defined benefit liabilities (32 ) Other noncurrent liabilities (5 ) $ 982 The trade notes and accounts receivable acquired in business combination transactions have a fair value of $165 million and a gross contractual amount of $167 million. The best estimates of the contractual cash flows not expected to be collected as of the acquisition date are $2 million. 3 ) Goodwill arising from acquisition IISI and Its Subsidiaries Consideration transferred $ 234 Add: Fair value of equity interest held before the acquisition date 327 Add: Noncontrolling interest (48.46% of the identifiable net assets of IISI and its subsidiaries) 476 Less: Fair value of identifiable net assets acquired (982 ) Goodwill arising from acquisition $ 55 The goodwill arising from the acquisition of IISI mainly represents the control premium. In addition, the consideration paid for the combination included amounts attributed to the benefits of expected synergies and the assembled workforces of IISI. These benefits are not recognized separately from goodwill because they do not meet the recognition criteria for identifiable intangible assets. Goodwill arising from business combinations is not deductible for tax purposes. 4 ) Net cash inflow on acquisition of subsidiaries IISI and Its Subsidiaries Cash and cash equivalents acquired $ 588 Less: Consideration paid in cash (234 ) $ 354 5 ) Impact of acquisition on the financial results of the Company The financial results of the acquiree since the acquisition date to December 31, 2020 included in the consolidated statements of comprehensive income are as follows: IISI and Its Subsidiaries Revenue $ 1,348 Profit $ 68 Had the business combination been in effect at the beginning of the annual reporting period, the Company’s revenue and profit would have been $208,605 million and $34,747 million for the year ended December 31, 2020, respectively. This pro-forma information is for illustrative purposes only and is not necessarily an indication of revenue and results of operations of the Company that actually would have been achieved had the acquisition been completed on January 1, 2020, nor is it intended to be a projection of future results. In determining the pro-forma revenue and profit of the Company had IISI been acquired at the beginning of the financial year, the management calculated amortization of intangible assets acquired on the basis of the fair values arising in the initial accounting for the business combination rather than the carrying amounts recognized in the pre-acquisition financial statements.

Investments Accounted for Using

Investments Accounted for Using Equity Method	12 Months Ended
Investments Accounted for Using Equity Method	Dec. 31, 2020
Disclosure In Investments In Associates And Joint Ventures [Abstract]
Investments Accounted for Using Equity Method	1 5 . INVESTMENTS ACCOUNTED FOR USING EQUITY METHOD December 31 2019 2020 NT$ NT$ (In Millions) Investments in associates $ 7,139 $ 6,685 Investment in joint venture — 10 $ 7,139 $ 6,695 a. Investments in associates Carrying Amount December 31 2019 2020 NT$ NT$ (In Millions) Material associate Next Commercial Bank Co., Ltd. (“NCB”) (Note) $ 4,074 $ 3,777 Associates that are not individually material Listed Senao Networks, Inc. (“SNI”) 803 841 KingwayTek Technology Co., Ltd. (“KWT”) 217 213 Non-listed ST-2 Satellite Ventures Pte. Ltd. (“STS”) 501 488 Viettel-CHT Co., Ltd. (“Viettel-CHT”) 317 363 Taiwan International Standard Electronics Co., Ltd. (“TISE”) 268 324 So-net Entertainment Taiwan Limited (“So-net”) 186 225 Chunghwa PChome Fund I Co., Ltd. (“CPFI”) 194 193 KKBOX Taiwan Co., Ltd. (“KKBOXTW”) 151 163 Taiwan International Ports Logistics Corporation (“TIPL”) 51 56 Click Force Co., Ltd. (“CF”) 37 33 Cornerstone Ventures Co., Ltd. (“CVC”) 5 6 Alliance Digital Tech Co., Ltd. (“ADT”) 3 3 UUPON Inc. (“UUPON”) (3 ) — International Integrated System, Inc. (“IISI”) 335 — MeWorks Limited (HK) (“MeWorks”) — — $ 7,139 $ 6,685 The percentages of ownership interests and voting rights in associates held by the Company as of balance sheet dates were as follows: % of Ownership Interests and Voting Rights December 31 2019 2020 Material associate Next Commercial Bank Co., Ltd. (“NCB”) (Note) 42 42 Associates that are not individually material Senao Networks, Inc. (“SNI”) 34 34 KingwayTek Technology Co., Ltd. (“KWT”) 23 23 ST-2 Satellite Ventures Pte., Ltd. (“STS”) 38 38 Viettel-CHT Co., Ltd. (“Viettel-CHT”) 30 30 Taiwan International Standard Electronics Co., Ltd. (“TISE”) 40 40 So-net Entertainment Taiwan Limited (“So-net”) 30 30 Chunghwa PChome Fund I Co., Ltd. (“CPFI”) 50 50 KKBOX Taiwan Co., Ltd. (“KKBOXTW”) 30 30 Taiwan International Ports Logistics Corporation (“TIPL”) 27 27 Click Force Co., Ltd. (“CF”) 49 49 Cornerstone Ventures Co., Ltd. (“CVC”) 49 49 Alliance Digital Tech Co., Ltd. (“ADT”) 14 14 UUPON Inc. (“UUPON”) 22 — International Integrated System, Inc. (“IISI”) 31 — MeWorks Limited (HK) (“MeWorks”) 20 — Note: NCB was a preparatory office on December 31, 2019. Summarized financial information of NCB was set out below: December 31 December 31 2019 2020 NT$ NT$ (In Millions) Assets $ 10,452 $ 9,907 Lliabilities (728 ) (789 ) Equity $ 9,724 $ 9,118 The percentage of ownership interests held by the Company 41.9 % 41.9 % Equity attributable to the Company $ 4,074 $ 3,820 Unrealized gain or loss from downstream transactions — (43 ) The carrying amount of investment $ 4,074 $ 3,777 Period from the Beginning Date of Preparation to December 31, 2019 Year Ended December 31, 2020 NT$ NT$ (In Millions) Revenues $ — $ — Net loss for the period $ (276 ) $ (605 ) Other comprehensive income — — Total comprehensive loss for the period $ (276 ) $ (605 ) Except for NCB, no associate is considered individually material to the Company. Summarized financial information of associates that are not individually material to the Company was as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) The Company’s share of profits $ 509 $ 575 $ 540 The Company’s share of other comprehensive income (loss) 5 (3 ) (8 ) The Company’s share of total comprehensive income $ 514 $ 572 $ 532 The Level 1 fair values of associates based on the closing market prices as of the balance sheet dates were as follows: December 31 2019 2020 NT$ NT$ (In Millions) SNI $ 2,014 $ 1,708 KWT $ 873 $ 676 The Company owns 14% equity shares of ADT. As the Company remains its seat in the Board of Directors of ADT and considers the relative size of ownership interest and the dispersion of shares owned by the other stockholders, the Company has significant influence over ADT. In June 2018, the stockholders of ADT approved to dissolve. The liquidation of ADT is still in process. HopeTech returned the proceeds of $19 million as a result of capital reduction in January 2018. The Company received $3 million by disposing all shares of HopeTech in June 2018 and recognized disposal loss of $0.1 million. HopeTech engages mainly in sale of information and communication technologies products. The Company invested 50% equity shares of CPFI in October 2018. The Company has only two out of five seats of the Board of Directors of CPFI, and has no control but significant influence over CPFI. Therefore, the Company recognized CPFI as investment in associate. CPFI engages mainly in investment business. The Company invested 49% equity shares of CVC in October 2018. The Company has only two out of five seats of the Board of Directors of CVC, and has no control but significant influence over CVC. Therefore, the Company recognized CVC as investment in associate. CVC engages mainly in investment business. The participation of establishing NCB was approved by Chunghwa’s Board of Directors in January 2019. The establishment of NCB was approved by the Financial Supervisory Commission in July 2019 and the incorporation of NCB was approved by the ROC’s Ministry of Economic Affairs Department of Commerce in January 2020. Chunghwa prepaid investment funds to NCB in February and November 2019 amounting to $4,190 million, for ownership interest of 41.90%. Although Chunghwa is the single largest stockholder of NCB, it only obtained six out of fifteen seats of the Board of Directors of NCB. In addition, the management considered the size of ownership interest and the dispersion of shares owned by the other stockholders, other holdings are not extremely dispersed. Chunghwa is not able to direct its relevant activities. Therefore, Chunghwa does not have control over NCB and merely has significant influence over NCB and treats it as an associate. NCB mainly engages in online banking business in Taiwan. IISI issued new shares in March, September 2019 and April 2020, as its employees exercised options; therefore, the Company’s ownership interest in IISI decreased to 31.47% and 31.16% as of December 31, 2019 and June 30, 2020, respectively. The additional investment of 20.58% ownership interest in IISI was approved by Chunghwa’s Board of Directors in January 2020 and the equity transaction was completed in July 2020. As the business combination was achieved in stages, the Company remeasured the previously held equity interest of IISI and recognized gain on disposal of $1 million on the acquisition date. The Company treated IISI as a subsidiary starting from the acquisition date and included IISI and its subsidiaries in the consolidated financial statements. Please refer to Note 14(c). The Company disposed some shares of KWT in April 2019 before KWT traded its shares on the General Stock Market of the Taipei Exchange according to the local requirements and recognized gain on disposal of $151 million. In addition, the Company did not participate in the capital increase of KWT in May 2019 and KWT repurchased its stock from December 2019 to February 2020. Therefore, the Company’s ownership interest in KWT changed to 22.52% and 22.72% as of December 31, 2019 and 2020, respectively. UUPON reduced 95.44% of its capital to offset accumulated deficits in September 2020 and the Company did not participate in the capital increase of UUPON in October 2020. Therefore, the Company’s ownership interest in UUPON decreased to 5.36% and lost its significant influence over UUPON. Hence the Company discontinued to treat UUPON as an associate. Instead, the Company treated it as a financial asset at fair value through other comprehensive income and recognized gain on disposal of $15 million. The aforementioned gains on disposal were included under “other gains and losses” in the consolidated statements of comprehensive income. The Company disposed of all shares of MeWorks in September 2020. b. Investment in joint venture Carrying Amount % of Ownership Interests and Voting Rights December 31 December 31 Name of Joint Venture 2019 2020 2019 2020 Non-listed Chunghwa SEA Holdings (“CHT SEA”) $ — $ 10 — 51 The Company invested $10 million to establish a joint venture, CHT SEA, with Delta Electronics, Inc and Kwang Hsing Industrial Co., Ltd. in December 2020 and obtained 51% equity shares of CHT SEA. However, according to the mutual agreements among stockholders, the Company does not individually direct CHT SEA’s relevant activities and has joint control with the other party; therefore, the Company treated CHT SEA as a joint venture.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
Property, Plant and Equipment	Dec. 31, 2020
Disclosure Of Property Plant And Equipment [Abstract]
Property, Plant and Equipment	16. PROPERTY, PLANT AND EQUIPMENT December 31 2018 NT$ (In Millions) Carrying amount Land $ 103,972 Land improvements 263 Buildings 44,784 Computer equipment 2,115 Telecommunications equipment 116,322 Transportation equipment 231 Miscellaneous equipment 2,582 Construction in progress and equipment to be accepted 18,645 $ 288,914 Land Land Improvements Buildings Computer Equipment Telecommuni- cations Equipment Transportation Equipment Miscellaneous Equipment Construction in Progress and Equipment to be Accepted Total NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Cost Balance on January 1, 2018 $ 104,079 $ 1,595 $ 72,694 $ 14,162 $ 722,054 $ 3,834 $ 9,515 $ 18,527 $ 946,460 Additions — — 21 52 159 — 334 27,413 27,979 Disposal (71 ) — — (643 ) (31,984 ) (29 ) (623 ) — (33,350 ) Effect of foreign exchange differences — — — — 60 — — — 60 Others (36 ) 6 196 687 25,459 77 648 (27,295 ) (258 ) Balance on December 31, 2018 $ 103,972 $ 1,601 $ 72,911 $ 14,258 $ 715,748 $ 3,882 $ 9,874 $ 18,645 $ 940,891 Accumulated depreciation and impairment Balance on January 1, 2018 $ — $ (1,293 ) $ (26,799 ) $ (11,788 ) $ (607,154 ) $ (3,513 ) $ (7,205 ) $ — $ (657,752 ) Depreciation expenses — (45 ) (1,356 ) (983 ) (24,236 ) (162 ) (679 ) — (27,461 ) Disposal — — — 632 31,952 29 615 — 33,228 Effect of foreign exchange differences — — — — (20 ) — — — (20 ) Others — — 28 (4 ) 32 (5 ) (23 ) — 28 Balance on December 31, 2018 $ — $ (1,338 ) $ (28,127 ) $ (12,143 ) $ (599,426 ) $ (3,651 ) $ (7,292 ) $ — $ (651,977 ) There was no indication that property, plant and equipment was impaired so the Company did not recognize any impairment loss for the year ended December 31, 2018. Depreciation expense in 2018 is computed using the straight-line method over the following estimated service lives: Land improvements 8-30 years Buildings Main buildings 35-60 years Other building facilities 3-20 years Computer equipment 2-8 years Telecommunications equipment Telecommunication circuits 2-30 years Telecommunication machinery and antennas equipment 2-30 years Transportation equipment 3-10 years Miscellaneous equipment Leasehold improvements 1-6 years Mechanical and air conditioner equipment 3-16 years Others 1-10 years December 31 2019 2020 NT$ NT$ (In Millions) Assets used by the Company $ 276,370 $ 273,823 Assets subject to operating leases 7,324 7,593 $ 283,694 $ 281,416 a. Assets used by the Company Land Land Improvements Buildings Computer Equipment Telecommuni- cations Equipment Transportation Equipment Miscellaneous Equipment Construction in Progress and Equipment to be Accepted Total NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Cost Balance on January 1, 2019 $ 103,972 $ 1,601 $ 72,911 $ 14,258 $ 715,748 $ 3,882 $ 9,874 $ 18,645 $ 940,891 Effect of retrospective application of IFRS 16 (3,617 ) (1 ) (3,583 ) — (3,885 ) — — — (11,086 ) Balance on January 1, 2019 as adjusted 100,355 1,600 69,328 14,258 711,863 3,882 9,874 18,645 929,805 Additions — — 1,221 57 120 1 149 21,612 23,160 Disposal (38 ) (7 ) (3 ) (1,916 ) (30,417 ) (51 ) (405 ) — (32,837 ) Effect of foreign exchange differences — — — — (37 ) — (1 ) (6 ) (44 ) Others (1,214 ) 25 455 606 24,503 80 473 (26,499 ) (1,571 ) Balance on December 31, 2019 $ 99,103 $ 1,618 $ 71,001 $ 13,005 $ 706,032 $ 3,912 $ 10,090 $ 13,752 $ 918,513 Accumulated depreciation and impairment Balance on January 1, 2019 $ — $ (1,338 ) $ (28,127 ) $ (12,143 ) $ (599,426 ) $ (3,651 ) $ (7,292 ) $ — $ (651,977 ) Effect of retrospective application of IFRS 16 — 1 1,265 — 2,576 — — — 3,842 Balance on January 1, 2019 as adjusted — (1,337 ) (26,862 ) (12,143 ) (596,850 ) (3,651 ) (7,292 ) — (648,135 ) Depreciation expenses — (43 ) (1,301 ) (827 ) (23,906 ) (91 ) (688 ) — (26,856 ) Disposal — 6 3 1,909 30,380 51 402 — 32,751 Impairment losses — — — — — — (64 ) (29 ) (93 ) Effect of foreign exchange differences — — — — 16 — 1 — 17 Others — (1 ) 183 (7 ) 22 (3 ) (21 ) — 173 Balance on December 31, 2019 $ — $ (1,375 ) $ (27,977 ) $ (11,068 ) $ (590,338 ) $ (3,694 ) $ (7,662 ) $ (29 ) $ (642,143 ) Balance on December 31, 2019, net $ 99,103 $ 243 $ 43,024 $ 1,937 $ 115,694 $ 218 $ 2,428 $ 13,723 $ 276,370 Cost Balance on January 1, 2020 $ 99,103 $ 1,618 $ 71,001 $ 13,005 $ 706,032 $ 3,912 $ 10,090 $ 13,752 $ 918,513 Additions 67 - 18 55 118 1 150 24,786 25,195 Disposal (270 ) (19 ) (49 ) (1,245 ) (20,619 ) (45 ) (520 ) (29 ) (22,796 ) Effect of foreign exchange differences — — — — (91 ) — — (7 ) (98 ) Acquired by business combinations (Note 14) — — — 70 — — 72 — 142 Others 3,091 31 (81 ) 521 25,336 26 508 (29,973 ) (541 ) Balance on December 31, 2020 $ 101,991 $ 1,630 $ 70,889 $ 12,406 $ 710,776 $ 3,894 $ 10,300 $ 8,529 $ 920,415 Accumulated depreciation and impairment Balance on January 1, 2020 $ — $ (1,375 ) $ (27,977 ) $ (11,068 ) $ (590,338 ) $ (3,694 ) $ (7,662 ) $ (29 ) $ (642,143 ) Depreciation expenses — (43 ) (1,366 ) (770 ) (23,994 ) (68 ) (666 ) — (26,907 ) Disposal — 19 49 1,243 20,600 45 504 29 22,489 Effect of foreign exchange differences — — — — 41 — — — 41 Acquired by business combinations (Note 14) — — — (40 ) — — (54 ) — (94 ) Others — — 47 (4 ) 28 (1 ) (48 ) — 22 Balance on December 31, 2020 $ — $ (1,399 ) $ (29,247 ) $ (10,639 ) $ (593,663 ) $ (3,718 ) $ (7,926 ) $ — $ (646,592 ) Balance on December 31, 2020, net $ 101,991 $ 231 $ 41,642 $ 1,767 $ 117,113 $ 176 $ 2,374 $ 8,529 $ 273,823 CHPT evaluated that certain miscellaneous equipment, construction in progress and equipment to be accepted used for manufacturing specific PCB will not be used in the future and there was no active market for sale; therefore, CHPT determined that the recoverable amount of such assets was nil and recognized impairment losses of $89 million for the year ended December 31, 2019. CHSI evaluated that certain miscellaneous equipment will not be used in the future and there was no active market for sale; therefore, CHSI determined that the recoverable amount of such assets was nil and recognized impairment losses of $4 million for the year ended December 31, 2019. The aforementioned impairment losses were included in other income and expenses of statements of comprehensive income. There was no indication that property, plant and equipment was impaired; therefore, the Company did not recognize any impairment loss for the year ended December 31, 2020. Chunghwa signed a joint development agreement with the MOTC previously which stated that the MOTC would provide the national land and Chunghwa would be in charge of the planning and construction for the MOTC’s office building, Chunghwa’s Renai office building, etc. According to the agreement, the MOTC and Chunghwa would each own a certain percentage of the buildings, and Chunghwa is to pay or get the reimbursement for the difference between the assessed value of the land and the construction cost paid by Chunghwa on behalf of the MOTC. The difference amounting to $1,057 million due to the MOTC was reported to Chunghwa’s Board of Directors in May 2020 and Chunghwa will complete the property registration of the respective asset once the payment is made. The Company participated in the government-led urban renewal project in Xingzheng Section, Xindian District, New Taipei City. The Company provided land as a building lot while Kindom Development Corp., chosen through public selection by the New Taipei City Government, acted as the urban renewal developer. The property registration was completed in 2020. With respect to the Company’s trade-in share of land and buildings, only the trade-in buildings had commercial substance. Therefore, the gain on the asset exchange transaction of $1,268 million (included in” gains and losses on disposal of property, plant and equipment”) was recognized at the difference between the carrying amount of the trade-out land of $37 million and the fair value of trade-in buildings of $1,305 million (included in “investment properties”). The aforementioned gain on disposal was included under “other income and expenses” in the statements of comprehensive income. Depreciation expense for assets used by the Company in 2019 and 2020 is computed using the straight-line method over the following estimated service lives: Land improvements 10-30 years Buildings Main buildings 20-60 years Other building facilities 3-15 years Computer equipment 2-8 years Telecommunications equipment Telecommunication circuits 2-30 years Telecommunication machinery and antennas equipment 2-30 years Transportation equipment 3-10 years Miscellaneous equipment Leasehold improvements 1-9 years Mechanical and air conditioner equipment 3-16 years Others 1-15 years b. Assets subject to operating leases Land Land Improvements Buildings Total NT$ NT$ NT$ NT$ (In Millions) Cost Balance on January 1, 2019 $ — $ — $ — $ — Effect of retrospective application of IFRS 16 3,617 1 3,583 7,201 Balance on January 1, 2019 as adjusted 3,617 1 3,583 7,201 Additions — — 4 4 Transferred from (to) assets used by the Company 1,362 (1 ) 255 1,616 Balance on December 31, 2019 $ 4,979 $ — $ 3,842 $ 8,821 Accumulated depreciation and impairment Balance on January 1, 2019 $ — $ — $ — $ — Effect of retrospective application of IFRS 16 — (1 ) (1,265 ) (1,266 ) Balance on January 1, 2019 as adjusted — (1 ) (1,265 ) (1,266 ) Depreciation expenses — — (74 ) (74 ) Transferred to (from) assets used by the company — 1 (158 ) (157 ) Balance on December 31, 2019 $ — $ — $ (1,497 ) $ (1,497 ) Balance on January 1, 2019 as adjusted, net $ 3,617 $ — $ 2,318 $ 5,935 Balance on December 31, 2019, net $ 4,979 $ — $ 2,345 $ 7,324 Cost Balance on January 1, 2020 $ 4,979 $ — $ 3,842 $ 8,821 Others (6 ) — 394 388 Balance on December 31, 2020 $ 4,973 $ — $ 4,236 $ 9,209 Accumulated depreciation and impairment Balance on January 1, 2020 $ — $ — $ (1,497 ) $ (1,497 ) Depreciation expenses — — (82 ) (82 ) Others — — (37 ) (37 ) Balance on December 31, 2020 $ — $ — $ (1,616 ) $ (1,616 ) Balance on December 31, 2020, net $ 4,973 $ — $ 2,620 $ 7,593 The Company leases out land and buildings with lease terms between 1 to 20 years. The lessees do not have bargain purchase options to acquire the assets at the expiry of the lease periods. The future aggregate lease collection under operating lease for the freehold plant, property and equipment was as follows: December 31 2019 2020 NT$ NT$ (In Millions) Year 1 $ 302 $ 347 Year 2 273 288 Year 3 234 231 Year 4 191 164 Year 5 130 125 Onwards 1,224 1,180 $ 2,354 $ 2,335 The above items of property, plant and equipment subject to operating leases are depreciated on a straight-line basis over their estimated useful lives as follows: Land improvements 10-30 years Buildings Main buildings 35-60 years Other building facilities 3-15 years

Lease Arrangements

Lease Arrangements	12 Months Ended
Lease Arrangements	Dec. 31, 2020
Disclosure Of Quantitative Information About Leases For Lessee [Abstract]
Lease Arrangements	17. LEASE ARRANGEMENTS a. December 31 2019 2020 NT$ NT$ (In Millions) Land and buildings Handsets base stations $ 6,845 $ 7,096 Others 1,916 1,708 Equipment 2,603 2,205 $ 11,364 $ 11,009 Year Ended December 31 2019 2020 NT$ NT$ (In Millions) Additions to right-of-use assets $ 3,803 $ 3,796 Depreciation charge for right-of-use assets Land and buildings Handsets base stations $ 2,728 $ 2,729 Others 821 786 Equipment 419 416 $ 3,968 $ 3,931 The Company did not have significant sublease or impairment of right-of-use assets for the years ended December 31, 2019 and 2020. b. Lease liabilities December 31 2019 2020 NT$ NT$ (In Millions) Lease liabilities Current $ 3,291 $ 3,382 Noncurrent 6,467 6,215 $ 9,758 $ 9,597 Ranges of discount rates for lease liabilities were as follows: December 31 2019 2020 Land and buildings Handsets base stations 0.58%-1.18% 0.46%-1.18% Others 0.58%-9.00% 0.46%-9.00% Equipment 0.58%-4.50% 0.46%-2.99% c. The Company mainly enters into lease-in agreements of land and buildings for handsets base stations located all over Taiwan with lease terms from 1 to 20 years. The lease agreements do not contain bargain purchase options to acquire the assets at the expiration of the respective leases. For majority of the lease-in agreements on handsets base station, the Company has the right to terminate the agreement prior to the expiration date if the Company is unable to build the required telecommunication equipment, either due to legal restrictions, controversial events, or other events. The Company also leases land and buildings for the use of offices, server rooms, and stores with lease terms from 1 to 30 years. Most of the lease agreements for national land adjust the lease payment according to the changes of the announced land values by the authority. At the expiry of the lease term, the Company does not have bargain purchase options to acquire the assets. The lease agreements for equipment include a contract between Chunghwa and ST-2 Satellite Ventures Pte., Ltd. on March 12, 2010 to lease capacity on the ST-2 satellite. For the information of lease agreements with related parties, please refer to Note 40 to the consolidated financial statements for details. d. Year Ended December 31 2019 2020 NT$ NT$ (In Millions) Expenses relating to low-value asset leases $ 7 $ 8 Expenses relating to variable lease payments not included in the measurement of lease liabilities $ 6 $ 5 Total cash outflow for leases $ 3,826 $ 3,776 The Company leases certain equipment which qualify as low-value asset leases. The Company has elected to apply the recognition exemption and, thus, not to recognize right-of-use assets and lease liabilities for these leases. Lease-out arrangements under operating leases for freehold property, plant, and equipment and investment properties were set out in Notes 16 and 18 to the consolidated financial statements.

Investment Properties

Investment Properties	12 Months Ended
Investment Properties	Dec. 31, 2020
Disclosure Of Investment Property [Abstract]
Investment Properties	18. INVESTMENT PROPERTIES December 31 2019 2020 NT$ NT$ (In Millions) Carrying amount Investment properties $ 8,169 $ 9,621 Investment Properties NT$ (In Millions) Cost Balance on January 1, 2018 $ 9,135 Additions 6 Reclassification 251 Balance on December 31, 2018 $ 9,392 Accumulated depreciation and impairment Balance on January 1, 2018 $ (1,087 ) Depreciation expense (21 ) Reclassification (16 ) Reversal of impairment loss 19 Balance on December 31, 2018 $ (1,105 ) Cost Balance on January 1, 2019 $ 9,392 Additions 1 Disposal (6 ) Reclassification (173 ) Balance on December 31, 2019 $ 9,214 Accumulated depreciation and impairment Balance on January 1, 2019 $ (1,105 ) Depreciation expense (25 ) Disposal 6 Reclassification 22 Reversal of impairment loss 57 Balance on December 31, 2019 $ (1,045 ) Cost Balance on January 1, 2020 $ 9,214 Additions (Note 16) 1,359 Disposal (37 ) Reclassification 126 Balance on December 31, 2020 $ 10,662 Accumulated depreciation and impairment Balance on January 1, 2020 $ (1,045 ) Depreciation expense (22 ) Reclassification (1 ) Reversal of impairment loss 27 Balance on December 31, 2020 $ (1,041 ) After the evaluation of land and buildings, the Company concluded the recoverable amount which represented the fair value less costs to sell of some land and buildings was higher than the carrying amount. Therefore, the Company recognized reversal of impairment losses of $19 million, $57 million and $27 million for the years ended December 31, 2018, 2019 and 2020, respectively, and the amounts were recognized only to the extent of impairment losses that had been recognized in prior years. The reversal of impairment loss was included in other income and expenses in the statements of comprehensive income. Depreciation expense is computed using the straight-line method over the following estimated service lives: Land improvements 10-30 years Buildings Main buildings 35-60 years Other building facilities 4-10 years The fair values of the Company’s investment properties as of December 31, 2019 and 2020 were determined by Level 3 fair value measurements inputs based on the appraisal reports conducted by independent appraisers. Those appraisal reports are based on the comparison approach, income approach or cost approach. Key assumptions and the fair values were as follows: December 31 2019 2020 NT$ NT$ (In Millions) Fair value $ 18,701 $ 22,644 Overall capital interest rate 1.03%-4.04% 0.93%-3.03% Profit margin ratio 12%-20% 12%-20% Discount rate — — Capitalization rate 0.79%-1.74% 0.73%-2.20% All of the Company’s investment properties are held under freehold interest. The future aggregate lease collection under operating lease for investment properties is as follows: December 31 2019 2020 NT$ NT$ (In Millions) Year 1 $ 113 $ 115 Year 2 91 95 Year 3 71 75 Year 4 61 53 Year 5 39 38 Onwards 96 58 $ 471 $ 434

Intangible Assets

Intangible Assets	12 Months Ended
Intangible Assets	Dec. 31, 2020
Disclosure Of Intangible Assets [Abstract]
Intangible Assets	19. INTANGIBLE ASSETS December 31 2019 2020 NT$ NT$ (In Millions) Carrying amount Mobile Broadband Concession $ 45,672 $ 89,019 Computer software 931 788 Goodwill 200 246 Others 244 232 $ 47,047 $ 90,285 Mobile Broadband Concession Computer Software Goodwill Others Total NT$ NT$ NT$ NT$ NT$ (In Millions) Cost Balance on January 1, 2018 $ 70,144 $ 3,312 $ 236 $ 418 $ 74,110 Additions-acquired separately — 485 — 13 498 Disposal — (371 ) — (58 ) (429 ) Effect of foreign exchange difference — — — — — Balance on December 31, 2018 $ 70,144 $ 3,426 $ 236 $ 373 $ 74,179 Accumulated amortization and impairment Balance on January 1, 2018 $ (16,675 ) $ (2,432 ) $ (27 ) $ (93 ) $ (19,227 ) Amortization expenses (3,957 ) (406 ) — (23 ) (4,386 ) Disposal — 371 — 58 429 Impairment losses — — — (51 ) (51 ) Effect of foreign exchange difference — — — — — Balance on December 31, 2018 $ (20,632 ) $ (2,467 ) $ (27 ) $ (109 ) $ (23,235 ) Balance on December 31, 2018, net $ 49,512 $ 959 $ 209 $ 264 $ 50,944 Cost Balance on January 1, 2019 $ 70,144 $ 3,426 $ 236 $ 373 $ 74,179 Additions-acquired separately — 358 — 5 363 Disposal (10,179 ) (356 ) — — (10,535 ) Effect of foreign exchange difference — — — — — Others — 2 — — 2 Balance on December 31, 2019 $ 59,965 $ 3,430 $ 236 $ 378 $ 64,009 Accumulated amortization and impairment Balance on January 1, 2019 $ (20,632 ) $ (2,467 ) $ (27 ) $ (109 ) $ (23,235 ) Amortization expenses (3,840 ) (388 ) — (25 ) (4,253 ) Disposal 10,179 356 — — 10,535 Impairment losses — — (9 ) — (9 ) Effect of foreign exchange difference — — — — — Balance on December 31, 2019 $ (14,293 ) $ (2,499 ) $ (36 ) $ (134 ) $ (16,962 ) Balance on December 31, 2019, net $ 45,672 $ 931 $ 200 $ 244 $ 47,047 Cost Balance on January 1, 2020 $ 59,965 $ 3,430 $ 236 $ 378 $ 64,009 Additions-acquired separately 48,373 226 — 6 48,605 Disposal — (338 ) — (3 ) (341 ) Effect of foreign exchange difference — — — — — Acquired by business combinations (Note 14) — 1 55 11 67 Others — 1 — — 1 Balance on December 31, 2020 $ 108,338 $ 3,320 $ 291 $ 392 $ 112,341 Accumulated amortization and impairment Balance on January 1, 2020 $ (14,293 ) $ (2,499 ) $ (36 ) $ (134 ) $ (16,962 ) Amortization expenses (5,026 ) (371 ) — (27 ) (5,424 ) Disposal — 338 — 1 339 Impairment losses — — (9 ) — (9 ) Effect of foreign exchange difference — — — — — Acquired by business combinations (Note 14) — — — — — Balance on December 31, 2020 $ (19,319 ) $ (2,532 ) $ (45 ) $ (160 ) $ (22,056 ) Balance on December 31, 2020, net $ 89,019 $ 788 $ 246 $ 232 $ 90,285 For long-term business development, Chunghwa participated in the 5G mobile broadband license bidding hosted by the NCC and paid the deposit for 5G spectrum bidding amounting to $1,000 million (included in other assets) in October 2019. Chunghwa paid $48,373 million, including the aforementioned deposit, in February 2020 for the aforementioned license to obtain 90MHz in the 3.5GHz spectrum and 600MHz in the 28GHz spectrum. The concessions are granted and issued by the NCC. The concession fees are amortized using the straight-line method over the period from the date operations commence through the date the license expires or the useful life, whichever is shorter. The carrying amount of 3G concession fee was fully amortized in December 2018, 4G concession fees will be fully amortized by December 2030 and December 2033, and 5G concession fees will be fully amortized by December 2040. The computer software is amortized using the straight-line method over the estimated useful lives of 1 to 10 years. Other intangible assets are amortized using the straight-line method over the estimated useful lives of 1 to 20 years. Goodwill is not amortized. SENAO evaluated the goodwill that arose in the acquisition of Youth and its subsidiaries at the end of each year. SENAO determined the smallest identifiable group of assets that generates cash inflows as single cash generating units by business type and evaluated the recoverable amount of those cash generating units by their value in use. The management of SENAO estimated the cash flow projections based on the financial budgets for the following five years. Discount rates were 13.7%, 12.3% and 12.1% as of December 31 2018, 2019 and 2020, respectively and were used to calculate the recoverable amount of related cash generating units by discounting aforementioned cash flows. SENAO concluded the recoverable amount of the goodwill was lower than the carrying value and recognized impairment loss of $9 million and $9 million f SENAO evaluated and determined that the recoverable amount of certain licensed contract was nil and recognized the impairment loss of $51 million for the year ended December 31, 2018. The recoverable amount was based on the value in use. The aforementioned impairment losses were included under “other income and expenses” in the statements of comprehensive income.

Other Assets

Other Assets	12 Months Ended
Other Assets	Dec. 31, 2020
Miscellaneous Assets [Abstract]
Other Assets	20. OTHER ASSETS December 31 2019 2020 NT$ NT$ (In Millions) Spare parts $ 2,336 $ 2,156 Refundable deposits 1,879 2,009 Other financial assets 1,000 1,000 Deposit for mobile broadband license bidding (Note 19) 1,000 — Others 2,316 2,450 $ 8,531 $ 7,615 Current Spare parts $ 2,336 $ 2,156 Others 94 193 $ 2,430 $ 2,349 Noncurrent Refundable deposits $ 1,879 $ 2,009 Other financial assets 1,000 1,000 Deposit for mobile broadband license bidding 1,000 — Others 2,222 2,257 $ 6,101 $ 5,266 Other financial assets - noncurrent was Piping Fund. As part of the government’s effort to upgrade the existing telecommunications infrastructure, Chunghwa and other public utility companies were required by the ROC government to contribute to a Piping Fund administered by the Taipei City Government. This fund was used to finance various telecommunications infrastructure projects. Net assets of this fund will be returned proportionately after the project is completed. Chunghwa evaluated that certain other assets will not be used in the future and there was no active market for sale; therefore, the Company determined that the recoverable amount of such assets was nil and recognized impairment losses of $44 million for the year ended December 31, 2019. The aforementioned impairment loss was included in other income and expenses in the statements of comprehensive income.

Hedging Financial Instruments

Hedging Financial Instruments	12 Months Ended
Hedging Financial Instruments	Dec. 31, 2020
Disclosure Of Detailed Information About Hedging Instruments [Abstract]
Hedging Financial Instruments	21. HEDGING FINANCIAL INSTRUMENTS Chunghwa’s hedge strategy is to enter into forward exchange contracts - buy to avoid its foreign currency exposure to certain foreign currency denominated equipment payments in the following six months. In addition, Chunghwa’s management considers the market condition to determine the hedge ratio and enters into forward exchange contracts with the banks to avoid the foreign currency risk. Chunghwa signed equipment purchase contracts with suppliers and entered into forward exchange contracts to avoid foreign currency risk exposure to Euro-denominated purchase commitments. Those forward exchange contracts were designated as cash flow hedges. When forecast purchases actually take place, basis adjustments are made to the initial carrying amounts of hedged items. For the hedges of highly probable forecast sales and purchases, as the critical terms (i.e. the notional amount, life and underlying) of the forward foreign exchange contracts and their corresponding hedged items are the same, the Company performs a qualitative assessment of effectiveness and it is expected that the value of the forward contracts and the value of the corresponding hedged items will systematically change in opposite direction in response to movements in the underlying exchange rates. The main source of hedge ineffectiveness in these hedging relationships is the effect of credit risks of the Company and the counterparty on the fair value of the forward exchange contracts. Such credit risks do not impact the fair value of the hedged item attributable to changes in foreign exchange rates. No other sources of ineffectiveness emerged from these hedging relationships. The following tables summarized the information relating to the hedges for foreign currency risk. December 31, 2018 Notional Forward Line Item in Carrying Amount Change in Fair Values of Hedging Instruments Used for Calculating Hedge Hedging Instruments Currency Amount Maturity Rate Balance Sheet Asset Liability Ineffectiveness (In Millions) NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast purchases - forward exchange contracts NT$/EUR NT$ 172/ EUR 5 2019.03 $ 34.98 Hedging financial assets (liabilities) $ 1 $ — $ 2 Change in Value of Hedged Item Used for Accumulated Gain or Loss on Hedging Instruments in Other Equity Hedged Items Calculating Hedge Ineffectiveness Continuing Hedges Hedge Accounting No Longer Applied NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast equipment purchases $ (2 ) $ 1 $ — December 31, 2019 Notional Forward Line Item in Carrying Amount Change in Fair Values of Hedging Instruments Used for Calculating Hedge Hedging Instruments Currency Amount Maturity Rate Balance Sheet Asset Liability Ineffectiveness (In Millions) NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast purchases - forward exchange contracts NT$/EUR NT$ 84/EUR 2 2020.03 $ 33.66 Hedging financial assets (liabilities) $ — $ — $ (1 ) Change in Value of Hedged Item Used for Accumulated Gain or Loss on Hedging Instruments in Other Equity Hedged Items Calculating Hedge Ineffectiveness Continuing Hedges Hedge Accounting No Longer Applied NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast equipment purchases $ 1 $ — $ — December 31, 2020 Notional Forward Line Item in Carrying Amount Change in Fair Values of Hedging Instruments Used for Calculating Hedge Hedging Instruments Currency Amount Maturity Rate Balance Sheet Asset Liability Ineffectiveness (In Millions) NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast purchases - forward exchange contracts NT$/EUR NT$ 201/ EUR 6 2021.03 $ 34.45 Hedging financial assets (liabilities) $ 2 $ — $ 2 Change in Value of Hedged Item Used for Accumulated Gain or Loss on Hedging Instruments in Other Equity Hedged Items Calculating Hedge Ineffectiveness Continuing Hedges Hedge Accounting No Longer Applied NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast equipment purchases $ (2 ) $ 2 $ — 2018 Comprehensive Income Reclassification from Equity to Profit or Loss and the Adjusted Line Item Hedging Gain or Loss Amount of Hedge Ineffectiveness Line Item in Which Hedge Amount Reclassified to P/L and Due to Hedged Future Cash Flows No Hedge Recognized Recognized in Ineffectiveness the Adjusted Longer Expected Transaction in OCI Profit or Loss is Included Line Item to Occur NT$ NT$ NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast equipment purchases $ 2 $ — — $ (4 ) $ — Construction in progress and equipment to be accepted Other gains and losses 2019 Comprehensive Income Reclassification from Equity to Profit or Loss and the Adjusted Line Item Hedging Gain or Loss Amount of Hedge Ineffectiveness Line Item in Which Hedge Amount Reclassified to P/L and Due to Hedged Future Cash Flows No Hedge Recognized Recognized in Ineffectiveness the Adjusted Longer Expected Transaction in OCI Profit or Loss is Included Line Item to Occur NT$ NT$ NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast equipment purchases $ (1 ) $ — — $ (2 ) $ — Construction in progress and equipment to be accepted Other gains and losses 2020 Comprehensive Income Reclassification from Equity to Profit or Loss and the Adjusted Line Item Hedging Gain or Loss Amount of Hedge Ineffectiveness Line Item in Which Hedge Amount Reclassified to P/L and Due to Hedged Future Cash Flows No Hedge Recognized Recognized in Ineffectiveness the Adjusted Longer Expected Transaction in OCI Profit or Loss is Included Line Item to Occur NT$ NT$ NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast equipment purchases $ 2 $ — — $ 21 $ — Construction in progress and equipment to be accepted Other gains and losses

Short-Term Loans

Short-Term Loans	12 Months Ended
Short-Term Loans	Dec. 31, 2020
Short-term loans [Member]
Disclosure of detailed information about borrowings [Line Items]
Loans	22. SHORT-TERM LOANS December 31 2019 2020 NT$ NT$ (In Millions) Unsecured bank loans $ 90 $ 67 The annual interest rates of bank loans were as follows: December 31 2019 2020 Unsecured bank loans 1.20%-2.50% 1.12%-2.33%

Short-term Bills Payable

Short-term Bills Payable	12 Months Ended
Short-term Bills Payable	Dec. 31, 2020
Short Term Bills Payable [Abstract]
Short-term Bills Payable	2 3 . SHORT-TERM BILLS PAYABLE December 31 2019 2020 NT$ NT$ (In Millions) Commercial paper payable $ — $ 7,000 Less: Discounts on commercial paper payable — $ (1 ) $ — $ 6,999 The annual interest rates of commercial paper payable were as follows: December 31 2019 2020 Commercial paper payable — 0.34%-0.36%

Long-Term Loans

Long-Term Loans	12 Months Ended
Long-Term Loans	Dec. 31, 2020
Long-term loans [Member]
Disclosure of detailed information about borrowings [Line Items]
Loans	2 4 . LONG-TERM LOANS December 31 2019 2020 NT$ NT$ (In Millions) Secured bank loans (Note 41) $ 1,600 $ 1,600 Less: Current portion — (1,600 ) $ 1,600 $ — The annual interest rates of bank loans were as follows: December 31 2019 2020 Secured loans 0.92% 0.72% LED obtained a secured loan from Chang Hwa Bank in September 2010. Interest is paid monthly. $300 million and $1,350 million were originally due in December 2014 and September 2015, respectively. In October 2014, the bank borrowing mentioned above was extended to September 2018 for one time repayment. LED made an early repayment of $50 million in April 2015. LED entered into a contract with Chang Hwa Bank to renew the contract upon the maturity of the aforementioned contract in December 2017 and the due date of the renew contract is September 2021.

Bonds Payable

Bonds Payable	12 Months Ended
Bonds Payable	Dec. 31, 2020
Disclosure Of Bonds Payable [Abstract]
Bonds Payable	2 5 . BONDS PAYABLE December 31 2019 2020 NT$ NT$ (In Millions) Unsecured domestic bonds $ — $ 20,000 Less: Discounts on bonds payable — (20 ) $ — $ 19,980 The major terms of unsecured domestic bonds issued by Chunghwa were as follows: Issuance Tranche Issuance Period Total Amount Coupon Rate Repayment and Interest Payment 2020-1 A July 2020 to July 2025 $ 8,800 0.50% One-time repayment upon maturity; interest payable annually B July 2020 to July 2027 7,500 0.54% The same as above C July 2020 to July 2030 3,700 0.59% The same as above

Trade Notes and Accounts Payabl

Trade Notes and Accounts Payable	12 Months Ended
Trade Notes and Accounts Payable	Dec. 31, 2020
Trade And Other Current Payables [Abstract]
Trade Notes and Accounts Payable	2 6 . TRADE NOTES AND ACCOUNTS PAYABLE December 31 2019 2020 NT$ NT$ (In Millions) Trade notes and accounts payable $ 15,312 $ 15,591 Trade notes and accounts payable were attributable to operating activities and the trading conditions were agreed separately.

Other Payables

Other Payables	12 Months Ended
Other Payables	Dec. 31, 2020
Trade And Other Current Payables [Abstract]
Other Payables	2 7 . OTHER PAYABLES December 31 2019 2020 NT$ NT$ (In Millions) Accrued salary and compensation $ 9,482 $ 9,450 Payables to contractors 1,892 1,779 Accrued compensation to employees and remuneration to directors and supervisors 1,441 1,691 Amounts collected for others 1,279 1,308 Payable on land (Note 16) — 1,057 Payables to equipment suppliers 296 1,049 Accrued maintenance costs 955 1,040 Accrued franchise fees 1,091 785 Others 6,517 5,829 $ 22,953 $ 23,988

Provisions

Provisions	12 Months Ended
Provisions	Dec. 31, 2020
Provisions [Abstract]
Provisions	2 8 . PROVISIONS December 31 2019 2020 NT$ NT$ (In Millions) Warranties $ 173 $ 182 Onerous contracts 67 171 Employee benefits 59 57 Others 5 5 $ 304 $ 415 Current $ 207 $ 314 Noncurrent 97 101 $ 304 $ 415 Warranties Onerous Contracts Employee Benefits Others Total NT$ NT$ NT$ NT$ NT$ (In Millions) Balance on January 1, 2018 $ 132 $ — $ 43 $ 5 $ 180 Additional provisions recognized 164 19 9 — 192 Used / forfeited during the year (164 ) — (1 ) — (165 ) Balance on December 31, 2018 $ 132 $ 19 $ 51 $ 5 $ 207 Balance on January 1, 2019 $ 132 $ 19 $ 51 $ 5 $ 207 Additional provisions recognized 127 48 9 — 184 Used / forfeited during the year (86 ) — (1 ) — (87 ) Balance on December 31, 2019 $ 173 $ 67 $ 59 $ 5 $ 304 Balance on January 1, 2020 $ 173 $ 67 $ 59 $ 5 $ 304 Additional/(reversal of) provisions recognized 131 92 (2 ) — 221 Used / forfeited during the year (122 ) (3 ) — — (125 ) Acquired by business combinations (Note 14) — 15 — — 15 Balance on December 31, 2020 $ 182 $ 171 $ 57 $ 5 $ 415 a. The provision for warranty claims represents the present value of the management’s best estimate of the future outflow of economic benefits that will be required under the Company’s obligation for warranties in sales agreements. The estimate has been made based on the historical warranty experience. b. The provision for employee benefits represents vested long-term service compensation accrued. c . The provision for onerous contracts represents the present obligation resulting from the measurement for the unavoidable costs of meeting the Company’s contractual obligations exceed the economic benefits expected to be received from the contracts.

Retirement Benefit Plans

Retirement Benefit Plans	12 Months Ended
Retirement Benefit Plans	Dec. 31, 2020
Disclosure Of Retirement Benefit Plans [Abstract]
Retirement Benefit Plans	2 9 . a. Defined contribution plans The pension plan under the Labor Pension Act of ROC (the “LPA”) is considered as a defined contribution plan. Based on the LPA, Chunghwa and its domestic subsidiaries make monthly contributions to employees’ individual pension accounts at 6% of monthly salaries and wages. Its foreign subsidiaries would make monthly contributions based on the local pension requirements. b. Defined benefit plans Chunghwa completed its privatization plans on August 12, 2005. Chunghwa is required to pay all accrued pension obligations including service clearance payment, lump sum payment under civil service plan, additional separation payments, etc. upon the completion of the privatization in accordance with the Statute Governing Privatization of Stated-owned Enterprises. After paying all pension obligations for privatization, the plan assets of Chunghwa should be transferred to the Fund for Privatization of Government-owned Enterprises (the “Privatization Fund”) under the Executive Yuan. On August 7, 2006, Chunghwa transferred the remaining balance of fund to the Privatization Fund. However, according to the instructions of MOTC, Chunghwa was requested to administer the distributions to employees for pension obligations including service clearance payment, lump sum payment under civil service plan, additional separation payments, etc. upon the completion of the privatization and recognized in other current monetary assets. Chunghwa and its subsidiaries SENAO, CHIEF, CHSI, SHE, IISI and UTC with the pension mechanism under the Labor Standards Law in the ROC are considered as defined benefit plans. These pension plans provide benefits based on an employee’s length of service and average six-month salary prior to retirement. Chunghwa and its subsidiaries contribute an amount no more than 15% of salaries paid each month to their respective pension funds (the Funds), which are administered by the Labor Pension Fund Supervisory Committee (the Committee) and deposited in the names of the Committees in the Bank of Taiwan. The plan assets are held in a commingled fund which is operated and managed by the government’s designated authorities; as such, the Company does not have any right to intervene in the investments of the funds. According to the Article 56 in the ROC of the Labor Standards Law, entities are required to contribute the difference in one appropriation to their pension funds before the end of next March when the balance of the Funds is insufficient to pay the eligible employees who meet the retirement criteria in the following year. The amounts included in the consolidated balance sheets arising from the Company’s obligation in respect of its defined benefit plans were as follows: December 31 2019 2020 NT$ NT$ (In Millions) Present value of funded defined benefit obligations $ 41,197 $ 39,536 Fair value of plan assets (39,820 ) (39,494 ) Funded status - deficit $ 1,377 $ 42 Net defined benefit liabilities $ 3,505 $ 3,415 Net defined benefit assets (2,128 ) (3,373 ) $ 1,377 $ 42 Movements in the defined benefit obligations and the fair value of plan assets were as follows: Present Value of Funded Defined Benefit Obligations Fair Value of Plan Assets Net Defined Benefit Liabilities (Assets) NT$ NT$ NT$ (In Millions) Balance on January 1, 2018 $ 37,663 $ 34,972 $ 2,691 Current service cost 3,024 — 3,024 Interest expense/interest income 550 544 6 Amounts recognized in profit or loss 3,574 544 3,030 Remeasurement on the net defined benefit liability Return on plan assets (excluding amounts included in net interest) — 875 (875 ) Actuarial losses recognized from changes in demographic assumptions 4 — 4 Actuarial losses recognized from changes in financial assumptions 1,273 — 1,273 Actuarial losses recognized from experience adjustments 813 — 813 Amounts recognized in other comprehensive income 2,090 875 1,215 Contributions from employer — 4,374 (4,374 ) Benefits paid (1,738 ) (1,738 ) — Benefits paid directly by the Company (192 ) — (192 ) Balance on December 31, 2018 41,397 39,027 2,370 Current service cost 2,927 — 2,927 Interest expense/interest income 400 390 10 Amounts recognized in profit or loss 3,327 390 2,937 Remeasurement on the net defined benefit liability Return on plan assets (excluding amounts included in net interest) — 1,338 (1,338 ) Actuarial losses recognized from changes in demographic assumptions 6 — 6 Actuarial losses recognized from changes in financial assumptions 647 — 647 Actuarial gains recognized from experience adjustments (842 ) — (842 ) Amounts recognized in other comprehensive income (189 ) 1,338 (1,527 ) Contributions from employer — 2,099 (2,099 ) Benefits paid (3,034 ) (3,034 ) — Benefits paid directly by the Company (304 ) — (304 ) Balance on December 31, 2019 41,197 39,820 1,377 Current service cost 2,052 — 2,052 Interest expense/interest income 298 297 1 Amounts recognized in profit or loss 2,350 297 2,053 Remeasurement on the net defined benefit liability Return on plan assets (excluding amounts included in net interest) — 1,308 (1,308 ) Actuarial losses recognized from changes in financial assumptions 590 — 590 Actuarial gains recognized from experience adjustments (475 ) — (475 ) Amounts recognized in other comprehensive income 115 1,308 (1,193 ) Contributions from employer — 1,964 (1,964 ) Benefits paid (3,919 ) (3,919 ) — Benefits paid directly by the Company (263 ) — (263 ) Acquired by business combinations (Note 14) 56 24 32 Balance on December 31, 2020 $ 39,536 $ 39,494 $ 42 Relevant pension costs recognized in profit and loss for defined benefit plans were as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Operating costs $ 1,796 $ 1,726 $ 1,205 Marketing expenses 886 866 603 General and administrative expenses 164 164 121 Research and development expenses 107 103 72 $ 2,953 $ 2,859 $ 2,001 The Company is exposed to following risks for the defined benefits plans under the Labor Standards Law: a. Investment risk Under the Labor Standards Law, the rate of return on assets shall not be lower than the average interest rate on a two-year time deposit published by the local banks and the government is responsible for any shortfall in the event that the rate of return is less than the required rate of return. The plan assets are held in a commingled fund mainly invested in foreign and domestic equity and debt securities and bank deposits which is operated and managed by the government’s designated authorities; as such, the Company does not have any right to intervene in the investments of the funds. b. Interest rate risk The decline in government bond interest rate will increase the present value of the obligation on the defined benefit plan, while the return on plan assets will increase. The net effect on the present value of the obligation on defined benefit plan is partially offset by the return on plan assets. c. Salary risk The calculation of the present value of defined benefit obligations is referred to the plan participants’ future salary. Hence, the increase in plan participants’ salary will increase the present value of the defined benefit obligations. The most recent actuarial valuation of plan assets and the present value of the defined benefit obligations were carried out by the independent actuary. The principal assumptions used for the purpose of the actuarial valuations were as follows: Measurement Date December 31 2019 2020 Discount rates 0.75% 0.50% Expected rates of salary increase 1.20%-2.00% 1.00%-2.00% If reasonably possible changes of the respective significant actuarial assumptions occur at the end of reporting periods, while holding all other assumptions constant, the present values of the defined benefit obligations would increase (decrease) as follows: December 31 2019 2020 NT$ NT$ (In Millions) Discount rates 0.5% increase $ (1,275 ) $ (1,208 ) 0.5% decrease $ 1,356 $ 1,284 Expected rates of salary increase 0.5% increase $ 1,448 $ 1,372 0.5% decrease $ (1,374 ) $ (1,303 ) The sensitivity analysis presented above may not be representative of the actual change in the present value of the defined benefit obligations as it is unlikely that the change in assumptions would occur in isolation of one another as some of the assumptions may be correlated. Furthermore, in presenting the above sensitivity analysis, the present value of the defined benefit obligations has been calculated using the projected unit credit method at the end of the reporting period, which is the same as that applied in calculating the defined benefit obligation liability recognized in the consolidated balance sheets. There is no change in the methods and assumptions used in preparing the sensitivity analysis from the previous period. December 31 2019 2020 NT$ NT$ (In Millions) The expected contributions to the plan for the next year $ 2,076 $ 1,932 The average duration of the defined benefit obligations 6.5-14 years 6.4-13 years As of December 31, 2020, the Company’s maturity analysis of the undiscounted benefit payments was as follows: Year Amount NT$ (In Millions) 2021 $ 3,285 2022 7,056 2023 10,669 2024 11,799 2025 and thereafter 39,497 $ 72,306

Equity

Equity	12 Months Ended
Equity	Dec. 31, 2020
Disclosure Of Classes Of Share Capital [Abstract]
Equity	30 . EQUITY a. Share capital 1) Common stocks December 31 2019 2020 NT$ NT$ (In Millions) Number of authorized shares 12,000 12,000 Authorized shares $ 120,000 $ 120,000 Number of issued and paid shares 7,757 7,757 Issued and outstanding shares $ 77,574 $ 77,574 Each issued common stock with par value of $10 entitled the right to vote and receive dividends. 2) Global depositary receipts The MOTC and some stockholders sold some common stocks of Chunghwa in an international offering of securities in the form of American Depositary Shares (“ADS”) (one ADS represents 10 common stocks) in July 2003, August 2005, and September 2006. The ADSs were traded on the New York Stock Exchange since July 17, 2003. As of December 31, 2020, the outstanding ADSs were 220 million common stocks, which equaled 22 million units and represented 2.84% of Chunghwa’s total outstanding common stocks. The ADS holders generally have the same rights and obligations as other common stockholders, subject to the provision of relevant laws. The exercise of such rights and obligations shall comply with the related regulations and deposit agreement, which stipulate, among other things, that ADS holders are entitled to, through deposit agents: a) Exercise their voting rights, b) Sell their ADSs, and c) Receive dividends declared and subscribe to the issuance of new shares. b. Additional paid-in capital The adjustments of additional paid-in capital for the years ended December 31, 2018, 2019 and 2020 were as follows: Share Premium Movements of Additional Paid-in Capital for Associates and Joint Ventures Accounted for Using Equity Method Movements of Additional Paid-in Capital Arising from Changes in Equities of Subsidiaries Difference between Consideration Received and Carrying Amount of the Subsidiaries’ Net Assets upon Disposal Donated Capital Stockholders’ Contribution Due to Privatization Total NT$ NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Balance on January 1, 2018 $ 126,045 $ — $ 1,221 $ 161 $ 16 $ 20,648 $ 148,091 Unclaimed dividend — — — — 2 — 2 Partial disposal of interests in subsidiaries — — — 826 — — 826 Change in additional paid-in capital for not participating in the capital increase of a subsidiary — — 777 — — — 777 Share-based payment transactions of subsidiaries — — 11 — — — 11 Treasury stock transfer of subsidiaries — — 55 — — — 55 Balance on December 31, 2018 $ 126,045 $ — $ 2,064 $ 987 $ 18 $ 20,648 $ 149,762 Balance on January 1, 2019 $ 126,045 $ — $ 2,064 $ 987 $ 18 $ 20,648 $ 149,762 Unclaimed dividend — — — — 1 — 1 Share-based payment transactions of subsidiaries — — (1 ) — — — (1 ) Balance on December 31, 2019 $ 126,045 $ — $ 2,063 $ 987 $ 19 $ 20,648 $ 149,762 Balance on January 1, 2020 $ 126,045 $ — $ 2,063 $ 987 $ 19 $ 20,648 $ 149,762 Unclaimed dividend — — — — 2 — 2 Change in additional paid-in capital for not participating in the capital increase of a subsidiary — — — — — — — Share-based payment transactions of subsidiaries — — 26 — — — 26 Balance on December 31, 2020 $ 126,045 $ — $ 2,089 $ 987 $ 21 $ 20,648 $ 149,790 Additional paid-in capital from share premium, donated capital and the difference between consideration received and the carrying amount of the subsidiaries’ net assets upon disposal may be utilized to offset deficits. Furthermore, when Chunghwa has no deficit, it may be distributed in cash or capitalized, which however is limited to a certain percentage of Chunghwa’s paid-in capital except the additional paid-in capital arising from unclaimed dividend can only be utilized to offset deficits. The additional paid-in capital from movements of paid-in capital arising from changes in equities of subsidiaries may only be utilized to offset deficits. Among additional paid-in capital from movements of investments in associates and joint ventures accounted for using equity method, the portion arising from the difference between consideration received and the carrying amount of the subsidiaries’ net assets upon disposal may be utilized to offset deficits; furthermore, when the Company has no deficit, it may be distributed in cash or capitalized. However, other additional paid-in capital recognized in proportion of share ownership may only be utilized to offset deficits. c. Retained earnings and dividends policy In accordance with the Chunghwa’s Articles of Incorporation, Chunghwa must pay all outstanding taxes, offset deficits in prior years and set aside a legal reserve equal to 10% of its net income before distributing a dividend or making any other distribution to stockholders, except when the accumulated amount of such legal reserve equals to Chunghwa’s total issued capital, and depending on its business needs or requirements, may also set aside or reverse special reserves. No less than 50% of the remaining earnings comprising remaining balance of net income, if any, plus cumulative undistributed earnings shall be distributed as stockholders’ dividends, of which cash dividends to be distributed shall not be less than 50% of the total amount of dividends to be distributed. If cash dividend to be distributed is less than $0.10 per share, such cash dividend shall be distributed in the form of common stocks. Special reserve was appropriated in accordance with the relevant laws and regulations or as requested by local authority. Pursuant to existing regulations, Chunghwa is required to set aside additional special reserve equivalent to debit balances under stockholder’s equity. For subsequent decrease in the deduction amount to stockholder’s equity, the decreased amount could be reversed from the special reserve to retained earnings. The appropriation for legal reserve shall be made until the accumulated reserve equals the aggregate par value of the outstanding capital stock of Chunghwa. This reserve can only be used to offset a deficit, or when the legal reserve has exceeded 25% of Chunghwa’s paid-in capital, the excess may be transferred to capital or distributed in cash. The appropriations of the 2018 and 2019 earnings of Chunghwa approved by the stockholders in their meetings on June 21, 2019 and May 29, 2020 were as follows: Appropriation of Earnings Dividends Per Share (NT$) For Fiscal Year 2018 For Fiscal Year 2019 For Fiscal Year 2018 For Fiscal Year 2019 Cash dividends $ 34,746 $ 32,783 $ 4.479 $ 4.226 The appropriations of earnings for 2020 had been proposed by Chunghwa’s Board of Directors on February 23, 2021. The appropriations and dividends per share were as follows: Appropriation of Earnings Dividends Per Share (NT$) Cash dividends $ 33,404 $ 4.306 The appropriations of earnings for 2020 are subject to the resolution of the stockholders’ meeting planned to be held on May 28, 2021. Information of the appropriation of Chunghwa’s earnings proposed by the Board of Directors and approved by the stockholders is available on the Market Observation Post System website. d. Others 1) Exchange differences arising from the translation of the foreign operations The exchange differences arising from the translation of the foreign operations from their functional currency to New Taiwan dollars were recognized as exchange differences arising from the translation of the foreign operations in other comprehensive income. 2 ) Unrealized gain or loss on financial assets at FVOCI Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Beginning balance $ 883 $ 538 $ 735 Unrealized gain or loss for the year Equity instruments (345 ) 197 522 Transferred accumulated gain or loss to unappropriated earnings resulting from the disposal of equity instruments (Note 9) — — (17 ) Ending balance $ 538 $ 735 $ 1,240 e. Noncontrolling interests Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Beginning balance $ 8,470 $ 9,857 $ 10,115 Effect of retrospective application of IFRS 16 — (20 ) — Beginning balance as adjusted 8,470 9,837 10,115 Attributable to noncontrolling interests Net income for the year 1,024 974 1,285 Exchange differences arising from the translation of the net investment in foreign operations (3 ) 8 (14 ) Unrealized gain or loss on financial assets at FVOCI (1 ) (26 ) (3 ) Remeasurements of defined benefit pension plans (9 ) 15 17 Income tax relating to remeasurements of defined benefit pension plans 3 (3 ) (3 ) Share of other comprehensive income (loss) of associates and joint ventures accounted for using equity method 1 (1 ) (1 ) Cash dividends distributed by subsidiaries (958 ) (710 ) (775 ) Partial disposal of interests in subsidiaries 349 — — Share-based payment transactions of subsidiaries 42 22 63 Change in additional paid-in capital for not proportionately participating in the capital increase of subsidiaries 700 — — Change in additional paid-in capital from investments in associates and joint ventures accounted for using equity method — — (2 ) Other changes in additional paid-in capital of subsidiaries — — — Net increase (decrease) in noncontrolling interests 239 (1 ) 476 Ending balance $ 9,857 $ 10,115 $ 11,158

Revenue

Revenue	12 Months Ended
Revenue	Dec. 31, 2020
Revenue [Abstract]
Revenue	31 . REVENUE Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Revenue from contracts with customers $ 214,461 $ 206,360 $ 206,396 Other revenues Rental income 640 818 843 Others 382 342 370 1,022 1,160 1,213 Total $ 215,483 $ 207,520 $ 207,609 For the information of performance obligations related to customer contracts, please refer to Note 3 Summary of Significant Accounting Policies for details. a. Disaggregation of revenue 2018 Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Main Products and Service Revenues Mobile services revenue $ — $ 63,906 $ — $ — $ — $ 63,906 Sales of products 1,731 35,702 4 251 3,601 41,289 Local telephone and domestic long distance telephone services revenue 29,996 — — — — 29,996 Broadband access and domestic leased line services revenue 22,453 — — — — 22,453 Data Communications internet services revenue — — 21,137 — — 21,137 International network and leased line services revenue — — — 8,724 — 8,724 Others 11,923 1,269 8,509 4,449 806 26,956 $ 66,103 $ 100,877 $ 29,650 $ 13,424 $ 4,407 $ 214,461 2019 Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Main Products and Service Revenues Mobile services revenue $ — $ 58,703 $ — $ — $ — $ 58,703 Sales of products 1,957 35,545 41 265 3,785 41,593 Local telephone and domestic long distance telephone services revenue 27,929 — — — — 27,929 Broadband access and domestic leased line services revenue 22,116 — — — — 22,116 Data Communications internet services revenue — — 21,003 — — 21,003 International network and leased line services revenue — — — 7,066 — 7,066 Others 13,064 1,142 8,790 4,144 810 27,950 $ 65,066 $ 95,390 $ 29,834 $ 11,475 $ 4,595 $ 206,360 2020 Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Main Products and Service Revenues Mobile services revenue $ — $ 56,724 $ — $ — $ — $ 56,724 Sales of products 2,214 32,112 107 313 4,645 39,391 Local telephone and domestic long distance telephone services revenue 26,475 — — — — 26,475 Broadband access and domestic leased line services revenue 22,420 — — — — 22,420 Data Communications internet services revenue — — 21,447 — — 21,447 International network and leased line services revenue — — — 3,884 — 3,884 Others 17,695 1,307 10,255 4,485 2,313 36,055 $ 68,804 $ 90,143 $ 31,809 $ 8,682 $ 6,958 $ 206,396 b. Contract balances January 1 December 31 2019 2019 2020 NT$ NT$ NT$ (In Millions) Trade notes and accounts receivable (Note 10) $ 30,076 $ 26,408 $ 22,622 Contract assets Products and service bundling $ 7,123 $ 6,943 $ 7,232 Others 109 116 612 Less : Loss allowance (19 ) (17 ) (18 ) $ 7,213 $ 7,042 $ 7,826 Current $ 4,869 $ 4,441 $ 5,331 Noncurrent 2,344 2,601 2,495 $ 7,213 $ 7,042 $ 7,826 Contract liabilities Telecommunications business $ 8,193 $ 12,772 $ 13,602 Project business 4,508 10,360 6,687 Products and service bundling 106 39 16 Others 476 510 421 $ 13,283 $ 23,681 $ 20,726 Current $ 10,688 $ 16,840 $ 13,437 Noncurrent 2,595 6,841 7,289 $ 13,283 $ 23,681 $ 20,726 The changes in the contract asset and the contract liability balances primarily result from the timing difference between the satisfaction of performance obligations and the payments collected from customers. Significant changes of contract assets and liabilities recognized resulting from product and service bundling were as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Contract assets Net increase of customer contracts $ 4,126 $ 6,066 $ 5,972 Reclassified to trade receivables (7,532 ) (6,405 ) (5,681 ) $ (3,406 ) $ (339 ) $ 291 Contract liabilities Net increase of customer contracts $ 16 $ 22 $ 7 Recognized as revenues (194 ) (89 ) (30 ) $ (178 ) $ (67 ) $ (23 ) The Company applies the simplified approach to recognize expected credit losses prescribed by IFRS 9, which permits the use of lifetime expected loss provision for receivables. Contract assets will be reclassified to trade receivables when the corresponding invoice is billed to the client. Contract assets have substantially the same risk characteristics as the trade receivables of the same types of contracts. Therefore, the Company concluded that the expected loss rates for trade receivables can be applied to the contract assets. Revenue recognized for the period that was included in the contract liability at the beginning of the year was as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Telecommunications business $ 7,157 $ 6,186 $ 5,492 Project business 627 3,973 6,092 Others 324 404 512 $ 8,108 $ 10,563 $ 12,096 c. Incremental costs of obtaining contracts December 31 2019 2020 NT$ NT$ (In Millions) Noncurrent Incremental costs of obtaining contracts $ 943 $ 1,000 The Company considered the past experience and the default clauses in the telecommunications service contracts and believes the commissions and equipment subsidies paid for obtaining such contracts are expected to be recoverable; therefore, such costs were capitalized. Amortization expenses for the years ended December 31 2018, 2019 and 2020 were $1,941 million, $1,173 million and $772 million, respectively. d. Remaining Performance Obligations As of December 31, 2020, the aggregate amount of transaction price allocated to performance obligations for non-cancellable telecommunications service contracts that are unsatisfied is $29,501 million. The Company recognizes revenue when service is provided over contract terms. The Company expects to recognize such revenue of $18,729 million, $9,082 million and $1,690 million in 2021, 2022 and 2023, respectively. The variable consideration collected from customers on nonrecurring basis resulting from exceeded usage from monthly fee and revenue recognized for contracts that the Company has a right to consideration from customers in the amount corresponding directly with the value to the customers of the Company’s performance completed to date have been excluded from the disclosure of remaining performance obligations. As of December 31, 2020, the aggregate amount of transaction price allocated to performance obligations for non-cancellable project business contracts that are unsatisfied is $18,555 million. The Company recognizes revenues when the project business contract is completed and accepted by customers. The Company expects to recognize such revenue of $7,977 million, $5,897 million and $4,681 million in 2021, 2022 and 2023, respectively. Project business contracts whose expected duration are less than a year have been excluded from the aforementioned disclosure.

Net Income

Net Income	12 Months Ended
Net Income	Dec. 31, 2020
Analysis Of Income And Expense [Abstract]
Net Income and Other Comprehensive Income (Loss)	3 2 . NET INCOME a. Other income and expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Gain (loss) on disposal of property, plant and equipment $ 142 $ (38 ) $ 1,428 Impairment loss on property, plant and equipment — (93 ) — Gain on disposal of investment properties — — 151 Reversal of impairment loss on investment properties 19 57 27 Loss on disposal of intangible assets — — (2 ) Impairment loss on intangible assets (51 ) (9 ) (9 ) Impairment loss on other assets — (44 ) — $ 110 $ (127 ) $ 1,595 b. Other income Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Dividend income $ 396 $ 296 $ 246 Rental income 70 85 70 Others 234 150 154 $ 700 $ 531 $ 470 c. Other gains and losses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Foreign currency exchange gain or loss, net $ 37 $ 16 $ (47 ) Gain or loss on disposal of investments accounted for using equity method — 151 10 Gain (loss) on disposal of financial instruments 6 4 (2 ) Valuation gain or loss on financial assets and liabilities at fair value through profit or loss, net (21 ) (38 ) (99 ) Others (68 ) (49 ) (21 ) $ (46 ) $ 84 $ (159 ) d. Interest expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Interest paid to financial institutions $ 16 $ 17 $ 79 Interest on lease liabilities — 85 80 Interest on bonds payable — — 46 Others 2 2 1 $ 18 $ 104 $ 206 e . Impairment loss (reversal of impairment loss) Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Contract assets $ 19 $ (2 ) $ 1 Trade notes and accounts receivable $ 805 $ (54 ) $ 49 Other receivables $ 96 $ (69 ) $ (5 ) Inventories $ 365 $ 475 $ 1,161 Property, plant and equipment $ — $ 93 $ — Investment properties $ (19 ) $ (57 ) $ (27 ) Intangible assets $ 51 $ 9 $ 9 Other assets $ — $ 44 $ — f . Depreciation and amortization expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Property, plant and equipment $ 27,461 $ 26,930 $ 26,989 Right-of-use assets — 3,968 3,931 Investment properties 21 25 22 Intangible assets 4,386 4,253 5,424 Incremental costs of obtaining contracts 1,941 1,173 772 Total depreciation and amortization expenses $ 33,809 $ 36,349 $ 37,138 Depreciation expenses summarized by functions Operating costs $ 25,996 $ 28,957 $ 29,056 Operating expenses 1,486 1,966 1,886 $ 27,482 $ 30,923 $ 30,942 Amortization expenses summarized by functions Operating costs $ 6,085 $ 5,196 $ 5,971 Marketing expenses 113 96 100 General and administrative expenses 93 95 82 Research and development expenses 36 39 43 $ 6,327 $ 5,426 $ 6,196 g . Employee benefit expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Post-employment benefit Defined contribution plans $ 640 $ 654 $ 708 Defined benefit plans 2,953 2,859 2,001 3,593 3,513 2,709 Share-based payment Equity-settled share-based payment 17 2 8 Other employee benefit Salaries 26,204 25,464 26,630 Insurance 2,740 2,746 2,712 Others 14,470 14,430 12,904 43,414 42,640 42,246 Total employee benefit expenses $ 47,024 $ 46,155 $ 44,963 Summary by functions Operating costs $ 24,367 $ 23,587 $ 23,005 Operating expenses 22,657 22,568 21,958 $ 47,024 $ 46,155 $ 44,963 Chunghwa distributes employees’ compensation at the rates from 1.7% to 4.3% and remuneration to directors not higher than 0.17%, respectively, of pre-tax income. As of December 31, 2020, the payables of the employees’ compensation and the remuneration to directors were $1,202 million and $36 million, respectively. Such amounts have been approved by the Chunghwa’s Board of Directors on February 23, 2021 and will be reported to the stockholders in their meeting planned to be held on May 28, 2021. If there is a change in the proposed amounts after the annual consolidated financial statements are authorized for issue, the difference is recorded as a change in accounting estimate. The compensation to the employees and remuneration to the directors of 2018 and 2019 approved by the Board of Directors on March 19, 2019 and February 26, 2020, respectively, were as follows: 2018 2019 Cash Cash NT$ NT$ (In Millions) Compensation distributed to the employees $ 1,404 $ 1,126 Remuneration paid to the directors 38 35 There was no difference between the initial accrual amounts and the amounts proposed in the Board of Directors in 2019 and 2020 of the aforementioned compensation to employees and the remuneration to directors.

Income Tax

Income Tax	12 Months Ended
Income Tax	Dec. 31, 2020
Major Components Of Tax Expense Income [Abstract]
Income Tax	3 3 . INCOME TAX a. Income tax recognized in profit or loss The major components of income tax expense were as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Current tax Current tax expenses recognized for the year $ 8,271 $ 8,109 $ 8,172 Income tax on unappropriated earnings (2,070 ) (20 ) 8 Income tax adjustments on prior years 7 (91 ) (22 ) Others 8 12 19 6,216 8,010 8,177 Deferred tax Deferred tax expense (benefits) recognized for the year 208 (63 ) (81 ) Income tax adjustments on prior years 19 (1 ) 26 Change in tax rate (38 ) — — 189 (64 ) (55 ) Income tax expense recognized in profit or loss $ 6,405 $ 7,946 $ 8,122 Reconciliation of accounting profit and income tax expense was as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Income before income tax $ 44,986 $ 41,867 $ 42,826 Income tax expense calculated at the statutory rate $ 8,997 $ 8,373 $ 8,565 Nondeductible income and expenses in determining taxable income 227 18 15 Unrecognized deductible temporary differences 1 3 (5 ) Unrecognized loss carryforwards 21 7 4 Tax-exempt income (580 ) (148 ) (367 ) Additional income tax under Alternative Minimum Tax Act 46 — — Income tax on unappropriated earnings (2,070 ) (20 ) 8 Investment credits (204 ) (203 ) (131 ) Change in tax rate (38 ) — — Effect of different tax rates of group entities operating in other jurisdictions (15 ) (9 ) 10 Income tax adjustments on prior years 26 (92 ) 4 Others (6 ) 17 19 Income tax expense recognized in profit or loss $ 6,405 $ 7,946 $ 8,122 Income Tax Act in the ROC was amended in February 2018 and the corporate income tax rate is adjusted from 17% to 20%. Such amendment is effective from 2018. In addition, the rate of the corporate surtax applicable to 2018 unappropriated earnings is reduced from 10% to 5%. The applicable tax rate used by subsidiaries in China is 25%, and tax rates used by other entities in the Company operating in other jurisdictions are based on the tax laws in those jurisdictions. In July 2019, the President of the ROC announced the amendments to the Statute of Industrial Innovation, which stipulate that the unappropriated earnings in 2018 and thereafter that are used to build or acquire certain assets or technologies are allowed as deduction when computing the income tax on unappropriated earnings. The Company has deducted the reinvested capital expenditure while calculating income tax on unappropriated earnings. b. Income tax recognized in other comprehensive income Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Deferred tax Remeasurement on defined benefit pension plans $ (243 ) $ 305 $ 239 Change in tax rate - defined benefit pension plans (207 ) — — Total income tax expense (benefit) recognized in other comprehensive income $ (450 ) $ 305 $ 239 c. Current tax assets and liabilities December 31 2019 2020 NT$ NT$ (In Millions) Current tax assets Tax refund receivable (included in other current assets - others) $ 1 $ 1 Current tax liabilities Income tax payable $ 5,812 $ 6,157 d. Deferred income tax assets and liabilities The movements of deferred income tax assets and liabilities were as follows: For the year ended December 31, 2018 January 1, 2018 Effect of Retrospective Application of IFRS 9 Recognized in Profit or Loss Recognized in Other Comprehensive Income December 31, 2018 NT$ NT$ NT$ NT$ NT$ (In Millions) Deferred income tax assets Temporary differences Defined benefit pension plans $ 1,723 $ — $ 134 $ 450 $ 2,307 Allowance for doubtful receivables over quota 289 — 146 — 435 Share of profits of associates and joint ventures accounted for using equity method 331 — 58 — 389 Valuation loss on inventory 23 — 65 — 88 Deferred revenue 106 — 5 — 111 Estimated warranty liabilities 22 — 4 — 26 Accrued award credits liabilities 15 — (1 ) — 14 Others 175 — (32 ) — 143 2,684 — 379 450 3,513 Loss carryforwards 46 — (5 ) — 41 $ 2,730 $ — $ 374 $ 450 $ 3,554 January 1, 2018 Effect of Retrospective Application of IFRS 9 Recognized in Profit or Loss Recognized in Other Comprehensive Income December 31, 2018 NT$ NT$ NT$ NT$ (In Millions) Deferred income tax liabilities Temporary differences Defined benefit pension plans $ (1,265 ) $ — $ (567 ) $ — $ (1,832 ) Land value incremental tax (95 ) — — — (95 ) Intangible assets (39 ) — 7 — (32 ) Deferred revenue for award credits (29 ) — (2 ) — (31 ) Others (2 ) 1 (1 ) — (2 ) $ (1,430 ) $ 1 $ (563 ) $ — $ (1,992 ) For the year ended December 31, 2019 January 1, 2019 Effect of Retrospective Application of IFRS 16 Recognized in Profit or Loss Recognized in Other Comprehensive Income December 31, 2019 NT$ NT$ NT$ NT$ NT$ (In Millions) Deferred income tax assets Temporary differences Defined benefit pension plans $ 2,307 $ — $ 32 $ (305 ) $ 2,034 Allowance for doubtful receivables over quota 435 — (31 ) — 404 Share of profits of associates and joint ventures accounted for using equity method 389 — 13 — 402 Valuation loss on inventory 88 — 53 — 141 Deferred revenue 111 — (13 ) — 98 Estimated warranty liabilities 26 — 8 — 34 Accrued award credits liabilities 14 — 3 — 17 Others 143 26 (68 ) — 101 3,513 26 (3 ) (305 ) 3,231 Loss carryforwards 41 — (13 ) — 28 $ 3,554 $ 26 $ (16 ) $ (305 ) $ 3,259 January 1, 2019 Effect of Retrospective Application of IFRS 16 Recognized in Profit or Loss Recognized in Other Comprehensive Income December 31, 2019 NT$ NT$ NT$ NT$ NT$ (In Millions) Deferred income tax liabilities Temporary differences Defined benefit pension plans $ (1,832 ) $ — $ 74 $ — $ (1,758 ) Land value incremental tax (95 ) — — — (95 ) Intangible assets (32 ) — 3 — (29 ) Deferred revenue for award credits (31 ) — 2 — (29 ) Others (2 ) — 1 — (1 ) $ (1,992 ) $ — $ 80 $ — $ (1,912 ) For the year ended December 31, 2020 January 1, 2020 Acquired by business combinations (Note 14) Recognized in Profit or Loss Recognized in Other Comprehensive Income December 31, 2020 NT$ NT$ NT$ NT$ NT$ (In Millions) Deferred income tax assets Temporary differences Defined benefit pension plans $ 2,034 $ 1 $ 20 $ (239 ) $ 1,816 Share of profits of associates and joint ventures accounted for using equity method 402 — (1 ) — 401 Allowance for doubtful receivables over quota 404 — (39 ) — 365 Valuation loss on inventory 141 3 155 — 299 Deferred revenue 98 — (25 ) — 73 Estimated warranty liabilities 34 — 2 — 36 Accrued award credits liabilities 17 — 1 — 18 Others 101 2 2 — 105 3,231 6 115 (239 ) 3,113 Loss carryforwards 28 — (8 ) — 20 $ 3,259 $ 6 $ 107 $ (239 ) $ 3,133 January 1, 2020 Acquired by business combinations (Note 14) Recognized in Profit or Loss Recognized in Other Comprehensive Income December 31, 2020 NT$ NT$ NT$ NT$ NT$ (In Millions) Deferred income tax liabilities Temporary differences Defined benefit pension plans $ (1,758 ) $ — $ (54 ) $ — $ (1,812 ) Land value incremental tax (95 ) — — — (95 ) Deferred revenue for award credits (29 ) — (1 ) — (30 ) Intangible assets (29 ) — 2 — (27 ) Others (1 ) (3 ) 1 — (3 ) $ (1,912 ) $ (3 ) $ (52 ) $ — $ (1,967 ) e. Items for which no deferred income tax assets have been recognized December 31 2019 2020 NT$ NT$ (In Millions) Loss carryforwards Expire in 2021 $ 13 $ 12 Expire in 2022 10 10 Expire in 2023 8 8 Expire in 2024 8 8 Expire in 2025 15 19 Expire in 2026 8 8 Expire in 2027 3 3 Expire in 2028 1 1 Expire in 2029 — 1 Expire in 2030 — — $ 66 $ 70 Deductible temporary differences $ 1 $ — f. Information about unused loss carryforwards As of December 31, 2020, unused loss carryforwards were as follows: Remaining Creditable Amount Expiry Year NT$ (In Millions) $ 14 2021 11 2022 9 2023 8 2024 22 2025 16 2026 3 2027 4 2028 2 2029 2 2030 $ 91 g . Income tax examinations Income tax returns of Chunghwa have been examined by the tax authorities through 2017. Income tax returns of SENAO, ISPOT, Youth, Youyi, SENYOUNG, Aval, CHIEF, CHSI, SHE, CHI, CHPT, SFD, CLPT, CHTSC, HHI, IISI and UTC have been examined by the tax authorities through 2018. Income tax returns of CHYP, LED, Unigate and CHST have been examined by the tax authorities through 2019.

Earnings Per Share

Earnings Per Share	12 Months Ended
Earnings Per Share	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share	3 4 . EARNINGS PER SHARE Net income and weighted average number of common stocks used in the calculation of earnings per share were as follows: Net Income Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Net income used to compute the basic earnings per share Net income attributable to the parent $ 37,557 $ 32,947 $ 33,419 Assumed conversion of all dilutive potential common stocks Employee stock options, employee compensation of subsidiaries (6 ) (4 ) (7 ) Net income used to compute the diluted earnings per share $ 37,551 $ 32,943 $ 33,412 Weighted Average Number of Common Stocks (Millions Shares) Year Ended December 31 2018 2019 2020 Weighted average number of common stocks used to compute the basic earnings per share 7,757 7,757 7,757 Assumed conversion of all dilutive potential common stocks Employee compensation 9 8 8 Weighted average number of common stocks used to compute the diluted earnings per share 7,766 7,765 7,765 As Chunghwa may settle the employee compensation in shares or cash, Chunghwa shall presume that it will be settled in shares and take those shares into consideration when calculating the weighted average number of outstanding shares used in the calculation of diluted EPS if the shares have a dilutive effect. The dilutive effect of the shares needs to be considered until the approval of the number of shares to be distributed to employees as compensation in the following year.

Share-based Payment Arrangement

Share-based Payment Arrangement	12 Months Ended
Share-based Payment Arrangement	Dec. 31, 2020
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Abstract]
Share-based Payment Arrangement	3 5 . SHARE-BASED PAYMENT ARRANGEMENT a. SENAO share-based compensation plan (“SENAO Plan”) described as follows: Effective Date Grant Date Stock Options Units Exercise Price (In Thousands) NT$ 2012.05.28 2013.05.07 10,000 $66.20 (Original price$93.00) Each option is eligible to subscribe for one common share when exercisable. Under the terms of the SENAO Plan, the options are granted at an exercise price equal to the closing price of the SENAO’s common stocks listed on the TWSE on the higher of closing price or par value. The SENAO Plan has an exercise price adjustment formula upon the changes in common stocks equity (including cash capital increase, new share issue through capitalization of earnings and additional paid-in capital, merger, spin off and new share issue for Global Depositary Shares, and so on) or distribution of cash dividends. The options of the SENAO Plan are valid for six years and the graded vesting schedule for which 50% of options granted will vest two years after the grant date and another two tranches of 25%, each will vest three and four years after the grant date respectively. SENAO modified the plan terms of the outstanding stock options in July 2018, the exercise price changed from $70.70 to $66.20 per share. The modification did not cause any incremental fair value granted. No compensation cost was recognized for the years ended December 31, 2018, 2019 and 2020. Information about SENAO’s outstanding stock options for the years ended December 31, 2018 and 2019 was as follows: Year Ended December 31, 2018 Granted on May 7, 2013 Number of Options Weighted- average Exercise Price (In Thousands) NT$ Employee stock options Options outstanding at beginning of the year 5,926 $ 70.70 Options forfeited (608 ) — Options outstanding at end of the year 5,318 66.20 Options exercisable at end of the year 5,318 66.20 Year Ended December 31, 2019 Granted on May 7, 2013 Number of Options Weighted- average Exercise Price (In Thousands) NT$ Employee stock options Options outstanding at beginning of the year 5,318 $ 66.20 Options forfeited (5,318 ) — Options outstanding at end of the year — — Options exercisable at end of the year — — As of December 31, 2019 and 2020,, there were no outstanding stock options. SENAO used the fair value method to evaluate the options using the Black-Scholes model and the related assumptions and the fair value of the options were as follows: Stock Options Granted on May 7, 2013 Grant-date share price (NT$) $ 93.00 Exercise price (NT$) $ 93.00 Dividend yield — Risk-free interest rate 0.91 % Expected life 4.375 years Expected volatility 36.22 % Weighted average fair value of grants (NT$) $ 28.72 Expected volatility was based on the historical share price volatility of SENAO over the period equal to the expected life of the SENAO Plan. b . SENAO transferred the treasury stock The Board of Directors of SENAO resolved to transfer treasury stock 6,658 thousand shares to specific employees in April 2018. The aforementioned treasury stock transferred to employees were measured at the fair value on the grant date. The compensation cost of $15.6 million was recognized for the year ended December 31, 2018. SENAO used the fair value method to evaluate share-based payment transaction using the Black-Scholes model and the related assumptions and the fair value of the options were as follows: Stock Options Granted on May 7, 2018 Grant-date share price (NT$) $ 51.60 Exercise price (NT$) $ 49.28 Dividend yield — Risk-free interest rate 0.59 % Expected life 18 days Expected volatility 8.78 % Weighted average fair value of grants (NT$) $ 2.34 Expected volatility was based on the historical share price volatility of SENAO over three months before the grant date. c . CHIEF share-based compensation plan (“CHIEF Plan”) described as follows: Effective Date Grant Date Stock Options Units Exercise Price NT$ 2015.11.17 2015.10.22 2,000.00 $34.40 (Original price$43.00) 2017.12.18 2017.12.19 950.00 $132.70 (Original price$147.00) 2018.10.31 50.00 $138.70 (Original price$147.00) 2020.09.16 2020.11.13 200.00 $206.00 Each option is eligible to subscribe for one thousand common stocks when exercisable. The options are granted to specific employees that meet the vesting conditions. The CHIEF Plan has an exercise price adjustment formula upon the changes in common stocks or distribution of cash dividends. The options of the CHIEF Plan are valid for five years and the graded vesting schedule will vest two years after the grant date. The compensation costs for stock options granted on October 22, 2015 were $1 million and $0.3 million for the years ended December 31, 2018 and 2019, respectively. No compensation cost was recognized for the year ended December 31, 2020. The compensation costs for stock options granted on December 19, 2017 were $0.6 million, $0.6 million and $0.2 million for the years ended December 31, 2018, 2019 and 2020, respectively. The compensation costs for stock options granted on October 31, 2018 were $0.1 million, $0.6 million and $0.3 million for the years ended December 31, 2018, 2019 and 2020, respectively. The Board of Directors of CHIEF resolved to issue stock options in October 26, 2020 and authorized the chairman to decide the grant date. Afterwards, the grant date was decided as November 13, 2020. The compensation costs were $1 million for the year ended December 31, 2020. CHIEF modified the plan terms of stock options granted on December 19, 2017 in June and August 2018 and the exercise price changed from $147.00 to $144.10 and $140.60 per share, respectively. The modification did not cause any incremental fair value granted. CHIEF modified the plan terms of stock options granted on December 19, 2017 in June 2019 and July 2020; therefore, the exercise price changed from $140.60 to $135.60 and $132.70 per share. The modification did not cause any incremental fair value granted. CHIEF modified the plan terms of stock options granted on October 31, 2018 in June 2019 and July 2020; therefore, the exercise price changed from $147.00 to $141.70 and $138.70 per share. The modification did not cause any incremental fair value granted. Information about CHIEF’s outstanding stock options for the years ended December 31, 2018, 2019 and 2020 was as follows: Year Ended December 31, 2018 Granted on October 22, 2015 Granted on December 19, 2017 Granted on October 31, 2018 Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Employee stock options Options outstanding at beginning of the year 1,936.00 $ 34.40 950.00 $ 147.00 — $ — Options granted — — — — 50.00 147.00 Options exercised (1,027.25 ) 34.40 — — — — Options forfeited (26.00 ) — (25.00 ) — — — Options outstanding at end of the year 882.75 34.40 925.00 140.60 50.00 147.00 Options exercisable at end of the year 416.50 34.40 — — — — Year Ended December 31, 2019 Granted on October 22, 2015 Granted on December 19, 2017 Granted on October 31, 2018 Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Employee stock options Options outstanding at beginning of the year 882.75 $ 34.40 925.00 $ 140.60 50.00 $ 147.00 Options exercised (547.25 ) 34.40 — — — — Options forfeited (21.25 ) — (28.00 ) — (4.00 ) — Options outstanding at end of the year 314.25 34.40 897.00 135.60 46.00 141.70 Options exercisable at end of the year 314.25 34.40 448.50 135.60 — — Year Ended December 31, 2020 Granted on October 22, 2015 Granted on December 19, 2017 Granted on October 31, 2018 Granted on November 13, 2020 Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Employee stock options Options outstanding at beginning of the year 314.25 $ 34.40 897.00 $ 135.60 46.00 $ 141.70 — $ — Options granted — — — — — — 200 206.00 Options exercised (314.25 ) 34.40 (448.50 ) 135.60 (21.00 ) 138.70 — — Options forfeited — — (21.00 ) — (4.00 ) — — — Options outstanding at end of the year — — 427.50 132.70 21.00 138.70 200.00 206.00 Options exercisable at end of the year — — 213.75 132.70 — — — — As of December 31, 2019, information about employee stock options outstanding was as follows: Granted on October 22, 2015 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 34.40 314.25 0.81 $ 34.40 314.25 $ 34.40 Granted on December 19, 2017 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 135.60 897.00 2.96 $ 135.60 448.50 $ 135.60 Granted on October 31, 2018 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 141.70 46.00 3.83 $ 141.70 — $ — As of December 31, 2020, information about employee stock options outstanding was as follows: Granted on December 19, 2017 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 132.70 427.50 1.96 $ 132.70 213.75 $ 132.70 Granted on October 31, 2018 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 138.70 21.00 2.83 $ 138.70 — $ — Granted on November 13, 2020 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 206.00 200.00 4.87 $ 206.00 — $ — As of December 31, 2020, all the stock options granted on October 22, 2015 were exercised or forfeited. CHIEF used the fair value method to evaluate the options using the Black-Scholes model and binomial option pricing model and the related assumptions and the fair value of the options were as follows: Stock Options Granted on October 22, 2015 Stock Options Granted on December 19, 2017 Stock Options Granted on October 31, 2018 Stock Options Granted on November 13, 2020 Grant-date share price (NT$) $ 39.55 $ 95.92 $ 166.00 $ 356.00 Exercise price (NT$) $ 43.00 $ 147.00 $ 147.00 $ 206.00 Dividend yield — — — — Risk-free interest rate 0.86 % 0.62 % 0.72 % 0.18 % Expected life 5 years 5 years 5 years 5 years Expected volatility 21.02 % 17.35 % 16.60 % 34.61 % Weighted average fair value of grants (NT$) $ 4,863 $ 2,318 $ 33,540 $ 173,893 The expected volatility for the options granted in 2020 was based on CHIEF’s average annualized historical share price volatility from June 5, 2018, CHIEF’s listing date on Taipei Exchange, to the grant date. The expected volatilities for the options granted from 2015 to 2018 were based on the average annualized historical share price volatility of CHIEF’s comparable companies before the grant date. d . New shares reserved for subscription by employees under cash injection of CHIEF In March 2018, the Board of Directors of CHIEF approved the cash injection to issue 7,842 thousand shares and simultaneously reserved 1,176 thousand shares for subscription by employees according to the Company Act of the ROC. Furthermore, when the employees subscribed some shares or discarded their rights to subscribe shares, the Board of Directors of CHIEF authorized the chairman of the Board of Directors to contact specific people or group to subscribe. The aforementioned options granted to employees are accounted for and measured at fair value of the grant date. No compensation cost was recognized for the year ended December 31, 2018. CHIEF used the fair value method to evaluate the options granted to employees on May 22, 2018 using the Black-Scholes model and the related assumptions and the fair value of the options were as follows: Stock Options Granted on May 22, 2018 Grant-date share price (NT$) $ 156.41 Exercise price (NT$) $ 170.00 Dividend yield — Risk-free interest rate 0.34 % Expected life 7 days Expected volatility 14.33 % Weighted average fair value of grants (NT$) $ — Expected volatility was based on the average annualized historical share price volatility of CHIEF’s comparable companies before the grant date. e . CHTSC share-based compensation plan (“CHTSC Plan”) described as follows: The Board of Directors of CHTSC resolved to issue 4,500 stock options that are granted to specific employees that meet the vesting conditions on December 20, 2019. Each option is eligible to subscribe for one thousand common stocks when exercisable, and the exercise price is $19.085. The CHTSC Plan has an exercise price adjustment formula upon the changes in common stocks. The options of the CHTSC Plan are valid for five years and the graded vesting schedule will vest one year after the grant date. The compensation costs of stock options granted were $0.2 million and $5.7 million for the years ended December 31, 2019 and 2020, respectively. Information about CHTSC’s outstanding stock options for the years ended December 31, 2019 and 2020 was as follows: Year Ended December 31, 2019 2020 Granted on December 20, 2019 Granted on December 20, 2019 Number of Options Weighted- average Exercise Price Number of Options Weighted- average Exercise Price NT$ NT$ Employee stock options Options outstanding at beginning of the year — $ — 4,500 $ 19.085 Options granted 4,500 19.085 — — Options forfeited — — (172 ) — Options outstanding at end of the year 4,500 19.085 4,328 19.085 Options exercisable at end of the year — — 1,082 19.085 As of December 31, 2019, information about employee stock options outstanding was as follows: Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 19.085 4,500 4.97 $ 19.085 — $ — As of December 31, 2020, information about employee stock options outstanding was as follows: Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 19.085 4,328 3.97 $ 19.085 1,082 $ 19.085 CHTSC used the fair value method to evaluate the options using the Black-Scholes model and the related assumptions and the fair value of the options were as follows: Stock Options Granted on December 20, 2019 Grant-date share price (NT$) $ 20.17 Exercise price (NT$) $ 19.085 Dividend yield 12.49 % Risk-free interest rate 0.54 % Expected life 5 years Expected volatility 42.41 % Weighted average fair value of grants (NT$) $ 2,470 Expected volatility was based on the average annualized historical share price volatility of CHTSC’s comparable companies before the grant date. f . IISI share-based compensation plan (“IISI Plan”) described as follows: IISI issued 1,335 and 1,665 options in August 2013 and January 2014, respectively. Each option is eligible to subscribe for one thousand common stocks when exercisable. The options are granted to specific employees of IISI and its subsidiaires that meet the vesting conditions. The options of the IISI Plan are valid for seven years and the graded vesting schedule will vest two years after the grant date. The exercise price of the original options is $14 per share. After the options are issued, if the common stocks of IISI change, the exercise price of the options should be adjusted according to the prescibed formula. No compensation cost of stock options granted was recognized for the six months ended December 31, 2020. Information about IISI’s outstanding stock options for the year ended December 31, 2020 was as follows: Year Ended December 31, 2020 Granted in August 2013 Granted in January 2014 Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Employee stock options Options outstanding at beginning of the year — $ — — $ — Options outstanding upon the date of business combination 1,022.96 14.00 580.00 14.00 Options exercised (432.50 ) 14.00 (50.00 ) 14.00 Options forfeited (590.46 ) — — — Options outstanding at end of the year — — 530.00 14.00 Options exercisable at end of the year — — 530.00 14.00 As of December 31, 2020, information about employee stock options outstanding was as follows: Granted in January 2014 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 14.00 530.00 0.04 $ 14.00 530.00 $ 14.00 As of December 31, 2020, the options granted to employees in 2013 have been fully exercised or forfeited. IISI used the fair value method to evaluate the options using the Black-Scholes model and the related assumptions and the fair value of the options were as follows: Stock Options Granted in August 2013 Stock Options Granted in January 2014 Grant-date share price (NT$) $ 12.51 $ 14.51 Exercise price (NT$) $ 14.00 $ 14.00 Dividend yield 6 % 6 % Risk-free interest rate 1.20%-1.39% 1.16%-1.32% Expected life 4.5-5.5 years 4.5-5.5 years Expected volatility 36.01%-36.62% 35.28%-35.97% Weighted average fair value of grants (NT$) $ 12.51 $ 14.51 Expected volatility was based on the average annualized historical share price volatility of IISI’s comparable companies before the grant date.

Non-cash Transactions

Non-cash Transactions	12 Months Ended
Non-cash Transactions	Dec. 31, 2020
Non Cash Transaction From Financing Activities [Abstract]
Non Cash Transactions	3 6 . NON-CASH TRANSACTIONS Except for those disclosed in other notes, the Company entered into the following non-cash investing and financing activities: Year Ended December 31 Investing activities 2018 2019 2020 NT$ NT$ NT$ (In Millions) Increase in property, plant and equipment $ 27,979 $ 23,164 $ 25,195 Other payables 571 1,002 (1,684 ) Acquisition of property, plant and equipment $ 28,550 $ 24,166 $ 23,511 Increase in investment properties $ 6 $ 1 $ 1,359 Trade-in investment properties from asset exchange transaction (Note 16) — — (1,305 ) Acquisition of investment properties $ 6 $ 1 $ 54 Increase in intangible assets $ 498 $ 363 $ 48,605 Changes in other assets — — (1,000 ) Acquisition of intangible assets $ 498 $ 363 $ 47,605 Disposal of property, plant and equipment, net $ 122 $ 86 $ 307 Gain (loss) on disposal of property, plant and equipment 142 (38 ) 1,428 Trade-in investment properties from asset exchange transaction (Note 16) — — (1,305 ) Changes in other payables — — (80 ) Changes in other current monetary assets — — (31 ) Proceeds from disposal of property, plant and equipment $ 264 $ 48 $ 319 Financing activities Balance on January 1, 2019 Cash Flows from Financing Activities Changes in Non-Cash Transactions Cash Flows from Operation Activities - Interest Paid Balance on December 31, 2019 Balance on January 1, 2019 Cash Flows from Financing Activities New Leases Others Cash Flows from Operation Activities - Interest Paid Balance on December 31, 2019 NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Lease liabilities $ 10,340 $ (3,728 ) $ 3,803 $ (572 ) $ (85 ) $ 9,758 Balance on January 1, 2020 Cash Flows from Financing Activities Changes in Non-Cash Transactions Cash Flows from Operation Activities - Interest Paid Balance on December 31, 2020 Balance on January 1, 2020 Cash Flows from Financing Activities New Leases Acquired by business combination (Note 14) Others Cash Flows from Operation Activities - Interest Paid Balance on December 31, 2020 NT$ NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Lease liabilities $ 9,758 $ (3,683 ) $ 3,796 $ 71 $ (265 ) $ (80 ) $ 9,597

Capital Management

Capital Management	12 Months Ended
Capital Management	Dec. 31, 2020
Capital Commitments [Abstract]
Capital Management	3 7 . CAPITAL MANAGEMENT The Company manages its capital to ensure that entities in the Company will be able to continue as going concerns while maximizing the return to stakeholders through the optimization of the debt and equity balance. The capital structure of the Company consists of debt of the Company and the equity attributable to the parent. Some consolidated entities are required to maintain minimum paid-in capital amount as prescribed by the applicable laws. The management reviews the capital structure of the Company as needed. As part of this review, the management considers the cost of capital and the risks associated with each class of capital. The management reviews the capital structure of the Company as needed. As part of this review, the management considers the cost of capital and the risks associated with each class of capital. According to the management’s suggestions, the Company maintains a balanced capital structure through paying cash dividends, increasing its share capital, purchasing outstanding shares, and issuing new debt or repaying debt.

Financial Instruments

Financial Instruments	12 Months Ended
Financial Instruments	Dec. 31, 2020
Disclosure Of Financial Instruments [Abstract]
Financial Instruments	3 8 . FINANCIAL INSTRUMENTS Categories of Financial Instruments December 31 2019 2020 NT$ NT$ (In Millions) Financial assets Measured at FVTPL Mandatorily measured at FVTPL $ 779 $ 687 Hedging financial assets — 2 Financial assets at amortized cost (Note a) 71,852 62,405 Financial assets at FVOCI 7,154 7,193 Financial liabilities Measured at FVTPL Held for trading — — Measured at amortized cost (Note b) 34,434 62,557 Note a: The balances included cash and cash equivalents, trade notes and accounts receivable, receivables from related parties, other current monetary assets and refundable deposits (classified as other noncurrent assets), which were financial assets measured at amortized cost. Note b: The balances included short-term loans, short-term bills payable, trade notes and accounts Financial Risk Management Objectives The main financial instruments of the Company include equity investments, trade notes and accounts receivable, trade notes and accounts payable, lease liabilities, loans, short-term bills payable and bonds payable. The Company’s Finance Department provides services to its business units, co-ordinates access to domestic and international capital markets, monitors and manages the financial risks relating to the operations of the Company through internal risk reports which analyze exposures by degree and magnitude of risks. These risks include market risk (including foreign currency risk, interest rate risk and other price risk), credit risk, and liquidity risk. The Company seeks to minimize the effects of these risks by using derivative financial instruments to hedge risk exposures. The use of financial derivatives is governed by the Company’s policies approved by the Board of Directors. Those derivatives are used to hedge the risks of exchange rate fluctuation arising from operating or investment activities. Compliance with policies and risk exposure limits is reviewed by the Company’s Finance Department on a continuous basis. The Company does not enter into or trade financial instruments, including derivative financial instruments, for speculative purposes. Chunghwa reports the significant risk exposures and related action plans timely and actively to the audit committee and if needed to the Board of Directors. a. Market risk The Company is exposed to market risks of changes in foreign currency exchange rates and interest rates. The Company uses forward exchange contracts to hedge the exchange rate risk arising from assets and liabilities denominated in foreign currencies. There were no changes to the Company’s exposure to market risks or the manner in which these risks are managed and measured. 1) Foreign currency risk The carrying amounts of the Company’s foreign currency denominated monetary assets and monetary liabilities at the balance sheet dates were as follows: December 31 2019 2020 NT$ NT$ (In Millions) Assets USD $ 5,782 $ 2,711 EUR 12 15 SGD 225 170 JPY 17 22 RMB 9 30 HKD — 69 Liabilities USD 4,121 768 EUR 206 957 SGD 1,263 1,049 JPY 14 10 RMB — — HKD 15 8 The carrying amounts of the Company’s derivatives with exchange rate risk exposures at the balance sheet dates were as follows: December 31 2019 2020 NT$ NT$ (In Millions) Assets USD $ — $ — EUR — 4 Liabilities USD — — EUR — — Foreign currency sensitivity analysis The Company is mainly exposed to the fluctuations of the currencies USD, EUR, SGD, JPY, RMB and HKD as listed above. The following table details the Company’s sensitivity to a 5% increase and decrease in the functional currency against the relevant foreign currencies. 5% is the sensitivity rate used when reporting foreign currency risk internally to key management personnel and represents management’s assessment of the reasonably possible changes in foreign exchange rates. The sensitivity analysis includes only outstanding foreign currency denominated monetary items and forward exchange contracts. A positive number below indicates an increase in pre-tax profit or equity where the functional currency weakens 5% against the relevant currency. Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Profit or loss Monetary assets and liabilities (a) USD $ (55 ) $ 83 $ 97 EUR (59 ) (10 ) (47 ) SGD 4 (52 ) (44 ) JPY — — 1 RMB — — 1 HKD — (1 ) 3 Derivatives (b) USD 3 1 (19 ) EUR 10 3 3 Equity Derivatives (c) EUR 9 4 10 a) This is mainly attributable to the exposure to foreign currency denominated receivables and payables of the Company outstanding at the balance sheet dates. b) This is mainly attributable to forward exchange contracts. c) This is mainly attributable to the changes in the fair value of derivatives that are designated as cash flow hedges. For a 5% strengthening of the functional currency against the relevant currencies, there would be an equal and opposite effect on the pre-tax profit or equity for the amounts shown above. 2) Interest rate risk The carrying amounts of the Company’s exposures to interest rates on financial assets and financial liabilities at the balance sheet dates were as follows: December 31 2019 2020 NT$ NT$ (In Millions) Fair value interest rate risk Financial assets $ 30,947 $ 24,218 Financial liabilities 9,758 36,576 Cash flow interest rate risk Financial assets 7,681 9,306 Financial liabilities 1,690 1,667 Interest rate sensitivity analysis The sensitivity analyses below have been determined based on the exposure to interest rates for non-derivative instruments at the end of the reporting period. A 25 basis point increase or decrease is used when reporting interest rate risk internally to key management personnel and represents management’s assessment of the reasonably possible change in interest rates. If interest rates had been 25 basis points higher/lower and all other variables were held constant, the Company’s pre-tax income would increase/decrease by $19 million, $15 million and $19 million for the years ended December 31, 2018, 2019 and 2020, respectively. This is mainly attributable to the Company’s exposure to floating interest rates on its financial assets and short-term and long-term loans. 3) Other price risk The Company is exposed to equity price risks arising from holding other company’s equity. Equity investments are held for strategic rather than trading purposes. The management managed the risk through holding various risk portfolios. Further, the Company assigned finance and investment departments to monitor the price risk. Equity price sensitivity analysis The sensitivity analyses below have been determined based on the exposure to equity price risks at the end of the reporting period. If equity prices had been 5% higher/lower, pre-tax profit and pre-tax other comprehensive income for the year ended December 31, 2018 would have increased/decreased by $26 million and $347 million as a result of the changes in fair value of financial assets at FVTPL and financial assets at FVOCI, respectively. If equity prices had been 5% higher/lower, pre-tax profit and pre-tax other comprehensive income for the year ended December 31, 2019 would have increased/decreased by $39 million and $358 million as a result of the changes in fair value of financial assets at FVTPL and financial assets at FVOCI, respectively. If equity prices had been 5% higher/lower, pre-tax profit and pre-tax other comprehensive income for the year ended December 31, 2020 would have increased/decreased by $34 million and $360 million as a result of the changes in fair value of financial assets at FVTPL and financial assets at FVOCI, respectively. b. Credit risk Credit risk refers to the risk that a counterparty would default on its contractual obligations resulting in financial loss to the Company. The maximum credit exposure of the aforementioned financial instruments is equal to their carrying amounts recognized in the consolidated balance sheet as of the balance sheet date. The Company has large trade receivables outstanding with its customers. A substantial majority of the Company’s outstanding trade receivables are not covered by collateral or credit insurance. The Company has implemented ongoing measures including enhancing credit assessments and strengthening overall risk management to reduce its credit risk. While the Company has procedures to monitor and limit exposure to credit risk on trade receivables, there can be no assurance such procedures will effectively limit its credit risk and avoid losses. This risk is heightened during periods when economic conditions worsen. As the Company serves a large number of unrelated consumers, the concentration of credit risk was limited. c. Liquidity risk The Company manages and maintains sufficient cash and cash equivalent position to support the operations and reduce the impact on fluctuation of cash flow. 1) Liquidity and interest risk tables The following tables detailed the Company’s remaining contractual maturity for its non-derivative financial liabilities with agreed repayment periods. The tables had been drawn up based on the undiscounted cash flows of financial liabilities based on the earliest date on which the Company is required to pay. December 31, 2019 Weighted Average Effective Interest Rate (%) Less than 1 Month 1-3 Months 3 Months to 1 Year 1-5 Years More than 5 Years Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Non-derivative financial liabilities Non-interest bearing — $ 36,387 $ — $ 2,532 $ 4,748 $ — $ 43,667 Floating interest rate instruments 0.98 50 10 30 1,600 — 1,690 $ 36,437 $ 10 $ 2,562 $ 6,348 $ — $ 45,357 Information about the maturity analysis for lease liabilities was as follows: Less than 1 Year 1-3 Years 3-5 Years More than 5 Years Total NT$ NT$ NT$ NT$ NT$ (In Millions) Lease liabilities $ 3,310 $ 4,394 $ 1,581 $ 645 $ 9,930 December 31, 2020 Weighted Average Effective Interest Rate (%) Less than 1 Month 1-3 Months 3 Months to 1 Year 1-5 Years More than 5 Years Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Non-derivative financial liabilities Non-interest bearing — $ 37,749 $ — $ 2,476 $ 4,827 $ — $ 45,052 Floating interest rate instruments 0.78 — 7 1,660 — — 1,667 Fixed interest rate instruments 0.50 7,000 — — 8,800 11,200 27,000 $ 44,749 $ 7 $ 4,136 $ 13,627 $ 11,200 $ 73,719 Information about the maturity analysis for lease liabilities was as follows: Less than 1 Year 1-3 Years 3-5 Years More than 5 Years Total NT$ NT$ NT$ NT$ NT$ (In Millions) Lease liabilities $ 3,397 $ 4,240 $ 1,691 $ 409 $ 9,737 The following table detailed the Company’s liquidity analysis for its derivative financial instruments. The table had been drawn up based on the undiscounted gross inflows and outflows on those derivatives that require gross settlement. Less than 1 Month 1-3 Months 3 Months to 1 Year 1-5 Years Total NT$ NT$ NT$ NT$ NT$ (In Millions) December 31, 2019 Gross settled Forward exchange contracts Inflows $ 26 $ 135 $ — $ — $ 161 Outflows 26 135 — — 161 $ — $ — $ — $ — $ — December 31, 2020 Gross settled Forward exchange contracts Inflows $ — $ 635 $ — $ — $ 635 Outflows — 631 — — 631 $ — $ 4 $ — $ — $ 4 2) Financing facilities December 31 2019 2020 NT$ NT$ (In Millions) Unsecured bank loan facility Amount used $ 121 $ 7,068 Amount unused 46,109 59,277 $ 46,230 $ 66,345 Secured bank loan facility Amount used $ 1,600 $ 1,600 Amount unused 1,340 20 $ 2,940 $ 1,620

Fair Value Information

Fair Value Information	12 Months Ended
Fair Value Information	Dec. 31, 2020
Disclosure Of Fair Value Measurement Of Financial Instruments [Abstract]
Fair Value Information	3 9 . FAIR VALUE INFORMATION The fair value measurement guidance establishes a framework for measuring fair value and expands disclosure about fair value measurements. The standard describes a fair value hierarchy based on three levels of inputs that may be used to measure fair value. These levels are: Level 1 fair value measurements: These measurements are those derived from quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 fair value measurements: These measurements are those derived from inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly (i.e. as prices) or indirectly (i.e. derived from prices). Level 3 fair value measurements: These measurements are those derived from valuation techniques that include inputs for the asset or liability that are not based on observable market data (unobservable inputs). a. Financial instruments that are not measured at fair value but for which fair value is disclosed Except those listed in the table below, the Company considers that the carrying amounts of financial assets and liabilities not measured at fair value approximate their fair values or the fair values cannot be reliable estimated. December 31, 2019 December 31, 2020 Carrying Value Fair Value Carrying Value Fair Value Financial liabilities Financial liabilities measured at amortized cost Bonds payable $ — $ — $ 19,980 $ 20,078 The fair value of bonds payable is measured using Level 2 inputs. The valuation of fair value is based on the quoted market prices provided by third party pricing services. b. Financial instruments that are measured at fair value on a recurring basis December 31, 2019 Level 1 Level 2 Level 3 Total Financial assets at FVTPL Derivatives $ — $ — $ — $ — Listed stocks 1 — — 1 Non-listed stocks — — 778 778 $ 1 $ — $ 778 $ 779 Hedging financial assets $ — $ — $ — $ — Financial assets at FVOCI Listed stocks $ 2,454 $ — $ — $ 2,454 Non-listed stocks — — 4,700 4,700 $ 2,454 $ — $ 4,700 $ 7,154 Financial liabilities at FVTPL Derivatives $ — $ — $ — $ — December 31, 2020 Level 1 Level 2 Level 3 Total Financial assets at FVTPL Derivatives $ — $ 2 $ — $ 2 Listed stocks 8 — — 8 Non-listed stocks — — 677 677 $ 8 $ 2 $ 677 $ 687 Hedging financial assets $ — $ 2 $ — $ 2 Financial assets at FVOCI Listed stocks $ 2,754 $ — $ — $ 2,754 Non-listed stocks — — 4,439 4,439 $ 2,754 $ — $ 4,439 $ 7,193 Financial liabilities at FVTPL Derivatives $ — $ — $ — $ — There were no transfers between Levels 1 and 2 for the years ended December 31, 2018, 2019 and 2020. The reconciliations for financial assets measured at Level 3 are listed below: 2018 Financial Assets Measured at Fair Value through Profit or Loss Measured at Fair Value through Other Comprehensive Income Total NT$ NT$ NT$ (In Millions) Balance at January 1, 2018 $ 543 $ 3,925 $ 4,468 Acquisition — 290 290 Recognized in profit or loss under “Other gains and losses” (26 ) — (26 ) Recognized in other comprehensive income under “Unrealized gain or loss on financial assets at fair value through other comprehensive income” — (175 ) (175 ) Proceeds from return of investees — (7 ) (7 ) Balance at December 31, 2018 $ 517 $ 4,033 $ 4,550 Unrealized loss in 2018 $ (26 ) 2019 Financial Assets Measured at Fair Value through Profit or Loss Measured at Fair Value through Other Comprehensive Income Total NT$ NT$ NT$ (In Millions) Balance at January 1, 2019 $ 517 $ 4,033 $ 4,550 Acquisition 300 — 300 Recognized in profit or loss under “Other gains and losses” (39 ) — (39 ) Recognized in other comprehensive income under “Unrealized gain or loss on financial assets at fair value through other comprehensive income” — 676 676 Proceed from return of investments — (9 ) (9 ) Balance at December 31, 2019 $ 778 $ 4,700 $ 5,478 Unrealized loss in 2019 $ (39 ) 2020 Financial Assets Measured at Fair Value through Profit or Loss Measured at Fair Value through Other Comprehensive Income Total NT$ NT$ NT$ (In Millions) Balance at January 1, 2020 $ 778 $ 4,700 $ 5,478 Reclassified from investments accounted for using equity method — 2 2 Recognized in profit or loss under “Other gains and losses” (101 ) — (101 ) Recognized in other comprehensive income under “Unrealized gain or loss on financial assets at fair value through other comprehensive income” — (263 ) (263 ) Balance at December 31, 2020 $ 677 $ 4,439 $ 5,116 Unrealized loss in 2020 $ (101 ) The fair values of financial assets and financial liabilities of Level 2 are determined as follows: 1) The fair values of financial assets and financial liabilities with standard terms and conditions and traded in active markets are determined with reference to quoted market prices. 2) For derivatives, fair values are estimated using discounted cash flow model. Future cash flows are estimated based on observable inputs including forward exchange rates at the end of the reporting periods and the forward and spot exchange rates stated in the contracts, discounted at a rate that reflects the credit risk of various counterparties. The fair values of non-listed domestic and foreign equity investments were Level 3 financial assets, and determined using the market approach by reference the Price-to-Book ratios (P/B ratios) of peer companies that traded in active market or using assets approach. December 31 2019 2020 Discount for lack of marketability 13.73%-20.00% 14.73%-20.00% Noncontrolling interests discount 21.45%-25.00% 17.29%-25.00% If the inputs to the valuation model were changed to reflect reasonably possible alternative assumptions while all the other variables were held constant, the fair values of equity investments would increase as below table. When related discounts increase, the fair value of equity investments would be the negative amount of the same amount. December 31 2019 2020 NT$ NT$ (In Millions) Discount for lack of marketability 5% decrease $ 342 $ 320 Noncontrolling interests discount 5% decrease $ 54 $ 47

Related Parties Transactions

Related Parties Transactions	12 Months Ended
Related Parties Transactions	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Parties Transactions	40 . RELATED PARTIES TRANSACTIONS The ROC Government, one of Chunghwa’s customers, has significant equity interest in Chunghwa. Chunghwa provides fixed-line services, wireless services, internet and data and other services to the various departments and institutions of the ROC Government in the normal course of business and at arm’s-length prices. Except for those disclosed in other notes or this note, the transactions with the ROC government bodies have not been disclosed because the transactions are not individually or collectively significant. However, the related revenues and operating costs have been appropriately recorded. a. The Company engages in business transactions with the following related parties: Company Relationship Taiwan International Standard Electronics Co., Ltd. Associate So-net Entertainment Taiwan Limited Associate KKBOX Taiwan Co., Ltd. Associate KingwayTek Technology Co., Ltd. Associate UUPON Inc. Associate (Note 2) Taiwan International Ports Logistics Corporation Associate International Integrated Systems, Inc. Subsidiary (Note 1) Senao Networks, Inc. Associate EnRack Tech. Co., Ltd. Subsidiary of the Company’s associate, Senao Networks, Inc. Emplus Technologies, Inc. Subsidiary of the Company’s associate, Senao Networks, Inc. ST-2 Satellite Ventures Pte., Ltd. Associate Viettel-CHT Co., Ltd. Associate Click Force Co., Ltd. Associate Alliance Digital Tech Co., Ltd. Associate Chunghwa PChome Fund I Co., Ltd. Associate Cornerstone Ventures Co., Ltd. Associate Next Commercial Bank Co., Ltd. Associate Chunghwa SEA Holdings Joint venture Other related parties Chunghwa Telecom Foundation A nonprofit organization of which the funds donated by Chunghwa exceeds one third of its total funds Senao Technical and Cultural Foundation A nonprofit organization of which the funds donated by SENAO exceeds one third of its total funds Sochamp Technology Co., Ltd. Investor of significant influence over CHST E-Life Mall Co., Ltd. One of the directors of E-Life Mall and a director of SENAO are members of an immediate family Engenius Technologies Co., Ltd. Chairman of Engenius Technologies Co., Ltd. is a member of SENAO’s management Cheng Keng Investment Co., Ltd. Chairman of Cheng Keng Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family Cheng Feng Investment Co., Ltd. Chairman of Cheng Feng Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family All Oriented Investment Co., Ltd. Chairman of All Oriented Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family Company Relationship Hwa Shun Investment Co., Ltd. Chairman of Hwa Shun Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family Yu Yu Investment Co., Ltd. Chairman of Yu Yu Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family United Daily News Co., Ltd. Investor of significant influence over SFD Shenzhen Century Communication Co., Ltd. Investor of significant influence over SCT Chunghwa Post Co., Ltd. Government-related entity as Chunghwa Telecom (Concluded) Note 1: IISI was an associate and has become a subsidiary starting from July 1, 2020. Please refer to Note 14 (c). All transactions between the Company were eliminated upon consolidation since the acquisition date. Note 2 : b. Balances and transactions between Chunghwa and its subsidiaries, which are related parties of Chunghwa, have been eliminated on consolidation and are not disclosed in this note. Terms of the foregoing transactions with related parties were not significantly different from transactions with non-related parties. When no similar transactions with non-related parties can be referenced, terms were determined in accordance with mutual agreements. Details of transactions between the Company and other related parties are disclosed below: 1) Operating transactions Revenues Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Associates $ 344 $ 274 $ 1,508 Others 94 76 66 $ 438 $ 350 $ 1,574 Operating Costs and Expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Associates $ 1,304 $ 964 $ 715 Others 75 76 68 $ 1,379 $ 1,040 $ 783 2) Non-operating transactions Non-operating Income and Expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Associates $ 31 $ 41 $ 37 Others — 4 3 $ 31 $ 45 $ 40 3) Receivables December 31 2019 2020 NT$ NT$ (In Millions) Associates $ 10 $ 229 Others 7 1 $ 17 $ 230 4) Contract liabilities-current December 31 2019 2020 NT$ NT$ (In Millions) Associates $ — $ 183 5 ) Payables December 31 2019 2020 NT$ NT$ (In Millions) Associates $ 651 $ 643 Others 3 3 $ 654 $ 646 6 ) Customers’ deposits December 31 2019 2020 NT$ NT$ (In Millions) Associates $ 8 $ 5 7 ) Acquisition of property, plant and equipment Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Associates $ 312 $ 242 $ 375 Others — — — $ 312 $ 242 $ 375 8 ) Acquisition of property, plant and equipment Proceeds Gain on Disposal Year Ended December 31 Year Ended December 31 2019 2020 2019 2020 Others $ — $ 386 $ — $ 310 9 ) Lease-in agreements Chunghwa entered into a contract with ST-2 Satellite Ventures Pte., Ltd. on March 12, 2010 to lease capacity on the ST-2 satellite. This lease term is for 15 years which should start from the official operation of ST-2 satellite and the total contract value is approximately $6,000 million (SGD$261 million), including a prepayment of $3,068 million at the inception of the lease, and the rest of amount should be paid annually when ST-2 satellite starts its official operation. ST-2 satellite was launched in May 2011 and began its official operation in August 2011. 2018 The total rental expense for the year ended December 31, 2018 was $394 million, which consisted of an offsetting credit of the prepayment of $204 million and an additional accrual of $190 million. The prepaid rents (classified as prepayments) as of December 31, 2018, was as follows: December 31, 2018 NT$ (In Millions) Prepaid rents - current $ 205 Prepaid rents - noncurrent 1,346 $ 1,551 Starting from 2019 The lease liabilities of ST-2 Satellite Ventures Pte., Ltd. as of December 31, 2019 and 2020 were as follows: December 31, 2019 2020 NT$ NT$ (In Millions) Lease liabilities - current $ 188 $ 182 Lease liabilities - noncurrent 1,024 817 $ 1,212 $ 999 The interest expense recognized for the aforementioned lease liabilities for the years ended December 31, 2019 and 2020 were $11 million and $9 million, respectively. c. Compensation of key management personnel The compensation of directors and other key management personnel for the years ended December 31, 2018, 2019 and 2020 were as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Short-term employee benefits $ 282 $ 263 $ 290 Post-employment benefits 10 9 11 Share-based payment 9 — — $ 301 $ 272 $ 301 The compensation of directors and key management personnel was mainly determined by the compensation committee having regard to the performances and market trends.

Pledged Assets

Pledged Assets	12 Months Ended
Pledged Assets	Dec. 31, 2020
Disclosure Of Collateral [Abstract]
Pledged Assets	41 . PLEDGED ASSETS The following assets are pledged as collaterals for bank loans, custom duties of the imported materials and warranties of contract performance. December 31 2019 2020 NT$ NT$ (In Millions) Property, plant and equipment $ 2,491 $ 2,462 Land held under development (included in inventories) 1,999 1,999 Restricted assets (included in other assets - others) 3 209 $ 4,493 $ 4,670

Significant Contingent Liabilit

Significant Contingent Liabilities and Unrecognized Commitments	12 Months Ended
	Dec. 31, 2020
Commitments And Contingencies [Abstract]
Significant Contingent Liabilities and Unrecognized Commitments	4 2 . SIGNIFICANT CONTINGENT LIABILITIES AND UNRECOGNIZED COMMITMENTS Except for those disclosed in other notes, the Company’s significant commitments and contingent liabilities as of December 31, 2020 were as follows: a. Acquisitions of land and buildings of $119 million. b. Acquisitions of telecommunications related inventory and equipment of $26,815 million. c. Unused letters of credit amounting to $10 million. d . A commitment to contribute $2,000 million to a Piping Fund administered by the Taipei City Government, of which $1,000 million was contributed by Chunghwa on August 15, 1996 (classified as other monetary assets - noncurrent). If the fund is not sufficient, Chunghwa will contribute the remaining $1,000 million upon notification from the Taipei City Government. e. Chunghwa committed that when its ownership interest in NCB is greater than 25% and NCB encounters financial difficulty or the capital adequacy ratio of NCB cannot meet the related regulation requirements, Chunghwa will provide financial support to assist NCB in maintaining a healthy financial condition.

Significant Events After the Re

Significant Events After the Reporting Period	12 Months Ended
Significant Events After the Reporting Period	Dec. 31, 2020
Disclosure Of Nonadjusting Events After Reporting Period [Abstract]
Significant Events After the Reporting Period	4 3 . SIGNIFICANT EVENTS AFTER THE REPORTING PERIOD The Company disposed of its remaining investment in China Airlines, Ltd. in January and February 2021 at fair value amounting to $2,635 million. The related unrealized gain on investments in equity instruments at fair value through other comprehensive income of $94 million was transferred from other equity to retained earnings upon the disposal.

Other Matters

Other Matters	12 Months Ended
Other Matters	Dec. 31, 2020
Miscellaneous Assets [Abstract]
Other Matters	4 4 . OTHER MATTERS The Company has assessed the economic impact of COVID-19 and determined that there were no significant impacts on the Company’s financial statements as of the date the consolidated financial statements were authorized for issue. The Company will continue to monitor developments of the pandemic and assess the related impacts.

Segment Information

Segment Information	12 Months Ended
Segment Information	Dec. 31, 2020
Disclosure Of Operating Segments [Abstract]
Segment Information	4 5 . SEGMENT INFORMATION The Company has the following reportable segments that provide different products or services. The reportable segments are managed separately because each segment represents a strategic business unit that serves different markets. Segment information is provided to the CEO who allocates resources and assesses segment performance. The Company’s measure of segment performance is mainly based on revenues and income before income tax. The Company’s reportable segments are as follows: a. Domestic fixed communications business - the provision of local telephone services, domestic long distance telephone services, broadband access, and related services; b. Mobile communications business - the provision of mobile services, sales of mobile handsets and data cards, and related services; c. Internet business - the provision of HiNet services and related services; d. International fixed communications business - the provision of international long distance telephone services and related services; e. Others - the provision of non-telecom services and the corporate related items not allocated to reportable segments. Some operating segments have been aggregated into a single operating segment taking into account the following factors: (a) similar economic characteristics such as long-term gross profit margins; (b) the nature of the telecommunications products and services are similar; (c) the nature of production processes of the telecommunications products and services are similar; (d) the type or class of customer for the telecommunications products and services are similar; and (e) the methods used to provide the services to the customers are similar. The accounting policies of the operating segments are the same as those described in Note 3. a. Segment revenues and operating results Analysis by reportable segment of revenues and operating results of continuing operations are as follows: Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Year ended December 31, 2018 Revenues From external customers $ 66,753 $ 100,937 $ 29,813 $ 13,435 $ 4,545 $ 215,483 Intersegment revenues 17,125 1,702 4,038 2,234 5,008 30,107 Segment revenues $ 83,878 $ 102,639 $ 33,851 $ 15,669 $ 9,553 245,590 Intersegment elimination (30,107 ) Consolidated revenues $ 215,483 Segment income (loss) before income tax $ 18,243 $ 15,328 $ 11,944 $ 1,024 $ (1,553 ) $ 44,986 Year ended December 31, 2019 Revenues From external customers $ 65,728 $ 95,469 $ 30,091 $ 11,485 $ 4,747 $ 207,520 Intersegment revenues 16,065 1,564 3,951 2,079 4,914 28,573 Segment revenues $ 81,793 $ 97,033 $ 34,042 $ 13,564 $ 9,661 236,093 Intersegment elimination (28,573 ) Consolidated revenues $ 207,520 Segment income (loss) before income tax $ 19,537 $ 11,250 $ 12,515 $ 799 $ (2,234 ) $ 41,867 Year ended December 31, 2020 Revenues From external customers $ 69,469 $ 90,230 $ 32,115 $ 8,695 $ 7,100 $ 207,609 Intersegment revenues 15,930 1,536 3,966 1,875 5,369 28,676 Segment revenues $ 85,399 $ 91,766 $ 36,081 $ 10,570 $ 12,469 236,285 Intersegment elimination (28,676 ) Consolidated revenues $ 207,609 Segment income (loss) before income tax $ 22,504 $ 8,777 $ 13,120 $ 829 $ (2,404 ) $ 42,826 b. Other segment information Other information reviewed by the chief operating decision maker or regularly provided to the chief operating decision maker was as follows: For the year ended December 31, 2018 Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Share of profits of associates and joint ventures accounted for using equity method $ — $ — $ — $ — $ 509 $ 509 Interest income $ 18 $ 12 $ 19 $ 28 $ 120 $ 197 Interest expenses $ — $ — $ — $ — $ 18 $ 18 Operating costs and expenses $ 59,430 $ 73,901 $ 13,766 $ 13,279 $ 11,573 $ 171,949 Depreciation and amortization $ 15,027 $ 13,788 $ 3,121 $ 1,425 $ 448 $ 33,809 Capital expenditure $ 12,693 $ 10,664 $ 2,729 $ 1,348 $ 1,116 $ 28,550 Reversal of impairment loss on investment properties $ 19 $ — $ — $ — $ — $ 19 Impairment loss on intangible assets $ — $ 51 $ — $ — $ — $ 51 For the year ended December 31, 2019 Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Share of profits of associates and joint ventures accounted for using equity method $ — $ — $ — $ — $ 459 $ 459 Interest income $ 15 $ 9 $ 20 $ 41 $ 166 $ 251 Interest expenses $ 5 $ 58 $ 1 $ 12 $ 28 $ 104 Operating costs and expenses $ 56,269 $ 72,952 $ 13,850 $ 11,427 $ 12,249 $ 166,747 Depreciation and amortization $ 14,842 $ 16,254 $ 2,914 $ 1,547 $ 792 $ 36,349 Capital expenditure $ 12,071 $ 7,773 $ 1,425 $ 1,117 $ 1,780 $ 24,166 Impairment loss on property, plant and equipment $ — $ — $ — $ — $ 93 $ 93 Reversal of impairment loss on investment properties $ 57 $ — $ — $ — $ — $ 57 Impairment loss on intangible assets $ — $ 9 $ — $ — $ — $ 9 Impairment loss on other assets $ 13 $ — $ 13 $ — $ 18 $ 44 For the year ended December 31, 2020 Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Share of profits of associates and joint ventures accounted for using equity method $ — $ — $ — $ — $ 244 $ 244 Interest income $ 13 $ 5 $ 17 $ 22 $ 59 $ 116 Interest expenses $ 6 $ 56 $ 1 $ 10 $ 133 $ 206 Operating costs and expenses $ 59,371 $ 69,211 $ 15,241 $ 8,573 $ 14,447 $ 166,843 Depreciation and amortization $ 14,250 $ 17,800 $ 2,669 $ 1,450 $ 969 $ 37,138 Capital expenditure $ 11,483 $ 8,827 $ 1,397 $ 779 $ 1,025 $ 23,511 Gain (loss) on disposal of property, plant and equipment $ 1,442 $ (3 ) $ — $ — $ (11 ) $ 1,428 Gain on disposal of investment properties $ 151 $ — $ — $ — $ — $ 151 Reversal of impairment loss on investment properties $ 27 $ — $ — $ — $ — $ 27 Impairment loss on intangible assets $ — $ 9 $ — $ — $ — $ 9 c. Main products and service revenues The following is an analysis of the Company’s revenue from its major products and services. Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Mobile services revenue $ 63,906 $ 58,703 $ 56,724 Sales of products 41,289 41,593 39,391 Local telephone and domestic long distance telephone services revenue 29,996 27,929 26,475 Broadband access and domestic leased line services revenue 22,453 22,116 22,420 Data communications internet services revenue 21,137 21,003 21,447 International network and leased line services revenue 8,724 7,066 3,884 Others 27,978 29,110 37,268 $ 215,483 $ 207,520 $ 207,609 d. Geographic information The users of the Company’s services are mainly from Taiwan, ROC. The revenues it derived outside Taiwan are mainly revenues from international long distance telephone and leased line services. The geographic information for revenues was as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Taiwan, ROC $ 205,696 $ 197,895 $ 200,881 Overseas 9,787 9,625 6,728 $ 215,483 $ 207,520 $ 207,609 The Company has long-lived assets in U.S., Singapore, Hong Kong, China, Vietnam, Japan, and Thailand and except for $4,063 million and $3,746 million as of December 31, 2019 and 2020, respectively, in the aforementioned areas, the other long-lived assets are located in Taiwan, ROC. e. Major customers As of December 31, 2018, 2019 and 2020, the Company did not have any single customer whose revenue exceeded 10% of the total revenues.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2020
Disclosure Of Summary Of Significant Accounting Policies [Abstract]
Statement of Compliance	Statement of Compliance The accompanying consolidated financial statements have been prepared in conformity with International Financial Reporting Standards as issued by the International Accounting Standards Board (collectively, “IFRSs”).
Basis of Preparation	Basis of Preparation The consolidated financial statements have been prepared on the historical cost basis except for certain financial instruments that are measured at fair values and net defined benefit liabilities (assets) which are measured at the present value of the defined benefit obligations less the fair value of plan assets.
Current and Noncurrent Assets and Liabilities	Current and Noncurrent Assets and Liabilities Current assets include: a. Assets held primarily for the purpose of trading; b. Assets expected to be realized within twelve months after the reporting period; and c. Cash and cash equivalents unless the asset is restricted from being exchanged or used to settle a liability for at least twelve months after the reporting period. Current liabilities include: a. Liabilities held primarily for the purpose of trading; b. Liabilities due to be settled within twelve months after the reporting period; and c. Liabilities for which the Company does not have an unconditional right to defer settlement for at least twelve months after the reporting period. Assets and liabilities that are not classified as current are classified as noncurrent. Light Era Development Co., Ltd. (LED) engages mainly in development of property for rent and sale. The assets and liabilities of LED related to property development within its operating cycle, which is over one year, are classified as current items.
Basis of Consolidation	Basis of Consolidation a. Principles for preparing consolidated financial statements The consolidated financial statements incorporate the financial statements of Chunghwa and entities controlled by Chunghwa (its subsidiaries). Income and expenses of subsidiaries acquired are included in the consolidated statements of comprehensive income from the acquisition date. When necessary, adjustments are made to the financial statements of subsidiaries to bring their accounting policies in line with those used by the Company. All inter-company transactions, balances, income and expenses are eliminated in full upon consolidation. Attribution of total comprehensive income to noncontrolling interests Total comprehensive income of subsidiaries is attributed to the stockholders of the parent and to the noncontrolling interests even if it results in the noncontrolling interests having a deficit balance. Changes in the Company’s ownership interests in subsidiaries Changes in the Company’s ownership interests in subsidiaries that do not result in the Company losing control over the subsidiaries are accounted for as equity transactions. The carrying amounts of the Company’s interests and the noncontrolling interests are adjusted to reflect the changes in their relative interests in the subsidiaries. Any difference between the amount by which the noncontrolling interests are adjusted and the fair value of the consideration paid or received is recognized directly in equity and attributed to stockholders of the parent. b. The subsidiaries in the consolidated financial statements The detail information of the subsidiaries at the end of reporting period was as follows: Percentage of Ownership interests December 31 Name of Investor Name of Investee Main Businesses and Products 2019 2020 Note Chunghwa Telecom Co., Ltd. Senao International Co., Ltd. (“SENAO”) Handset and peripherals retailer, sales of CHT mobile phone plans as an agent 28 28 a) Light Era Development Co., Ltd. (“LED”) Planning and development of real estate and intelligent buildings, and property management 100 100 Donghwa Telecom Co., Ltd. (“DHT”) International private leased circuit, IP VPN service, and IP transit services 100 100 Chunghwa Telecom Singapore Pte., Ltd. (“CHTS”) International private leased circuit, IP VPN service, and IP transit services 100 100 Chunghwa System Integration Co., Ltd. (“CHSI”) Providing system integration services and telecommunications equipment 100 100 Chunghwa Investment Co., Ltd. (“CHI”) Investment 89 89 CHIEF Telecom Inc. (“CHIEF”) Network integration, internet data center (“IDC”), communications integration and cloud application services 57 56 b) CHYP Multimedia Marketing & Communications Co., Ltd. (“CHYP”) Digital information supply services and advertisement services 100 100 Prime Asia Investments Group Ltd. (B.V.I.) (“Prime Asia”) Investment 100 100 Spring House Entertainment Tech. Inc. (“SHE”) Software design services, internet contents production and play, and motion picture production and distribution 56 56 c) Chunghwa Telecom Global, Inc. (“CHTG”) International private leased circuit, internet services, and transit services 100 100 Chunghwa Telecom Vietnam Co., Ltd. (“CHTV”) Intelligent energy saving solutions, international circuit, and information and communication technology (“ICT”) services 100 100 Smartfun Digital Co., Ltd. (“SFD”) Providing diversified family education digital services 65 65 Chunghwa Telecom Japan Co., Ltd. (“CHTJ”) International private leased circuit, IP VPN service, and IP transit services 100 100 Chunghwa Sochamp Technology Inc. (“CHST”) Design, development and production of Automatic License Plate Recognition software and hardware 51 51 Honghwa International Co., Ltd. (“HHI”) Telecommunications engineering, sales agent of mobile phone plan application and other business services, etc. 100 100 Chunghwa Leading Photonics Tech Co., Ltd. (“CLPT”) Production and sale of electronic components and finished products 75 75 Chunghwa Telecom (Thailand) Co., Ltd. (“CHTT”) International private leased circuit, IP VPN service, ICT and cloud VAS services 100 100 d) (Continued) Percentage of Ownership interests December 31 Name of Investor Name of Investee Main Businesses and Products 2019 2020 Note CHT Security Co., Ltd. (“CHTSC”) Computing equipment installation, wholesale of computing and business machinery equipment and software, management consulting services, data processing services, digital information supply services and internet identify services 80 80 International Integrated Systems, Inc. (“IISI”) IT solution provider, IT application consultation, system integration and package solution — 51 e) Senao International Co., Ltd. Senao International (Samoa) Holding Ltd. (“SIS”) International investment 100 100 f) Youth Co., Ltd. (“Youth”) Sale of information and communication technologies products 93 96 g) Aval Technologies Co., Ltd. (“Aval”) Sale of information and communication technologies products 100 100 Senyoung Insurance Agent Co., Ltd. (“SENYOUNG”) Property and liability insurance agency 100 100 Youth Co., Ltd. ISPOT Co., Ltd. (“ISPOT”) Sale of information and communication technologies products 100 100 Youyi Co., Ltd. (“Youyi”) Maintenance of information and communication technologies products 100 100 Aval Technologies Co., Ltd. Wiin Technology Co., Ltd. (“Wiin”) Sale of information and communication technologies products 100 100 h) Senyoung Insurance Agent Co., Ltd. Senaolife Insurance Agent Co., Ltd. (“Senaolife”) Life insurance services 100 100 i) Light Era Development Co., Ltd. Taoyuan Asia Silicon Valley Innovation Co., Ltd. (“TASVI”) Development of real estate — — j) CHIEF Telecom Inc. Unigate Telecom Inc. (“Unigate”) Telecommunications and internet service 100 100 Chief International Corp. (“CIC”) Telecommunications and internet service 100 100 Shanghai Chief Telecom Co., Ltd. (“SCT”) Telecommunications and internet service 49 49 k) Chunghwa Investment Co., Ltd. Chunghwa Precision Test Tech. Co., Ltd. (“CHPT”) Production and sale of semiconductor testing components and printed circuit board 34 34 l) Chunghwa Precision Test Tech. Co., Ltd. Chunghwa Precision Test Tech. USA Corporation (“CHPT (US)”) Design and after-sale services of semiconductor testing components and printed circuit board 100 100 CHPT Japan Co., Ltd. (“CHPT (JP)”) Related services of electronic parts, machinery processed products and printed circuit board 100 100 Chunghwa Precision Test Tech. International, Ltd. (“CHPT (International)”) Wholesale and retail of electronic materials, and investment 100 100 Senao International (Samoa) Holding Ltd. Senao International HK Limited (“SIHK”) International investment 100 100 m) (Continued) Percentage of Ownership interests December 31 Name of Investor Name of Investee Main Businesses and Products 2019 2020 Note Senao International HK Limited Senao Trading (Fujian) Co., Ltd. (“STF”) Sale of information and communication technologies products — — n) Senao International Trading (Shanghai) Co., Ltd. (“SITS”) Sale of information and communication technologies products 100 100 o) Senao International Trading (Jiangsu) Co., Ltd. (“SITJ”) Sale of information and communication technologies products — — p) Prime Asia Investments Group Ltd. (B.V.I.) Chunghwa Hsingta Co., Ltd. (“CHC”) Investment 100 100 Chunghwa Hsingta Co., Ltd. Chunghwa Telecom (China) Co., Ltd. (“CTC”) Integrated information and communication solution services for enterprise clients, and intelligent energy network service 100 100 q) Chunghwa Precision Test Tech. International, Ltd. Shanghai Taihua Electronic Technology Limited (“STET”) Design of printed circuit board and related consultation service 100 100 Su Zhou Precision Test Tech. Ltd. (“SZPT”) Assembly processed of circuit board, design of printed circuit board and related consultation service 100 100 r) International Integrated Systems, Inc. Infoexplorer International Co., Ltd.(“IESA”) Investment — 100 s) IISI Investment Co., Ltd. (“IICL”) Investment — 100 s) Unitronics Technology Corp. (“UTC”) Development and maintenance of information system — 99.96 s) Infoexplorer International Co., Ltd. International Integrated Systems (Hong Kong) Limited (“IEHK”) Investment and technical consulting service — 100 s) IISI Investment Co., Ltd. Leading Tech Co., Ltd. (“LTCL”) Investment — 100 s) Leading Tech Co., Ltd. Leading Systems Co., Ltd. (“LSCL”) Investment — 100 s) Leading Systems Co., Ltd. International Integrated Systems Inc. (Shanghai) (“IISS”) Development and maintenance of information system — 100 s) International Integrated Systems Inc. (Shanghai) Huiyu Shanghai Management Consultancy Co., Ltd. (“HSMC”) Development and maintenance of information system — — s) t) (Concluded) a ) Chunghwa continues to control six out of eleven seats of the Board of Directors of SENAO through the support of large beneficial stockholders. As a result, the Company treated SENAO as a subsidiary. b ) CHIEF issued new shares in March 2019, November 2019, March 2020 and December 2020 as its employees exercised options. Therefore, the Company’s ownership interest in CHIEF decreased to 59.75% and 59.08% as of December 31, 2019 and 2020, respectively. c ) SHE reduced 19.72% of its capital to offset accumulated deficits in December 2019 and the Company’s ownership interest in SHE remained the same. d ) The Company increased its investment in CHTT proportionally in October 2019 and the Company’s ownership interest in CHTT remained the same. e ) Chunghwa obtained 20.38% ownership interest in IISI in July 2020 and Chunghwa’s ownership interest in IISI increased to 51.54% by considering the previously held ownership interest in IISI. Chunghwa obtained over half of the seats of the Board of Directors of IISI; therefore, Chunghwa gained control over IISI and treated it as a subsidiary. IISI issued new shares in September 2020 as its employees exercised options; therefore, the Company’s ownership interest in IISI decreased to 51.20% as of December 31, 2020. f ) SIS reduced and returned its capital to its stakeholders in November 2020. The Company’s ownership interest in SIS remained the same. g ) SENAO subscribed for all the shares in the capital increase of Youth in April 2020. Therefore, the Company’s ownership interest in Youth increased from 92.89% to 95.79%. h ) Aval invested 100% equity shares of Wiin Technology Co., Ltd. (“Wiin”) in September 2019. i ) SENYOUNG invested 100% equity shares of Senaolife Insurance Agent Co., Ltd. (“Senaolife”) in November 2019. j ) TASVI completed its liquidation in September 2019. k ) CHIEF has two out of three seats of the Board of Directors of SCT according to the mutual agreements among stockholders and gained control over SCT; hence, SCT is deemed as a subsidiary of the Company. l ) Though the Company’s ownership interest in CHPT is less than 50%, the management considered the absolute and relative size of ownership interest, and the dispersion of shares owned by the other stockholders and concluded that the Company has a sufficiently dominant voting interest to direct the relevant activities; hence, CHPT is deemed as a subsidiary of the Company. m ) SIHK reduced and returned its capital to its stakeholders in November 2020. The Company’s ownership interest in SIHK remained the same. n ) STF completed its liquidation in May 2019. o ) SITS was approved to end and dissolve its business in December 2020. The liquidation of SITS is still in process. p ) SITJ completed its liquidation in March 2019. q ) CTC was approved to end and dissolve its business in August 2020. The liquidation of CTC is still in process. r ) s ) It is a subsidiary of IISI. t) HSMC completed its liquidation in December 2020. The following diagram presented information regarding the relationship and percentages of ownership interests between Chunghwa and its subsidiaries as of December 31, 2020.
Business Combinations	Business Combinations Acquisitions of businesses are accounted for using the acquisition method. Acquisition-related costs are generally recognized in profit or loss as they are incurred. Goodwill is measured as the excess of the sum of the consideration transferred and the fair value of the acquirer’s previously held equity interests in the acquiree over the net of the acquisition-date amounts of the identifiable assets acquired and the liabilities assumed. Noncontrolling interests that are present ownership interests and entitle their holders to a proportionate share of the entity’s net assets in the event of liquidation are measured at the noncontrolling interests’ proportionate share of the recognized amounts of the acquiree’s identifiable net assets. When a business combination is achieved in stages, the Company’s previously held equity interest in an acquiree is remeasured to fair value at the acquisition date and the resulting gain or loss is recognized in profit or loss. Amounts arising from interests in the acquiree prior to the acquisition date that have previously been recognized in other comprehensive income are recognized on the same basis as would be required had those interests been directly disposed of by the Company.
Foreign Currencies	Foreign Currencies In preparing the financial statements of each individual entity, transactions in currencies other than the entity’s functional currency (foreign currencies) are recognized at the rates of exchange prevailing at the dates of the transactions. At the end of each reporting period, monetary items denominated in foreign currencies are retranslated at the rates prevailing at that date. Exchange differences on monetary items arising from settlement or translation are recognized in profit or loss in the period in which they arise. Non-monetary items carried at fair value that are denominated in foreign currencies are retranslated at the rates prevailing at the date when the fair value was determined and related exchange differences are recognized in profit or loss. Conversely, when the fair value changes were recognized in other comprehensive income, related exchange difference shall be recognized in other comprehensive income. Non-monetary items that are measured at historical cost in a foreign currency are not retranslated. Chunghwa uses New Taiwan dollars (NT$) as the functional currency. For the purposes of presenting consolidated financial statements, the assets and liabilities of the Company’s foreign operations (including of the subsidiaries, associates and joint ventures in other countries or currencies used different with Chunghwa) are translated into New Taiwan dollars using exchange rates prevailing at the end of each reporting period. Income and expense items are translated at the average exchange rates for the period. Exchange differences arising, if any, are recognized in other comprehensive income and attributed to stockholders of the parent and noncontrolling interests as appropriate.
Cash Equivalents	Cash Equivalents Cash equivalents include commercial paper, negotiable certificates of deposit, time deposits, repurchase agreements collateralized by bonds with original maturities within three months from the date of acquisition and government stimulus vouchers, highly liquid, readily convertible to a known amount of cash and are subject to an insignificant risk of changes in value. These cash equivalents are held for the purpose of meeting short-term cash commitments.
Inventories	Inventories Inventories are stated at the lower of cost or net realizable value item by item, except for those that may be appropriate to group items of similar or related inventories. Net realizable value is the estimated selling price of inventories less all estimated costs of completion and costs necessary to make the sale. The calculation of the cost of inventory is derived using the weighted-average method.
Buildings and Land Consigned to Construction Contractors	Buildings and Land Consigned to Construction Contractors Inventories of LED are stated at the lower of cost or net realizable value item by item, except for those that may be appropriate to group as similar items or related inventories. Land acquired before construction is classified as land held for development, and then reclassified as land held under development after LED begins its construction project. Upon the completion of the construction project, LED recognizes revenues in the amount of proceeds from customers for land and buildings and related costs when ownership is transferred to the customers. The unsold portion of the completed construction project is transferred to land and building held for sale.
Investments in Associates and Joint Ventures	Investments in Associates and Joint Ventures An associate is an entity over which the Company has significant influence and that is neither a subsidiary nor an interest in a joint venture. A joint venture is a joint arrangement whereby the Company and other parties that have joint control of the arrangement have rights to the net assets of the arrangement. Investments accounted for using the equity method include investments in associates and interests in joint ventures. Under the equity method, an investment in an associate or a joint venture is initially recognized at cost and adjusted thereafter to recognize the Company’s share of profit or loss and other comprehensive income of the associate and joint venture as well as the distribution received. The Company also recognizes its share in changes in the associates and joint ventures. When the Company subscribes for new shares of an associate and a joint venture at a percentage different from its existing ownership percentage, the resulting carrying amount of the investment differs from the amount of the Company’s proportionate interest in the associate and joint venture. The Company records such a difference as an adjustment to investments with the corresponding amount charged or credited to additional paid-in capital. When the adjustment should be debited to additional paid-in capital but the additional paid-in capital recognized from investments accounted for using equity method is insufficient, the shortage is debited to retained earnings. Any excess of the cost of acquisition over the Company’s share of the fair value of the identifiable net assets and liabilities of an associate and a joint venture at the date of acquisition is recognized as goodwill, which is included within the carrying amount of the investment and shall not be amortized. Any excess of the Company’s share of the net fair value of the identifiable assets and liabilities over the cost of acquisition is recognized immediately in profit or loss. The entire carrying amount of an investment (including goodwill) is tested for impairment as a single asset by comparing its recoverable amount with its carrying amount. Any impairment loss recognized is not allocated to any asset, including goodwill, that forms part of the carrying amount of the investment. Any reversal of that impairment loss is recognized to the extent that the recoverable amount of the investment subsequently increases. The Company discontinues the use of the equity method from the date on which its investment ceases to be an associate and a joint venture. Any retained investment is measured at fair value at that date, and the fair value is regarded as the investment’s fair value on initial recognition as a financial asset. The difference between the previous carrying amount of the associate and joint venture attributable to the retained interest and its fair value is included in the determination of the gain or loss on disposal of the associate and joint venture. The Company accounts for all amounts previously recognized in other comprehensive income in relation to that associate and joint venture on the same basis as would be required had that associate and joint venture directly disposed of the related assets or liabilities. When the Company transacts with its associate and joint venture, profits and losses resulting from the transactions with the associate and joint venture are recognized in the Company’s consolidated financial statements only to the extent of interests in the associate and joint venture that are not related to the Company.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are initially measured at cost and subsequently measured at cost less accumulated depreciation and accumulated impairment loss. Property, plant and equipment in the course of construction are depreciated and classified to the appropriate categories of property, plant and equipment when completed and ready for their intended use. Depreciation on property, plant and equipment is recognized using the straight-line method. Each significant part is depreciated separately. Freehold land is not depreciated. The estimated useful lives, residual values and depreciation method are reviewed at the end of each year, with the effect of any changes in estimate accounted for on a prospective basis. On derecognition of an item of property, plant and equipment, the difference between the net disposal proceeds and the carrying amount of the asset is recognized in profit or loss in the period in which the property is derecognized.
Investment Properties	Investment Properties Investment properties are properties held to earn rentals and/or for capital appreciation. Investment properties also include land held for a currently undetermined future use. Investment properties are measured initially at cost, including transaction costs. Subsequent to initial recognition, investment properties are measured at cost less accumulated depreciation and accumulated impairment loss. Depreciation is recognized using the straight-line method. For a transfer from the investment properties to property, plant and equipment, the deemed cost of the property, plant and equipment for subsequent accounting is its carrying amount at the commencement of owner-occupation. For a transfer from the property, plant and equipment to investment properties, the deemed cost of the investment properties for subsequent accounting is its carrying amount at the end of owner-occupation. For a contract where a land owner provides land for the construction of buildings by a property developer in exchange for a certain percentage of the buildings, any exchange gain or loss is recognized when the exchange transaction occurs if the exchange transaction has commercial substance. On derecognition of the investment properties, the difference between the net disposal proceeds and the carrying amount of the asset is recognized in profit or loss in the period in which the property is derecognized.
Goodwill	Goodwill Goodwill arising from the acquisition of a business is carried at cost as established at the date of acquisition of the business less accumulated impairment loss. For the purpose of impairment testing, goodwill is allocated to each of the Company’s cash-generating units or groups of cash-generating units (referred to as “cash-generating unit”) that are expected to benefit from the synergies of the business combination. A cash-generating unit to which goodwill has been allocated is tested for impairment annually, or more frequently when there is an indication that the unit may be impaired, by comparing its carrying amount, including the attributable goodwill, with its recoverable amount. However, if the goodwill allocated to a cash-generating unit was acquired in a business combination during the current annual period, that unit shall be tested for impairment before the end of the current annual period. If the recoverable amount of the cash-generating unit is less than its carrying amount, the impairment loss is allocated first to reduce the carrying amount of any goodwill allocated to the unit and then to the other assets of the unit pro rata based on the carrying amount of each asset in the unit. Any impairment loss is recognized directly in profit or loss. An impairment loss recognized for goodwill is not reversed in subsequent periods.
Intangible Assets Other Than Goodwill	Intangible Assets Other Than Goodwill Intangible assets with finite useful lives that are acquired separately are initially measured at cost and subsequently measured at cost less accumulated amortization and accumulated impairment loss. Amortization is recognized on a straight-line basis. The estimated useful life, residual value, and amortization method are reviewed at the end of each reporting period, with the effect of any changes in estimate being accounted for on a prospective basis. The residual value of an intangible asset with a finite useful life shall be assumed to be zero unless the Company expects to dispose of the intangible asset before the end of its economic life. Intangible assets acquired in a business combination and recognized separately from goodwill are initially recognized at their fair value at the acquisition date (which is regarded as their cost). Subsequent to initial recognition, they are measured on the same basis as intangible assets that are acquired separately. Gains or losses arising from derecognition of an intangible asset, measured as the difference between the net disposal proceeds and the carrying amount of the asset, are recognized in profit or loss in the period in which the asset is derecognized.
Impairment of Property, Plant and Equipment, Right-of-use Assets, Intangible Assets Other Than Goodwill and Incremental Costs of Obtaining Contracts	Impairment of Property, Plant and Equipment, Right-of-use Assets, Intangible Assets Other Than Goodwill and Incremental Costs of Obtaining Contracts At the end of each reporting period, the Company reviews the carrying amounts of its property, plant and equipment, right-of-use assets and intangible assets, excluding goodwill, to determine whether there is any indication that those assets have suffered an impairment loss. If any such indication exists, the recoverable amount of the asset is estimated in order to determine the extent of the impairment loss. When it is not possible to estimate the recoverable amount of an individual asset, the Company estimates the recoverable amount of the cash-generating unit to which the asset belongs. Intangible assets not yet available for use are tested for impairment at least annually, and whenever there is an indication that the asset may be impaired. Recoverable amount is the higher of fair value less costs to sell and value in use. If the recoverable amount of an asset or cash-generating unit is estimated to be less than its carrying amount, the carrying amount of the asset or cash-generating unit is reduced to its recoverable amount, with the resulting impairment loss recognized in profit or loss. Impairment loss from the assets related to incremental cost of obtaining contracts is recognized to the extent that the carrying amount of the assets exceeds the remaining amount of consideration that the Company expects to receive in exchange for related goods or services less the costs which relate directly to providing those goods or services. When an impairment loss is subsequently reversed, the carrying amount of the asset or cash-generating unit is increased to the revised estimate of its recoverable amount, but only to the extent of the carrying amount that would have been determined had no impairment loss been recognized for the asset or cash-generating unit in prior years. A reversal of an impairment loss is recognized in profit or loss.
Financial Instruments	Financial Instruments Financial assets and financial liabilities are recognized when the Company becomes a party to the contractual provisions of the instruments. Financial assets and financial liabilities are initially measured at fair value. Transaction costs that are directly attributable to the acquisition of financial assets and financial liabilities (other than financial assets and financial liabilities at fair value through profit or loss) are added to the fair value of the financial assets or financial liabilities, as appropriate, on initial recognition. Transaction costs directly attributable to the acquisition of financial assets or financial liabilities at fair value through profit or loss are recognized immediately in profit or loss. a. Financial assets All regular way purchases or sales of financial assets are recognized and derecognized on a trade date basis. The regular way of transaction means the purchase or sale of financial assets delivered within the time frame established by regulation or convention in the marketplace. 1) Measurement category a) Financial assets at fair value through profit or loss (FVTPL) Financial asset is classified as at FVTPL when the financial asset is mandatorily classified as at FVTPL. Financial assets mandatorily classified as at FVTPL include investments in equity instruments which are not designated as at fair value through other comprehensive income (FVOCI). Financial assets at FVTPL are stated at fair value, with any gains or losses arising on remeasurement recognized in profit or loss. The net gain or loss recognized in profit or loss does not incorporate any dividend earned on the financial asset. Fair value is determined in the manner described in Note 38. b) Financial assets at amortized cost Financial assets that meet the following conditions are subsequently measured at amortized cost: i. The financial asset is held within a business model whose objective is to hold financial assets in order to collect contractual cash flows; and ii. The contractual terms of the financial asset give rise on specified dates to cash flows that are solely payments of principal and interest on the principal amount outstanding. Subsequent to initial recognition, financial assets at amortized cost are measured at amortized cost, which equals to gross carrying amount determined by the effective interest method less any impairment loss, except for short-term receivables as the effect of discounting is immaterial. Exchange differences are recognized in profit or loss. Interest income is calculated by applying the effective interest rate to the gross carrying amount of such financial assets. c) Investments in equity instruments at FVOCI On initial recognition, the Company may make an irrevocable election to designate investments in equity instruments as at FVOCI. Designation at FVOCI is not permitted if the equity investment is held for trading or if it is contingent consideration recognized by an acquirer in a business combination. Investments in equity instruments at FVOCI are subsequently measured at fair value with gains and losses arising from changes in fair value recognized in other comprehensive income and accumulated in other equity. The cumulative gain or loss will not be reclassified to profit or loss on disposal of the equity investments. Instead, it will be transferred to retained earnings. Dividends on these investments in equity instruments are recognized in profit or loss when the Company’s right to receive the dividends is established, unless the dividends clearly represent a recovery of part of the cost of the investment. 2) Impairment of financial assets and contract assets The Company recognizes a loss allowance for expected credit losses on financial assets at amortized cost (including accounts receivable) and contract assets. The Company recognizes lifetime Expected Credit Loss (ECL) for accounts receivable and contract assets. For all other financial instruments, the Company recognizes lifetime ECL when there has been a significant increase in credit risk since initial recognition. If, on the other hand, the credit risk on the financial instrument has not increased significantly since initial recognition, the Company measures the loss allowance for that financial instrument at an amount equal to 12-month ECL. Expected credit losses reflect the weighted average of credit losses with the respective risks of a default occurring as the weights. Lifetime ECL represents the expected credit losses that will result from all possible default events over the expected life of a financial instrument. In contrast, 12-month ECL represents the portion of ECL that is expected to result from default events on a financial instrument that are possible within 12 months after the reporting date. The Company recognizes an impairment loss for all financial instruments with a corresponding adjustment to their carrying amount through a loss allowance account. 3) Derecognition of financial assets The Company derecognizes a financial asset only when the contractual rights to the cash flows from the asset expire, or when it transfers the financial asset and substantially all the risks and rewards of ownership of the asset to another entity. On derecognition of a financial asset measured at amortized cost in its entirety, the difference between the asset’s carrying amount and the sum of the consideration received and receivable is recognized in profit or loss. On derecognition of investments in equity instruments at FVOCI in its entirety, the cumulative gain or loss is directly transferred to retained earnings, and it is not reclassified to profit or loss. b . Financial liabilities 1) Subsequent measurement Except for financial liabilities at FVTPL, all the financial liabilities are subsequently measured at amortized cost using the effective interest method. 2) Derecognition of financial liabilities The Company derecognizes financial liabilities when, and only when, the Company’s obligations are discharged, cancelled or expired. The difference between the carrying amount of the financial liability derecognized and the consideration paid and payable, including any non-cash assets transferred or liabilities assumed, is recognized in profit or loss. c . Derivative financial instruments The Company enters into derivative financial instruments to manage its exposure to foreign exchange rate risks, including forward exchange contracts. Derivatives are initially measured at fair value at the date the derivative contracts are entered into and are subsequently remeasured to their fair value at the end of each reporting period. The resulting gain or loss is recognized in profit or loss immediately unless the derivative is designated and effective as a hedging instrument, in which event the timing of the recognition in profit or loss depends on the nature of the hedge relationship. When the fair value of derivative financial instruments is positive, the derivative is recognized as a financial asset; when the fair value of derivative financial instruments is negative, the derivative is recognized as a financial liability.
Hedge Accounting	Hedge Accounting The Company designates some derivatives instruments as cash flow hedges. Hedges of foreign exchange risk on firm commitments are accounted for as cash flow hedges. The effective portion of changes in the fair value of derivatives that are designated and qualify as cash flow hedges is recognized in other comprehensive income. The gain or loss relating to the ineffective portion is recognized immediately in profit or loss. The associated gains or losses that were recognized in other comprehensive income are reclassified from equity to profit or loss as a reclassification adjustment in the line item relating to the hedged item in the same period when the hedged item affects profit or loss. If a hedge of a forecast transaction subsequently results in the recognition of a non-financial asset or a non-financial liability, the associated gains and losses that were recognized in other comprehensive income are removed from equity and are included in the initial cost of the non-financial asset or non-financial liability. The Company discontinues hedge accounting only when the hedging relationship ceases to meet the qualifying criteria; for instance, when the hedging instrument expires or is sold, terminated or exercised. The cumulative gain or loss on the hedging instrument that has been previously recognized in other comprehensive income from the period when the hedge was effective remains separately in equity until the forecast transaction occurs. When a forecast transaction is no longer expected to occur, the gain or loss accumulated in equity is recognized immediately in profit or loss.
Provisions	Provisions Provisions are measured at the best estimate of the expenditure required to settle the Company’s obligation at the end of the reporting period, taking into account the risks and uncertainties surrounding the obligation. The provisions for warranties claims are made by management according to the sales agreements which represent the management’s best estimate of the future outflow of economic benefits. The provisions of warranties claims are recognized as operating cost in the period in which the goods are sold. The provision for onerous contracts represents the present obligation resulting from the measurement for the unavoidable costs of meeting the Company’s contractual obligations exceed the economic benefits expected to be received from the contracts.
Revenue Recognition	Revenue Recognition The Company identifies the performance obligations in the contract with the customers, allocates transaction price to each performance obligation and recognizes revenue when performance obligations are satisfied. Sales of products are recognized as revenue when the Company delivers products and the customer accepts and controls the product. Except for consumer electronic products such as mobile devices sold in channel stores usually in the form of cash, the Company recognizes revenues for sale of other electronic devices and corresponding trade notes and accounts receivable. Usage revenues from fixed-line services (including local, domestic long distance and international long distance telephone services), mobile services, internet and data services, and interconnection and call transfer fees from other telecommunications companies and carriers are billed in arrears and are recognized based upon seconds or minutes of traffic processed when the services are provided in accordance with contract terms. The usage revenues and corresponding trade notes and accounts receivable are recognized monthly. Other revenues are recognized as follows: (a) one-time subscriber connection fees (on fixed-line services) are first recognized as contract liabilities and revenues are recognized subsequently over the average expected customer service periods, (b) monthly fees (on fixed-line services, mobile, internet and data services) and related receivables are accrued monthly, and (c) prepaid services (fixed-line, mobile, internet and data services) are recognized as contract liabilities upon collection considerations from customers and are recognized as revenues subsequently based upon actual usage by customers. Where the Company enters into transactions which involve both the provision of telecommunications service bundled with products such as handsets, total consideration received from products and telecommunications service in these arrangements are allocated based on their relative standalone selling price. The amount of sales revenue recognized for products is not limited to the amount paid by the customer for the products. When the amount of sales revenue recognized for products exceeded the amount paid by the customer for the products, the difference is recognized as contract assets. Contract assets are reclassified to accounts receivable when the amounts become collectible from customers subsequently. When the amount of sales revenue recognized for products was less than the amount paid by the customer for the products, the difference is recognized as contract liabilities and revenues are recognized subsequently when the telecommunications services are provided. For project business contracts, if a substantial part of the Company’s promise to customers is to manage and coordinate the various tasks and assume the risks of those tasks to ensure the individual goods or services are incorporated into the combined output, they are treated as a single performance obligation since the Company provides a significant integration service. The Company recognizes revenues and corresponding accounts receivable when the project business contract is completed and accepted by customers. For some project contracts, the Company does not create an asset with an alternative use to the Company and has an enforceable right to payment for performance completed to date; therefore, performance obligations are satisfied and revenues are recognized over time. For service contracts such as maintenance and warranties, customers simultaneously receive and consume the benefits provided by the Company; thus, revenues and corresponding accounts receivable of service contracts are recognized over the related service period. When another party is involved in providing goods or services to a customer, the Company is acting as a principal if it controls the specified good or service before that good or service is transferred to a customer; otherwise, the Company is acting as an agent. When the Company is acting as a principal, gross inflow of economic benefits arising from transactions is recognized as revenue. When the Company is acting as an agent, revenue is recognized as its share of transaction.
Incremental costs of obtaining contracts	Incremental Costs of Obtaining Contracts Commissions and equipment subsidy related to telecommunications service as a result of obtaining contracts are recognized as an asset under the incremental costs of obtaining contracts to the extent the costs are expected to be recovered and are amortized over the contract period. However, the Company elects not to capitalize the incremental costs of obtaining contracts if the amortization period of the assets that the Company otherwise would have recognized is expected to be one year or less.
Leasing	Leasing 2018 a. The Company as lessor Rental income from operating leases is recognized on a straight-line basis over the term of the relevant lease. b. The Company as lessee Operating lease payments are recognized as an expense on a straight-line basis over the lease term. Starting from 2019 At inception of a contract, the Company assesses whether the contract is, or contains, a lease. a. The Company as lessor Rental income from operating leases is recognized on a straight-line basis over the term of the relevant lease. b. The Company as lessee The Company recognizes right-of-use assets and lease liabilities for all leases at the commencement date of a lease, except for lease payments for low-value assets are recognized as expenses on a straight-line basis over the lease terms accounted for applying recognition exemption. Right-of-use assets are initially measured at cost, which comprises the initial measurement of lease liabilities and for lease payments made at or before the commencement date. Right-of-use assets are subsequently measured at cost less accumulated depreciation and accumulated impairment losses and adjusted for any remeasurement of the lease liabilities. Right-of-use assets are presented separately on the consolidated balance sheets. Right-of-use assets are depreciated using the straight-line basis from the commencement dates to the earlier of the end of the useful lives of the right-of-use assets or the end of the lease terms. Lease liabilities were initially measured at the present value of the lease payments, which comprise fixed payments, in-substance fixed payments, variable lease payments which depend on an index or a rate. The lease payments are discounted using the interest rate implicit in a lease, if that rate can be readily determined. If such rate cannot be readily determined, the lessee’s incremental borrowing rate is used. Lease liabilities are subsequently measured at amortized cost using the effective interest method, with interest expense recognized over the lease terms. When there is a change in a lease term or a change in future lease payments resulting from a change in an index or a rate used to determine those payments, the Company remeasures the lease liabilities with a corresponding adjustment to the right-of-use-assets. However, if the carrying amount of the right-of-use assets is reduced to zero, any remaining amount of the remeasurement is recognized in profit or loss. The Company accounts for the remeasurement of the lease liability as a result of the decrease of lease scope by decreasing the carrying amount of the right-of-use assets and recognizes in profit or loss any gain or loss on the partial or full termination of the lease. Lease liabilities are presented separately on the consolidated balance sheets. Variable lease payments not depending on an index or a rate are recognized as expenses in the periods in which they are incurred.
Borrowing Costs	Borrowing Costs All borrowing costs are recognized in profit or loss in the period in which they are incurred.
Government Grants	Government Grants Government grants are not recognized until there is reasonable assurance that the Company will comply with the conditions attached to government grants and that the grants will be received. Government grants related to income are recognized in profit or loss on a systematic basis over the periods in which the Company recognizes expenses of the related costs for which the grants are intended to compensate. Specifically, government grants whose primary condition is that the Company should construct noncurrent assets are recognized as deferred revenue and transferred to profit or loss on a systematic and rational basis over the useful lives of the related assets.
Employee Benefits	Employee Benefits a. Short-term employee benefits Liabilities recognized in respect of short-term employee benefits are measured at the undiscounted amount of the benefits expected to be paid in exchange for the related service. b. Retirement benefits Payments to defined contribution retirement benefit plans are recognized as an expense when employees have rendered service entitling them to the contributions. Defined benefit costs (including service cost, net interest and remeasurement) under the defined benefit retirement benefit plans are determined using the projected unit credit method. Service cost (including current service cost and gains or losses on settlements) and net interest on the net defined benefit liability (asset) are recognized as employee benefits expense in the period they occur. Remeasurement, comprising (a) actuarial gains and losses; and (b) the return on plan assets, excluding amounts included in net interest on the net defined benefit liability (asset), is recognized in other comprehensive income in the period in which they occur. Remeasurement recognized in other comprehensive income is reflected immediately in retained earnings and will not be reclassified to profit or loss. Net defined benefit liability (asset) represents the actual deficit (surplus) in the Company’s defined benefit plan. Any surplus resulting from this calculation is limited to the present value of any refunds from the plans or reductions in future contributions to the plans. c. Other long-term employee benefits Other long-term employee benefits are accounted for in the same way as the accounting required for defined benefit plan except that remeasurement is recognized in profit or loss.
Share-based Payment Arrangements - Employee Stock Options	Share-based Payment Arrangements - Employee Stock Options The fair value determined at the grant date of the employee share options is expensed on a straight-line basis over the vesting period, based on the Company’s estimate of employee stock options that are expected to ultimately vest, with a corresponding increase in additional paid-in capital - employee stock options. If the equity instruments granted vest immediately at the grant date, expenses are recognized in full in profit or loss. At the end of each reporting period, the Company revises its estimate of the number of employee share options expected to vest. The impact of the revision of the original estimates, if any, is recognized in profit or loss such that the cumulative expense reflects the revised estimate, with a corresponding adjustment to additional paid-in capital - employee stock options.
Income Tax	Income Tax Income tax expense represents the sum of the tax currently payable and deferred tax. a. Current tax The current tax is based on taxable profit for the year. Taxable profit differs from profit as reported in the consolidated statements of comprehensive income because of items of income or expense that are taxable or deductible in other years and items that are never taxable or deductible. The Company’s liability for current tax is calculated using tax rates that have been enacted or substantively enacted by the end of the reporting period. Income tax on unappropriated earnings is accrued during the period the earnings arise and adjusted to the extent that distributions are approved by the stockholders in the following year. Adjustments of prior years’ tax liabilities are added to or deducted from the current year’s tax provision. b. Deferred tax Deferred tax is recognized on temporary differences between the carrying amounts of assets and liabilities in the consolidated financial statements and the corresponding tax bases used in the computation of taxable profit. A deferred tax liability is not recognized on taxable temporary difference arising from initial recognition of goodwill. Deferred tax liabilities are generally recognized for all taxable temporary differences. Deferred tax assets are generally recognized for all deductible temporary differences, unused loss carry forward and unused tax credits from purchases of machinery, equipment and technology and research, and development expenditures, etc. to the extent that it is probable that taxable profits will be available against which those deductible temporary differences can be utilized. Deferred tax liabilities are recognized for taxable temporary differences associated with investments in subsidiaries, associates, and joint ventures, except where the Company is able to control the reversal of the temporary difference and it is probable that the temporary difference will not reverse in the foreseeable future. Deferred tax assets arising from deductible temporary differences associated with such investments and interests are only recognized to the extent that it is probable that there will be sufficient taxable profits against which to utilize the benefits of the temporary differences and they are expected to reverse in the foreseeable future. The carrying amount of deferred tax assets is reviewed at the end of each reporting period and reduced to the extent that it is no longer probable that sufficient taxable profits will be available to allow all or part of the asset to be recovered. A previously unrecognized deferred tax asset is also reviewed at the end of each reporting period and recognized to the extent that it has become probable that future taxable profit will allow the deferred tax asset to be recovered. Deferred tax assets and liabilities are measured at the tax rates that are expected to apply in the period in which the liability is settled or the asset realized, based on tax rates (and tax laws) that have been enacted or substantively enacted by the end of the reporting period. The measurement of deferred tax assets and liabilities reflects the tax consequences that would follow from the manner in which the Company expects, at the end of the reporting period, to recover or settle the carrying amount of its assets and liabilities. c. Current and deferred tax Current and deferred tax are recognized in profit or loss, except when they relate to items that are recognized in other comprehensive income, in which case, the current and deferred tax are also recognized in other comprehensive income. Where current tax or deferred tax arises from the initial accounting for a business combination, the tax effect is included in the accounting for the business combination.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
Summary of Significant Accounting Policies (Tables)	Dec. 31, 2020
Disclosure Of Significant Investments In Subsidiaries [Abstract]
Detail Information of Subsidiaries	The detail information of the subsidiaries at the end of reporting period was as follows: Percentage of Ownership interests December 31 Name of Investor Name of Investee Main Businesses and Products 2019 2020 Note Chunghwa Telecom Co., Ltd. Senao International Co., Ltd. (“SENAO”) Handset and peripherals retailer, sales of CHT mobile phone plans as an agent 28 28 a) Light Era Development Co., Ltd. (“LED”) Planning and development of real estate and intelligent buildings, and property management 100 100 Donghwa Telecom Co., Ltd. (“DHT”) International private leased circuit, IP VPN service, and IP transit services 100 100 Chunghwa Telecom Singapore Pte., Ltd. (“CHTS”) International private leased circuit, IP VPN service, and IP transit services 100 100 Chunghwa System Integration Co., Ltd. (“CHSI”) Providing system integration services and telecommunications equipment 100 100 Chunghwa Investment Co., Ltd. (“CHI”) Investment 89 89 CHIEF Telecom Inc. (“CHIEF”) Network integration, internet data center (“IDC”), communications integration and cloud application services 57 56 b) CHYP Multimedia Marketing & Communications Co., Ltd. (“CHYP”) Digital information supply services and advertisement services 100 100 Prime Asia Investments Group Ltd. (B.V.I.) (“Prime Asia”) Investment 100 100 Spring House Entertainment Tech. Inc. (“SHE”) Software design services, internet contents production and play, and motion picture production and distribution 56 56 c) Chunghwa Telecom Global, Inc. (“CHTG”) International private leased circuit, internet services, and transit services 100 100 Chunghwa Telecom Vietnam Co., Ltd. (“CHTV”) Intelligent energy saving solutions, international circuit, and information and communication technology (“ICT”) services 100 100 Smartfun Digital Co., Ltd. (“SFD”) Providing diversified family education digital services 65 65 Chunghwa Telecom Japan Co., Ltd. (“CHTJ”) International private leased circuit, IP VPN service, and IP transit services 100 100 Chunghwa Sochamp Technology Inc. (“CHST”) Design, development and production of Automatic License Plate Recognition software and hardware 51 51 Honghwa International Co., Ltd. (“HHI”) Telecommunications engineering, sales agent of mobile phone plan application and other business services, etc. 100 100 Chunghwa Leading Photonics Tech Co., Ltd. (“CLPT”) Production and sale of electronic components and finished products 75 75 Chunghwa Telecom (Thailand) Co., Ltd. (“CHTT”) International private leased circuit, IP VPN service, ICT and cloud VAS services 100 100 d) (Continued) Percentage of Ownership interests December 31 Name of Investor Name of Investee Main Businesses and Products 2019 2020 Note CHT Security Co., Ltd. (“CHTSC”) Computing equipment installation, wholesale of computing and business machinery equipment and software, management consulting services, data processing services, digital information supply services and internet identify services 80 80 International Integrated Systems, Inc. (“IISI”) IT solution provider, IT application consultation, system integration and package solution — 51 e) Senao International Co., Ltd. Senao International (Samoa) Holding Ltd. (“SIS”) International investment 100 100 f) Youth Co., Ltd. (“Youth”) Sale of information and communication technologies products 93 96 g) Aval Technologies Co., Ltd. (“Aval”) Sale of information and communication technologies products 100 100 Senyoung Insurance Agent Co., Ltd. (“SENYOUNG”) Property and liability insurance agency 100 100 Youth Co., Ltd. ISPOT Co., Ltd. (“ISPOT”) Sale of information and communication technologies products 100 100 Youyi Co., Ltd. (“Youyi”) Maintenance of information and communication technologies products 100 100 Aval Technologies Co., Ltd. Wiin Technology Co., Ltd. (“Wiin”) Sale of information and communication technologies products 100 100 h) Senyoung Insurance Agent Co., Ltd. Senaolife Insurance Agent Co., Ltd. (“Senaolife”) Life insurance services 100 100 i) Light Era Development Co., Ltd. Taoyuan Asia Silicon Valley Innovation Co., Ltd. (“TASVI”) Development of real estate — — j) CHIEF Telecom Inc. Unigate Telecom Inc. (“Unigate”) Telecommunications and internet service 100 100 Chief International Corp. (“CIC”) Telecommunications and internet service 100 100 Shanghai Chief Telecom Co., Ltd. (“SCT”) Telecommunications and internet service 49 49 k) Chunghwa Investment Co., Ltd. Chunghwa Precision Test Tech. Co., Ltd. (“CHPT”) Production and sale of semiconductor testing components and printed circuit board 34 34 l) Chunghwa Precision Test Tech. Co., Ltd. Chunghwa Precision Test Tech. USA Corporation (“CHPT (US)”) Design and after-sale services of semiconductor testing components and printed circuit board 100 100 CHPT Japan Co., Ltd. (“CHPT (JP)”) Related services of electronic parts, machinery processed products and printed circuit board 100 100 Chunghwa Precision Test Tech. International, Ltd. (“CHPT (International)”) Wholesale and retail of electronic materials, and investment 100 100 Senao International (Samoa) Holding Ltd. Senao International HK Limited (“SIHK”) International investment 100 100 m) (Continued) Percentage of Ownership interests December 31 Name of Investor Name of Investee Main Businesses and Products 2019 2020 Note Senao International HK Limited Senao Trading (Fujian) Co., Ltd. (“STF”) Sale of information and communication technologies products — — n) Senao International Trading (Shanghai) Co., Ltd. (“SITS”) Sale of information and communication technologies products 100 100 o) Senao International Trading (Jiangsu) Co., Ltd. (“SITJ”) Sale of information and communication technologies products — — p) Prime Asia Investments Group Ltd. (B.V.I.) Chunghwa Hsingta Co., Ltd. (“CHC”) Investment 100 100 Chunghwa Hsingta Co., Ltd. Chunghwa Telecom (China) Co., Ltd. (“CTC”) Integrated information and communication solution services for enterprise clients, and intelligent energy network service 100 100 q) Chunghwa Precision Test Tech. International, Ltd. Shanghai Taihua Electronic Technology Limited (“STET”) Design of printed circuit board and related consultation service 100 100 Su Zhou Precision Test Tech. Ltd. (“SZPT”) Assembly processed of circuit board, design of printed circuit board and related consultation service 100 100 r) International Integrated Systems, Inc. Infoexplorer International Co., Ltd.(“IESA”) Investment — 100 s) IISI Investment Co., Ltd. (“IICL”) Investment — 100 s) Unitronics Technology Corp. (“UTC”) Development and maintenance of information system — 99.96 s) Infoexplorer International Co., Ltd. International Integrated Systems (Hong Kong) Limited (“IEHK”) Investment and technical consulting service — 100 s) IISI Investment Co., Ltd. Leading Tech Co., Ltd. (“LTCL”) Investment — 100 s) Leading Tech Co., Ltd. Leading Systems Co., Ltd. (“LSCL”) Investment — 100 s) Leading Systems Co., Ltd. International Integrated Systems Inc. (Shanghai) (“IISS”) Development and maintenance of information system — 100 s) International Integrated Systems Inc. (Shanghai) Huiyu Shanghai Management Consultancy Co., Ltd. (“HSMC”) Development and maintenance of information system — — s) t) (Concluded) a ) Chunghwa continues to control six out of eleven seats of the Board of Directors of SENAO through the support of large beneficial stockholders. As a result, the Company treated SENAO as a subsidiary. b ) CHIEF issued new shares in March 2019, November 2019, March 2020 and December 2020 as its employees exercised options. Therefore, the Company’s ownership interest in CHIEF decreased to 59.75% and 59.08% as of December 31, 2019 and 2020, respectively. c ) SHE reduced 19.72% of its capital to offset accumulated deficits in December 2019 and the Company’s ownership interest in SHE remained the same. d ) The Company increased its investment in CHTT proportionally in October 2019 and the Company’s ownership interest in CHTT remained the same. e ) Chunghwa obtained 20.38% ownership interest in IISI in July 2020 and Chunghwa’s ownership interest in IISI increased to 51.54% by considering the previously held ownership interest in IISI. Chunghwa obtained over half of the seats of the Board of Directors of IISI; therefore, Chunghwa gained control over IISI and treated it as a subsidiary. IISI issued new shares in September 2020 as its employees exercised options; therefore, the Company’s ownership interest in IISI decreased to 51.20% as of December 31, 2020. f ) SIS reduced and returned its capital to its stakeholders in November 2020. The Company’s ownership interest in SIS remained the same. g ) SENAO subscribed for all the shares in the capital increase of Youth in April 2020. Therefore, the Company’s ownership interest in Youth increased from 92.89% to 95.79%. h ) Aval invested 100% equity shares of Wiin Technology Co., Ltd. (“Wiin”) in September 2019. i ) SENYOUNG invested 100% equity shares of Senaolife Insurance Agent Co., Ltd. (“Senaolife”) in November 2019. j ) TASVI completed its liquidation in September 2019. k ) CHIEF has two out of three seats of the Board of Directors of SCT according to the mutual agreements among stockholders and gained control over SCT; hence, SCT is deemed as a subsidiary of the Company. l ) Though the Company’s ownership interest in CHPT is less than 50%, the management considered the absolute and relative size of ownership interest, and the dispersion of shares owned by the other stockholders and concluded that the Company has a sufficiently dominant voting interest to direct the relevant activities; hence, CHPT is deemed as a subsidiary of the Company. m ) SIHK reduced and returned its capital to its stakeholders in November 2020. The Company’s ownership interest in SIHK remained the same. n ) STF completed its liquidation in May 2019. o ) SITS was approved to end and dissolve its business in December 2020. The liquidation of SITS is still in process. p ) SITJ completed its liquidation in March 2019. q ) CTC was approved to end and dissolve its business in August 2020. The liquidation of CTC is still in process. r ) s ) It is a subsidiary of IISI. t) HSMC completed its liquidation in December 2020.

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	12 Months Ended
Cash and Cash Equivalents (Tables)	Dec. 31, 2020
Cash And Cash Equivalents [Abstract]
Summary of Cash and Cash Equivalents	December 31 2019 2020 NT$ NT$ (In Millions) Cash Cash on hand $ 353 $ 487 Bank deposits 9,433 10,961 9,786 11,448 Cash equivalents (investments with maturities of less than three months) Commercial paper $ 20,110 $ 14,061 Negotiable certificates of deposit 1,700 2,600 Time deposits 2,451 2,308 Repurchase agreements collateralized by bonds 3 — Government stimulus vouchers — 3 24,264 18,972 $ 34,050 $ 30,420
Annual Yield Rates of Bank Deposits, Commercial Paper, Negotiable Certificates of Deposit and Time Deposits and Repurchase Agreements Collateralized by Bonds	The annual yield rates of bank deposits, commercial paper, negotiable certificates of deposit, time deposits and repurchase agreements collateralized by bonds as of balance sheet dates were as follows: December 31 2019 2020 Bank deposits 0.00%-0.74% 0.00%-0.40% Commercial paper 0.47%-0.54% 0.14%-0.26% Negotiable certificates of deposit 0.58%-0.60% 0.24%-0.30% Time deposits 0.09%-4.40% 0.10%-3.60% Repurchase agreements collateralized by bonds 1.90% —

Financial Instruments at Fair_2

Financial Instruments at Fair Value Through Profit or Loss (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Financial Instruments At Fair Value Through Profit Or Loss [Abstract]
Summary of Financial Instruments at Fair Value through Profit or Loss	December 31 2019 2020 NT$ NT$ (In Millions) Financial assets-current Mandatorily measured at FVTPL Derivatives (not designated for hedge) Forward exchange contracts $ — $ 2 Non-derivatives Listed stocks - domestic 1 8 $ 1 $ 10 Financial assets-noncurrent Mandatorily measured at FVTPL Non-derivatives Non-listed stocks - domestic $ 511 $ 441 Non-listed stocks - foreign 267 236 $ 778 $ 677 Financial liabilities-current Held for trading Derivatives (not designated for hedge) Forward exchange contracts $ — $ —
Disclosure of Detailed Information Outstanding Derivative Contracts Not Designated for Hedge Explanatory	Outstanding forward exchange contracts not designated for hedge as of balance sheet dates were as follows: Maturity Contract Amount Currency Period (In Millions) December 31, 2019 Forward exchange contracts - buy NT$/EUR 2020.03 NT$51/EUR2 Forward exchange contracts - buy NT$/US$ 2020.01 NT$26/US$1 December 31, 2020 Forward exchange contracts - buy NT$/EUR 2021.03 NT$50/EUR2 Forward exchange contracts - sell US$/NT$ 2021.02-03 US$14/NT379

Financial Assets at Fair Valu_2

Financial Assets at Fair Value through Other Comprehensive Income Noncurrent (Tables)	12 Months Ended
	Dec. 31, 2020
Noncurrent Financial Assets At Fair Value Through Other Comprehensive Income [Abstract]
Summary of Financial Assets at Fair Value through Other Comprehensive Income Noncurrent	December 31 2019 2020 NT$ NT$ (In Millions) Domestic investments Listed stocks $ 2,454 $ 2,754 Non-listed stocks 4,566 4,325 Foreign investments Non-listed stocks 134 114 $ 7,154 $ 7,193

Trade Notes and Accounts Rece_2

Trade Notes and Accounts Receivable, Net (Tables)	12 Months Ended
Trade Notes and Accounts Receivable, Net (Tables)	Dec. 31, 2020
Disclosure Of Financial Assets [Line Items]
Movements of Allowance for Doubtful Accounts, Trade Notes and Accounts Receivable	Movements of loss allowance for trade notes and accounts receivable were as follows: Year Ended December 31 2019 2020 NT$ NT$ (In Millions) Beginning balance $ 2,602 $ 2,360 Add: Provision for (reversal of) credit loss (54 ) 49 Add: Acquired by business combinations (Note 14) — 2 Less: Amounts written off (188 ) (257 ) Ending balance $ 2,360 $ 2,154
Trade notes and accounts receivable [Member]
Disclosure Of Financial Assets [Line Items]
Summary of Trade Notes and Accounts Receivable, Net	December 31 2019 2020 NT$ NT$ (In Millions) Trade notes and accounts receivable $ 28,768 $ 24,776 Less: Loss allowance (2,360 ) (2,154 ) $ 26,408 $ 22,622
Provision Matrix Arising from Telecommunications and Project Business	provision matrix arising from telecommunications business and project business is disclosed below: December 31, 2019 Not Past Due Past Due Less than 30 Days Pass Due 31 to 60 Days Pass Due 61 to 90 Days Pass Due 91 to 120 Days Pass Due 121 to 180 Days Pass Due over 180 Days Total NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Telecommunications business Expected credit loss rate (Note a) 0%-2% 0%-25% 0%-68% 0%-83% 11%-90% 17%-96% 100% Gross carrying amount $ 19,020 $ 268 $ 75 $ 47 $ 41 $ 28 $ 601 $ 20,080 Loss allowance (Lifetime ECL) (56 ) (26 ) (28 ) (35 ) (26 ) (27 ) (601 ) (799 ) Amortized cost $ 18,964 $ 242 $ 47 $ 12 $ 15 $ 1 $ — $ 19,281 Project business Expected credit loss rate (Note b) 0%-5% 5% 10% 30% 50% 80% 100% Gross carrying amount $ 4,054 $ 78 $ 52 $ 30 $ 12 $ 1 $ 1,472 $ 5,699 Loss allowance (Lifetime ECL) (3 ) (5 ) (5 ) (11 ) (5 ) (1 ) (1,472 ) (1,502 ) Amortized cost $ 4,051 $ 73 $ 47 $ 19 $ 7 $ — $ — $ 4,197 December 31, 2020 Not Past Due Past Due Less than 30 Days Pass Due 31 to 60 Days Pass Due 61 to 90 Days Pass Due 91 to 120 Days Pass Due 121 to 180 Days Pass Due over 180 Days Total NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Telecommunications business Expected credit loss rate (Note a) 0%-2% 2%-24% 3%-68% 11%-83% 28%-90% 52%-96% 100% Gross carrying amount $ 15,839 $ 204 $ 51 $ 31 $ 30 $ 25 $ 626 $ 16,806 Loss allowance (Lifetime ECL) (56 ) (21 ) (24 ) (25 ) (24 ) (21 ) (626 ) (797 ) Amortized cost $ 15,783 $ 183 $ 27 $ 6 $ 6 $ 4 $ — $ 16,009 Project business Expected credit loss rate (Note b) 0%-5% 5% 10% 30% 50% 80% 100% Gross carrying amount $ 3,473 $ 64 $ 27 $ 9 $ 2 $ 3 $ 1,288 $ 4,866 Loss allowance (Lifetime ECL) (20 ) (3 ) (3 ) (3 ) (1 ) (2 ) (1,288 ) (1,320 ) Amortized cost $ 3,453 $ 61 $ 24 $ 6 $ 1 $ 1 $ — $ 3,546 Note a: Please refer to Notes 31 and 45 for the information of disaggregation of telecommunications service revenue. The expected credit loss rate applicable to different business revenue varies so as to reflect the risk level indicating by factors like historical experience. Note b : The project business has different loss types according to the customer types. The expected credit loss rate listed above is for general customers. When the customer is a government-affiliated entity, it is anticipated that there will not be an instance of credit loss. Customers with past history of bounced checks or accounts receivable exceeding six months overdue are classified as high-risk customers, with an expected credit loss rate of 50%, increasing by period as the days overdue increase.

Inventories (Tables)

Inventories (Tables)	12 Months Ended
Inventories (Tables)	Dec. 31, 2020
Classes Of Inventories [Abstract]
Summary of Inventories	December 31 2019 2020 NT$ NT$ (In Millions) Merchandise $ 3,858 $ 3,903 Project in process 11,113 6,167 Work in process 141 126 Raw materials 156 137 15,268 10,333 Land held under development 1,999 1,999 Construction in progress 77 77 $ 17,344 $ 12,409

Prepayments (Tables)

Prepayments (Tables)	12 Months Ended
Prepayments (Tables)	Dec. 31, 2020
Prepayments And Accrued Income [Abstract]
Summary of Prepayments	December 31 2019 2020 NT$ NT$ (In Millions) Prepaid rents $ 3,382 $ 2,864 Others 1,180 1,656 $ 4,562 $ 4,520 Current Prepaid rents $ 704 $ 652 Others 1,179 1,654 $ 1,883 $ 2,306 Noncurrent Prepaid rents $ 2,678 $ 2,212 Others 1 2 $ 2,679 $ 2,214

Other Current Monetary Assets (

Other Current Monetary Assets (Tables)	12 Months Ended
Other Current Monetary Assets (Tables)	Dec. 31, 2020
Disclosure Of Other Current Monetary Assets [Abstract]
Summary of Other Current Monetary Assets	December 31 2019 2020 NT$ NT$ (In Millions) Time deposits and negotiable certificates of deposit with maturities of more than three months $ 5,959 $ 4,596 Repurchase agreements collateralized by bonds with maturities of more than three months 15 — Others 1,524 1,528 $ 7,498 $ 6,124
Annual Yield Rates of Time Deposits, Negotiable Certificates of Deposits and Repurchase Agreements Collateralized by Bonds with Maturities of more Than Three Months	The annual yield rates of time deposits, negotiable certificates of deposit and repurchase agreements collateralized by bonds with maturities of more than three months at the balance sheet dates were as follows: December 31 2019 2020 Time deposits and negotiable certificates of deposit with maturities of more than three months 0.03%-2.73% 0.07%-2.25% Repurchase agreements collateralized by bonds with maturities of more than three months 2.50% —

Subsidiaries (Tables)

Subsidiaries (Tables)	12 Months Ended
Subsidiaries (Tables)	Dec. 31, 2020
Disclosure of subsidiaries [Line Items]
Detail Information of Subsidiaries	The detail information of the subsidiaries at the end of reporting period was as follows: Percentage of Ownership interests December 31 Name of Investor Name of Investee Main Businesses and Products 2019 2020 Note Chunghwa Telecom Co., Ltd. Senao International Co., Ltd. (“SENAO”) Handset and peripherals retailer, sales of CHT mobile phone plans as an agent 28 28 a) Light Era Development Co., Ltd. (“LED”) Planning and development of real estate and intelligent buildings, and property management 100 100 Donghwa Telecom Co., Ltd. (“DHT”) International private leased circuit, IP VPN service, and IP transit services 100 100 Chunghwa Telecom Singapore Pte., Ltd. (“CHTS”) International private leased circuit, IP VPN service, and IP transit services 100 100 Chunghwa System Integration Co., Ltd. (“CHSI”) Providing system integration services and telecommunications equipment 100 100 Chunghwa Investment Co., Ltd. (“CHI”) Investment 89 89 CHIEF Telecom Inc. (“CHIEF”) Network integration, internet data center (“IDC”), communications integration and cloud application services 57 56 b) CHYP Multimedia Marketing & Communications Co., Ltd. (“CHYP”) Digital information supply services and advertisement services 100 100 Prime Asia Investments Group Ltd. (B.V.I.) (“Prime Asia”) Investment 100 100 Spring House Entertainment Tech. Inc. (“SHE”) Software design services, internet contents production and play, and motion picture production and distribution 56 56 c) Chunghwa Telecom Global, Inc. (“CHTG”) International private leased circuit, internet services, and transit services 100 100 Chunghwa Telecom Vietnam Co., Ltd. (“CHTV”) Intelligent energy saving solutions, international circuit, and information and communication technology (“ICT”) services 100 100 Smartfun Digital Co., Ltd. (“SFD”) Providing diversified family education digital services 65 65 Chunghwa Telecom Japan Co., Ltd. (“CHTJ”) International private leased circuit, IP VPN service, and IP transit services 100 100 Chunghwa Sochamp Technology Inc. (“CHST”) Design, development and production of Automatic License Plate Recognition software and hardware 51 51 Honghwa International Co., Ltd. (“HHI”) Telecommunications engineering, sales agent of mobile phone plan application and other business services, etc. 100 100 Chunghwa Leading Photonics Tech Co., Ltd. (“CLPT”) Production and sale of electronic components and finished products 75 75 Chunghwa Telecom (Thailand) Co., Ltd. (“CHTT”) International private leased circuit, IP VPN service, ICT and cloud VAS services 100 100 d) (Continued) Percentage of Ownership interests December 31 Name of Investor Name of Investee Main Businesses and Products 2019 2020 Note CHT Security Co., Ltd. (“CHTSC”) Computing equipment installation, wholesale of computing and business machinery equipment and software, management consulting services, data processing services, digital information supply services and internet identify services 80 80 International Integrated Systems, Inc. (“IISI”) IT solution provider, IT application consultation, system integration and package solution — 51 e) Senao International Co., Ltd. Senao International (Samoa) Holding Ltd. (“SIS”) International investment 100 100 f) Youth Co., Ltd. (“Youth”) Sale of information and communication technologies products 93 96 g) Aval Technologies Co., Ltd. (“Aval”) Sale of information and communication technologies products 100 100 Senyoung Insurance Agent Co., Ltd. (“SENYOUNG”) Property and liability insurance agency 100 100 Youth Co., Ltd. ISPOT Co., Ltd. (“ISPOT”) Sale of information and communication technologies products 100 100 Youyi Co., Ltd. (“Youyi”) Maintenance of information and communication technologies products 100 100 Aval Technologies Co., Ltd. Wiin Technology Co., Ltd. (“Wiin”) Sale of information and communication technologies products 100 100 h) Senyoung Insurance Agent Co., Ltd. Senaolife Insurance Agent Co., Ltd. (“Senaolife”) Life insurance services 100 100 i) Light Era Development Co., Ltd. Taoyuan Asia Silicon Valley Innovation Co., Ltd. (“TASVI”) Development of real estate — — j) CHIEF Telecom Inc. Unigate Telecom Inc. (“Unigate”) Telecommunications and internet service 100 100 Chief International Corp. (“CIC”) Telecommunications and internet service 100 100 Shanghai Chief Telecom Co., Ltd. (“SCT”) Telecommunications and internet service 49 49 k) Chunghwa Investment Co., Ltd. Chunghwa Precision Test Tech. Co., Ltd. (“CHPT”) Production and sale of semiconductor testing components and printed circuit board 34 34 l) Chunghwa Precision Test Tech. Co., Ltd. Chunghwa Precision Test Tech. USA Corporation (“CHPT (US)”) Design and after-sale services of semiconductor testing components and printed circuit board 100 100 CHPT Japan Co., Ltd. (“CHPT (JP)”) Related services of electronic parts, machinery processed products and printed circuit board 100 100 Chunghwa Precision Test Tech. International, Ltd. (“CHPT (International)”) Wholesale and retail of electronic materials, and investment 100 100 Senao International (Samoa) Holding Ltd. Senao International HK Limited (“SIHK”) International investment 100 100 m) (Continued) Percentage of Ownership interests December 31 Name of Investor Name of Investee Main Businesses and Products 2019 2020 Note Senao International HK Limited Senao Trading (Fujian) Co., Ltd. (“STF”) Sale of information and communication technologies products — — n) Senao International Trading (Shanghai) Co., Ltd. (“SITS”) Sale of information and communication technologies products 100 100 o) Senao International Trading (Jiangsu) Co., Ltd. (“SITJ”) Sale of information and communication technologies products — — p) Prime Asia Investments Group Ltd. (B.V.I.) Chunghwa Hsingta Co., Ltd. (“CHC”) Investment 100 100 Chunghwa Hsingta Co., Ltd. Chunghwa Telecom (China) Co., Ltd. (“CTC”) Integrated information and communication solution services for enterprise clients, and intelligent energy network service 100 100 q) Chunghwa Precision Test Tech. International, Ltd. Shanghai Taihua Electronic Technology Limited (“STET”) Design of printed circuit board and related consultation service 100 100 Su Zhou Precision Test Tech. Ltd. (“SZPT”) Assembly processed of circuit board, design of printed circuit board and related consultation service 100 100 r) International Integrated Systems, Inc. Infoexplorer International Co., Ltd.(“IESA”) Investment — 100 s) IISI Investment Co., Ltd. (“IICL”) Investment — 100 s) Unitronics Technology Corp. (“UTC”) Development and maintenance of information system — 99.96 s) Infoexplorer International Co., Ltd. International Integrated Systems (Hong Kong) Limited (“IEHK”) Investment and technical consulting service — 100 s) IISI Investment Co., Ltd. Leading Tech Co., Ltd. (“LTCL”) Investment — 100 s) Leading Tech Co., Ltd. Leading Systems Co., Ltd. (“LSCL”) Investment — 100 s) Leading Systems Co., Ltd. International Integrated Systems Inc. (Shanghai) (“IISS”) Development and maintenance of information system — 100 s) International Integrated Systems Inc. (Shanghai) Huiyu Shanghai Management Consultancy Co., Ltd. (“HSMC”) Development and maintenance of information system — — s) t) (Concluded) a ) Chunghwa continues to control six out of eleven seats of the Board of Directors of SENAO through the support of large beneficial stockholders. As a result, the Company treated SENAO as a subsidiary. b ) CHIEF issued new shares in March 2019, November 2019, March 2020 and December 2020 as its employees exercised options. Therefore, the Company’s ownership interest in CHIEF decreased to 59.75% and 59.08% as of December 31, 2019 and 2020, respectively. c ) SHE reduced 19.72% of its capital to offset accumulated deficits in December 2019 and the Company’s ownership interest in SHE remained the same. d ) The Company increased its investment in CHTT proportionally in October 2019 and the Company’s ownership interest in CHTT remained the same. e ) Chunghwa obtained 20.38% ownership interest in IISI in July 2020 and Chunghwa’s ownership interest in IISI increased to 51.54% by considering the previously held ownership interest in IISI. Chunghwa obtained over half of the seats of the Board of Directors of IISI; therefore, Chunghwa gained control over IISI and treated it as a subsidiary. IISI issued new shares in September 2020 as its employees exercised options; therefore, the Company’s ownership interest in IISI decreased to 51.20% as of December 31, 2020. f ) SIS reduced and returned its capital to its stakeholders in November 2020. The Company’s ownership interest in SIS remained the same. g ) SENAO subscribed for all the shares in the capital increase of Youth in April 2020. Therefore, the Company’s ownership interest in Youth increased from 92.89% to 95.79%. h ) Aval invested 100% equity shares of Wiin Technology Co., Ltd. (“Wiin”) in September 2019. i ) SENYOUNG invested 100% equity shares of Senaolife Insurance Agent Co., Ltd. (“Senaolife”) in November 2019. j ) TASVI completed its liquidation in September 2019. k ) CHIEF has two out of three seats of the Board of Directors of SCT according to the mutual agreements among stockholders and gained control over SCT; hence, SCT is deemed as a subsidiary of the Company. l ) Though the Company’s ownership interest in CHPT is less than 50%, the management considered the absolute and relative size of ownership interest, and the dispersion of shares owned by the other stockholders and concluded that the Company has a sufficiently dominant voting interest to direct the relevant activities; hence, CHPT is deemed as a subsidiary of the Company. m ) SIHK reduced and returned its capital to its stakeholders in November 2020. The Company’s ownership interest in SIHK remained the same. n ) STF completed its liquidation in May 2019. o ) SITS was approved to end and dissolve its business in December 2020. The liquidation of SITS is still in process. p ) SITJ completed its liquidation in March 2019. q ) CTC was approved to end and dissolve its business in August 2020. The liquidation of CTC is still in process. r ) s ) It is a subsidiary of IISI. t) HSMC completed its liquidation in December 2020.
Detailed Information of Equity Transactions	The detailed information of the equity transactions for the years ended December 31, 2018, 2019 and 2020 was as follows: Year Ended December 31, 2018 SENAO not Proportionately participating in the Capital Increase of Youth SENAO Transferred its Treasury Stock CHI Disposed Some Shares of CHPT Chunghwa and CHI Did Not Participate in the Capital Increase of CHIEF Chunghwa and CHI Disposed Some Shares of CHIEF Share-Based Payment of CHIEF NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Cash consideration received from noncontrolling interests $ — $ 327 $ 1,042 $ 1,477 $ 133 $ 35 The proportionate share of the carrying amount of the net assets of the subsidiary transferred to noncontrolling interests — (272 ) (330 ) (700 ) (19 ) (24 ) Differences arising from equity transactions $ — $ 55 $ 712 $ 777 $ 114 $ 11 Line items for equity transaction adjustments Additional paid-in capital - difference between consideration received or paid and the carrying amount of the subsidiaries’ net assets upon actual disposal or acquisition $ — $ — $ 712 $ — $ 114 $ — Additional paid-in capital - arising from changes in equities of subsidiaries $ — $ 55 $ — $ 777 $ — $ 11 Year Ended December 31, 2019 CHIEF Share-Based Payment NT$ (In Millions) Cash consideration received from noncontrolling interests $ 19 The proportionate share of the carrying amount of the net assets of the subsidiary transferred to noncontrolling interests (20 ) Differences arising from equity transactions $ (1 ) Line items for equity transaction adjustments Additional paid-in capital - arising from changes in equities of subsidiaries $ (1 ) Year Ended December 31, 2020 CHIEF Share-Based Payment SENAO Not Proportionately Participating in the Capital Increase of Youth IISI Share-Based Payment NT$ NT$ NT$ (In Millions) Cash consideration received from noncontrolling interests $ 75 $ — $ 7 The proportionate share of the carrying amount of the net assets of the subsidiary transferred to noncontrolling interests (49 ) — (7 ) Differences arising from equity transactions $ 26 $ — $ — Line items for equity transaction adjustments Additional paid-in capital - arising from changes in equities of subsidiaries $ 26 $ — $ —
Summary of Assets Acquired and Liabilities Assumed	2 ) Assets acquired and liabilities assumed at acquisition date IISI and Its Subsidiaries Current assets Cash and cash equivalents $ 588 Contract assets 583 Trade notes and accounts receivable 165 Inventories 141 Prepayments 114 Other current monetary assets 114 Other current assets 75 Noncurrent assets Property, plant and equipment 48 Right-of-use assets 70 Intangible assets 12 Deferred income tax assets 6 Other noncurrent assets 102 Current liabilities Short-term loans (4 ) Contract liabilities (334 ) Trade notes and accounts payable (257 ) Current tax liabilities (19 ) Lease liabilities (26 ) Other payables (266 ) Provisions (15 ) Other current liabilities (30 ) Noncurrent liabilities Deferred income tax liabilities (3 ) Lease liabilities (45 ) Net defined benefit liabilities (32 ) Other noncurrent liabilities (5 ) $ 982
Summary of Goodwill Arising from Acquisition	3 ) Goodwill arising from acquisition IISI and Its Subsidiaries Consideration transferred $ 234 Add: Fair value of equity interest held before the acquisition date 327 Add: Noncontrolling interest (48.46% of the identifiable net assets of IISI and its subsidiaries) 476 Less: Fair value of identifiable net assets acquired (982 ) Goodwill arising from acquisition $ 55
Summary of Net Cash Inflow on Acquisition of Subsidiaries	4 ) Net cash inflow on acquisition of subsidiaries IISI and Its Subsidiaries Cash and cash equivalents acquired $ 588 Less: Consideration paid in cash (234 ) $ 354
Summary of Impact of Acquisition on Financial Results of Company	5 ) Impact of acquisition on the financial results of the Company The financial results of the acquiree since the acquisition date to December 31, 2020 included in the consolidated statements of comprehensive income are as follows: IISI and Its Subsidiaries Revenue $ 1,348 Profit $ 68
Less than wholly owned subsidiaries that have material noncontrolling interests [Member]
Disclosure of subsidiaries [Line Items]
Detail Information of Subsidiaries	The table below shows details of less than wholly owned subsidiaries of the Company that have material noncontrolling interests: Place of Incorporation Proportion of Ownership Interests and Voting Rights Held by Noncontrolling Interests and Principal December 31 Subsidiaries Place of Business 2019 2020 SENAO Taiwan 72% 72% CHPT Taiwan 66% 66% Profit Allocated to Noncontrolling Interests Accumulated Noncontrolling Interests Year Ended December 31 December 31 2018 2019 2020 2019 2020 NT$ NT$ NT$ NT$ NT$ (In Millions) SENAO $ 326 $ 291 $ 312 $ 4,146 $ 4,189 CHPT $ 477 $ 414 $ 604 4,217 4,606 Individually immaterial subsidiaries with noncontrolling interests 1,752 2,363 $ 10,115 $ 11,158
Summarized Financial Information Before Intercompany Eliminations	The summarized financial information below represented amounts before intercompany eliminations. December 31 2019 2020 NT$ NT$ (In Millions) Current assets $ 6,751 $ 6,834 Noncurrent assets $ 3,173 $ 3,194 Current liabilities $ 3,637 $ 3,854 Noncurrent liabilities $ 590 $ 416 Equity attributable to the parent $ 1,551 $ 1,569 Equity attributable to noncontrolling interests $ 4,146 $ 4,189 Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Revenues and income $ 31,540 $ 29,131 $ 27,232 Costs and expenses 31,081 28,725 26,797 Profit for the year $ 459 $ 406 $ 435 Profit attributable to the parent $ 133 $ 115 $ 123 Profit attributable to noncontrolling interests 326 291 312 Profit for the year $ 459 $ 406 $ 435 Other comprehensive income (loss) attributable to the parent $ (2 ) $ (7 ) $ 1 Other comprehensive income (loss) attributable to noncontrolling interests (10 ) 22 2 Other comprehensive income (loss) for the year $ (12 ) $ 15 $ 3 Total comprehensive income attributable to the parent $ 131 $ 108 $ 124 Total comprehensive income attributable to noncontrolling interests 316 313 314 Total comprehensive income for the year $ 447 $ 421 $ 438 Net cash flow from operating activities $ 696 $ 538 $ 862 Net cash flow from investing activities (13 ) 235 54 Net cash flow from financing activities (491 ) (718 ) (687 ) Effect of exchange rate changes on cash and cash equivalents 1 — — Net cash inflow $ 193 $ 55 $ 229 Dividends paid to noncontrolling interests $ 587 $ 269 $ 269 December 31 2019 2020 NT$ NT$ (In Millions) Current assets $ 3,710 $ 4,122 Noncurrent assets $ 4,044 $ 4,013 Current liabilities $ 1,316 $ 1,115 Noncurrent liabilities $ 22 $ 12 Equity attributable to CHI $ 2,199 $ 2,402 Equity attributable to noncontrolling interests $ 4,217 $ 4,606 Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Revenues and income $ 3,299 $ 3,404 $ 4,221 Costs and expenses 2,549 2,775 3,301 Profit for the year $ 750 $ 629 $ 920 Profit attributable to CHI $ 273 $ 215 $ 316 Profit attributable to noncontrolling interests 477 414 604 Profit for the year $ 750 $ 629 $ 920 Other comprehensive loss attributable to CHI $ — $ (1 ) $ — Other comprehensive loss attributable to noncontrolling interests — (2 ) — Other comprehensive loss for the year $ — $ (3 ) $ — Total comprehensive income attributable to CHI $ 273 $ 214 $ 316 Total comprehensive income attributable to noncontrolling interests 477 412 604 Total comprehensive income for the year $ 750 $ 626 $ 920 Net cash flow from operating activities $ 862 $ 507 $ 1,483 Net cash flow from investing activities (733 ) (1,426 ) (533 ) Net cash flow from financing activities (328 ) (349 ) (349 ) Effect of exchange rate changes on cash and cash equivalents 1 (5 ) 1 Net cash inflow (outflow) $ (198 ) $ (1,273 ) $ 602 Dividends paid to noncontrolling interests $ 210 $ 216 $ 216

Investments Accounted for Usi_2

Investments Accounted for Using Equity Method (Tables)	12 Months Ended
Investments Accounted for Using Equity Method (Tables)	Dec. 31, 2020
Disclosure Of Significant Investments In Associates And Joint Ventures [Abstract]
Summary of Investments Accounted for Using Equity Method	December 31 2019 2020 NT$ NT$ (In Millions) Investments in associates $ 7,139 $ 6,685 Investment in joint venture — 10 $ 7,139 $ 6,695
Investments in Associates	a. Investments in associates Carrying Amount December 31 2019 2020 NT$ NT$ (In Millions) Material associate Next Commercial Bank Co., Ltd. (“NCB”) (Note) $ 4,074 $ 3,777 Associates that are not individually material Listed Senao Networks, Inc. (“SNI”) 803 841 KingwayTek Technology Co., Ltd. (“KWT”) 217 213 Non-listed ST-2 Satellite Ventures Pte. Ltd. (“STS”) 501 488 Viettel-CHT Co., Ltd. (“Viettel-CHT”) 317 363 Taiwan International Standard Electronics Co., Ltd. (“TISE”) 268 324 So-net Entertainment Taiwan Limited (“So-net”) 186 225 Chunghwa PChome Fund I Co., Ltd. (“CPFI”) 194 193 KKBOX Taiwan Co., Ltd. (“KKBOXTW”) 151 163 Taiwan International Ports Logistics Corporation (“TIPL”) 51 56 Click Force Co., Ltd. (“CF”) 37 33 Cornerstone Ventures Co., Ltd. (“CVC”) 5 6 Alliance Digital Tech Co., Ltd. (“ADT”) 3 3 UUPON Inc. (“UUPON”) (3 ) — International Integrated System, Inc. (“IISI”) 335 — MeWorks Limited (HK) (“MeWorks”) — — $ 7,139 $ 6,685 The percentages of ownership interests and voting rights in associates held by the Company as of balance sheet dates were as follows: % of Ownership Interests and Voting Rights December 31 2019 2020 Material associate Next Commercial Bank Co., Ltd. (“NCB”) (Note) 42 42 Associates that are not individually material Senao Networks, Inc. (“SNI”) 34 34 KingwayTek Technology Co., Ltd. (“KWT”) 23 23 ST-2 Satellite Ventures Pte., Ltd. (“STS”) 38 38 Viettel-CHT Co., Ltd. (“Viettel-CHT”) 30 30 Taiwan International Standard Electronics Co., Ltd. (“TISE”) 40 40 So-net Entertainment Taiwan Limited (“So-net”) 30 30 Chunghwa PChome Fund I Co., Ltd. (“CPFI”) 50 50 KKBOX Taiwan Co., Ltd. (“KKBOXTW”) 30 30 Taiwan International Ports Logistics Corporation (“TIPL”) 27 27 Click Force Co., Ltd. (“CF”) 49 49 Cornerstone Ventures Co., Ltd. (“CVC”) 49 49 Alliance Digital Tech Co., Ltd. (“ADT”) 14 14 UUPON Inc. (“UUPON”) 22 — International Integrated System, Inc. (“IISI”) 31 — MeWorks Limited (HK) (“MeWorks”) 20 — Summarized financial information of NCB was set out below: December 31 December 31 2019 2020 NT$ NT$ (In Millions) Assets $ 10,452 $ 9,907 Lliabilities (728 ) (789 ) Equity $ 9,724 $ 9,118 The percentage of ownership interests held by the Company 41.9 % 41.9 % Equity attributable to the Company $ 4,074 $ 3,820 Unrealized gain or loss from downstream transactions — (43 ) The carrying amount of investment $ 4,074 $ 3,777 Period from the Beginning Date of Preparation to December 31, 2019 Year Ended December 31, 2020 NT$ NT$ (In Millions) Revenues $ — $ — Net loss for the period $ (276 ) $ (605 ) Other comprehensive income — — Total comprehensive loss for the period $ (276 ) $ (605 ) Summarized financial information of associates that are not individually material to the Company was as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) The Company’s share of profits $ 509 $ 575 $ 540 The Company’s share of other comprehensive income (loss) 5 (3 ) (8 ) The Company’s share of total comprehensive income $ 514 $ 572 $ 532 The Level 1 fair values of associates based on the closing market prices as of the balance sheet dates were as follows: December 31 2019 2020 NT$ NT$ (In Millions) SNI $ 2,014 $ 1,708 KWT $ 873 $ 676
Investments in Joint Ventures	b. Investment in joint venture Carrying Amount % of Ownership Interests and Voting Rights December 31 December 31 Name of Joint Venture 2019 2020 2019 2020 Non-listed Chunghwa SEA Holdings (“CHT SEA”) $ — $ 10 — 51

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
Property, Plant and Equipment (Tables)	Dec. 31, 2020
Disclosure Of Property Plant And Equipment [Line Items]
Summary of Property, Plant and Equipment	December 31 2018 NT$ (In Millions) Carrying amount Land $ 103,972 Land improvements 263 Buildings 44,784 Computer equipment 2,115 Telecommunications equipment 116,322 Transportation equipment 231 Miscellaneous equipment 2,582 Construction in progress and equipment to be accepted 18,645 $ 288,914 Land Land Improvements Buildings Computer Equipment Telecommuni- cations Equipment Transportation Equipment Miscellaneous Equipment Construction in Progress and Equipment to be Accepted Total NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Cost Balance on January 1, 2018 $ 104,079 $ 1,595 $ 72,694 $ 14,162 $ 722,054 $ 3,834 $ 9,515 $ 18,527 $ 946,460 Additions — — 21 52 159 — 334 27,413 27,979 Disposal (71 ) — — (643 ) (31,984 ) (29 ) (623 ) — (33,350 ) Effect of foreign exchange differences — — — — 60 — — — 60 Others (36 ) 6 196 687 25,459 77 648 (27,295 ) (258 ) Balance on December 31, 2018 $ 103,972 $ 1,601 $ 72,911 $ 14,258 $ 715,748 $ 3,882 $ 9,874 $ 18,645 $ 940,891 Accumulated depreciation and impairment Balance on January 1, 2018 $ — $ (1,293 ) $ (26,799 ) $ (11,788 ) $ (607,154 ) $ (3,513 ) $ (7,205 ) $ — $ (657,752 ) Depreciation expenses — (45 ) (1,356 ) (983 ) (24,236 ) (162 ) (679 ) — (27,461 ) Disposal — — — 632 31,952 29 615 — 33,228 Effect of foreign exchange differences — — — — (20 ) — — — (20 ) Others — — 28 (4 ) 32 (5 ) (23 ) — 28 Balance on December 31, 2018 $ — $ (1,338 ) $ (28,127 ) $ (12,143 ) $ (599,426 ) $ (3,651 ) $ (7,292 ) $ — $ (651,977 )
Disclosure Of Property Plant And Equipment Estimated Useful Life Explanatory	Depreciation expense in 2018 is computed using the straight-line method over the following estimated service lives: Land improvements 8-30 years Buildings Main buildings 35-60 years Other building facilities 3-20 years Computer equipment 2-8 years Telecommunications equipment Telecommunication circuits 2-30 years Telecommunication machinery and antennas equipment 2-30 years Transportation equipment 3-10 years Miscellaneous equipment Leasehold improvements 1-6 years Mechanical and air conditioner equipment 3-16 years Others 1-10 years
Summary of Assets Used by the Company	December 31 2019 2020 NT$ NT$ (In Millions) Assets used by the Company $ 276,370 $ 273,823 Assets subject to operating leases 7,324 7,593 $ 283,694 $ 281,416
Summary of Future Aggregate Lease Collection under Operating Lease for Freehold Plant, Property and Equipment	The future aggregate lease collection under operating lease for investment properties is as follows: December 31 2019 2020 NT$ NT$ (In Millions) Year 1 $ 113 $ 115 Year 2 91 95 Year 3 71 75 Year 4 61 53 Year 5 39 38 Onwards 96 58 $ 471 $ 434
Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Summary of Property, Plant and Equipment	b. Assets subject to operating leases Land Land Improvements Buildings Total NT$ NT$ NT$ NT$ (In Millions) Cost Balance on January 1, 2019 $ — $ — $ — $ — Effect of retrospective application of IFRS 16 3,617 1 3,583 7,201 Balance on January 1, 2019 as adjusted 3,617 1 3,583 7,201 Additions — — 4 4 Transferred from (to) assets used by the Company 1,362 (1 ) 255 1,616 Balance on December 31, 2019 $ 4,979 $ — $ 3,842 $ 8,821 Accumulated depreciation and impairment Balance on January 1, 2019 $ — $ — $ — $ — Effect of retrospective application of IFRS 16 — (1 ) (1,265 ) (1,266 ) Balance on January 1, 2019 as adjusted — (1 ) (1,265 ) (1,266 ) Depreciation expenses — — (74 ) (74 ) Transferred to (from) assets used by the company — 1 (158 ) (157 ) Balance on December 31, 2019 $ — $ — $ (1,497 ) $ (1,497 ) Balance on January 1, 2019 as adjusted, net $ 3,617 $ — $ 2,318 $ 5,935 Balance on December 31, 2019, net $ 4,979 $ — $ 2,345 $ 7,324 Cost Balance on January 1, 2020 $ 4,979 $ — $ 3,842 $ 8,821 Others (6 ) — 394 388 Balance on December 31, 2020 $ 4,973 $ — $ 4,236 $ 9,209 Accumulated depreciation and impairment Balance on January 1, 2020 $ — $ — $ (1,497 ) $ (1,497 ) Depreciation expenses — — (82 ) (82 ) Others — — (37 ) (37 ) Balance on December 31, 2020 $ — $ — $ (1,616 ) $ (1,616 ) Balance on December 31, 2020, net $ 4,973 $ — $ 2,620 $ 7,593
Disclosure Of Property Plant And Equipment Estimated Useful Life Explanatory	The above items of property, plant and equipment subject to operating leases are depreciated on a straight-line basis over their estimated useful lives as follows: Land improvements 10-30 years Buildings Main buildings 35-60 years Other building facilities 3-15 years
Summary of Future Aggregate Lease Collection under Operating Lease for Freehold Plant, Property and Equipment	The future aggregate lease collection under operating lease for the freehold plant, property and equipment was as follows: December 31 2019 2020 NT$ NT$ (In Millions) Year 1 $ 302 $ 347 Year 2 273 288 Year 3 234 231 Year 4 191 164 Year 5 130 125 Onwards 1,224 1,180 $ 2,354 $ 2,335
Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Summary of Property, Plant and Equipment	a. Assets used by the Company Land Land Improvements Buildings Computer Equipment Telecommuni- cations Equipment Transportation Equipment Miscellaneous Equipment Construction in Progress and Equipment to be Accepted Total NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Cost Balance on January 1, 2019 $ 103,972 $ 1,601 $ 72,911 $ 14,258 $ 715,748 $ 3,882 $ 9,874 $ 18,645 $ 940,891 Effect of retrospective application of IFRS 16 (3,617 ) (1 ) (3,583 ) — (3,885 ) — — — (11,086 ) Balance on January 1, 2019 as adjusted 100,355 1,600 69,328 14,258 711,863 3,882 9,874 18,645 929,805 Additions — — 1,221 57 120 1 149 21,612 23,160 Disposal (38 ) (7 ) (3 ) (1,916 ) (30,417 ) (51 ) (405 ) — (32,837 ) Effect of foreign exchange differences — — — — (37 ) — (1 ) (6 ) (44 ) Others (1,214 ) 25 455 606 24,503 80 473 (26,499 ) (1,571 ) Balance on December 31, 2019 $ 99,103 $ 1,618 $ 71,001 $ 13,005 $ 706,032 $ 3,912 $ 10,090 $ 13,752 $ 918,513 Accumulated depreciation and impairment Balance on January 1, 2019 $ — $ (1,338 ) $ (28,127 ) $ (12,143 ) $ (599,426 ) $ (3,651 ) $ (7,292 ) $ — $ (651,977 ) Effect of retrospective application of IFRS 16 — 1 1,265 — 2,576 — — — 3,842 Balance on January 1, 2019 as adjusted — (1,337 ) (26,862 ) (12,143 ) (596,850 ) (3,651 ) (7,292 ) — (648,135 ) Depreciation expenses — (43 ) (1,301 ) (827 ) (23,906 ) (91 ) (688 ) — (26,856 ) Disposal — 6 3 1,909 30,380 51 402 — 32,751 Impairment losses — — — — — — (64 ) (29 ) (93 ) Effect of foreign exchange differences — — — — 16 — 1 — 17 Others — (1 ) 183 (7 ) 22 (3 ) (21 ) — 173 Balance on December 31, 2019 $ — $ (1,375 ) $ (27,977 ) $ (11,068 ) $ (590,338 ) $ (3,694 ) $ (7,662 ) $ (29 ) $ (642,143 ) Balance on December 31, 2019, net $ 99,103 $ 243 $ 43,024 $ 1,937 $ 115,694 $ 218 $ 2,428 $ 13,723 $ 276,370 Cost Balance on January 1, 2020 $ 99,103 $ 1,618 $ 71,001 $ 13,005 $ 706,032 $ 3,912 $ 10,090 $ 13,752 $ 918,513 Additions 67 - 18 55 118 1 150 24,786 25,195 Disposal (270 ) (19 ) (49 ) (1,245 ) (20,619 ) (45 ) (520 ) (29 ) (22,796 ) Effect of foreign exchange differences — — — — (91 ) — — (7 ) (98 ) Acquired by business combinations (Note 14) — — — 70 — — 72 — 142 Others 3,091 31 (81 ) 521 25,336 26 508 (29,973 ) (541 ) Balance on December 31, 2020 $ 101,991 $ 1,630 $ 70,889 $ 12,406 $ 710,776 $ 3,894 $ 10,300 $ 8,529 $ 920,415 Accumulated depreciation and impairment Balance on January 1, 2020 $ — $ (1,375 ) $ (27,977 ) $ (11,068 ) $ (590,338 ) $ (3,694 ) $ (7,662 ) $ (29 ) $ (642,143 ) Depreciation expenses — (43 ) (1,366 ) (770 ) (23,994 ) (68 ) (666 ) — (26,907 ) Disposal — 19 49 1,243 20,600 45 504 29 22,489 Effect of foreign exchange differences — — — — 41 — — — 41 Acquired by business combinations (Note 14) — — — (40 ) — — (54 ) — (94 ) Others — — 47 (4 ) 28 (1 ) (48 ) — 22 Balance on December 31, 2020 $ — $ (1,399 ) $ (29,247 ) $ (10,639 ) $ (593,663 ) $ (3,718 ) $ (7,926 ) $ — $ (646,592 ) Balance on December 31, 2020, net $ 101,991 $ 231 $ 41,642 $ 1,767 $ 117,113 $ 176 $ 2,374 $ 8,529 $ 273,823
Disclosure Of Property Plant And Equipment Estimated Useful Life Explanatory	Depreciation expense for assets used by the Company in 2019 and 2020 is computed using the straight-line method over the following estimated service lives: Land improvements 10-30 years Buildings Main buildings 20-60 years Other building facilities 3-15 years Computer equipment 2-8 years Telecommunications equipment Telecommunication circuits 2-30 years Telecommunication machinery and antennas equipment 2-30 years Transportation equipment 3-10 years Miscellaneous equipment Leasehold improvements 1-9 years Mechanical and air conditioner equipment 3-16 years Others 1-15 years

Lease Arrangements (Tables)

Lease Arrangements (Tables)	12 Months Ended
Lease Arrangements (Tables)	Dec. 31, 2020
Disclosure Of Quantitative Information About Leases For Lessee [Abstract]
Summary of Right-of-use Assets	a. December 31 2019 2020 NT$ NT$ (In Millions) Land and buildings Handsets base stations $ 6,845 $ 7,096 Others 1,916 1,708 Equipment 2,603 2,205 $ 11,364 $ 11,009 Year Ended December 31 2019 2020 NT$ NT$ (In Millions) Additions to right-of-use assets $ 3,803 $ 3,796 Depreciation charge for right-of-use assets Land and buildings Handsets base stations $ 2,728 $ 2,729 Others 821 786 Equipment 419 416 $ 3,968 $ 3,931
Summary of Lease Liabilities	b. Lease liabilities December 31 2019 2020 NT$ NT$ (In Millions) Lease liabilities Current $ 3,291 $ 3,382 Noncurrent 6,467 6,215 $ 9,758 $ 9,597
Summary of Range of Discount Rate for Lease Liabilities	Ranges of discount rates for lease liabilities were as follows: December 31 2019 2020 Land and buildings Handsets base stations 0.58%-1.18% 0.46%-1.18% Others 0.58%-9.00% 0.46%-9.00% Equipment 0.58%-4.50% 0.46%-2.99%
Summary of Total Cash Outflow for Leases	d. Year Ended December 31 2019 2020 NT$ NT$ (In Millions) Expenses relating to low-value asset leases $ 7 $ 8 Expenses relating to variable lease payments not included in the measurement of lease liabilities $ 6 $ 5 Total cash outflow for leases $ 3,826 $ 3,776

Investment Properties (Tables)

Investment Properties (Tables)	12 Months Ended
Investment Properties (Tables)	Dec. 31, 2020
Disclosure Of Investment Property [Abstract]
Summary of Investment Properties	December 31 2019 2020 NT$ NT$ (In Millions) Carrying amount Investment properties $ 8,169 $ 9,621 Investment Properties NT$ (In Millions) Cost Balance on January 1, 2018 $ 9,135 Additions 6 Reclassification 251 Balance on December 31, 2018 $ 9,392 Accumulated depreciation and impairment Balance on January 1, 2018 $ (1,087 ) Depreciation expense (21 ) Reclassification (16 ) Reversal of impairment loss 19 Balance on December 31, 2018 $ (1,105 ) Cost Balance on January 1, 2019 $ 9,392 Additions 1 Disposal (6 ) Reclassification (173 ) Balance on December 31, 2019 $ 9,214 Accumulated depreciation and impairment Balance on January 1, 2019 $ (1,105 ) Depreciation expense (25 ) Disposal 6 Reclassification 22 Reversal of impairment loss 57 Balance on December 31, 2019 $ (1,045 ) Cost Balance on January 1, 2020 $ 9,214 Additions (Note 16) 1,359 Disposal (37 ) Reclassification 126 Balance on December 31, 2020 $ 10,662 Accumulated depreciation and impairment Balance on January 1, 2020 $ (1,045 ) Depreciation expense (22 ) Reclassification (1 ) Reversal of impairment loss 27 Balance on December 31, 2020 $ (1,041 )
Estimated Service Lives of Investment Properties	Depreciation expense is computed using the straight-line method over the following estimated service lives: Land improvements 10-30 years Buildings Main buildings 35-60 years Other building facilities 4-10 years
Key Assumptions and Fair Values of Investment Properties	The fair values of the Company’s investment properties as of December 31, 2019 and 2020 were determined by Level 3 fair value measurements inputs based on the appraisal reports conducted by independent appraisers. Those appraisal reports are based on the comparison approach, income approach or cost approach. Key assumptions and the fair values were as follows: December 31 2019 2020 NT$ NT$ (In Millions) Fair value $ 18,701 $ 22,644 Overall capital interest rate 1.03%-4.04% 0.93%-3.03% Profit margin ratio 12%-20% 12%-20% Discount rate — — Capitalization rate 0.79%-1.74% 0.73%-2.20%
Summary of Future Aggregate Lease Collection under Operating Lease for Freehold Plant, Property and Equipment	The future aggregate lease collection under operating lease for investment properties is as follows: December 31 2019 2020 NT$ NT$ (In Millions) Year 1 $ 113 $ 115 Year 2 91 95 Year 3 71 75 Year 4 61 53 Year 5 39 38 Onwards 96 58 $ 471 $ 434

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
Intangible Assets (Tables)	Dec. 31, 2020
Disclosure Of Intangible Assets [Abstract]
Summary of Intangible Assets	December 31 2019 2020 NT$ NT$ (In Millions) Carrying amount Mobile Broadband Concession $ 45,672 $ 89,019 Computer software 931 788 Goodwill 200 246 Others 244 232 $ 47,047 $ 90,285 Mobile Broadband Concession Computer Software Goodwill Others Total NT$ NT$ NT$ NT$ NT$ (In Millions) Cost Balance on January 1, 2018 $ 70,144 $ 3,312 $ 236 $ 418 $ 74,110 Additions-acquired separately — 485 — 13 498 Disposal — (371 ) — (58 ) (429 ) Effect of foreign exchange difference — — — — — Balance on December 31, 2018 $ 70,144 $ 3,426 $ 236 $ 373 $ 74,179 Accumulated amortization and impairment Balance on January 1, 2018 $ (16,675 ) $ (2,432 ) $ (27 ) $ (93 ) $ (19,227 ) Amortization expenses (3,957 ) (406 ) — (23 ) (4,386 ) Disposal — 371 — 58 429 Impairment losses — — — (51 ) (51 ) Effect of foreign exchange difference — — — — — Balance on December 31, 2018 $ (20,632 ) $ (2,467 ) $ (27 ) $ (109 ) $ (23,235 ) Balance on December 31, 2018, net $ 49,512 $ 959 $ 209 $ 264 $ 50,944 Cost Balance on January 1, 2019 $ 70,144 $ 3,426 $ 236 $ 373 $ 74,179 Additions-acquired separately — 358 — 5 363 Disposal (10,179 ) (356 ) — — (10,535 ) Effect of foreign exchange difference — — — — — Others — 2 — — 2 Balance on December 31, 2019 $ 59,965 $ 3,430 $ 236 $ 378 $ 64,009 Accumulated amortization and impairment Balance on January 1, 2019 $ (20,632 ) $ (2,467 ) $ (27 ) $ (109 ) $ (23,235 ) Amortization expenses (3,840 ) (388 ) — (25 ) (4,253 ) Disposal 10,179 356 — — 10,535 Impairment losses — — (9 ) — (9 ) Effect of foreign exchange difference — — — — — Balance on December 31, 2019 $ (14,293 ) $ (2,499 ) $ (36 ) $ (134 ) $ (16,962 ) Balance on December 31, 2019, net $ 45,672 $ 931 $ 200 $ 244 $ 47,047 Cost Balance on January 1, 2020 $ 59,965 $ 3,430 $ 236 $ 378 $ 64,009 Additions-acquired separately 48,373 226 — 6 48,605 Disposal — (338 ) — (3 ) (341 ) Effect of foreign exchange difference — — — — — Acquired by business combinations (Note 14) — 1 55 11 67 Others — 1 — — 1 Balance on December 31, 2020 $ 108,338 $ 3,320 $ 291 $ 392 $ 112,341 Accumulated amortization and impairment Balance on January 1, 2020 $ (14,293 ) $ (2,499 ) $ (36 ) $ (134 ) $ (16,962 ) Amortization expenses (5,026 ) (371 ) — (27 ) (5,424 ) Disposal — 338 — 1 339 Impairment losses — — (9 ) — (9 ) Effect of foreign exchange difference — — — — — Acquired by business combinations (Note 14) — — — — — Balance on December 31, 2020 $ (19,319 ) $ (2,532 ) $ (45 ) $ (160 ) $ (22,056 ) Balance on December 31, 2020, net $ 89,019 $ 788 $ 246 $ 232 $ 90,285

Other Assets (Tables)

Other Assets (Tables)	12 Months Ended
Other Assets (Tables)	Dec. 31, 2020
Miscellaneous Assets [Abstract]
Summary of Other Assets	December 31 2019 2020 NT$ NT$ (In Millions) Spare parts $ 2,336 $ 2,156 Refundable deposits 1,879 2,009 Other financial assets 1,000 1,000 Deposit for mobile broadband license bidding (Note 19) 1,000 — Others 2,316 2,450 $ 8,531 $ 7,615 Current Spare parts $ 2,336 $ 2,156 Others 94 193 $ 2,430 $ 2,349 Noncurrent Refundable deposits $ 1,879 $ 2,009 Other financial assets 1,000 1,000 Deposit for mobile broadband license bidding 1,000 — Others 2,222 2,257 $ 6,101 $ 5,266

Hedging Financial Instruments (

Hedging Financial Instruments (Tables)	12 Months Ended
Hedging Financial Instruments (Tables)	Dec. 31, 2020
Disclosure Of Detailed Information About Hedging Instruments [Line Items]
Summary of Hedging Transaction and Reclassification Affected Comprehensive Income	2018 Comprehensive Income Reclassification from Equity to Profit or Loss and the Adjusted Line Item Hedging Gain or Loss Amount of Hedge Ineffectiveness Line Item in Which Hedge Amount Reclassified to P/L and Due to Hedged Future Cash Flows No Hedge Recognized Recognized in Ineffectiveness the Adjusted Longer Expected Transaction in OCI Profit or Loss is Included Line Item to Occur NT$ NT$ NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast equipment purchases $ 2 $ — — $ (4 ) $ — Construction in progress and equipment to be accepted Other gains and losses 2019 Comprehensive Income Reclassification from Equity to Profit or Loss and the Adjusted Line Item Hedging Gain or Loss Amount of Hedge Ineffectiveness Line Item in Which Hedge Amount Reclassified to P/L and Due to Hedged Future Cash Flows No Hedge Recognized Recognized in Ineffectiveness the Adjusted Longer Expected Transaction in OCI Profit or Loss is Included Line Item to Occur NT$ NT$ NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast equipment purchases $ (1 ) $ — — $ (2 ) $ — Construction in progress and equipment to be accepted Other gains and losses 2020 Comprehensive Income Reclassification from Equity to Profit or Loss and the Adjusted Line Item Hedging Gain or Loss Amount of Hedge Ineffectiveness Line Item in Which Hedge Amount Reclassified to P/L and Due to Hedged Future Cash Flows No Hedge Recognized Recognized in Ineffectiveness the Adjusted Longer Expected Transaction in OCI Profit or Loss is Included Line Item to Occur NT$ NT$ NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast equipment purchases $ 2 $ — — $ 21 $ — Construction in progress and equipment to be accepted Other gains and losses
Foreign currency risk [Member]
Disclosure Of Detailed Information About Hedging Instruments [Line Items]
Summary of Hedging Derivative Financial Instruments	The following tables summarized the information relating to the hedges for foreign currency risk. December 31, 2018 Notional Forward Line Item in Carrying Amount Change in Fair Values of Hedging Instruments Used for Calculating Hedge Hedging Instruments Currency Amount Maturity Rate Balance Sheet Asset Liability Ineffectiveness (In Millions) NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast purchases - forward exchange contracts NT$/EUR NT$ 172/ EUR 5 2019.03 $ 34.98 Hedging financial assets (liabilities) $ 1 $ — $ 2 Change in Value of Hedged Item Used for Accumulated Gain or Loss on Hedging Instruments in Other Equity Hedged Items Calculating Hedge Ineffectiveness Continuing Hedges Hedge Accounting No Longer Applied NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast equipment purchases $ (2 ) $ 1 $ — December 31, 2019 Notional Forward Line Item in Carrying Amount Change in Fair Values of Hedging Instruments Used for Calculating Hedge Hedging Instruments Currency Amount Maturity Rate Balance Sheet Asset Liability Ineffectiveness (In Millions) NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast purchases - forward exchange contracts NT$/EUR NT$ 84/EUR 2 2020.03 $ 33.66 Hedging financial assets (liabilities) $ — $ — $ (1 ) Change in Value of Hedged Item Used for Accumulated Gain or Loss on Hedging Instruments in Other Equity Hedged Items Calculating Hedge Ineffectiveness Continuing Hedges Hedge Accounting No Longer Applied NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast equipment purchases $ 1 $ — $ — December 31, 2020 Notional Forward Line Item in Carrying Amount Change in Fair Values of Hedging Instruments Used for Calculating Hedge Hedging Instruments Currency Amount Maturity Rate Balance Sheet Asset Liability Ineffectiveness (In Millions) NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast purchases - forward exchange contracts NT$/EUR NT$ 201/ EUR 6 2021.03 $ 34.45 Hedging financial assets (liabilities) $ 2 $ — $ 2 Change in Value of Hedged Item Used for Accumulated Gain or Loss on Hedging Instruments in Other Equity Hedged Items Calculating Hedge Ineffectiveness Continuing Hedges Hedge Accounting No Longer Applied NT$ NT$ NT$ (In Millions) Cash flow hedge Forecast equipment purchases $ (2 ) $ 2 $ —

Short-Term Loans (Tables)

Short-Term Loans (Tables)	12 Months Ended
Short-Term Loans (Tables)	Dec. 31, 2020
Short-term loans [Member]
Disclosure of detailed information about borrowings [Line Items]
Summary of Loans	December 31 2019 2020 NT$ NT$ (In Millions) Unsecured bank loans $ 90 $ 67 The annual interest rates of bank loans were as follows: December 31 2019 2020 Unsecured bank loans 1.20%-2.50% 1.12%-2.33%

Short-term Bills Payable (Table

Short-term Bills Payable (Tables)	12 Months Ended
Short-term Bills Payable (Tables)	Dec. 31, 2020
Short Term Bills Payable [Abstract]
Summary of Short-term Bills Payable	December 31 2019 2020 NT$ NT$ (In Millions) Commercial paper payable $ — $ 7,000 Less: Discounts on commercial paper payable — $ (1 ) $ — $ 6,999
Summary of Annual Interest Rates of Commercial Paper Payable	The annual interest rates of commercial paper payable were as follows: December 31 2019 2020 Commercial paper payable — 0.34%-0.36%

Long-Term Loans (Tables)

Long-Term Loans (Tables)	12 Months Ended
Long-Term Loans (Tables)	Dec. 31, 2020
Long-term loans [Member]
Disclosure of detailed information about borrowings [Line Items]
Summary of Loans	December 31 2019 2020 NT$ NT$ (In Millions) Secured bank loans (Note 41) $ 1,600 $ 1,600 Less: Current portion — (1,600 ) $ 1,600 $ — The annual interest rates of bank loans were as follows: December 31 2019 2020 Secured loans 0.92% 0.72%

Bonds Payable (Tables)

Bonds Payable (Tables)	12 Months Ended
Bonds Payable (Tables)	Dec. 31, 2020
Disclosure Of Bonds Payable [Abstract]
Summary of Bonds Payable	December 31 2019 2020 NT$ NT$ (In Millions) Unsecured domestic bonds $ — $ 20,000 Less: Discounts on bonds payable — (20 ) $ — $ 19,980
Summary of Major Terms of Unsecured Domestic Bonds Issued	The major terms of unsecured domestic bonds issued by Chunghwa were as follows: Issuance Tranche Issuance Period Total Amount Coupon Rate Repayment and Interest Payment 2020-1 A July 2020 to July 2025 $ 8,800 0.50% One-time repayment upon maturity; interest payable annually B July 2020 to July 2027 7,500 0.54% The same as above C July 2020 to July 2030 3,700 0.59% The same as above

Trade Notes and Accounts Paya_2

Trade Notes and Accounts Payable (Tables)	12 Months Ended
Trade Notes and Accounts Payable (Tables)	Dec. 31, 2020
Trade And Other Current Payables [Abstract]
Summary of Trade Notes and Accounts Payable	December 31 2019 2020 NT$ NT$ (In Millions) Trade notes and accounts payable $ 15,312 $ 15,591

Other Payables (Tables)

Other Payables (Tables)	12 Months Ended
Other Payables (Tables)	Dec. 31, 2020
Trade And Other Current Payables [Abstract]
Summary of Other Payables	December 31 2019 2020 NT$ NT$ (In Millions) Accrued salary and compensation $ 9,482 $ 9,450 Payables to contractors 1,892 1,779 Accrued compensation to employees and remuneration to directors and supervisors 1,441 1,691 Amounts collected for others 1,279 1,308 Payable on land (Note 16) — 1,057 Payables to equipment suppliers 296 1,049 Accrued maintenance costs 955 1,040 Accrued franchise fees 1,091 785 Others 6,517 5,829 $ 22,953 $ 23,988

Provisions (Tables)

Provisions (Tables)	12 Months Ended
Provisions (Tables)	Dec. 31, 2020
Provisions [Abstract]
Summary of Provisions	December 31 2019 2020 NT$ NT$ (In Millions) Warranties $ 173 $ 182 Onerous contracts 67 171 Employee benefits 59 57 Others 5 5 $ 304 $ 415 Current $ 207 $ 314 Noncurrent 97 101 $ 304 $ 415
Movements in Provisions	Warranties Onerous Contracts Employee Benefits Others Total NT$ NT$ NT$ NT$ NT$ (In Millions) Balance on January 1, 2018 $ 132 $ — $ 43 $ 5 $ 180 Additional provisions recognized 164 19 9 — 192 Used / forfeited during the year (164 ) — (1 ) — (165 ) Balance on December 31, 2018 $ 132 $ 19 $ 51 $ 5 $ 207 Balance on January 1, 2019 $ 132 $ 19 $ 51 $ 5 $ 207 Additional provisions recognized 127 48 9 — 184 Used / forfeited during the year (86 ) — (1 ) — (87 ) Balance on December 31, 2019 $ 173 $ 67 $ 59 $ 5 $ 304 Balance on January 1, 2020 $ 173 $ 67 $ 59 $ 5 $ 304 Additional/(reversal of) provisions recognized 131 92 (2 ) — 221 Used / forfeited during the year (122 ) (3 ) — — (125 ) Acquired by business combinations (Note 14) — 15 — — 15 Balance on December 31, 2020 $ 182 $ 171 $ 57 $ 5 $ 415 a. The provision for warranty claims represents the present value of the management’s best estimate of the future outflow of economic benefits that will be required under the Company’s obligation for warranties in sales agreements. The estimate has been made based on the historical warranty experience. b. The provision for employee benefits represents vested long-term service compensation accrued. c . The provision for onerous contracts represents the present obligation resulting from the measurement for the unavoidable costs of meeting the Company’s contractual obligations exceed the economic benefits expected to be received from the contracts.

Retirement Benefit Plans (Table

Retirement Benefit Plans (Tables)	12 Months Ended
Retirement Benefit Plans (Tables)	Dec. 31, 2020
Disclosure Of Retirement Benefit Plans [Abstract]
Amounts Included in Consolidated Balance Sheets from Obligation in Respect of Defined Benefit Plans	The amounts included in the consolidated balance sheets arising from the Company’s obligation in respect of its defined benefit plans were as follows: December 31 2019 2020 NT$ NT$ (In Millions) Present value of funded defined benefit obligations $ 41,197 $ 39,536 Fair value of plan assets (39,820 ) (39,494 ) Funded status - deficit $ 1,377 $ 42 Net defined benefit liabilities $ 3,505 $ 3,415 Net defined benefit assets (2,128 ) (3,373 ) $ 1,377 $ 42
Movements in Defined Benefit Obligation and Fair Value of Plan Assets	Movements in the defined benefit obligations and the fair value of plan assets were as follows: Present Value of Funded Defined Benefit Obligations Fair Value of Plan Assets Net Defined Benefit Liabilities (Assets) NT$ NT$ NT$ (In Millions) Balance on January 1, 2018 $ 37,663 $ 34,972 $ 2,691 Current service cost 3,024 — 3,024 Interest expense/interest income 550 544 6 Amounts recognized in profit or loss 3,574 544 3,030 Remeasurement on the net defined benefit liability Return on plan assets (excluding amounts included in net interest) — 875 (875 ) Actuarial losses recognized from changes in demographic assumptions 4 — 4 Actuarial losses recognized from changes in financial assumptions 1,273 — 1,273 Actuarial losses recognized from experience adjustments 813 — 813 Amounts recognized in other comprehensive income 2,090 875 1,215 Contributions from employer — 4,374 (4,374 ) Benefits paid (1,738 ) (1,738 ) — Benefits paid directly by the Company (192 ) — (192 ) Balance on December 31, 2018 41,397 39,027 2,370 Current service cost 2,927 — 2,927 Interest expense/interest income 400 390 10 Amounts recognized in profit or loss 3,327 390 2,937 Remeasurement on the net defined benefit liability Return on plan assets (excluding amounts included in net interest) — 1,338 (1,338 ) Actuarial losses recognized from changes in demographic assumptions 6 — 6 Actuarial losses recognized from changes in financial assumptions 647 — 647 Actuarial gains recognized from experience adjustments (842 ) — (842 ) Amounts recognized in other comprehensive income (189 ) 1,338 (1,527 ) Contributions from employer — 2,099 (2,099 ) Benefits paid (3,034 ) (3,034 ) — Benefits paid directly by the Company (304 ) — (304 ) Balance on December 31, 2019 41,197 39,820 1,377 Current service cost 2,052 — 2,052 Interest expense/interest income 298 297 1 Amounts recognized in profit or loss 2,350 297 2,053 Remeasurement on the net defined benefit liability Return on plan assets (excluding amounts included in net interest) — 1,308 (1,308 ) Actuarial losses recognized from changes in financial assumptions 590 — 590 Actuarial gains recognized from experience adjustments (475 ) — (475 ) Amounts recognized in other comprehensive income 115 1,308 (1,193 ) Contributions from employer — 1,964 (1,964 ) Benefits paid (3,919 ) (3,919 ) — Benefits paid directly by the Company (263 ) — (263 ) Acquired by business combinations (Note 14) 56 24 32 Balance on December 31, 2020 $ 39,536 $ 39,494 $ 42
Pension Costs Recognized in Profit and Loss for Defined Benefit Plans	Relevant pension costs recognized in profit and loss for defined benefit plans were as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Operating costs $ 1,796 $ 1,726 $ 1,205 Marketing expenses 886 866 603 General and administrative expenses 164 164 121 Research and development expenses 107 103 72 $ 2,953 $ 2,859 $ 2,001
Principal Assumptions Used for Actuarial Valuations	The principal assumptions used for the purpose of the actuarial valuations were as follows: Measurement Date December 31 2019 2020 Discount rates 0.75% 0.50% Expected rates of salary increase 1.20%-2.00% 1.00%-2.00%
Effect on Present Value of Defined Benefit Obligation Due to a Reasonably Possible Change of the Significant Actuarial Assumptions	If reasonably possible changes of the respective significant actuarial assumptions occur at the end of reporting periods, while holding all other assumptions constant, the present values of the defined benefit obligations would increase (decrease) as follows: December 31 2019 2020 NT$ NT$ (In Millions) Discount rates 0.5% increase $ (1,275 ) $ (1,208 ) 0.5% decrease $ 1,356 $ 1,284 Expected rates of salary increase 0.5% increase $ 1,448 $ 1,372 0.5% decrease $ (1,374 ) $ (1,303 )
Summary of Sensitivity Analysis	December 31 2019 2020 NT$ NT$ (In Millions) The expected contributions to the plan for the next year $ 2,076 $ 1,932 The average duration of the defined benefit obligations 6.5-14 years 6.4-13 years
Maturity Analysis of Undiscounted Benefit Payments	As of December 31, 2020, the Company’s maturity analysis of the undiscounted benefit payments was as follows: Year Amount NT$ (In Millions) 2021 $ 3,285 2022 7,056 2023 10,669 2024 11,799 2025 and thereafter 39,497 $ 72,306

Equity (Tables)

Equity (Tables)	12 Months Ended
Equity (Tables)	Dec. 31, 2020
Disclosure Of Classes Of Share Capital [Line Items]
Summary of Common Stocks	1) Common stocks December 31 2019 2020 NT$ NT$ (In Millions) Number of authorized shares 12,000 12,000 Authorized shares $ 120,000 $ 120,000 Number of issued and paid shares 7,757 7,757 Issued and outstanding shares $ 77,574 $ 77,574
Adjustments of Additional Paid-in Capital	The adjustments of additional paid-in capital for the years ended December 31, 2018, 2019 and 2020 were as follows: Share Premium Movements of Additional Paid-in Capital for Associates and Joint Ventures Accounted for Using Equity Method Movements of Additional Paid-in Capital Arising from Changes in Equities of Subsidiaries Difference between Consideration Received and Carrying Amount of the Subsidiaries’ Net Assets upon Disposal Donated Capital Stockholders’ Contribution Due to Privatization Total NT$ NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Balance on January 1, 2018 $ 126,045 $ — $ 1,221 $ 161 $ 16 $ 20,648 $ 148,091 Unclaimed dividend — — — — 2 — 2 Partial disposal of interests in subsidiaries — — — 826 — — 826 Change in additional paid-in capital for not participating in the capital increase of a subsidiary — — 777 — — — 777 Share-based payment transactions of subsidiaries — — 11 — — — 11 Treasury stock transfer of subsidiaries — — 55 — — — 55 Balance on December 31, 2018 $ 126,045 $ — $ 2,064 $ 987 $ 18 $ 20,648 $ 149,762 Balance on January 1, 2019 $ 126,045 $ — $ 2,064 $ 987 $ 18 $ 20,648 $ 149,762 Unclaimed dividend — — — — 1 — 1 Share-based payment transactions of subsidiaries — — (1 ) — — — (1 ) Balance on December 31, 2019 $ 126,045 $ — $ 2,063 $ 987 $ 19 $ 20,648 $ 149,762 Balance on January 1, 2020 $ 126,045 $ — $ 2,063 $ 987 $ 19 $ 20,648 $ 149,762 Unclaimed dividend — — — — 2 — 2 Change in additional paid-in capital for not participating in the capital increase of a subsidiary — — — — — — — Share-based payment transactions of subsidiaries — — 26 — — — 26 Balance on December 31, 2020 $ 126,045 $ — $ 2,089 $ 987 $ 21 $ 20,648 $ 149,790
Appropriations of Earnings	The appropriations of the 2018 and 2019 earnings of Chunghwa approved by the stockholders in their meetings on June 21, 2019 and May 29, 2020 were as follows: Appropriation of Earnings Dividends Per Share (NT$) For Fiscal Year 2018 For Fiscal Year 2019 For Fiscal Year 2018 For Fiscal Year 2019 Cash dividends $ 34,746 $ 32,783 $ 4.479 $ 4.226 The appropriations of earnings for 2020 had been proposed by Chunghwa’s Board of Directors on February 23, 2021. The appropriations and dividends per share were as follows: Appropriation of Earnings Dividends Per Share (NT$) Cash dividends $ 33,404 $ 4.306
Noncontrolling Interests	e. Noncontrolling interests Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Beginning balance $ 8,470 $ 9,857 $ 10,115 Effect of retrospective application of IFRS 16 — (20 ) — Beginning balance as adjusted 8,470 9,837 10,115 Attributable to noncontrolling interests Net income for the year 1,024 974 1,285 Exchange differences arising from the translation of the net investment in foreign operations (3 ) 8 (14 ) Unrealized gain or loss on financial assets at FVOCI (1 ) (26 ) (3 ) Remeasurements of defined benefit pension plans (9 ) 15 17 Income tax relating to remeasurements of defined benefit pension plans 3 (3 ) (3 ) Share of other comprehensive income (loss) of associates and joint ventures accounted for using equity method 1 (1 ) (1 ) Cash dividends distributed by subsidiaries (958 ) (710 ) (775 ) Partial disposal of interests in subsidiaries 349 — — Share-based payment transactions of subsidiaries 42 22 63 Change in additional paid-in capital for not proportionately participating in the capital increase of subsidiaries 700 — — Change in additional paid-in capital from investments in associates and joint ventures accounted for using equity method — — (2 ) Other changes in additional paid-in capital of subsidiaries — — — Net increase (decrease) in noncontrolling interests 239 (1 ) 476 Ending balance $ 9,857 $ 10,115 $ 11,158
FVOCI [Member]
Disclosure Of Classes Of Share Capital [Line Items]
Unrealized Gain or Loss on Financial Assets at FVOCI	2 ) Unrealized gain or loss on financial assets at FVOCI Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Beginning balance $ 883 $ 538 $ 735 Unrealized gain or loss for the year Equity instruments (345 ) 197 522 Transferred accumulated gain or loss to unappropriated earnings resulting from the disposal of equity instruments (Note 9) — — (17 ) Ending balance $ 538 $ 735 $ 1,240

Revenue (Tables)

Revenue (Tables)	12 Months Ended
Revenue (Tables)	Dec. 31, 2020
Revenue [Abstract]
Summary of Revenue	Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Revenue from contracts with customers $ 214,461 $ 206,360 $ 206,396 Other revenues Rental income 640 818 843 Others 382 342 370 1,022 1,160 1,213 Total $ 215,483 $ 207,520 $ 207,609
Summary of Disaggregation of Revenue	a. Disaggregation of revenue 2018 Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Main Products and Service Revenues Mobile services revenue $ — $ 63,906 $ — $ — $ — $ 63,906 Sales of products 1,731 35,702 4 251 3,601 41,289 Local telephone and domestic long distance telephone services revenue 29,996 — — — — 29,996 Broadband access and domestic leased line services revenue 22,453 — — — — 22,453 Data Communications internet services revenue — — 21,137 — — 21,137 International network and leased line services revenue — — — 8,724 — 8,724 Others 11,923 1,269 8,509 4,449 806 26,956 $ 66,103 $ 100,877 $ 29,650 $ 13,424 $ 4,407 $ 214,461 2019 Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Main Products and Service Revenues Mobile services revenue $ — $ 58,703 $ — $ — $ — $ 58,703 Sales of products 1,957 35,545 41 265 3,785 41,593 Local telephone and domestic long distance telephone services revenue 27,929 — — — — 27,929 Broadband access and domestic leased line services revenue 22,116 — — — — 22,116 Data Communications internet services revenue — — 21,003 — — 21,003 International network and leased line services revenue — — — 7,066 — 7,066 Others 13,064 1,142 8,790 4,144 810 27,950 $ 65,066 $ 95,390 $ 29,834 $ 11,475 $ 4,595 $ 206,360 2020 Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Main Products and Service Revenues Mobile services revenue $ — $ 56,724 $ — $ — $ — $ 56,724 Sales of products 2,214 32,112 107 313 4,645 39,391 Local telephone and domestic long distance telephone services revenue 26,475 — — — — 26,475 Broadband access and domestic leased line services revenue 22,420 — — — — 22,420 Data Communications internet services revenue — — 21,447 — — 21,447 International network and leased line services revenue — — — 3,884 — 3,884 Others 17,695 1,307 10,255 4,485 2,313 36,055 $ 68,804 $ 90,143 $ 31,809 $ 8,682 $ 6,958 $ 206,396
Summary of Contract Balances	b. Contract balances January 1 December 31 2019 2019 2020 NT$ NT$ NT$ (In Millions) Trade notes and accounts receivable (Note 10) $ 30,076 $ 26,408 $ 22,622 Contract assets Products and service bundling $ 7,123 $ 6,943 $ 7,232 Others 109 116 612 Less : Loss allowance (19 ) (17 ) (18 ) $ 7,213 $ 7,042 $ 7,826 Current $ 4,869 $ 4,441 $ 5,331 Noncurrent 2,344 2,601 2,495 $ 7,213 $ 7,042 $ 7,826 Contract liabilities Telecommunications business $ 8,193 $ 12,772 $ 13,602 Project business 4,508 10,360 6,687 Products and service bundling 106 39 16 Others 476 510 421 $ 13,283 $ 23,681 $ 20,726 Current $ 10,688 $ 16,840 $ 13,437 Noncurrent 2,595 6,841 7,289 $ 13,283 $ 23,681 $ 20,726
Summary of Changes in Contract Assets and Contract Liabilities	Significant changes of contract assets and liabilities recognized resulting from product and service bundling were as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Contract assets Net increase of customer contracts $ 4,126 $ 6,066 $ 5,972 Reclassified to trade receivables (7,532 ) (6,405 ) (5,681 ) $ (3,406 ) $ (339 ) $ 291 Contract liabilities Net increase of customer contracts $ 16 $ 22 $ 7 Recognized as revenues (194 ) (89 ) (30 ) $ (178 ) $ (67 ) $ (23 )
Summary of Revenue Recognized	Revenue recognized for the period that was included in the contract liability at the beginning of the year was as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Telecommunications business $ 7,157 $ 6,186 $ 5,492 Project business 627 3,973 6,092 Others 324 404 512 $ 8,108 $ 10,563 $ 12,096
Summary of Incremental Costs of Obtaining Contracts	c. Incremental costs of obtaining contracts December 31 2019 2020 NT$ NT$ (In Millions) Noncurrent Incremental costs of obtaining contracts $ 943 $ 1,000

Net Income (Tables)

Net Income (Tables)	12 Months Ended
Net Income (Tables)	Dec. 31, 2020
Analysis Of Income And Expense [Abstract]
Other Income and Expenses	a. Other income and expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Gain (loss) on disposal of property, plant and equipment $ 142 $ (38 ) $ 1,428 Impairment loss on property, plant and equipment — (93 ) — Gain on disposal of investment properties — — 151 Reversal of impairment loss on investment properties 19 57 27 Loss on disposal of intangible assets — — (2 ) Impairment loss on intangible assets (51 ) (9 ) (9 ) Impairment loss on other assets — (44 ) — $ 110 $ (127 ) $ 1,595
Other Income	b. Other income Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Dividend income $ 396 $ 296 $ 246 Rental income 70 85 70 Others 234 150 154 $ 700 $ 531 $ 470
Other Gains and Losses	c. Other gains and losses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Foreign currency exchange gain or loss, net $ 37 $ 16 $ (47 ) Gain or loss on disposal of investments accounted for using equity method — 151 10 Gain (loss) on disposal of financial instruments 6 4 (2 ) Valuation gain or loss on financial assets and liabilities at fair value through profit or loss, net (21 ) (38 ) (99 ) Others (68 ) (49 ) (21 ) $ (46 ) $ 84 $ (159 )
Interest Expenses	d. Interest expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Interest paid to financial institutions $ 16 $ 17 $ 79 Interest on lease liabilities — 85 80 Interest on bonds payable — — 46 Others 2 2 1 $ 18 $ 104 $ 206
Impairment Loss (Reversal of Impairment Loss) on Financial Instruments and Non-financial Assets	e . Impairment loss (reversal of impairment loss) Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Contract assets $ 19 $ (2 ) $ 1 Trade notes and accounts receivable $ 805 $ (54 ) $ 49 Other receivables $ 96 $ (69 ) $ (5 ) Inventories $ 365 $ 475 $ 1,161 Property, plant and equipment $ — $ 93 $ — Investment properties $ (19 ) $ (57 ) $ (27 ) Intangible assets $ 51 $ 9 $ 9 Other assets $ — $ 44 $ —
Depreciation and Amortization Expenses	f . Depreciation and amortization expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Property, plant and equipment $ 27,461 $ 26,930 $ 26,989 Right-of-use assets — 3,968 3,931 Investment properties 21 25 22 Intangible assets 4,386 4,253 5,424 Incremental costs of obtaining contracts 1,941 1,173 772 Total depreciation and amortization expenses $ 33,809 $ 36,349 $ 37,138 Depreciation expenses summarized by functions Operating costs $ 25,996 $ 28,957 $ 29,056 Operating expenses 1,486 1,966 1,886 $ 27,482 $ 30,923 $ 30,942 Amortization expenses summarized by functions Operating costs $ 6,085 $ 5,196 $ 5,971 Marketing expenses 113 96 100 General and administrative expenses 93 95 82 Research and development expenses 36 39 43 $ 6,327 $ 5,426 $ 6,196
Employee Benefit Expenses	g . Employee benefit expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Post-employment benefit Defined contribution plans $ 640 $ 654 $ 708 Defined benefit plans 2,953 2,859 2,001 3,593 3,513 2,709 Share-based payment Equity-settled share-based payment 17 2 8 Other employee benefit Salaries 26,204 25,464 26,630 Insurance 2,740 2,746 2,712 Others 14,470 14,430 12,904 43,414 42,640 42,246 Total employee benefit expenses $ 47,024 $ 46,155 $ 44,963 Summary by functions Operating costs $ 24,367 $ 23,587 $ 23,005 Operating expenses 22,657 22,568 21,958 $ 47,024 $ 46,155 $ 44,963 The compensation to the employees and remuneration to the directors of 2018 and 2019 approved by the Board of Directors on March 19, 2019 and February 26, 2020, respectively, were as follows: 2018 2019 Cash Cash NT$ NT$ (In Millions) Compensation distributed to the employees $ 1,404 $ 1,126 Remuneration paid to the directors 38 35

Income Tax (Tables)

Income Tax (Tables)	12 Months Ended
Income Tax (Tables)	Dec. 31, 2020
Major Components Of Tax Expense Income [Abstract]
Major Components of Income Tax Expense	The major components of income tax expense were as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Current tax Current tax expenses recognized for the year $ 8,271 $ 8,109 $ 8,172 Income tax on unappropriated earnings (2,070 ) (20 ) 8 Income tax adjustments on prior years 7 (91 ) (22 ) Others 8 12 19 6,216 8,010 8,177 Deferred tax Deferred tax expense (benefits) recognized for the year 208 (63 ) (81 ) Income tax adjustments on prior years 19 (1 ) 26 Change in tax rate (38 ) — — 189 (64 ) (55 ) Income tax expense recognized in profit or loss $ 6,405 $ 7,946 $ 8,122
Reconciliation of Accounting Profit and Income Tax Expense	Reconciliation of accounting profit and income tax expense was as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Income before income tax $ 44,986 $ 41,867 $ 42,826 Income tax expense calculated at the statutory rate $ 8,997 $ 8,373 $ 8,565 Nondeductible income and expenses in determining taxable income 227 18 15 Unrecognized deductible temporary differences 1 3 (5 ) Unrecognized loss carryforwards 21 7 4 Tax-exempt income (580 ) (148 ) (367 ) Additional income tax under Alternative Minimum Tax Act 46 — — Income tax on unappropriated earnings (2,070 ) (20 ) 8 Investment credits (204 ) (203 ) (131 ) Change in tax rate (38 ) — — Effect of different tax rates of group entities operating in other jurisdictions (15 ) (9 ) 10 Income tax adjustments on prior years 26 (92 ) 4 Others (6 ) 17 19 Income tax expense recognized in profit or loss $ 6,405 $ 7,946 $ 8,122
Income Tax Recognized in Other Comprehensive Income	b. Income tax recognized in other comprehensive income Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Deferred tax Remeasurement on defined benefit pension plans $ (243 ) $ 305 $ 239 Change in tax rate - defined benefit pension plans (207 ) — — Total income tax expense (benefit) recognized in other comprehensive income $ (450 ) $ 305 $ 239
Current Tax Assets and Liabilities	c. Current tax assets and liabilities December 31 2019 2020 NT$ NT$ (In Millions) Current tax assets Tax refund receivable (included in other current assets - others) $ 1 $ 1 Current tax liabilities Income tax payable $ 5,812 $ 6,157
Movements of Deferred Income Tax Assets and Liabilities	Deferred income tax assets and liabilities The movements of deferred income tax assets and liabilities were as follows: For the year ended December 31, 2018 January 1, 2018 Effect of Retrospective Application of IFRS 9 Recognized in Profit or Loss Recognized in Other Comprehensive Income December 31, 2018 NT$ NT$ NT$ NT$ NT$ (In Millions) Deferred income tax assets Temporary differences Defined benefit pension plans $ 1,723 $ — $ 134 $ 450 $ 2,307 Allowance for doubtful receivables over quota 289 — 146 — 435 Share of profits of associates and joint ventures accounted for using equity method 331 — 58 — 389 Valuation loss on inventory 23 — 65 — 88 Deferred revenue 106 — 5 — 111 Estimated warranty liabilities 22 — 4 — 26 Accrued award credits liabilities 15 — (1 ) — 14 Others 175 — (32 ) — 143 2,684 — 379 450 3,513 Loss carryforwards 46 — (5 ) — 41 $ 2,730 $ — $ 374 $ 450 $ 3,554 January 1, 2018 Effect of Retrospective Application of IFRS 9 Recognized in Profit or Loss Recognized in Other Comprehensive Income December 31, 2018 NT$ NT$ NT$ NT$ (In Millions) Deferred income tax liabilities Temporary differences Defined benefit pension plans $ (1,265 ) $ — $ (567 ) $ — $ (1,832 ) Land value incremental tax (95 ) — — — (95 ) Intangible assets (39 ) — 7 — (32 ) Deferred revenue for award credits (29 ) — (2 ) — (31 ) Others (2 ) 1 (1 ) — (2 ) $ (1,430 ) $ 1 $ (563 ) $ — $ (1,992 ) For the year ended December 31, 2019 January 1, 2019 Effect of Retrospective Application of IFRS 16 Recognized in Profit or Loss Recognized in Other Comprehensive Income December 31, 2019 NT$ NT$ NT$ NT$ NT$ (In Millions) Deferred income tax assets Temporary differences Defined benefit pension plans $ 2,307 $ — $ 32 $ (305 ) $ 2,034 Allowance for doubtful receivables over quota 435 — (31 ) — 404 Share of profits of associates and joint ventures accounted for using equity method 389 — 13 — 402 Valuation loss on inventory 88 — 53 — 141 Deferred revenue 111 — (13 ) — 98 Estimated warranty liabilities 26 — 8 — 34 Accrued award credits liabilities 14 — 3 — 17 Others 143 26 (68 ) — 101 3,513 26 (3 ) (305 ) 3,231 Loss carryforwards 41 — (13 ) — 28 $ 3,554 $ 26 $ (16 ) $ (305 ) $ 3,259 January 1, 2019 Effect of Retrospective Application of IFRS 16 Recognized in Profit or Loss Recognized in Other Comprehensive Income December 31, 2019 NT$ NT$ NT$ NT$ NT$ (In Millions) Deferred income tax liabilities Temporary differences Defined benefit pension plans $ (1,832 ) $ — $ 74 $ — $ (1,758 ) Land value incremental tax (95 ) — — — (95 ) Intangible assets (32 ) — 3 — (29 ) Deferred revenue for award credits (31 ) — 2 — (29 ) Others (2 ) — 1 — (1 ) $ (1,992 ) $ — $ 80 $ — $ (1,912 ) For the year ended December 31, 2020 January 1, 2020 Acquired by business combinations (Note 14) Recognized in Profit or Loss Recognized in Other Comprehensive Income December 31, 2020 NT$ NT$ NT$ NT$ NT$ (In Millions) Deferred income tax assets Temporary differences Defined benefit pension plans $ 2,034 $ 1 $ 20 $ (239 ) $ 1,816 Share of profits of associates and joint ventures accounted for using equity method 402 — (1 ) — 401 Allowance for doubtful receivables over quota 404 — (39 ) — 365 Valuation loss on inventory 141 3 155 — 299 Deferred revenue 98 — (25 ) — 73 Estimated warranty liabilities 34 — 2 — 36 Accrued award credits liabilities 17 — 1 — 18 Others 101 2 2 — 105 3,231 6 115 (239 ) 3,113 Loss carryforwards 28 — (8 ) — 20 $ 3,259 $ 6 $ 107 $ (239 ) $ 3,133 January 1, 2020 Acquired by business combinations (Note 14) Recognized in Profit or Loss Recognized in Other Comprehensive Income December 31, 2020 NT$ NT$ NT$ NT$ NT$ (In Millions) Deferred income tax liabilities Temporary differences Defined benefit pension plans $ (1,758 ) $ — $ (54 ) $ — $ (1,812 ) Land value incremental tax (95 ) — — — (95 ) Deferred revenue for award credits (29 ) — (1 ) — (30 ) Intangible assets (29 ) — 2 — (27 ) Others (1 ) (3 ) 1 — (3 ) $ (1,912 ) $ (3 ) $ (52 ) $ — $ (1,967 )
Items for Which No Deferred Income Tax Assets Have Been Recognized	e. Items for which no deferred income tax assets have been recognized December 31 2019 2020 NT$ NT$ (In Millions) Loss carryforwards Expire in 2021 $ 13 $ 12 Expire in 2022 10 10 Expire in 2023 8 8 Expire in 2024 8 8 Expire in 2025 15 19 Expire in 2026 8 8 Expire in 2027 3 3 Expire in 2028 1 1 Expire in 2029 — 1 Expire in 2030 — — $ 66 $ 70 Deductible temporary differences $ 1 $ —
Information About Unused Loss Carryforwards	As of December 31, 2020, unused loss carryforwards were as follows: Remaining Creditable Amount Expiry Year NT$ (In Millions) $ 14 2021 11 2022 9 2023 8 2024 22 2025 16 2026 3 2027 4 2028 2 2029 2 2030 $ 91

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
Earnings Per Share (Tables)	Dec. 31, 2020
Earnings Per Share [Abstract]
Net Income and Weighted Average Number of Common Stocks Used in Calculation of Earnings Per Share	Net income and weighted average number of common stocks used in the calculation of earnings per share were as follows: Net Income Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Net income used to compute the basic earnings per share Net income attributable to the parent $ 37,557 $ 32,947 $ 33,419 Assumed conversion of all dilutive potential common stocks Employee stock options, employee compensation of subsidiaries (6 ) (4 ) (7 ) Net income used to compute the diluted earnings per share $ 37,551 $ 32,943 $ 33,412 Weighted Average Number of Common Stocks (Millions Shares) Year Ended December 31 2018 2019 2020 Weighted average number of common stocks used to compute the basic earnings per share 7,757 7,757 7,757 Assumed conversion of all dilutive potential common stocks Employee compensation 9 8 8 Weighted average number of common stocks used to compute the diluted earnings per share 7,766 7,765 7,765

Share-based Payment Arrangeme_2

Share-based Payment Arrangement (Tables)	12 Months Ended
Share-based Payment Arrangement (Tables)	Dec. 31, 2020
Senao International Co., Ltd. (SENAO) [Member]
Statement [LineItems]
Share-based Compensation Plan	a. SENAO share-based compensation plan (“SENAO Plan”) described as follows: Effective Date Grant Date Stock Options Units Exercise Price (In Thousands) NT$ 2012.05.28 2013.05.07 10,000 $66.20 (Original price$93.00)
Outstanding Stock Options	Information about SENAO’s outstanding stock options for the years ended December 31, 2018 and 2019 was as follows: Year Ended December 31, 2018 Granted on May 7, 2013 Number of Options Weighted- average Exercise Price (In Thousands) NT$ Employee stock options Options outstanding at beginning of the year 5,926 $ 70.70 Options forfeited (608 ) — Options outstanding at end of the year 5,318 66.20 Options exercisable at end of the year 5,318 66.20 Year Ended December 31, 2019 Granted on May 7, 2013 Number of Options Weighted- average Exercise Price (In Thousands) NT$ Employee stock options Options outstanding at beginning of the year 5,318 $ 66.20 Options forfeited (5,318 ) — Options outstanding at end of the year — — Options exercisable at end of the year — —
Assumptions used to Evaluate Options and Fair Value of Options	SENAO used the fair value method to evaluate the options using the Black-Scholes model and the related assumptions and the fair value of the options were as follows: Stock Options Granted on May 7, 2013 Grant-date share price (NT$) $ 93.00 Exercise price (NT$) $ 93.00 Dividend yield — Risk-free interest rate 0.91 % Expected life 4.375 years Expected volatility 36.22 % Weighted average fair value of grants (NT$) $ 28.72 SENAO used the fair value method to evaluate share-based payment transaction using the Black-Scholes model and the related assumptions and the fair value of the options were as follows: Stock Options Granted on May 7, 2018 Grant-date share price (NT$) $ 51.60 Exercise price (NT$) $ 49.28 Dividend yield — Risk-free interest rate 0.59 % Expected life 18 days Expected volatility 8.78 % Weighted average fair value of grants (NT$) $ 2.34
Share-based Compensation Plan	a. SENAO share-based compensation plan (“SENAO Plan”) described as follows: Effective Date Grant Date Stock Options Units Exercise Price (In Thousands) NT$ 2012.05.28 2013.05.07 10,000 $66.20 (Original price$93.00)
Outstanding Stock Options	Information about SENAO’s outstanding stock options for the years ended December 31, 2018 and 2019 was as follows: Year Ended December 31, 2018 Granted on May 7, 2013 Number of Options Weighted- average Exercise Price (In Thousands) NT$ Employee stock options Options outstanding at beginning of the year 5,926 $ 70.70 Options forfeited (608 ) — Options outstanding at end of the year 5,318 66.20 Options exercisable at end of the year 5,318 66.20 Year Ended December 31, 2019 Granted on May 7, 2013 Number of Options Weighted- average Exercise Price (In Thousands) NT$ Employee stock options Options outstanding at beginning of the year 5,318 $ 66.20 Options forfeited (5,318 ) — Options outstanding at end of the year — — Options exercisable at end of the year — —
CHIEF Telecom Inc. (CHIEF) [Member]
Statement [LineItems]
Share-based Compensation Plan	c . CHIEF share-based compensation plan (“CHIEF Plan”) described as follows: Effective Date Grant Date Stock Options Units Exercise Price NT$ 2015.11.17 2015.10.22 2,000.00 $34.40 (Original price$43.00) 2017.12.18 2017.12.19 950.00 $132.70 (Original price$147.00) 2018.10.31 50.00 $138.70 (Original price$147.00) 2020.09.16 2020.11.13 200.00 $206.00
Outstanding Stock Options	Information about CHIEF’s outstanding stock options for the years ended December 31, 2018, 2019 and 2020 was as follows: Year Ended December 31, 2018 Granted on October 22, 2015 Granted on December 19, 2017 Granted on October 31, 2018 Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Employee stock options Options outstanding at beginning of the year 1,936.00 $ 34.40 950.00 $ 147.00 — $ — Options granted — — — — 50.00 147.00 Options exercised (1,027.25 ) 34.40 — — — — Options forfeited (26.00 ) — (25.00 ) — — — Options outstanding at end of the year 882.75 34.40 925.00 140.60 50.00 147.00 Options exercisable at end of the year 416.50 34.40 — — — — Year Ended December 31, 2019 Granted on October 22, 2015 Granted on December 19, 2017 Granted on October 31, 2018 Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Employee stock options Options outstanding at beginning of the year 882.75 $ 34.40 925.00 $ 140.60 50.00 $ 147.00 Options exercised (547.25 ) 34.40 — — — — Options forfeited (21.25 ) — (28.00 ) — (4.00 ) — Options outstanding at end of the year 314.25 34.40 897.00 135.60 46.00 141.70 Options exercisable at end of the year 314.25 34.40 448.50 135.60 — — Year Ended December 31, 2020 Granted on October 22, 2015 Granted on December 19, 2017 Granted on October 31, 2018 Granted on November 13, 2020 Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Employee stock options Options outstanding at beginning of the year 314.25 $ 34.40 897.00 $ 135.60 46.00 $ 141.70 — $ — Options granted — — — — — — 200 206.00 Options exercised (314.25 ) 34.40 (448.50 ) 135.60 (21.00 ) 138.70 — — Options forfeited — — (21.00 ) — (4.00 ) — — — Options outstanding at end of the year — — 427.50 132.70 21.00 138.70 200.00 206.00 Options exercisable at end of the year — — 213.75 132.70 — — — —
Employee Stock Options Outstanding	As of December 31, 2019, information about employee stock options outstanding was as follows: Granted on October 22, 2015 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 34.40 314.25 0.81 $ 34.40 314.25 $ 34.40 Granted on December 19, 2017 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 135.60 897.00 2.96 $ 135.60 448.50 $ 135.60 Granted on October 31, 2018 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 141.70 46.00 3.83 $ 141.70 — $ — As of December 31, 2020, information about employee stock options outstanding was as follows: Granted on December 19, 2017 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 132.70 427.50 1.96 $ 132.70 213.75 $ 132.70 Granted on October 31, 2018 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 138.70 21.00 2.83 $ 138.70 — $ — Granted on November 13, 2020 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 206.00 200.00 4.87 $ 206.00 — $ — As of December 31, 2020, all the stock options granted on October 22, 2015 were exercised or forfeited.
Assumptions used to Evaluate Options and Fair Value of Options	CHIEF used the fair value method to evaluate the options using the Black-Scholes model and binomial option pricing model and the related assumptions and the fair value of the options were as follows: Stock Options Granted on October 22, 2015 Stock Options Granted on December 19, 2017 Stock Options Granted on October 31, 2018 Stock Options Granted on November 13, 2020 Grant-date share price (NT$) $ 39.55 $ 95.92 $ 166.00 $ 356.00 Exercise price (NT$) $ 43.00 $ 147.00 $ 147.00 $ 206.00 Dividend yield — — — — Risk-free interest rate 0.86 % 0.62 % 0.72 % 0.18 % Expected life 5 years 5 years 5 years 5 years Expected volatility 21.02 % 17.35 % 16.60 % 34.61 % Weighted average fair value of grants (NT$) $ 4,863 $ 2,318 $ 33,540 $ 173,893 CHIEF used the fair value method to evaluate the options granted to employees on May 22, 2018 using the Black-Scholes model and the related assumptions and the fair value of the options were as follows: Stock Options Granted on May 22, 2018 Grant-date share price (NT$) $ 156.41 Exercise price (NT$) $ 170.00 Dividend yield — Risk-free interest rate 0.34 % Expected life 7 days Expected volatility 14.33 % Weighted average fair value of grants (NT$) $ —
Share-based Compensation Plan	c . CHIEF share-based compensation plan (“CHIEF Plan”) described as follows: Effective Date Grant Date Stock Options Units Exercise Price NT$ 2015.11.17 2015.10.22 2,000.00 $34.40 (Original price$43.00) 2017.12.18 2017.12.19 950.00 $132.70 (Original price$147.00) 2018.10.31 50.00 $138.70 (Original price$147.00) 2020.09.16 2020.11.13 200.00 $206.00
Outstanding Stock Options	Information about CHIEF’s outstanding stock options for the years ended December 31, 2018, 2019 and 2020 was as follows: Year Ended December 31, 2018 Granted on October 22, 2015 Granted on December 19, 2017 Granted on October 31, 2018 Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Employee stock options Options outstanding at beginning of the year 1,936.00 $ 34.40 950.00 $ 147.00 — $ — Options granted — — — — 50.00 147.00 Options exercised (1,027.25 ) 34.40 — — — — Options forfeited (26.00 ) — (25.00 ) — — — Options outstanding at end of the year 882.75 34.40 925.00 140.60 50.00 147.00 Options exercisable at end of the year 416.50 34.40 — — — — Year Ended December 31, 2019 Granted on October 22, 2015 Granted on December 19, 2017 Granted on October 31, 2018 Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Employee stock options Options outstanding at beginning of the year 882.75 $ 34.40 925.00 $ 140.60 50.00 $ 147.00 Options exercised (547.25 ) 34.40 — — — — Options forfeited (21.25 ) — (28.00 ) — (4.00 ) — Options outstanding at end of the year 314.25 34.40 897.00 135.60 46.00 141.70 Options exercisable at end of the year 314.25 34.40 448.50 135.60 — — Year Ended December 31, 2020 Granted on October 22, 2015 Granted on December 19, 2017 Granted on October 31, 2018 Granted on November 13, 2020 Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Employee stock options Options outstanding at beginning of the year 314.25 $ 34.40 897.00 $ 135.60 46.00 $ 141.70 — $ — Options granted — — — — — — 200 206.00 Options exercised (314.25 ) 34.40 (448.50 ) 135.60 (21.00 ) 138.70 — — Options forfeited — — (21.00 ) — (4.00 ) — — — Options outstanding at end of the year — — 427.50 132.70 21.00 138.70 200.00 206.00 Options exercisable at end of the year — — 213.75 132.70 — — — —
Employee Stock Options Outstanding	As of December 31, 2019, information about employee stock options outstanding was as follows: Granted on October 22, 2015 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 34.40 314.25 0.81 $ 34.40 314.25 $ 34.40 Granted on December 19, 2017 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 135.60 897.00 2.96 $ 135.60 448.50 $ 135.60 Granted on October 31, 2018 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 141.70 46.00 3.83 $ 141.70 — $ — As of December 31, 2020, information about employee stock options outstanding was as follows: Granted on December 19, 2017 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 132.70 427.50 1.96 $ 132.70 213.75 $ 132.70 Granted on October 31, 2018 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 138.70 21.00 2.83 $ 138.70 — $ — Granted on November 13, 2020 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 206.00 200.00 4.87 $ 206.00 — $ — As of December 31, 2020, all the stock options granted on October 22, 2015 were exercised or forfeited.
CHT Security Co., Ltd. (CHTSC) [Member]
Statement [LineItems]
Outstanding Stock Options	Information about CHTSC’s outstanding stock options for the years ended December 31, 2019 and 2020 was as follows: Year Ended December 31, 2019 2020 Granted on December 20, 2019 Granted on December 20, 2019 Number of Options Weighted- average Exercise Price Number of Options Weighted- average Exercise Price NT$ NT$ Employee stock options Options outstanding at beginning of the year — $ — 4,500 $ 19.085 Options granted 4,500 19.085 — — Options forfeited — — (172 ) — Options outstanding at end of the year 4,500 19.085 4,328 19.085 Options exercisable at end of the year — — 1,082 19.085
Employee Stock Options Outstanding	As of December 31, 2019, information about employee stock options outstanding was as follows: Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 19.085 4,500 4.97 $ 19.085 — $ — As of December 31, 2020, information about employee stock options outstanding was as follows: Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 19.085 4,328 3.97 $ 19.085 1,082 $ 19.085
Assumptions used to Evaluate Options and Fair Value of Options	CHTSC used the fair value method to evaluate the options using the Black-Scholes model and the related assumptions and the fair value of the options were as follows: Stock Options Granted on December 20, 2019 Grant-date share price (NT$) $ 20.17 Exercise price (NT$) $ 19.085 Dividend yield 12.49 % Risk-free interest rate 0.54 % Expected life 5 years Expected volatility 42.41 % Weighted average fair value of grants (NT$) $ 2,470
Outstanding Stock Options	Information about CHTSC’s outstanding stock options for the years ended December 31, 2019 and 2020 was as follows: Year Ended December 31, 2019 2020 Granted on December 20, 2019 Granted on December 20, 2019 Number of Options Weighted- average Exercise Price Number of Options Weighted- average Exercise Price NT$ NT$ Employee stock options Options outstanding at beginning of the year — $ — 4,500 $ 19.085 Options granted 4,500 19.085 — — Options forfeited — — (172 ) — Options outstanding at end of the year 4,500 19.085 4,328 19.085 Options exercisable at end of the year — — 1,082 19.085
Employee Stock Options Outstanding	As of December 31, 2019, information about employee stock options outstanding was as follows: Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 19.085 4,500 4.97 $ 19.085 — $ — As of December 31, 2020, information about employee stock options outstanding was as follows: Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 19.085 4,328 3.97 $ 19.085 1,082 $ 19.085
IISI Plan [Member]
Statement [LineItems]
Outstanding Stock Options	Information about IISI’s outstanding stock options for the year ended December 31, 2020 was as follows: Year Ended December 31, 2020 Granted in August 2013 Granted in January 2014 Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Employee stock options Options outstanding at beginning of the year — $ — — $ — Options outstanding upon the date of business combination 1,022.96 14.00 580.00 14.00 Options exercised (432.50 ) 14.00 (50.00 ) 14.00 Options forfeited (590.46 ) — — — Options outstanding at end of the year — — 530.00 14.00 Options exercisable at end of the year — — 530.00 14.00
Employee Stock Options Outstanding	As of December 31, 2020, information about employee stock options outstanding was as follows: Granted in January 2014 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 14.00 530.00 0.04 $ 14.00 530.00 $ 14.00
Assumptions used to Evaluate Options and Fair Value of Options	IISI used the fair value method to evaluate the options using the Black-Scholes model and the related assumptions and the fair value of the options were as follows: Stock Options Granted in August 2013 Stock Options Granted in January 2014 Grant-date share price (NT$) $ 12.51 $ 14.51 Exercise price (NT$) $ 14.00 $ 14.00 Dividend yield 6 % 6 % Risk-free interest rate 1.20%-1.39% 1.16%-1.32% Expected life 4.5-5.5 years 4.5-5.5 years Expected volatility 36.01%-36.62% 35.28%-35.97% Weighted average fair value of grants (NT$) $ 12.51 $ 14.51
Outstanding Stock Options	Information about IISI’s outstanding stock options for the year ended December 31, 2020 was as follows: Year Ended December 31, 2020 Granted in August 2013 Granted in January 2014 Number of Options Weighted Average Exercise Price (NT$) Number of Options Weighted Average Exercise Price (NT$) Employee stock options Options outstanding at beginning of the year — $ — — $ — Options outstanding upon the date of business combination 1,022.96 14.00 580.00 14.00 Options exercised (432.50 ) 14.00 (50.00 ) 14.00 Options forfeited (590.46 ) — — — Options outstanding at end of the year — — 530.00 14.00 Options exercisable at end of the year — — 530.00 14.00
Employee Stock Options Outstanding	As of December 31, 2020, information about employee stock options outstanding was as follows: Granted in January 2014 Options Outstanding Options Exercisable Range of Exercise Price Number of Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number of Options Weighted Average Exercise Price NT$ (Years) NT$ NT$ $ 14.00 530.00 0.04 $ 14.00 530.00 $ 14.00

Non-cash Transactions (Tables)

Non-cash Transactions (Tables)	12 Months Ended
Non-cash Transactions (Tables)	Dec. 31, 2020
Non Cash Transaction From Financing Activities [Abstract]
Non-cash Investing Activities	Except for those disclosed in other notes, the Company entered into the following non-cash investing and financing activities: Year Ended December 31 Investing activities 2018 2019 2020 NT$ NT$ NT$ (In Millions) Increase in property, plant and equipment $ 27,979 $ 23,164 $ 25,195 Other payables 571 1,002 (1,684 ) Acquisition of property, plant and equipment $ 28,550 $ 24,166 $ 23,511 Increase in investment properties $ 6 $ 1 $ 1,359 Trade-in investment properties from asset exchange transaction (Note 16) — — (1,305 ) Acquisition of investment properties $ 6 $ 1 $ 54 Increase in intangible assets $ 498 $ 363 $ 48,605 Changes in other assets — — (1,000 ) Acquisition of intangible assets $ 498 $ 363 $ 47,605 Disposal of property, plant and equipment, net $ 122 $ 86 $ 307 Gain (loss) on disposal of property, plant and equipment 142 (38 ) 1,428 Trade-in investment properties from asset exchange transaction (Note 16) — — (1,305 ) Changes in other payables — — (80 ) Changes in other current monetary assets — — (31 ) Proceeds from disposal of property, plant and equipment $ 264 $ 48 $ 319
Summary of Changes in Liabilities Arising From Financing Activities Including Non-cash Transactions	Financing activities Balance on January 1, 2019 Cash Flows from Financing Activities Changes in Non-Cash Transactions Cash Flows from Operation Activities - Interest Paid Balance on December 31, 2019 Balance on January 1, 2019 Cash Flows from Financing Activities New Leases Others Cash Flows from Operation Activities - Interest Paid Balance on December 31, 2019 NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Lease liabilities $ 10,340 $ (3,728 ) $ 3,803 $ (572 ) $ (85 ) $ 9,758 Balance on January 1, 2020 Cash Flows from Financing Activities Changes in Non-Cash Transactions Cash Flows from Operation Activities - Interest Paid Balance on December 31, 2020 Balance on January 1, 2020 Cash Flows from Financing Activities New Leases Acquired by business combination (Note 14) Others Cash Flows from Operation Activities - Interest Paid Balance on December 31, 2020 NT$ NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Lease liabilities $ 9,758 $ (3,683 ) $ 3,796 $ 71 $ (265 ) $ (80 ) $ 9,597

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
Financial Instruments (Tables)	Dec. 31, 2020
Disclosure of detailed information about financial instruments [Line Items]
Summary of Categories of Financial Instruments	Categories of Financial Instruments December 31 2019 2020 NT$ NT$ (In Millions) Financial assets Measured at FVTPL Mandatorily measured at FVTPL $ 779 $ 687 Hedging financial assets — 2 Financial assets at amortized cost (Note a) 71,852 62,405 Financial assets at FVOCI 7,154 7,193 Financial liabilities Measured at FVTPL Held for trading — — Measured at amortized cost (Note b) 34,434 62,557 Note a: The balances included cash and cash equivalents, trade notes and accounts receivable, receivables from related parties, other current monetary assets and refundable deposits (classified as other noncurrent assets), which were financial assets measured at amortized cost. Note b: The balances included short-term loans, short-term bills payable, trade notes and accounts
Maturity Analysis For Nonderivative Financial Liabilities	The following tables detailed the Company’s remaining contractual maturity for its non-derivative financial liabilities with agreed repayment periods. The tables had been drawn up based on the undiscounted cash flows of financial liabilities based on the earliest date on which the Company is required to pay. December 31, 2019 Weighted Average Effective Interest Rate (%) Less than 1 Month 1-3 Months 3 Months to 1 Year 1-5 Years More than 5 Years Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Non-derivative financial liabilities Non-interest bearing — $ 36,387 $ — $ 2,532 $ 4,748 $ — $ 43,667 Floating interest rate instruments 0.98 50 10 30 1,600 — 1,690 $ 36,437 $ 10 $ 2,562 $ 6,348 $ — $ 45,357 December 31, 2020 Weighted Average Effective Interest Rate (%) Less than 1 Month 1-3 Months 3 Months to 1 Year 1-5 Years More than 5 Years Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Non-derivative financial liabilities Non-interest bearing — $ 37,749 $ — $ 2,476 $ 4,827 $ — $ 45,052 Floating interest rate instruments 0.78 — 7 1,660 — — 1,667 Fixed interest rate instruments 0.50 7,000 — — 8,800 11,200 27,000 $ 44,749 $ 7 $ 4,136 $ 13,627 $ 11,200 $ 73,719
Information About the Maturity Analysis for Lease Liabilities	December 31, 2019 Information about the maturity analysis for lease liabilities was as follows: Less than 1 Year 1-3 Years 3-5 Years More than 5 Years Total NT$ NT$ NT$ NT$ NT$ (In Millions) Lease liabilities $ 3,310 $ 4,394 $ 1,581 $ 645 $ 9,930 December 31, 2020 Information about the maturity analysis for lease liabilities was as follows: Less than 1 Year 1-3 Years 3-5 Years More than 5 Years Total NT$ NT$ NT$ NT$ NT$ (In Millions) Lease liabilities $ 3,397 $ 4,240 $ 1,691 $ 409 $ 9,737
Liquidity Analysis for Derivative Financial Instruments	The following table detailed the Company’s liquidity analysis for its derivative financial instruments. The table had been drawn up based on the undiscounted gross inflows and outflows on those derivatives that require gross settlement. Less than 1 Month 1-3 Months 3 Months to 1 Year 1-5 Years Total NT$ NT$ NT$ NT$ NT$ (In Millions) December 31, 2019 Gross settled Forward exchange contracts Inflows $ 26 $ 135 $ — $ — $ 161 Outflows 26 135 — — 161 $ — $ — $ — $ — $ — December 31, 2020 Gross settled Forward exchange contracts Inflows $ — $ 635 $ — $ — $ 635 Outflows — 631 — — 631 $ — $ 4 $ — $ — $ 4
Financing Facilities	2) Financing facilities December 31 2019 2020 NT$ NT$ (In Millions) Unsecured bank loan facility Amount used $ 121 $ 7,068 Amount unused 46,109 59,277 $ 46,230 $ 66,345 Secured bank loan facility Amount used $ 1,600 $ 1,600 Amount unused 1,340 20 $ 2,940 $ 1,620
Foreign currency risk [Member]
Disclosure of detailed information about financial instruments [Line Items]
Carrying Amounts of Assets and Liabilities Related to Market Risk	1) Foreign currency risk The carrying amounts of the Company’s foreign currency denominated monetary assets and monetary liabilities at the balance sheet dates were as follows: December 31 2019 2020 NT$ NT$ (In Millions) Assets USD $ 5,782 $ 2,711 EUR 12 15 SGD 225 170 JPY 17 22 RMB 9 30 HKD — 69 Liabilities USD 4,121 768 EUR 206 957 SGD 1,263 1,049 JPY 14 10 RMB — — HKD 15 8 The carrying amounts of the Company’s derivatives with exchange rate risk exposures at the balance sheet dates were as follows: December 31 2019 2020 NT$ NT$ (In Millions) Assets USD $ — $ — EUR — 4 Liabilities USD — — EUR — —
Foreign Currency Risk Sensitivity Analysis	The following table details the Company’s sensitivity to a 5% increase and decrease in the functional currency against the relevant foreign currencies. 5% is the sensitivity rate used when reporting foreign currency risk internally to key management personnel and represents management’s assessment of the reasonably possible changes in foreign exchange rates. The sensitivity analysis includes only outstanding foreign currency denominated monetary items and forward exchange contracts. A positive number below indicates an increase in pre-tax profit or equity where the functional currency weakens 5% against the relevant currency. Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Profit or loss Monetary assets and liabilities (a) USD $ (55 ) $ 83 $ 97 EUR (59 ) (10 ) (47 ) SGD 4 (52 ) (44 ) JPY — — 1 RMB — — 1 HKD — (1 ) 3 Derivatives (b) USD 3 1 (19 ) EUR 10 3 3 Equity Derivatives (c) EUR 9 4 10 a) This is mainly attributable to the exposure to foreign currency denominated receivables and payables of the Company outstanding at the balance sheet dates. b) This is mainly attributable to forward exchange contracts. c) This is mainly attributable to the changes in the fair value of derivatives that are designated as cash flow hedges.
Interest rate risk [member]
Disclosure of detailed information about financial instruments [Line Items]
Carrying Amounts of Assets and Liabilities Related to Market Risk	The carrying amounts of the Company’s exposures to interest rates on financial assets and financial liabilities at the balance sheet dates were as follows: December 31 2019 2020 NT$ NT$ (In Millions) Fair value interest rate risk Financial assets $ 30,947 $ 24,218 Financial liabilities 9,758 36,576 Cash flow interest rate risk Financial assets 7,681 9,306 Financial liabilities 1,690 1,667

Fair Value Information (Tables)

Fair Value Information (Tables)	12 Months Ended
Fair Value Information (Tables)	Dec. 31, 2020
Disclosure of fair value measurement of assets and liabilities [Line Items]
Schedule of Carrying Amounts of Financial Assets and Liabilities Not Measured at Fair Value	a. Financial instruments that are not measured at fair value but for which fair value is disclosed Except those listed in the table below, the Company considers that the carrying amounts of financial assets and liabilities not measured at fair value approximate their fair values or the fair values cannot be reliable estimated. December 31, 2019 December 31, 2020 Carrying Value Fair Value Carrying Value Fair Value Financial liabilities Financial liabilities measured at amortized cost Bonds payable $ — $ — $ 19,980 $ 20,078
Carrying Amounts And Fair Value of Financial Assets and Liabilities	b. Financial instruments that are measured at fair value on a recurring basis December 31, 2019 Level 1 Level 2 Level 3 Total Financial assets at FVTPL Derivatives $ — $ — $ — $ — Listed stocks 1 — — 1 Non-listed stocks — — 778 778 $ 1 $ — $ 778 $ 779 Hedging financial assets $ — $ — $ — $ — Financial assets at FVOCI Listed stocks $ 2,454 $ — $ — $ 2,454 Non-listed stocks — — 4,700 4,700 $ 2,454 $ — $ 4,700 $ 7,154 Financial liabilities at FVTPL Derivatives $ — $ — $ — $ — December 31, 2020 Level 1 Level 2 Level 3 Total Financial assets at FVTPL Derivatives $ — $ 2 $ — $ 2 Listed stocks 8 — — 8 Non-listed stocks — — 677 677 $ 8 $ 2 $ 677 $ 687 Hedging financial assets $ — $ 2 $ — $ 2 Financial assets at FVOCI Listed stocks $ 2,754 $ — $ — $ 2,754 Non-listed stocks — — 4,439 4,439 $ 2,754 $ — $ 4,439 $ 7,193 Financial liabilities at FVTPL Derivatives $ — $ — $ — $ —
Schedule of Percentage Decrease in Discount for Lack of Marketability or Noncontrolling Interests	A decrease in discount for the lack of marketability or noncontrolling interests discount would result in increases in the fair values. December 31 2019 2020 Discount for lack of marketability 13.73%-20.00% 14.73%-20.00% Noncontrolling interests discount 21.45%-25.00% 17.29%-25.00%
Schedule of Impact of Decrease in Discount for Lack of Marketability or Noncontrolling Interests	December 31 2019 2020 NT$ NT$ (In Millions) Discount for lack of marketability 5% decrease $ 342 $ 320 Noncontrolling interests discount 5% decrease $ 54 $ 47
Level 3 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Schedule of Reconciliations for Financial Assets	The reconciliations for financial assets measured at Level 3 are listed below: 2018 Financial Assets Measured at Fair Value through Profit or Loss Measured at Fair Value through Other Comprehensive Income Total NT$ NT$ NT$ (In Millions) Balance at January 1, 2018 $ 543 $ 3,925 $ 4,468 Acquisition — 290 290 Recognized in profit or loss under “Other gains and losses” (26 ) — (26 ) Recognized in other comprehensive income under “Unrealized gain or loss on financial assets at fair value through other comprehensive income” — (175 ) (175 ) Proceeds from return of investees — (7 ) (7 ) Balance at December 31, 2018 $ 517 $ 4,033 $ 4,550 Unrealized loss in 2018 $ (26 ) 2019 Financial Assets Measured at Fair Value through Profit or Loss Measured at Fair Value through Other Comprehensive Income Total NT$ NT$ NT$ (In Millions) Balance at January 1, 2019 $ 517 $ 4,033 $ 4,550 Acquisition 300 — 300 Recognized in profit or loss under “Other gains and losses” (39 ) — (39 ) Recognized in other comprehensive income under “Unrealized gain or loss on financial assets at fair value through other comprehensive income” — 676 676 Proceed from return of investments — (9 ) (9 ) Balance at December 31, 2019 $ 778 $ 4,700 $ 5,478 Unrealized loss in 2019 $ (39 ) 2020 Financial Assets Measured at Fair Value through Profit or Loss Measured at Fair Value through Other Comprehensive Income Total NT$ NT$ NT$ (In Millions) Balance at January 1, 2020 $ 778 $ 4,700 $ 5,478 Reclassified from investments accounted for using equity method — 2 2 Recognized in profit or loss under “Other gains and losses” (101 ) — (101 ) Recognized in other comprehensive income under “Unrealized gain or loss on financial assets at fair value through other comprehensive income” — (263 ) (263 ) Balance at December 31, 2020 $ 677 $ 4,439 $ 5,116 Unrealized loss in 2020 $ (101 )

Related Parties Transactions (T

Related Parties Transactions (Tables)	12 Months Ended
Related Parties Transactions (Tables)	Dec. 31, 2020
Related Party Transactions [Abstract]
Summary of Related Parties	a. The Company engages in business transactions with the following related parties: Company Relationship Taiwan International Standard Electronics Co., Ltd. Associate So-net Entertainment Taiwan Limited Associate KKBOX Taiwan Co., Ltd. Associate KingwayTek Technology Co., Ltd. Associate UUPON Inc. Associate (Note 2) Taiwan International Ports Logistics Corporation Associate International Integrated Systems, Inc. Subsidiary (Note 1) Senao Networks, Inc. Associate EnRack Tech. Co., Ltd. Subsidiary of the Company’s associate, Senao Networks, Inc. Emplus Technologies, Inc. Subsidiary of the Company’s associate, Senao Networks, Inc. ST-2 Satellite Ventures Pte., Ltd. Associate Viettel-CHT Co., Ltd. Associate Click Force Co., Ltd. Associate Alliance Digital Tech Co., Ltd. Associate Chunghwa PChome Fund I Co., Ltd. Associate Cornerstone Ventures Co., Ltd. Associate Next Commercial Bank Co., Ltd. Associate Chunghwa SEA Holdings Joint venture Other related parties Chunghwa Telecom Foundation A nonprofit organization of which the funds donated by Chunghwa exceeds one third of its total funds Senao Technical and Cultural Foundation A nonprofit organization of which the funds donated by SENAO exceeds one third of its total funds Sochamp Technology Co., Ltd. Investor of significant influence over CHST E-Life Mall Co., Ltd. One of the directors of E-Life Mall and a director of SENAO are members of an immediate family Engenius Technologies Co., Ltd. Chairman of Engenius Technologies Co., Ltd. is a member of SENAO’s management Cheng Keng Investment Co., Ltd. Chairman of Cheng Keng Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family Cheng Feng Investment Co., Ltd. Chairman of Cheng Feng Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family All Oriented Investment Co., Ltd. Chairman of All Oriented Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family Company Relationship Hwa Shun Investment Co., Ltd. Chairman of Hwa Shun Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family Yu Yu Investment Co., Ltd. Chairman of Yu Yu Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family United Daily News Co., Ltd. Investor of significant influence over SFD Shenzhen Century Communication Co., Ltd. Investor of significant influence over SCT Chunghwa Post Co., Ltd. Government-related entity as Chunghwa Telecom Note 1: IISI was an associate and has become a subsidiary starting from July 1, 2020. Please refer to Note 14 (c). All transactions between the Company were eliminated upon consolidation since the acquisition date. Note 2 : 1) Operating transactions Revenues Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Associates $ 344 $ 274 $ 1,508 Others 94 76 66 $ 438 $ 350 $ 1,574 Operating Costs and Expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Associates $ 1,304 $ 964 $ 715 Others 75 76 68 $ 1,379 $ 1,040 $ 783 2) Non-operating transactions Non-operating Income and Expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Associates $ 31 $ 41 $ 37 Others — 4 3 $ 31 $ 45 $ 40 3) Receivables December 31 2019 2020 NT$ NT$ (In Millions) Associates $ 10 $ 229 Others 7 1 $ 17 $ 230 4) Contract liabilities-current December 31 2019 2020 NT$ NT$ (In Millions) Associates $ — $ 183 5 ) Payables December 31 2019 2020 NT$ NT$ (In Millions) Associates $ 651 $ 643 Others 3 3 $ 654 $ 646 6 ) Customers’ deposits December 31 2019 2020 NT$ NT$ (In Millions) Associates $ 8 $ 5 7 ) Acquisition of property, plant and equipment Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Associates $ 312 $ 242 $ 375 Others — — — $ 312 $ 242 $ 375 8 ) Acquisition of property, plant and equipment Proceeds Gain on Disposal Year Ended December 31 Year Ended December 31 2019 2020 2019 2020 Others $ — $ 386 $ — $ 310 1) Operating transactions Revenues Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Associates $ 344 $ 274 $ 1,508 Others 94 76 66 $ 438 $ 350 $ 1,574 Operating Costs and Expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Associates $ 1,304 $ 964 $ 715 Others 75 76 68 $ 1,379 $ 1,040 $ 783 2) Non-operating transactions Non-operating Income and Expenses Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Associates $ 31 $ 41 $ 37 Others — 4 3 $ 31 $ 45 $ 40 3) Receivables December 31 2019 2020 NT$ NT$ (In Millions) Associates $ 10 $ 229 Others 7 1 $ 17 $ 230 4) Contract liabilities-current December 31 2019 2020 NT$ NT$ (In Millions) Associates $ — $ 183 5 ) Payables December 31 2019 2020 NT$ NT$ (In Millions) Associates $ 651 $ 643 Others 3 3 $ 654 $ 646 6 ) Customers’ deposits December 31 2019 2020 NT$ NT$ (In Millions) Associates $ 8 $ 5 7 ) Acquisition of property, plant and equipment December 31, 2018 NT$ (In Millions) Prepaid rents - current $ 205 Prepaid rents - noncurrent 1,346 $ 1,551
Summary of Lease Liabilities	The lease liabilities of ST-2 Satellite Ventures Pte., Ltd. as of December 31, 2019 and 2020 were as follows: December 31, 2019 2020 NT$ NT$ (In Millions) Lease liabilities - current $ 188 $ 182 Lease liabilities - noncurrent 1,024 817 $ 1,212 $ 999
Compensation of Directors and Other Key Management Personnel	The compensation of directors and other key management personnel for the years ended December 31, 2018, 2019 and 2020 were as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Short-term employee benefits $ 282 $ 263 $ 290 Post-employment benefits 10 9 11 Share-based payment 9 — — $ 301 $ 272 $ 301

Pledged Assets (Tables)

Pledged Assets (Tables)	12 Months Ended
Pledged Assets (Tables)	Dec. 31, 2020
Disclosure Of Collateral [Abstract]
Assets Pledged as Collaterals	The following assets are pledged as collaterals for bank loans, custom duties of the imported materials and warranties of contract performance. December 31 2019 2020 NT$ NT$ (In Millions) Property, plant and equipment $ 2,491 $ 2,462 Land held under development (included in inventories) 1,999 1,999 Restricted assets (included in other assets - others) 3 209 $ 4,493 $ 4,670

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
Segment Information (Tables)	Dec. 31, 2020
Disclosure Of Operating Segments [Abstract]
Analysis by Reportable Segment of Revenue and Operating Results of Continuing Operations	Analysis by reportable segment of revenues and operating results of continuing operations are as follows: Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Year ended December 31, 2018 Revenues From external customers $ 66,753 $ 100,937 $ 29,813 $ 13,435 $ 4,545 $ 215,483 Intersegment revenues 17,125 1,702 4,038 2,234 5,008 30,107 Segment revenues $ 83,878 $ 102,639 $ 33,851 $ 15,669 $ 9,553 245,590 Intersegment elimination (30,107 ) Consolidated revenues $ 215,483 Segment income (loss) before income tax $ 18,243 $ 15,328 $ 11,944 $ 1,024 $ (1,553 ) $ 44,986 Year ended December 31, 2019 Revenues From external customers $ 65,728 $ 95,469 $ 30,091 $ 11,485 $ 4,747 $ 207,520 Intersegment revenues 16,065 1,564 3,951 2,079 4,914 28,573 Segment revenues $ 81,793 $ 97,033 $ 34,042 $ 13,564 $ 9,661 236,093 Intersegment elimination (28,573 ) Consolidated revenues $ 207,520 Segment income (loss) before income tax $ 19,537 $ 11,250 $ 12,515 $ 799 $ (2,234 ) $ 41,867 Year ended December 31, 2020 Revenues From external customers $ 69,469 $ 90,230 $ 32,115 $ 8,695 $ 7,100 $ 207,609 Intersegment revenues 15,930 1,536 3,966 1,875 5,369 28,676 Segment revenues $ 85,399 $ 91,766 $ 36,081 $ 10,570 $ 12,469 236,285 Intersegment elimination (28,676 ) Consolidated revenues $ 207,609 Segment income (loss) before income tax $ 22,504 $ 8,777 $ 13,120 $ 829 $ (2,404 ) $ 42,826
Other Segment Information	Other information reviewed by the chief operating decision maker or regularly provided to the chief operating decision maker was as follows: For the year ended December 31, 2018 Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Share of profits of associates and joint ventures accounted for using equity method $ — $ — $ — $ — $ 509 $ 509 Interest income $ 18 $ 12 $ 19 $ 28 $ 120 $ 197 Interest expenses $ — $ — $ — $ — $ 18 $ 18 Operating costs and expenses $ 59,430 $ 73,901 $ 13,766 $ 13,279 $ 11,573 $ 171,949 Depreciation and amortization $ 15,027 $ 13,788 $ 3,121 $ 1,425 $ 448 $ 33,809 Capital expenditure $ 12,693 $ 10,664 $ 2,729 $ 1,348 $ 1,116 $ 28,550 Reversal of impairment loss on investment properties $ 19 $ — $ — $ — $ — $ 19 Impairment loss on intangible assets $ — $ 51 $ — $ — $ — $ 51 For the year ended December 31, 2019 Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Share of profits of associates and joint ventures accounted for using equity method $ — $ — $ — $ — $ 459 $ 459 Interest income $ 15 $ 9 $ 20 $ 41 $ 166 $ 251 Interest expenses $ 5 $ 58 $ 1 $ 12 $ 28 $ 104 Operating costs and expenses $ 56,269 $ 72,952 $ 13,850 $ 11,427 $ 12,249 $ 166,747 Depreciation and amortization $ 14,842 $ 16,254 $ 2,914 $ 1,547 $ 792 $ 36,349 Capital expenditure $ 12,071 $ 7,773 $ 1,425 $ 1,117 $ 1,780 $ 24,166 Impairment loss on property, plant and equipment $ — $ — $ — $ — $ 93 $ 93 Reversal of impairment loss on investment properties $ 57 $ — $ — $ — $ — $ 57 Impairment loss on intangible assets $ — $ 9 $ — $ — $ — $ 9 Impairment loss on other assets $ 13 $ — $ 13 $ — $ 18 $ 44 For the year ended December 31, 2020 Domestic Fixed Communi- cations Business Mobile Communi- cations Business Internet Business International Fixed Communi- cations Business Others Total NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Share of profits of associates and joint ventures accounted for using equity method $ — $ — $ — $ — $ 244 $ 244 Interest income $ 13 $ 5 $ 17 $ 22 $ 59 $ 116 Interest expenses $ 6 $ 56 $ 1 $ 10 $ 133 $ 206 Operating costs and expenses $ 59,371 $ 69,211 $ 15,241 $ 8,573 $ 14,447 $ 166,843 Depreciation and amortization $ 14,250 $ 17,800 $ 2,669 $ 1,450 $ 969 $ 37,138 Capital expenditure $ 11,483 $ 8,827 $ 1,397 $ 779 $ 1,025 $ 23,511 Gain (loss) on disposal of property, plant and equipment $ 1,442 $ (3 ) $ — $ — $ (11 ) $ 1,428 Gain on disposal of investment properties $ 151 $ — $ — $ — $ — $ 151 Reversal of impairment loss on investment properties $ 27 $ — $ — $ — $ — $ 27 Impairment loss on intangible assets $ — $ 9 $ — $ — $ — $ 9
Main Products and Service Revenues	The following is an analysis of the Company’s revenue from its major products and services. Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Mobile services revenue $ 63,906 $ 58,703 $ 56,724 Sales of products 41,289 41,593 39,391 Local telephone and domestic long distance telephone services revenue 29,996 27,929 26,475 Broadband access and domestic leased line services revenue 22,453 22,116 22,420 Data communications internet services revenue 21,137 21,003 21,447 International network and leased line services revenue 8,724 7,066 3,884 Others 27,978 29,110 37,268 $ 215,483 $ 207,520 $ 207,609
Geographic Information	The geographic information for revenues was as follows: Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ (In Millions) Taiwan, ROC $ 205,696 $ 197,895 $ 200,881 Overseas 9,787 9,625 6,728 $ 215,483 $ 207,520 $ 207,609

General - Additional Informatio

General - Additional Information (Detail)	12 Months Ended
General - Additional Information (Detail)	Dec. 31, 2020
General Information [Abstract]
Description of percentage of ownership interest	below 50%

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Detail Information of Subsidiaries (Detail)	12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jul. 31, 2020	Dec. 31, 2019	Nov. 30, 2019	Oct. 31, 2019
Light Era Development Co., Ltd. ("LED") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Planning and development of real estate and intelligent buildings, and property management
Percentage of Ownership interests	100.00%			100.00%
Donghwa Telecom Co., Ltd. ("DHT") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	International private leased circuit, IP VPN service, and IP transit services
Percentage of Ownership interests	100.00%			100.00%
Chunghwa Telecom Singapore Pte., Ltd. ("CHTS") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	International private leased circuit, IP VPN service, and IP transit services
Percentage of Ownership interests	100.00%			100.00%
Chunghwa System Integration Co., Ltd. ("CHSI") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Providing system integration services and telecommunications equipment
Percentage of Ownership interests	100.00%			100.00%
Chunghwa Investment Co., Ltd. ("CHI") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Investment
Percentage of Ownership interests	89.00%			89.00%
CHYP Multimedia Marketing & Communications Co., Ltd. ("CHYP") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Digital information supply services and advertisement services
Percentage of Ownership interests	100.00%			100.00%
Prime Asia Investments Group Ltd. (B.V.I.) ("Prime Asia") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Investment
Percentage of Ownership interests	100.00%			100.00%
Spring House Entertainment Tech. Inc. ("SHE") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Software design services, internet contents production and play, and motion picture production and distribution
Percentage of Ownership interests	56.00%			56.00%
Chunghwa Telecom Global, Inc. ("CHTG") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	International private leased circuit, internet services, and transit services
Percentage of Ownership interests	100.00%			100.00%
Chunghwa Telecom Vietnam Co., Ltd. ("CHTV") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Intelligent energy saving solutions, international circuit, and information and communication technology (“ICT”) services
Percentage of Ownership interests	100.00%			100.00%
Smartfun Digital Co., Ltd. ("SFD") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Providing diversified family education digital services
Percentage of Ownership interests	65.00%			65.00%
Chunghwa Telecom Japan Co., Ltd. ("CHTJ") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	International private leased circuit, IP VPN service, and IP transit services
Percentage of Ownership interests	100.00%			100.00%
Chunghwa Sochamp Technology Inc. ("CHST") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Design, development and production of Automatic License Plate Recognition software and hardware
Percentage of Ownership interests	51.00%			51.00%
Honghwa International Co., Ltd. ("HHI") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Telecommunications engineering, sales agent of mobile phone plan application and other business services, etc.
Percentage of Ownership interests	100.00%			100.00%
Chunghwa Leading Photonics Tech Co., Ltd. ("CLPT") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Production and sale of electronic components and finished products
Percentage of Ownership interests	75.00%			75.00%
Chunghwa Telecom (Thailand) Co., Ltd. ("CHTT") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	International private leased circuit, IP VPN service, ICT and cloud VAS services
Percentage of Ownership interests	100.00%			100.00%
CHT Security Co., Ltd. ("CHTSC") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Computing equipment installation, wholesale of computing and business machinery equipment and software, management consulting services, data processing services, digital information supply services and internet identify services
Percentage of Ownership interests	80.00%			80.00%
International Integrated Systems, Inc. ("IISI") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	IT solution provider, IT application consultation, system integration and package solution
Percentage of Ownership interests	51.00%	51.20%	51.54%	0.00%
Chunghwa Telecom Co., Ltd. ("Chunghwa") [Member] \| Senao International Co., Ltd. ("SENAO") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Handset and peripherals retailer, sales of CHT mobile phone plans as an agent
Percentage of Ownership interests	28.00%			28.00%
Chunghwa Telecom Co., Ltd. ("Chunghwa") [Member] \| CHIEF Telecom Inc. ("CHIEF") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Network integration, internet data center (“IDC”), communications integration and cloud application services
Percentage of Ownership interests	56.00%			57.00%
Senao International Co., Ltd. ("SENAO") [Member] \| Senao International (Samoa) Holding Ltd. ("SIS") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	International investment
Percentage of Ownership interests	100.00%			100.00%
Senao International Co., Ltd. ("SENAO") [Member] \| SENYOUNG Insurance Agent Co., Ltd. ("SENYOUNG") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Property and liability insurance agency
Percentage of Ownership interests	100.00%			100.00%
Senao International Co., Ltd. ("SENAO") [Member] \| Youth Co., Ltd. ("Youth") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Sale of information and communication technologies products
Percentage of Ownership interests	96.00%			93.00%
Senao International Co., Ltd. ("SENAO") [Member] \| Aval Technologies Co., Ltd. ("Aval") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Sale of information and communication technologies products
Percentage of Ownership interests	100.00%			100.00%
Chunghwa Precision Test Tech. Co., Ltd. ("CHPT") [Member] \| CHPT Japan Co., Ltd. ("CHPT (JP)") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Related services of electronic parts, machinery processed products and printed circuit board
Percentage of Ownership interests	100.00%			100.00%
Chunghwa Precision Test Tech. Co., Ltd. ("CHPT") [Member] \| Chunghwa Precision Test Tech. International Ltd. ("CHPT (International)") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Wholesale and retail of electronic materials, and investment
Percentage of Ownership interests	100.00%			100.00%
Chunghwa Precision Test Tech. Co., Ltd. ("CHPT") [Member] \| Chunghwa Precision Test Tech. USA Corporation ("CHPT (US)") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Design and after-sale services of semiconductor testing components and printed circuit board
Percentage of Ownership interests	100.00%			100.00%
Youth Co., Ltd. ("Youth") [Member] \| ISPOT Co., Ltd. ("ISPOT") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Sale of information and communication technologies products
Percentage of Ownership interests	100.00%			100.00%
Youth Co., Ltd. ("Youth") [Member] \| Youyi Co., Ltd. ("Youyi") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Maintenance of information and communication technologies products
Percentage of Ownership interests	100.00%			100.00%
Aval Technologies Co., Ltd. ("Aval") [Member] \| Wiin Technology Co., Ltd. ("Wiin") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Sale of information and communication technologies products
Percentage of Ownership interests	100.00%			100.00%
SENYOUNG Insurance Agent Co., Ltd. ("SENYOUNG") [Member] \| Senaolife Insurance Agent Co., Ltd. ("Senaolife") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Life insurance services
Percentage of Ownership interests	100.00%			100.00%	100.00%
Light Era Development Co., Ltd. ("LED") [Member] \| Taoyuan Asia Silicon Valley Innovation Co., Ltd. ("TASVI") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Development of real estate
Percentage of Ownership interests	0.00%			0.00%
CHIEF Telecom Inc. ("CHIEF") [Member] \| Unigate Telecom Inc. ("Unigate") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Telecommunications and internet service
Percentage of Ownership interests	100.00%			100.00%
CHIEF Telecom Inc. ("CHIEF") [Member] \| Chief International Corp. ("CIC") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Telecommunications and internet service
Percentage of Ownership interests	100.00%			100.00%
CHIEF Telecom Inc. ("CHIEF") [Member] \| Shanghai Chief Telecom Co., Ltd. ("SCT") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Telecommunications and internet service
Percentage of Ownership interests	49.00%			49.00%
Chunghwa Investment Co., Ltd. ("CHI") [Member] \| Chunghwa Precision Test Tech. Co., Ltd. ("CHPT") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Production and sale of semiconductor testing components and printed circuit board
Percentage of Ownership interests	34.00%			34.00%
Senao International (Samoa) Holding Ltd. ("SIS") [Member] \| Senao International HK Limited ("SIHK") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	International investment
Percentage of Ownership interests	100.00%			100.00%
Senao International HK Limited ("SIHK") [Member] \| Senao Trading (Fujian) Co., Ltd. ("STF") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Sale of information and communication technologies products
Percentage of Ownership interests	0.00%			0.00%
Senao International HK Limited ("SIHK") [Member] \| Senao International Trading (Shanghai) Co., Ltd. ("SITS") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Sale of information and communication technologies products
Percentage of Ownership interests	100.00%			100.00%
Senao International HK Limited ("SIHK") [Member] \| Senao International Trading (Jiangsu) Co., Ltd. ("SITJ") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Sale of information and communication technologies products
Percentage of Ownership interests	0.00%			0.00%
Prime Asia Investments Group Ltd. (B.V.I.) ("Prime Asia") [Member] \| Chunghwa Hsingta Co., Ltd. ("CHC") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Investment
Percentage of Ownership interests	100.00%			100.00%
Chunghwa Precision Test Tech. International Ltd. ("CHPT (International)") [Member] \| Su Zhou Precision Test Tech. Ltd. ("SZPT") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Assembly processed of circuit board, design of printed circuit board and related consultation service
Percentage of Ownership interests	100.00%			100.00%		100.00%
Chunghwa Precision Test Tech. International Ltd. ("CHPT (International)") [Member] \| Shanghai Taihua Electronic Technology Limited ("STET") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Design of printed circuit board and related consultation service
Percentage of Ownership interests	100.00%			100.00%
Chunghwa Hsingta Co., Ltd. ("CHC") [Member] \| Chunghwa Telecom (China) Co., Ltd. ("CTC") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Integrated information and communication solution services for enterprise clients, and intelligent energy network service
Percentage of Ownership interests	100.00%			100.00%
International Integrated Systems, Inc. ("IISI") [Member] \| Unitronics Technology Corp. ("UTC") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Development and maintenance of information system
Percentage of Ownership interests	99.96%			0.00%
International Integrated Systems, Inc. ("IISI") [Member] \| IISI Investment Co., Ltd. ("IICL") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Investment
Percentage of Ownership interests	100.00%			0.00%
International Integrated Systems, Inc. ("IISI") [Member] \| Infoexplorer International Co., Ltd.("IESA") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Investment
Percentage of Ownership interests	100.00%			0.00%
Infoexplorer International Co., Ltd.("IESA") [Member] \| International Integrated Systems (Hong Kong) Limited ("IEHK") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Investment and technical consulting service
Percentage of Ownership interests	100.00%			0.00%
IISI Investment Co., Ltd. ("IICL") [Member] \| Leading Tech Co., Ltd. ("LTCL") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Investment
Percentage of Ownership interests	100.00%			0.00%
Leading Tech Co., Ltd. ("LTCL") [Member] \| Leading Systems Co., Ltd. ("LSCL") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Investment
Percentage of Ownership interests	100.00%			0.00%
Leading Systems Co., Ltd. ("LSCL") [Member] \| International Integrated Systems Inc. (Shanghai) ("IISS") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Development and maintenance of information system
Percentage of Ownership interests	100.00%			0.00%
International Integrated Systems Inc. (Shanghai) ("IISS") [Member] \| Huiyu Shanghai Management Consultancy Co., Ltd. ("HSMC") [Member]
Disclosure of subsidiaries [Line Items]
Main Businesses and Products	Development and maintenance of information system
Percentage of Ownership interests	0.00%			0.00%

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Detail Information of Subsidiaries (Parenthetical) (Detail)	Dec. 31, 2020	Sep. 30, 2020	Jul. 31, 2020	Jul. 01, 2020	Apr. 30, 2020	Dec. 31, 2019	Nov. 30, 2019	Oct. 31, 2019	Sep. 30, 2019
Spring House Entertainment Tech. Inc. ("SHE") [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	56.00%					56.00%
Percentage of Ownership						19.72%
International Integrated Systems, Inc. ("IISI") [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	51.00%	51.20%	51.54%			0.00%
Percentage of additional ownership interest obtained				20.38%
Chunghwa Telecom Co., Ltd. and Chunghwa Investment Co., Ltd. [Member] \| Senao International Co., Ltd. (SENAO) [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	28.18%					28.18%
Chunghwa Telecom Co., Ltd. and Chunghwa Investment Co., Ltd. [Member] \| CHIEF Telecom Inc. ("CHIEF") [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	59.08%					59.75%
Youth Co., Ltd. ("Youth") [Member] \| Senao International Co., Ltd. (SENAO) [Member] \| Bottom of Range [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests					92.89%
Youth Co., Ltd. ("Youth") [Member] \| Senao International Co., Ltd. (SENAO) [Member] \| Top of Range [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests					95.79%
Aval Technologies Co., Ltd. ("Aval") [Member] \| Wiin Technology Co., Ltd. ("Wiin") [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests									100.00%
SENYOUNG Insurance Agent Co., Ltd. ("SENYOUNG") [Member] \| Senaolife Insurance Agent Co., Ltd. [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	100.00%					100.00%	100.00%
Light Era Development Co., Ltd. ("LED") [Member] \| Taoyuan Asia Silicon Valley Innovation Co., Ltd [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	0.00%					0.00%
Chunghwa Investment Co., Ltd. ("CHI") [Member] \| Chunghwa Precision Test Tech. Co., Ltd. ("CHPT") [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	34.25%					34.25%
Chunghwa Investment Co., Ltd. ("CHI") [Member] \| Chunghwa Precision Test Tech. Co., Ltd. ("CHPT") [Member] \| Bottom of Range [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	50.00%
Chunghwa Precision Test Tech. International Ltd. ("CHPT (International)") [Member] \| Su Zhou Precision Test Tech. Ltd. ("SZPT") [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	100.00%					100.00%		100.00%

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Additional information (Detail) - Chunghwa Investment Co., Ltd. ("CHI") [Member]	Dec. 31, 2020
CHIEF Telecom Inc. ("CHIEF") [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	2.95%
Senao International Co., Ltd. (SENAO) [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	0.39%

Critical Accounting Judgments_2

Critical Accounting Judgments and Key Sources of Estimation, Uncertainty and Assumption - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020
Top of Range [Member]
Disclosure Of Accounting Judgements And Estimates [Line Items]
Proportion of ownership interest held in some of entities	50.00%

U.S. Dollar Amounts - Additiona

U.S. Dollar Amounts - Additional Information (Detail)	Dec. 31, 2020TWD ($)
Foreign Exchange Rates [Abstract]
Exchange rate used for convenience translations	28.08

Cash and Cash Equivalents - Sum

Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2017TWD ($)
Cash
Cash on hand	$ 487		$ 353
Bank deposits	10,961		9,433
Cash	11,448		9,786
Cash equivalents (investments with maturities of less than three months)
Commercial paper	14,061		20,110
Negotiable certificates of deposit	2,600		1,700
Time deposits	2,308		2,451
Repurchase agreements collateralized by bonds	0		3
Government stimulus vouchers	3		0
Cash equivalents	18,972		24,264
Cash and cash equivalents	$ 30,420	$ 1,083	$ 34,050	$ 1,212	$ 27,645	$ 28,825

Cash and Cash Equivalents - Ann

Cash and Cash Equivalents - Annual Yield Rates of Bank Deposits, Commercial Paper, Negotiable Certificates of Deposit and Time Deposits and Repurchase Agreements Collateralized by Bonds (Detail)	Dec. 31, 2020	Dec. 31, 2019
Bank deposits [Member] \| Bottom of range [Member]
Disclosure of cash and cash equivalents [Line Items]
Yield rate	0.00%	0.00%
Bank deposits [Member] \| Top of Range [Member]
Disclosure of cash and cash equivalents [Line Items]
Yield rate	0.40%	0.74%
Commercial paper [Member] \| Bottom of range [Member]
Disclosure of cash and cash equivalents [Line Items]
Yield rate	0.14%	0.47%
Commercial paper [Member] \| Top of Range [Member]
Disclosure of cash and cash equivalents [Line Items]
Yield rate	0.26%	0.54%
Negotiable certificates of deposit [Member] \| Bottom of range [Member]
Disclosure of cash and cash equivalents [Line Items]
Yield rate	0.24%	0.58%
Negotiable certificates of deposit [Member] \| Top of Range [Member]
Disclosure of cash and cash equivalents [Line Items]
Yield rate	0.30%	0.60%
Time deposits [Member] \| Bottom of range [Member]
Disclosure of cash and cash equivalents [Line Items]
Yield rate	0.10%	0.09%
Time deposits [Member] \| Top of Range [Member]
Disclosure of cash and cash equivalents [Line Items]
Yield rate	3.60%	4.40%
Repurchase agreements collateralized by bonds [Member]
Disclosure of cash and cash equivalents [Line Items]
Yield rate		1.90%

Financial Instruments at Fair_3

Financial Instruments at Fair Value Through Profit or Loss - Summary of Financial Instruments at Fair Value through Profit or Loss (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Financial assets-current
Financial assets-current, Mandatorily measured at FVTPL	$ 10		$ 1
Financial assets-noncurrent
Non-derivatives	677		778
Financial liabilities-current
Financial liabilities held for trading, Derivatives (not designated for hedge), Forward exchange contracts	0	$ 0	0
Forward exchange contracts [Member]
Financial assets-current
Derivatives (not designated for hedge)	2		0
Listed stocks domestic [Member]
Financial assets-current
Non-derivatives	8		1
Non listed stocks domestic [Member]
Financial assets-noncurrent
Non-derivatives	441		511
Non listed stocks foreign [Member]
Financial assets-noncurrent
Non-derivatives	$ 236		$ 267

Financial Instruments at Fair_4

Financial Instruments at Fair Value Through Profit or Loss - Additional Information (Detail) - Taiwania Capital Buffalo Fund Co Ltd [Member] - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Oct. 31, 2019
Disclosure of detailed information about financial instruments [Line Items]
Amount invested in investment entity		$ 300
Ownership percentage in investment entity	12.90%

Financial Instruments at Fair_5

Financial Instruments at Fair Value Through Profit or Loss - Outstanding Forward Exchange Contracts Not Designated for Hedge (Detail) - Forward exchange contracts [Member] € in Millions, $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2020EUR (€)	Dec. 31, 2019USD ($)	Dec. 31, 2019EUR (€)
EUR [Member]
Disclosure of detailed information about financial instruments [Line Items]
Currency	NT$/EUR	NT$/EUR
Maturity Period	2021.03	2020.03
Contract Amount	$ 50	$ 51		€ 2		€ 2
USD [Member]
Disclosure of detailed information about financial instruments [Line Items]
Currency		NT$/US$
Maturity Period		2020.01
Contract Amount		$ 26			$ 1
Taiwan, New Dollars
Disclosure of detailed information about financial instruments [Line Items]
Currency	US$/NT$
Maturity Period	2021.02-03
Contract Amount	$ 379		$ 14

Financial Assets at Fair Valu_3

Financial Assets at Fair Value through Other Comprehensive Income Noncurrent - Summary of Financial Assets at Fair Value through Other Comprehensive Income Noncurrent (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of financial assets [Line Items]
Financial assets at fair value through other comprehensive income	$ 7,193	$ 256	$ 7,154
Domestic listed stocks [Member]
Disclosure of financial assets [Line Items]
Financial assets at fair value through other comprehensive income	2,754		2,454
Domestic non-listed stocks [Member]
Disclosure of financial assets [Line Items]
Financial assets at fair value through other comprehensive income	4,325		4,566
Foreign non-listed stocks [Member]
Disclosure of financial assets [Line Items]
Financial assets at fair value through other comprehensive income	$ 114		$ 134

Financial Assets at Fair Valu_4

Financial Assets at Fair Value through Other Comprehensive Income Noncurrent - Additional Information (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Noncurrent Financial Assets At Fair Value Through Other Comprehensive Income [Abstract]
fair value amount	$ 568
Investment settlement fuds	270
Unrealized gain on investments in equity instruments at fair value through other comprehensive income	17
Dividends received	$ 246	$ 296	$ 396

Trade Notes and Accounts Rece_3

Trade Notes and Accounts Receivable, Net - Summary of Trade Notes and Accounts Receivable, Net (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Jan. 01, 2019TWD ($)
Disclosure Of Financial Assets [Line Items]
Trade notes and accounts receivable	$ 22,622	$ 806	$ 26,408	$ 30,076
Less: Loss allowance	(2,154)		(2,360)
Gross carrying amount [Member]
Disclosure Of Financial Assets [Line Items]
Trade notes and accounts receivable	$ 24,776		$ 28,768

Trade Notes and Accounts Rece_4

Trade Notes and Accounts Receivable, Net - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Bottom of Range [Member]
Disclosure Of Financial Assets [Line Items]
Main credit terms	30 days	30 days
Top of Range [Member]
Disclosure Of Financial Assets [Line Items]
Main credit terms	90 days	90 days

Trade Notes and Accounts Rece_5

Trade Notes and Accounts Receivable, Net - Provision Matrix Arising from Telecommunications and Project Business (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Jan. 01, 2019TWD ($)
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 22,622	$ 806	$ 26,408	$ 30,076
Less: Loss allowance	(2,154)		(2,360)
Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	24,776		28,768
Telecommunications Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	(797)		(799)
Telecommunications Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	16,806		20,080
Telecommunications Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 16,009		19,281
Project Business [Member] \| Bottom of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	50.00%	50.00%
Project Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (1,320)		(1,502)
Project Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	4,866		5,699
Project Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 3,546		$ 4,197
Not Past Due [Member] \| Telecommunications Business [Member] \| Bottom of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	0.00%	0.00%	0.00%
Not Past Due [Member] \| Telecommunications Business [Member] \| Top of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	2.00%	2.00%	2.00%
Not Past Due [Member] \| Telecommunications Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (56)		$ (56)
Not Past Due [Member] \| Telecommunications Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	15,839		19,020
Not Past Due [Member] \| Telecommunications Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 15,783		$ 18,964
Not Past Due [Member] \| Project Business [Member] \| Bottom of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	0.00%	0.00%	0.00%
Not Past Due [Member] \| Project Business [Member] \| Top of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	5.00%	5.00%	5.00%
Not Past Due [Member] \| Project Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (20)		$ (3)
Not Past Due [Member] \| Project Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	3,473		4,054
Not Past Due [Member] \| Project Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 3,453		$ 4,051
Less Than 30 Days [Member] \| Telecommunications Business [Member] \| Bottom of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	2.00%	2.00%	0.00%
Less Than 30 Days [Member] \| Telecommunications Business [Member] \| Top of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	24.00%	24.00%	25.00%
Less Than 30 Days [Member] \| Telecommunications Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (21)		$ (26)
Less Than 30 Days [Member] \| Telecommunications Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	204		268
Less Than 30 Days [Member] \| Telecommunications Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 183		$ 242
Less Than 30 Days [Member] \| Project Business [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	5.00%	5.00%	5.00%
Less Than 30 Days [Member] \| Project Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (3)		$ (5)
Less Than 30 Days [Member] \| Project Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	64		78
Less Than 30 Days [Member] \| Project Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 61		$ 73
31-60 Days [Member] \| Telecommunications Business [Member] \| Bottom of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	3.00%	3.00%	0.00%
31-60 Days [Member] \| Telecommunications Business [Member] \| Top of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	68.00%	68.00%	68.00%
31-60 Days [Member] \| Telecommunications Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (24)		$ (28)
31-60 Days [Member] \| Telecommunications Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	51		75
31-60 Days [Member] \| Telecommunications Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 27		$ 47
31-60 Days [Member] \| Project Business [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	10.00%	10.00%	10.00%
31-60 Days [Member] \| Project Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (3)		$ (5)
31-60 Days [Member] \| Project Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	27		52
31-60 Days [Member] \| Project Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 24		$ 47
61-90 Days [Member] \| Telecommunications Business [Member] \| Bottom of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	11.00%	11.00%	0.00%
61-90 Days [Member] \| Telecommunications Business [Member] \| Top of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	83.00%	83.00%	83.00%
61-90 Days [Member] \| Telecommunications Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (25)		$ (35)
61-90 Days [Member] \| Telecommunications Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	31		47
61-90 Days [Member] \| Telecommunications Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 6		$ 12
61-90 Days [Member] \| Project Business [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	30.00%	30.00%	30.00%
61-90 Days [Member] \| Project Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (3)		$ (11)
61-90 Days [Member] \| Project Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	9		30
61-90 Days [Member] \| Project Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 6		$ 19
91-120 Days [Member] \| Telecommunications Business [Member] \| Bottom of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	28.00%	28.00%	11.00%
91-120 Days [Member] \| Telecommunications Business [Member] \| Top of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	90.00%	90.00%	90.00%
91-120 Days [Member] \| Telecommunications Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (24)		$ (26)
91-120 Days [Member] \| Telecommunications Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	30		41
91-120 Days [Member] \| Telecommunications Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 6		$ 15
91-120 Days [Member] \| Project Business [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	50.00%	50.00%	50.00%
91-120 Days [Member] \| Project Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (1)		$ (5)
91-120 Days [Member] \| Project Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	2		12
91-120 Days [Member] \| Project Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 1		$ 7
121-180 Days [Member] \| Telecommunications Business [Member] \| Bottom of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	52.00%	52.00%	17.00%
121-180 Days [Member] \| Telecommunications Business [Member] \| Top of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	96.00%	96.00%	96.00%
121-180 Days [Member] \| Telecommunications Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (21)		$ (27)
121-180 Days [Member] \| Telecommunications Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	25		28
121-180 Days [Member] \| Telecommunications Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 4		$ 1
121-180 Days [Member] \| Project Business [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	80.00%	80.00%	80.00%
121-180 Days [Member] \| Project Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (2)		$ (1)
121-180 Days [Member] \| Project Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	3		1
121-180 Days [Member] \| Project Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 1		$ 0
Over 180 Days [Member] \| Telecommunications Business [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	100.00%	100.00%	100.00%
Over 180 Days [Member] \| Telecommunications Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (626)		$ (601)
Over 180 Days [Member] \| Telecommunications Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	626		601
Over 180 Days [Member] \| Telecommunications Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 0		$ 0
Over 180 Days [Member] \| Project Business [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	100.00%	100.00%	100.00%
Over 180 Days [Member] \| Project Business [Member] \| Loss allowance [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Less: Loss allowance	$ (1,288)		$ (1,472)
Over 180 Days [Member] \| Project Business [Member] \| Gross carrying amount [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	1,288		1,472
Over 180 Days [Member] \| Project Business [Member] \| Amortized Cost [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Trade notes and accounts receivable	$ 0		$ 0

Trade Notes and Accounts Rece_6

Trade Notes and Accounts Receivable, Net - Provision Matrix Arising from Telecommunications and Project Business (Parenthetical) (Detail)	Dec. 31, 2020
Project Business [Member] \| Bottom of Range [Member]
Disclosure of financial assets that are either past due or impaired [Line Items]
Expected credit loss rate	50.00%

Trade Notes and Accounts Rece_7

Trade Notes and Accounts Receivable, Net - Movements of Allowance for Doubtful Accounts, Trade Notes and Accounts Receivable (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Financial Assets [Line Items]
Beginning balance	$ 2,360
Add: Provision for (reversal of) credit loss	49	$ (54)	$ 805
Ending balance	2,154	2,360
Trade notes and accounts receivable [Member]
Disclosure Of Financial Assets [Line Items]
Beginning balance	2,360	2,602
Add: Provision for (reversal of) credit loss	49	(54)
Add: Acquired by business combinations (Note 14)	2
Less: Amounts written off	(257)	(188)
Ending balance	$ 2,154	$ 2,360	$ 2,602

Inventories - Summary of Invent

Inventories - Summary of Inventories (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Classes Of Inventories [Abstract]
Merchandise	$ 3,903		$ 3,858
Project in process	6,167		11,113
Work in process	126		141
Raw materials	137		156
Inventories subtotal	10,333		15,268
Land held under development	1,999		1,999
Construction in progress	77		77
Inventories	$ 12,409	$ 442	$ 17,344

Inventories - Additional Inform

Inventories - Additional Information (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Classes Of Inventories [Abstract]
Operating costs related to inventories	$ 53,847		$ 49,258	$ 48,649
Valuation loss on inventories recognized as operating costs	1,161	$ 41	475	$ 365
Inventory to be recovered longer than twelve months	$ 2,076		$ 2,076

Prepayments - Summary of Prepay

Prepayments - Summary of Prepayments (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Prepayments [Abstract]
Prepaid rents	$ 2,864		$ 3,382
Others	1,656		1,180
Prepayments	4,520		4,562
Prepaid rents	652		704
Others	1,654		1,179
Current prepayments	2,306	$ 82	1,883
Prepaid rents	2,212		2,678
Others	2		1
Noncurrent prepayments	$ 2,214	$ 79	$ 2,679

Other Current Monetary Assets -

Other Current Monetary Assets - Summary of Other Current Monetary Assets (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure Of Other Current Monetary Assets [Abstract]
Time deposits and negotiable certificates of deposit with maturities of more than three months	$ 4,596		$ 5,959
Repurchase agreements collateralized by bonds with maturities of more than three months	0		15
Others	1,528		1,524
Other current monetary assets	$ 6,124	$ 218	$ 7,498

Other Current Monetary Assets_2

Other Current Monetary Assets - Annual Yield Rates of Time Deposits, Negotiable Certificates of Deposits and Repurchase Agreements Collateralized by Bonds with Maturities of more Than Three Months (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020
Disclosure of annual yield rates of other current monetary assets [Line Items]
Repurchase agreements collateralized by bonds with maturities of more than three months	2.50%
Bottom of range [Member]
Disclosure of annual yield rates of other current monetary assets [Line Items]
Time deposits and negotiable certificates of deposit with maturities of more than three months	0.03%	0.07%
Top of Range [Member]
Disclosure of annual yield rates of other current monetary assets [Line Items]
Time deposits and negotiable certificates of deposit with maturities of more than three months	2.73%	2.25%

Subsidiaries - Less Than Wholly

Subsidiaries - Less Than Wholly Owned Subsidiaries of the Company That Have Material Noncontrolling Interests (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2020USD ($)
Disclosure of subsidiaries [Line Items]
Profit Allocated to Noncontrolling Interests	$ 1,285	$ 46	$ 974	$ 1,024
Accumulated Noncontrolling Interests	$ 11,158		$ 10,115		$ 397
Senao International Co., Ltd. (SENAO) [Member]
Disclosure of subsidiaries [Line Items]
Place of Incorporation	Taiwan	Taiwan
Principal Place of Business	Taiwan	Taiwan
Proportion of Ownership Interests Held by Noncontrolling Interests	72.00%	72.00%	72.00%
Proportion of Voting Rights Held by Noncontrolling Interests	72.00%	72.00%	72.00%
Profit Allocated to Noncontrolling Interests	$ 312		$ 291	326
Accumulated Noncontrolling Interests	$ 4,189		$ 4,146
Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member]
Disclosure of subsidiaries [Line Items]
Place of Incorporation	Taiwan	Taiwan
Principal Place of Business	Taiwan	Taiwan
Proportion of Ownership Interests Held by Noncontrolling Interests	66.00%	66.00%	66.00%
Proportion of Voting Rights Held by Noncontrolling Interests	66.00%	66.00%	66.00%
Profit Allocated to Noncontrolling Interests	$ 604		$ 414	$ 477
Accumulated Noncontrolling Interests	4,606		4,217
Individually immaterial subsidiaries with noncontrolling interests [Member]
Disclosure of subsidiaries [Line Items]
Accumulated Noncontrolling Interests	$ 2,363		$ 1,752

Subsidiaries - Summarized Finan

Subsidiaries - Summarized Financial Information Before Intercompany Eliminations (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2020USD ($)
Disclosure of subsidiaries [Line Items]
Current assets	$ 81,803		$ 94,072		$ 2,913
Noncurrent assets	424,377		383,056		15,113
Current liabilities	73,223		66,143		2,608
Noncurrent liabilities	45,684		26,713		1,627
Equity attributable to the parent	376,115		374,157		13,394
NONCONTROLLING INTERESTS	11,158		10,115		$ 397
NET INCOME	34,704	$ 1,236	33,921	$ 38,581
Profit attributable to the parent	33,419	1,190	32,947	37,557
Profit attributable to noncontrolling interests	1,285	46	974	1,024
Other comprehensive income (loss) for the year	1,290	46	1,328	(1,014)
Total comprehensive income attributable to the parent	34,713	1,236	34,282	36,552
Total comprehensive income attributable to noncontrolling interests	1,281	46	967	1,015
TOTAL COMPREHENSIVE INCOME	35,994	1,282	35,249	37,567
Net cash flow from operating activities	74,456	2,652	72,427	66,366
Net cash flow from investing activities	(68,254)	(2,431)	(27,127)	(32,614)
Net cash flow from financing activities	(9,802)	(349)	(38,934)	(35,035)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	(30)	(1)	39	103
Net cash inflow	(3,630)	$ (129)	6,405	(1,180)
Senao International Co., Ltd. (SENAO) [Member]
Disclosure of subsidiaries [Line Items]
Current assets	6,834		6,751
Noncurrent assets	3,194		3,173
Current liabilities	3,854		3,637
Noncurrent liabilities	416		590
Equity attributable to the parent	1,569		1,551
NONCONTROLLING INTERESTS	4,189		4,146
Revenues and income	27,232		29,131	31,540
Costs and expenses	26,797		28,725	31,081
NET INCOME	435		406	459
Profit attributable to the parent	123		115	133
Profit attributable to noncontrolling interests	312		291	326
Other comprehensive income (loss) attributable to the parent	1		(7)	(2)
Other comprehensive income (loss) attributable to noncontrolling interests	2		22	(10)
Other comprehensive income (loss) for the year	3		15	(12)
Total comprehensive income attributable to the parent	124		108	131
Total comprehensive income attributable to noncontrolling interests	314		313	316
TOTAL COMPREHENSIVE INCOME	438		421	447
Net cash flow from operating activities	862		538	696
Net cash flow from investing activities	54		235	(13)
Net cash flow from financing activities	(687)		(718)	(491)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	0		0	1
Net cash inflow	229		55	193
Dividends paid to noncontrolling interests	269		269	587
Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member]
Disclosure of subsidiaries [Line Items]
Current assets	4,122		3,710
Noncurrent assets	4,013		4,044
Current liabilities	1,115		1,316
Noncurrent liabilities	12		22
Equity attributable to the parent	2,402		2,199
NONCONTROLLING INTERESTS	4,606		4,217
Revenues and income	4,221		3,404	3,299
Costs and expenses	3,301		2,775	2,549
NET INCOME	920		629	750
Profit attributable to the parent	316		215	273
Profit attributable to noncontrolling interests	604		414	477
Other comprehensive income (loss) attributable to the parent	0		(1)	0
Other comprehensive income (loss) attributable to noncontrolling interests	0		(2)	0
Other comprehensive income (loss) for the year	0		(3)	0
Total comprehensive income attributable to the parent	316		214	273
Total comprehensive income attributable to noncontrolling interests	604		412	477
TOTAL COMPREHENSIVE INCOME	920		626	750
Net cash flow from operating activities	1,483		507	862
Net cash flow from investing activities	(533)		(1,426)	(733)
Net cash flow from financing activities	(349)		(349)	(328)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	1		(5)	1
Net cash inflow	602		(1,273)	(198)
Dividends paid to noncontrolling interests	$ 216		$ 216	$ 210

Subsidiaries - Additional Infor

Subsidiaries - Additional Information (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Sep. 30, 2020	Jul. 31, 2020	Jul. 01, 2020TWD ($)
Disclosure of subsidiaries [Line Items]
Revenue	$ 207,609	$ 7,393	$ 207,520	$ 215,483
IISI and its Subsidiaries [Member]
Disclosure of subsidiaries [Line Items]
Fair value of trade notes and accounts receivable acquired							$ 165
Gross contractual amount							167
Best estimates of contractual cash flows not expected to be collected as of acquisition date							$ 2
Revenue	208,605
Profit	$ 34,747
International Integrated Systems, Inc. ("IISI") [Member]
Disclosure of subsidiaries [Line Items]
Equity ownership percentage	51.00%	51.00%	0.00%		51.20%	51.54%
Percentage of additional ownership interest obtained							20.38%
Chunghwa Investment Co., Ltd. ("CHI") [Member] \| Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member]
Disclosure of subsidiaries [Line Items]
Equity ownership percentage	34.25%	34.25%	34.25%
Chunghwa Telecom Co., Ltd. and Chunghwa Investment Co., Ltd. (CHI) [Member] \| CHIEF Telecom Inc. (CHIEF) [Member]
Disclosure of subsidiaries [Line Items]
Equity ownership percentage	59.08%	59.08%	59.75%
Chunghwa Telecom Co., Ltd. and Chunghwa Investment Co., Ltd. (CHI) [Member] \| Senao International Co., Ltd. (SENAO) [Member]
Disclosure of subsidiaries [Line Items]
Equity ownership percentage	28.18%	28.18%	28.18%
Senao International Co., Ltd. (SENAO) [Member] \| Youth Co., Ltd. ("Youth") [Member]
Disclosure of subsidiaries [Line Items]
Equity ownership percentage	96.00%	96.00%	93.00%

Subsidiaries - Detailed Informa

Subsidiaries - Detailed Information of Equity Transactions (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Senao International Co Ltd Transferred Its Treasury Stock [Member]
Disclosure Of Classes Of Share Capital [Line Items]
Cash consideration received from noncontrolling interests			$ 327
The proportionate share of the carrying amount of the net assets of the subsidiary transferred (to) from noncontrolling interests			(272)
Differences arising from equity transactions			55
Additional paid-in capital - arising from changes in equities of subsidiaries			55
Chunghwa Telecom Co Ltd and Chunghwa Investment Co Ltd Disposed Some Shares of CHIEF Telecom Inc [Member]
Disclosure Of Classes Of Share Capital [Line Items]
Cash consideration received from noncontrolling interests			133
The proportionate share of the carrying amount of the net assets of the subsidiary transferred (to) from noncontrolling interests			(19)
Differences arising from equity transactions			114
Additional paid-in capital - difference between consideration received or paid and the carrying amount of the subsidiaries net assets upon actual disposal or acquisition			114
Chunghwa Investment Co Ltd Disposed Some Shares Of Chunghwa Precision Test Tech Co Ltd
Disclosure Of Classes Of Share Capital [Line Items]
Cash consideration received from noncontrolling interests			1,042
The proportionate share of the carrying amount of the net assets of the subsidiary transferred (to) from noncontrolling interests			(330)
Differences arising from equity transactions			712
Additional paid-in capital - difference between consideration received or paid and the carrying amount of the subsidiaries net assets upon actual disposal or acquisition			712
Chunghwa Telecom Co Ltd and Chunghwa Investment Co Ltd Did Not Participate in the Capital Increase of CHIEF Telecom Inc [Member]
Disclosure Of Classes Of Share Capital [Line Items]
Cash consideration received from noncontrolling interests			1,477
The proportionate share of the carrying amount of the net assets of the subsidiary transferred (to) from noncontrolling interests			(700)
Differences arising from equity transactions			777
Additional paid-in capital - arising from changes in equities of subsidiaries			777
Share-Based Payment of CHIEF Telecom Inc [Member]
Disclosure Of Classes Of Share Capital [Line Items]
Cash consideration received from noncontrolling interests	$ 75	$ 19	35
The proportionate share of the carrying amount of the net assets of the subsidiary transferred (to) from noncontrolling interests	(49)	(20)	(24)
Differences arising from equity transactions	26	(1)	11
Additional paid-in capital - arising from changes in equities of subsidiaries	26	$ (1)	11
SENAO not Proportionately participating in the Capital Increase of Youth [Member]
Disclosure Of Classes Of Share Capital [Line Items]
Cash consideration received from noncontrolling interests	0		0
The proportionate share of the carrying amount of the net assets of the subsidiary transferred (to) from noncontrolling interests	0		0
Differences arising from equity transactions	0		0
Additional paid-in capital - arising from changes in equities of subsidiaries	0		$ 0
IISI Share-Based Payment [Member]
Disclosure Of Classes Of Share Capital [Line Items]
Cash consideration received from noncontrolling interests	7
The proportionate share of the carrying amount of the net assets of the subsidiary transferred (to) from noncontrolling interests	(7)
Differences arising from equity transactions	0
Additional paid-in capital - arising from changes in equities of subsidiaries	$ 0

Subsidiaries - Summary of Asset

Subsidiaries - Summary of Assets Acquired and Liabilities Assumed (Detail) $ in Millions	Jul. 01, 2020TWD ($)
Current liabilities
Provisions	$ (15)
IISI and its Subsidiaries [Member]
Current assets
Cash and cash equivalents	588
Contract assets	583
Trade notes and accounts receivable	165
Inventories	141
Prepayments	114
Other current monetary assets	114
Other current assets	75
Noncurrent assets
Property, plant and equipment	48
Right-of-use assets	70
Intangible assets	12
Deferred income tax assets	6
Other noncurrent assets	102
Current liabilities
Short-term loans	(4)
Contract liabilities	(334)
Trade notes and accounts payable	(257)
Current tax liabilities	(19)
Lease liabilities	(26)
Other payables	(266)
Provisions	(15)
Other current liabilities	(30)
Noncurrent liabilities
Deferred income tax liabilities	(3)
Lease liabilities	(45)
Net defined benefit liabilities	(32)
Other noncurrent liabilities	(5)
Identifiable assets acquired (liabilities assumed)	$ 982

Subsidiaries - Summary of Goodw

Subsidiaries - Summary of Goodwill Arising from Acquisition (Detail) - IISI and its Subsidiaries [Member] $ in Millions	Jul. 01, 2020TWD ($)
Disclosure Of Business Combinations [Line Items]
Consideration transferred	$ 234
Add: Fair value of equity interest held before the acquisition date	327
Add: Noncontrolling interest (48.46% of the identifiable net assets of IISI and its subsidiaries)	476
Less: Fair value of identifiable net assets acquired	(982)
Goodwill arising from acquisition	$ 55

Subsidiaries - Summary of Goo_2

Subsidiaries - Summary of Goodwill Arising from Acquisition (Parenthetical) (Detail)	Jul. 01, 2020
IISI and its Subsidiaries [Member]
Disclosure Of Business Combinations [Line Items]
Percentage of noncontrolling interest in identifiable net assets	48.46%

Subsidiaries - Summary of Net C

Subsidiaries - Summary of Net Cash Inflow on Acquisition of Subsidiaries (Detail) - IISI and its Subsidiaries [Member] $ in Millions	Jul. 01, 2020TWD ($)
Disclosure Of Business Combinations [Line Items]
Cash and cash equivalents acquired	$ 588
Less: Consideration paid in cash	(234)
Net cash inflow on acquisition of subsidiaries	$ 354

Subsidiaries - Summary of Impac

Subsidiaries - Summary of Impact of Acquisition on Financial Results of Company (Detail) - IISI and its Subsidiaries [Member] $ in Millions	6 Months Ended
	Dec. 31, 2020TWD ($)
Disclosure Of Business Combinations [Line Items]
Revenue	$ 1,348
Profit	$ 68

Investments Accounted for Usi_3

Investments Accounted for Using Equity Method - Investments in Associates (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2020USD ($)	Jun. 30, 2020	Nov. 30, 2019TWD ($)	Feb. 28, 2019
Disclosure of associates [Line Items]
Investments in associates	$ 6,685,000,000		$ 7,139,000,000
Investment in joint venture	10,000,000		0
Investments accounted for using equity method	6,695,000,000		7,139,000,000		$ 238
The Company’s share of profits	244,000,000	$ 9	459,000,000	$ 509,000,000
Next Commercial Bank Co., Ltd. (“NCB”) [Member]
Disclosure of associates [Line Items]
Investments in associates	3,777,000,000		4,074,000,000				$ 4,190,000,000
Investments accounted for using equity method	$ 3,777,000,000		$ 4,074,000,000
Percentage of ownership in associates	41.90%		41.90%		41.90%		41.90%	41.90%
Percentage of voting rights in associates	42.00%		42.00%		42.00%
Senao Networks, Inc. ("SNI") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 841,000,000		$ 803,000,000
Percentage of ownership in associates	34.00%		34.00%		34.00%
Percentage of voting rights in associates	34.00%		34.00%		34.00%
Fair values based on the closing market prices	$ 1,708,000,000		$ 2,014,000,000
ST-2 Satellite Ventures Pte., Ltd. ("STS") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 488,000,000		$ 501,000,000
Percentage of ownership in associates	38.00%		38.00%		38.00%
Percentage of voting rights in associates	38.00%		38.00%		38.00%
International Integrated Systems, Inc. ("IISI") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 0		$ 335,000,000
Percentage of ownership in associates	0.00%		31.47%		0.00%	31.16%
Percentage of voting rights in associates	0.00%		31.00%		0.00%
Viettel-CHT Co., Ltd. ("Viettel-CHT") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 363,000,000		$ 317,000,000
Percentage of ownership in associates	30.00%		30.00%		30.00%
Percentage of voting rights in associates	30.00%		30.00%		30.00%
Taiwan International Standard Electronics Co., Ltd. ("TISE") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 324,000,000		$ 268,000,000
Percentage of ownership in associates	40.00%		40.00%		40.00%
Percentage of voting rights in associates	40.00%		40.00%		40.00%
Chunghwa PChome Fund I Co., Ltd. ("CPFI") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 193,000,000		$ 194,000,000
Percentage of ownership in associates	50.00%		50.00%		50.00%
Percentage of voting rights in associates	50.00%		50.00%		50.00%
KingwayTek Technology Co., Ltd. ("KWT") - Listed [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 213,000,000		$ 217,000,000
So-net Entertainment Taiwan Limited ("So-net") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 225,000,000		$ 186,000,000
Percentage of ownership in associates	30.00%		30.00%		30.00%
Percentage of voting rights in associates	30.00%		30.00%		30.00%
Taiwan International Ports Logistics Corporation ("TIPL") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 56,000,000		$ 51,000,000
Percentage of ownership in associates	27.00%		27.00%		27.00%
Percentage of voting rights in associates	27.00%		27.00%		27.00%
Click Force Co., Ltd. ("CF") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 33,000,000		$ 37,000,000
Percentage of ownership in associates	49.00%		49.00%		49.00%
Percentage of voting rights in associates	49.00%		49.00%		49.00%
KKBOX Taiwan Co., Ltd. ("KKBOXTW") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 163,000,000		$ 151,000,000
Percentage of ownership in associates	30.00%		30.00%		30.00%
Percentage of voting rights in associates	30.00%		30.00%		30.00%
Alliance Digital Tech Co., Ltd. ("ADT") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 3,000,000		$ 3,000,000
Percentage of ownership in associates	14.00%		14.00%		14.00%
Percentage of voting rights in associates	14.00%		14.00%		14.00%
Cornerstone Ventures Co., Ltd. ("CVC") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 6,000,000		$ 5,000,000
Percentage of ownership in associates	49.00%		49.00%		49.00%
Percentage of voting rights in associates	49.00%		49.00%		49.00%
MeWorks LIMITED (HK) ("MeWorks") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 0		$ 0
Percentage of ownership in associates	0.00%		20.00%		0.00%
Percentage of voting rights in associates	0.00%		20.00%		0.00%
UUPON Inc. ("UUPON") [Member]
Disclosure of associates [Line Items]
Investments in associates	$ 0
Increase (decrease) in Investments in associates			$ (3,000,000)
Percentage of ownership in associates	0.00%		22.00%		0.00%
Percentage of voting rights in associates	0.00%		22.00%		0.00%
KingwayTek Technology Co., Ltd. ("KWT") [Member]
Disclosure of associates [Line Items]
Percentage of ownership in associates	22.72%		22.52%		22.72%
Percentage of voting rights in associates	23.00%		23.00%		23.00%
Fair values based on the closing market prices	$ 676,000,000		$ 873,000,000
Associates [Member]
Disclosure of associates [Line Items]
The Company’s share of profits	540,000,000		575,000,000	509,000,000
The Company’s share of other comprehensive income (loss)	(8,000,000)		(3,000,000)	5,000,000
The Company’s share of total comprehensive income	$ 532,000,000		$ 572,000,000	$ 514,000,000

Investments Accounted For Usi_4

Investments Accounted For Using Equity Method - Additional Information (Detail)	Jul. 01, 2020TWD ($)	Sep. 30, 2020	Apr. 30, 2019TWD ($)	Jun. 30, 2018TWD ($)	Jan. 31, 2018TWD ($)	Dec. 31, 2020TWD ($)NumberofSeat	Dec. 31, 2019TWD ($)	Jun. 30, 2020	Jan. 31, 2020	Nov. 30, 2019TWD ($)	Feb. 28, 2019	Oct. 31, 2018
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Investments in associates						$ 6,685,000,000	$ 7,139,000,000
Investment in joint venture						$ 10,000,000	$ 0
KingwayTek Technology Co., Ltd. ("KWT") [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Percentage of ownership in associates						22.72%	22.52%
Gain on disposal of investment			$ 151,000,000
Taiwan International Ports Logistics Corporation ("TIPL") [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Percentage of ownership in associates						27.00%	27.00%
Investments in associates						$ 56,000,000	$ 51,000,000
Click Force Co., Ltd. ("CF") [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Percentage of ownership in associates						49.00%	49.00%
Investments in associates						$ 33,000,000	$ 37,000,000
Alliance Digital Tech Co., Ltd. ("ADT") [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Ownership interest in associates						14.00%
Percentage of ownership in associates						14.00%	14.00%
Investments in associates						$ 3,000,000	$ 3,000,000
MeWorks LIMITED (HK) ("MeWorks") [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Percentage of ownership in associates						0.00%	20.00%
Investments in associates						$ 0	$ 0
Next Commercial Bank Co., Ltd. (“NCB”) [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Percentage of ownership in associates						41.90%	41.90%			41.90%	41.90%
Investments in associates						$ 3,777,000,000	$ 4,074,000,000			$ 4,190,000,000
International Integrated Systems, Inc. ("IISI") [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Percentage of ownership in associates						0.00%	31.47%	31.16%
Investments in associates						$ 0	$ 335,000,000
International Integrated Systems, Inc. ("IISI") [Member] \| Subsequent Events [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Investment percentage of ownership interest									20.58%
Gain on disposal of investment	$ 1,000,000
UUPON Inc. ("UUPON") [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Ownership interest in associates						5.36%
Percentage of ownership in associates						0.00%	22.00%
Investments in associates						$ 0
Gain on disposal of investment						15,000,000
Reduction percentage of capital to offset accumulated deficit		95.44%
Chunghwa SEA Holdings (“CHT SEA”) [Member] \| Joint ventures [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Investment in joint venture						$ 10,000,000	$ 0
Percentage of ownership in joint venture						51.00%	0.00%
HopeTech Technologies Limited [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Proceeds From Capital Reduction					$ 19,000,000
Proceeds from disposal of shares				$ 3,000,000
Losses on disposals recognized				$ 100,000
Chunghwa PChome Fund I Co., Ltd. ("CPFI") [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Percentage of ownership in associates												50.00%
No of seats allotted \| NumberofSeat						2
Number of seats available for board of directors \| NumberofSeat						5
Cornerstone Ventures Co., Ltd. ("CVC") [Member]
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items]
Percentage of ownership in associates												49.00%
No of seats allotted \| NumberofSeat						2
Number of seats available for board of directors \| NumberofSeat						5

Investments Accounted for Usi_5

Investments Accounted for Using Equity Method - Summary of Financial Information of Investments in Associates (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2020USD ($)	Nov. 30, 2019	Feb. 28, 2019	Dec. 31, 2017TWD ($)
Condensed Financial Statements Captions [Line Items]
Assets	$ 506,180		$ 477,128		$ 18,026
Liabilities	(118,907)		(92,856)		(4,235)
Total equity	387,273		384,272	$ 384,529	13,791			$ 382,124
Investments accounted for using equity method	6,695		7,139		$ 238
Revenues	207,609	$ 7,393	207,520	215,483
Net loss for the period	34,704	1,236	33,921	38,581
Total other comprehensive income (loss), net of income tax	1,290	46	1,328	(1,014)
TOTAL COMPREHENSIVE INCOME	35,994	$ 1,282	35,249	$ 37,567
Next Commercial Bank Co., Ltd. (“NCB”) [Member]
Condensed Financial Statements Captions [Line Items]
Assets	9,907		10,452
Liabilities	(789)		(728)
Total equity	$ 9,118		$ 9,724
Percentage of ownership in associates	41.90%		41.90%		41.90%	41.90%	41.90%
Equity attributable to the Company	$ 3,820		$ 4,074
Unrealized gain or loss from downstream transactions	(43)
Investments accounted for using equity method	3,777		4,074
Net loss for the period	(605)		(276)
TOTAL COMPREHENSIVE INCOME	$ (605)		$ (276)

Investments Accounted for Usi_6

Investments Accounted for Using Equity Method - Investments in Joint Ventures (Detail) - TWD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of joint ventures [Line Items]
Investment in joint venture	$ 10,000,000	$ 0
Joint ventures [Member] \| Chunghwa SEA Holdings (“CHT SEA”) [Member]
Disclosure of joint ventures [Line Items]
Investment in joint venture	$ 10,000,000	$ 0
Percentage of ownership in joint venture	51.00%	0.00%
Percentage of voting rights in joint venture	51.00%	0.00%

Property, Plant and Equipment -

Property, Plant and Equipment - Summary of Property, Plant and Equipment (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	$ 283,694		$ 288,914
Depreciation expenses	(26,989)		(26,930)	$ (27,461)
Additions	25,195		23,164	27,979
Disposal	(307)		(86)	(122)
Impairment losses	0	$ 0	93	0
Ending balance	$ 281,416	$ 10,022	283,694	288,914
Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			940,891	946,460
Additions				27,979
Disposal				(33,350)
Effect of foreign exchange differences				60
Others				(258)
Ending balance				940,891
Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(651,977)	(657,752)
Depreciation expenses				(27,461)
Disposal				33,228
Effect of foreign exchange differences				(20)
Others				28
Ending balance				(651,977)
Land [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			103,972
Ending balance				103,972
Land [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			103,972	104,079
Additions				0
Disposal				(71)
Effect of foreign exchange differences				0
Others				(36)
Ending balance				103,972
Land [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			0	0
Depreciation expenses				0
Disposal				0
Effect of foreign exchange differences				0
Others				0
Ending balance				0
Land improvements [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			263
Ending balance				263
Land improvements [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			1,601	1,595
Additions				0
Disposal				0
Effect of foreign exchange differences				0
Others				6
Ending balance				1,601
Land improvements [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(1,338)	(1,293)
Depreciation expenses				(45)
Disposal				0
Effect of foreign exchange differences				0
Others				0
Ending balance				(1,338)
Buildings [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			44,784
Ending balance				44,784
Buildings [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			72,911	72,694
Additions				21
Disposal				0
Effect of foreign exchange differences				0
Others				196
Ending balance				72,911
Buildings [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(28,127)	(26,799)
Depreciation expenses				(1,356)
Disposal				0
Effect of foreign exchange differences				0
Others				28
Ending balance				(28,127)
Computer equipment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			2,115
Ending balance				2,115
Computer equipment [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			14,258	14,162
Additions				52
Disposal				(643)
Effect of foreign exchange differences				0
Others				687
Ending balance				14,258
Computer equipment [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(12,143)	(11,788)
Depreciation expenses				(983)
Disposal				632
Effect of foreign exchange differences				0
Others				(4)
Ending balance				(12,143)
Telecommunications equipment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			116,322
Ending balance				116,322
Telecommunications equipment [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			715,748	722,054
Additions				159
Disposal				(31,984)
Effect of foreign exchange differences				60
Others				25,459
Ending balance				715,748
Telecommunications equipment [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(599,426)	(607,154)
Depreciation expenses				(24,236)
Disposal				31,952
Effect of foreign exchange differences				(20)
Others				32
Ending balance				(599,426)
Transportation equipment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			231
Ending balance				231
Transportation equipment [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			3,882	3,834
Additions				0
Disposal				(29)
Effect of foreign exchange differences				0
Others				77
Ending balance				3,882
Transportation equipment [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(3,651)	(3,513)
Depreciation expenses				(162)
Disposal				29
Effect of foreign exchange differences				0
Others				(5)
Ending balance				(3,651)
Miscellaneous equipment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			2,582
Ending balance				2,582
Miscellaneous equipment [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			9,874	9,515
Additions				334
Disposal				(623)
Effect of foreign exchange differences				0
Others				648
Ending balance				9,874
Miscellaneous equipment [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(7,292)	(7,205)
Depreciation expenses				(679)
Disposal				615
Effect of foreign exchange differences				0
Others				(23)
Ending balance				(7,292)
Construction in progress and equipment to be accepted [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			18,645
Ending balance				18,645
Construction in progress and equipment to be accepted [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			18,645	18,527
Additions				27,413
Disposal				0
Effect of foreign exchange differences				0
Others				(27,295)
Ending balance				18,645
Construction in progress and equipment to be accepted [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			$ 0	0
Depreciation expenses				0
Disposal				0
Effect of foreign exchange differences				0
Others				0
Ending balance				$ 0

Property, Plant and Equipment_2

Property, Plant and Equipment - Estimated Service Lives of Property, Plant and Equipment (Detail)	12 Months Ended
	Dec. 31, 2018
Land improvements [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P8Y
Land improvements [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P30Y
Main buildings [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P35Y
Main buildings [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P60Y
Other building facilities [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P3Y
Other building facilities [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P20Y
Computer equipment [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P2Y
Computer equipment [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P8Y
Telecommunication circuits [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P2Y
Telecommunication circuits [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P30Y
Telecommunication machinery and antennas equipment [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P2Y
Telecommunication machinery and antennas equipment [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P30Y
Transportation equipment [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P3Y
Transportation equipment [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P10Y
Leasehold improvements [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P1Y
Leasehold improvements [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P6Y
Mechanical and air conditioner equipment [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P3Y
Mechanical and air conditioner equipment [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P16Y
Others [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P1Y
Others [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P10Y

Property, Plant and Equipment_3

Property, Plant and Equipment - Summary of Assets Used by the Company (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure Of Property Plant And Equipment [Line Items]
Assets used by the Company	$ 281,416	$ 10,022	$ 283,694	$ 288,914
Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Assets used by the Company	7,593		7,324
Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Assets used by the Company	$ 273,823		$ 276,370

Property, Plant and Equipment_4

Property, Plant and Equipment - Summary of Property, Plant and Equipment - Asset Used by The Company (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	$ 283,694,000,000		$ 288,914,000,000
Depreciation expenses	(26,989,000,000)		(26,930,000,000)	$ (27,461,000,000)
Additions	25,195,000,000		23,164,000,000	27,979,000,000
Disposal	(307,000,000)		(86,000,000)	(122,000,000)
Impairment losses	0	$ 0	93,000,000	0
Ending balance	281,416,000,000	$ 10,022	283,694,000,000	288,914,000,000
Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	276,370,000,000
Impairment losses	0
Ending balance	273,823,000,000		276,370,000,000
Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			940,891,000,000	946,460,000,000
Additions				27,979,000,000
Disposal				(33,350,000,000)
Effect of foreign exchange differences				60,000,000
Others				(258,000,000)
Ending balance				940,891,000,000
Carrying Amount [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	918,513,000,000		940,891,000,000
Effect of retrospective application of IFRS 16			(11,086,000,000)
Additions	25,195,000,000		23,160,000,000
Disposal	(22,796,000,000)		(32,837,000,000)
Effect of foreign exchange differences	(98,000,000)		(44,000,000)
Acquired by business combinations (Note 14)	142,000,000
Others	(541,000,000)		(1,571,000,000)
Ending balance	920,415,000,000		918,513,000,000	940,891,000,000
Carrying Amount [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			929,805,000,000
Ending balance				929,805,000,000
Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(651,977,000,000)	(657,752,000,000)
Depreciation expenses				(27,461,000,000)
Disposal				33,228,000,000
Effect of foreign exchange differences				(20,000,000)
Others				28,000,000
Ending balance				(651,977,000,000)
Accumulated depreciation, amortization and impairment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	(642,143,000,000)		(651,977,000,000)
Depreciation expenses	(26,907,000,000)		(26,856,000,000)
Effect of retrospective application of IFRS 16			3,842,000,000
Disposal	22,489,000,000		32,751,000,000
Impairment losses			(93,000,000)
Effect of foreign exchange differences	41,000,000		17,000,000
Acquired by business combinations (Note 14)	(94,000,000)
Others	22,000,000		173,000,000
Ending balance	(646,592,000,000)		(642,143,000,000)	(651,977,000,000)
Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(648,135,000,000)
Ending balance				(648,135,000,000)
Land [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			103,972,000,000
Ending balance				103,972,000,000
Land [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	99,103,000,000
Ending balance	101,991,000,000		99,103,000,000
Land [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			103,972,000,000	104,079,000,000
Additions				0
Disposal				(71,000,000)
Effect of foreign exchange differences				0
Others				(36,000,000)
Ending balance				103,972,000,000
Land [Member] \| Carrying Amount [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	99,103,000,000		103,972,000,000
Effect of retrospective application of IFRS 16			(3,617,000,000)
Additions	67,000,000		0
Disposal	(270,000,000)		(38,000,000)
Effect of foreign exchange differences	0		0
Acquired by business combinations (Note 14)	0
Others	3,091,000,000		(1,214,000,000)
Ending balance	101,991,000,000		99,103,000,000	103,972,000,000
Land [Member] \| Carrying Amount [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			100,355,000,000
Ending balance				100,355,000,000
Land [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			0	0
Depreciation expenses				0
Disposal				0
Effect of foreign exchange differences				0
Others				0
Ending balance				0
Land [Member] \| Accumulated depreciation, amortization and impairment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	0		0
Depreciation expenses	0		0
Effect of retrospective application of IFRS 16			0
Disposal	0		0
Impairment losses			0
Effect of foreign exchange differences	0		0
Acquired by business combinations (Note 14)	0
Others	0		0
Ending balance	0		0	0
Land [Member] \| Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			0
Ending balance				0
Land improvements [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			263,000,000
Ending balance				263,000,000
Land improvements [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	243,000,000
Ending balance	231,000,000		243,000,000
Land improvements [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			1,601,000,000	1,595,000,000
Additions				0
Disposal				0
Effect of foreign exchange differences				0
Others				6,000,000
Ending balance				1,601,000,000
Land improvements [Member] \| Carrying Amount [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	1,618,000,000		1,601,000,000
Effect of retrospective application of IFRS 16			(1,000,000)
Additions	0		0
Disposal	(19,000,000)		(7,000,000)
Effect of foreign exchange differences	0		0
Acquired by business combinations (Note 14)	0
Others	31,000,000		25,000,000
Ending balance	1,630,000,000		1,618,000,000	1,601,000,000
Land improvements [Member] \| Carrying Amount [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			1,600,000,000
Ending balance				1,600,000,000
Land improvements [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(1,338,000,000)	(1,293,000,000)
Depreciation expenses				(45,000,000)
Disposal				0
Effect of foreign exchange differences				0
Others				0
Ending balance				(1,338,000,000)
Land improvements [Member] \| Accumulated depreciation, amortization and impairment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	(1,375,000,000)		(1,338,000,000)
Depreciation expenses	(43,000,000)		(43,000,000)
Effect of retrospective application of IFRS 16			1,000,000
Disposal	19,000,000		6,000,000
Impairment losses			0
Effect of foreign exchange differences	0		0
Acquired by business combinations (Note 14)	0
Others	0		(1,000,000)
Ending balance	(1,399,000,000)		(1,375,000,000)	(1,338,000,000)
Land improvements [Member] \| Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(1,337,000,000)
Ending balance				(1,337,000,000)
Buildings [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			44,784,000,000
Ending balance				44,784,000,000
Buildings [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	43,024,000,000
Ending balance	41,642,000,000		43,024,000,000
Buildings [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			72,911,000,000	72,694,000,000
Additions				21,000,000
Disposal				0
Effect of foreign exchange differences				0
Others				196,000,000
Ending balance				72,911,000,000
Buildings [Member] \| Carrying Amount [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	71,001,000,000		72,911,000,000
Effect of retrospective application of IFRS 16			(3,583,000,000)
Additions	18,000,000		1,221,000,000
Disposal	(49,000,000)		(3,000,000)
Effect of foreign exchange differences	0		0
Acquired by business combinations (Note 14)	0
Others	(81,000,000)		455,000,000
Ending balance	70,889,000,000		71,001,000,000	72,911,000,000
Buildings [Member] \| Carrying Amount [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			69,328,000,000
Ending balance				69,328,000,000
Buildings [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(28,127,000,000)	(26,799,000,000)
Depreciation expenses				(1,356,000,000)
Disposal				0
Effect of foreign exchange differences				0
Others				28,000,000
Ending balance				(28,127,000,000)
Buildings [Member] \| Accumulated depreciation, amortization and impairment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	(27,977,000,000)		(28,127,000,000)
Depreciation expenses	(1,366,000,000)		(1,301,000,000)
Effect of retrospective application of IFRS 16			1,265,000,000
Disposal	49,000,000		3,000,000
Impairment losses			0
Effect of foreign exchange differences	0		0
Acquired by business combinations (Note 14)	0
Others	47,000,000		183,000,000
Ending balance	(29,247,000,000)		(27,977,000,000)	(28,127,000,000)
Buildings [Member] \| Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(26,862,000,000)
Ending balance				(26,862,000,000)
Computer equipment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			2,115,000,000
Ending balance				2,115,000,000
Computer equipment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	1,937,000,000
Ending balance	1,767,000,000		1,937,000,000
Computer equipment [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			14,258,000,000	14,162,000,000
Additions				52,000,000
Disposal				(643,000,000)
Effect of foreign exchange differences				0
Others				687,000,000
Ending balance				14,258,000,000
Computer equipment [Member] \| Carrying Amount [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	13,005,000,000		14,258,000,000
Effect of retrospective application of IFRS 16			0
Additions	55,000,000		57,000,000
Disposal	(1,245,000,000)		(1,916,000,000)
Effect of foreign exchange differences	0		0
Acquired by business combinations (Note 14)	70,000,000
Others	521,000,000		606,000,000
Ending balance	12,406,000,000		13,005,000,000	14,258,000,000
Computer equipment [Member] \| Carrying Amount [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			14,258,000,000
Ending balance				14,258,000,000
Computer equipment [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(12,143,000,000)	(11,788,000,000)
Depreciation expenses				(983,000,000)
Disposal				632,000,000
Effect of foreign exchange differences				0
Others				(4,000,000)
Ending balance				(12,143,000,000)
Computer equipment [Member] \| Accumulated depreciation, amortization and impairment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	(11,068,000,000)		(12,143,000,000)
Depreciation expenses	(770,000,000)		(827,000,000)
Effect of retrospective application of IFRS 16			0
Disposal	1,243,000,000		1,909,000,000
Impairment losses			0
Effect of foreign exchange differences	0		0
Acquired by business combinations (Note 14)	(40,000,000)
Others	(4,000,000)		(7,000,000)
Ending balance	(10,639,000,000)		(11,068,000,000)	(12,143,000,000)
Computer equipment [Member] \| Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(12,143,000,000)
Ending balance				(12,143,000,000)
Telecommunications equipment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			116,322,000,000
Ending balance				116,322,000,000
Telecommunications equipment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	115,694,000,000
Ending balance	117,113,000,000		115,694,000,000
Telecommunications equipment [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			715,748,000,000	722,054,000,000
Additions				159,000,000
Disposal				(31,984,000,000)
Effect of foreign exchange differences				60,000,000
Others				25,459,000,000
Ending balance				715,748,000,000
Telecommunications equipment [Member] \| Carrying Amount [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	706,032,000,000		715,748,000,000
Effect of retrospective application of IFRS 16			(3,885,000,000)
Additions	118,000,000		120,000,000
Disposal	(20,619,000,000)		(30,417,000,000)
Effect of foreign exchange differences	(91,000,000)		(37,000,000)
Acquired by business combinations (Note 14)	0
Others	25,336,000,000		24,503,000,000
Ending balance	710,776,000,000		706,032,000,000	715,748,000,000
Telecommunications equipment [Member] \| Carrying Amount [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			711,863,000,000
Ending balance				711,863,000,000
Telecommunications equipment [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(599,426,000,000)	(607,154,000,000)
Depreciation expenses				(24,236,000,000)
Disposal				31,952,000,000
Effect of foreign exchange differences				(20,000,000)
Others				32,000,000
Ending balance				(599,426,000,000)
Telecommunications equipment [Member] \| Accumulated depreciation, amortization and impairment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	(590,338,000,000)		(599,426,000,000)
Depreciation expenses	(23,994,000,000)		(23,906,000,000)
Effect of retrospective application of IFRS 16			2,576,000,000
Disposal	20,600,000,000		30,380,000,000
Impairment losses			0
Effect of foreign exchange differences	41,000,000		16,000,000
Acquired by business combinations (Note 14)	0
Others	28,000,000		22,000,000
Ending balance	(593,663,000,000)		(590,338,000,000)	(599,426,000,000)
Telecommunications equipment [Member] \| Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(596,850,000,000)
Ending balance				(596,850,000,000)
Transportation equipment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			231,000,000
Ending balance				231,000,000
Transportation equipment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	218,000,000
Ending balance	176,000,000		218,000,000
Transportation equipment [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			3,882,000,000	3,834,000,000
Additions				0
Disposal				(29,000,000)
Effect of foreign exchange differences				0
Others				77,000,000
Ending balance				3,882,000,000
Transportation equipment [Member] \| Carrying Amount [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	3,912,000,000		3,882,000,000
Effect of retrospective application of IFRS 16			0
Additions	1,000,000		1,000,000
Disposal	(45,000,000)		(51,000,000)
Effect of foreign exchange differences	0		0
Acquired by business combinations (Note 14)	0
Others	26,000,000		80,000,000
Ending balance	3,894,000,000		3,912,000,000	3,882,000,000
Transportation equipment [Member] \| Carrying Amount [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			3,882,000,000
Ending balance				3,882,000,000
Transportation equipment [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(3,651,000,000)	(3,513,000,000)
Depreciation expenses				(162,000,000)
Disposal				29,000,000
Effect of foreign exchange differences				0
Others				(5,000,000)
Ending balance				(3,651,000,000)
Transportation equipment [Member] \| Accumulated depreciation, amortization and impairment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	(3,694,000,000)		(3,651,000,000)
Depreciation expenses	(68,000,000)		(91,000,000)
Effect of retrospective application of IFRS 16			0
Disposal	45,000,000		51,000,000
Impairment losses			0
Effect of foreign exchange differences	0		0
Acquired by business combinations (Note 14)	0
Others	(1,000,000)		(3,000,000)
Ending balance	(3,718,000,000)		(3,694,000,000)	(3,651,000,000)
Transportation equipment [Member] \| Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(3,651,000,000)
Ending balance				(3,651,000,000)
Miscellaneous equipment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			2,582,000,000
Ending balance				2,582,000,000
Miscellaneous equipment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	2,428,000,000
Ending balance	2,374,000,000		2,428,000,000
Miscellaneous equipment [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			9,874,000,000	9,515,000,000
Additions				334,000,000
Disposal				(623,000,000)
Effect of foreign exchange differences				0
Others				648,000,000
Ending balance				9,874,000,000
Miscellaneous equipment [Member] \| Carrying Amount [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	10,090,000,000		9,874,000,000
Effect of retrospective application of IFRS 16			0
Additions	150,000,000		149,000,000
Disposal	(520,000,000)		(405,000,000)
Effect of foreign exchange differences	0		(1,000,000)
Acquired by business combinations (Note 14)	72,000,000
Others	508,000,000		473,000,000
Ending balance	10,300,000,000		10,090,000,000	9,874,000,000
Miscellaneous equipment [Member] \| Carrying Amount [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			9,874,000,000
Ending balance				9,874,000,000
Miscellaneous equipment [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(7,292,000,000)	(7,205,000,000)
Depreciation expenses				(679,000,000)
Disposal				615,000,000
Effect of foreign exchange differences				0
Others				(23,000,000)
Ending balance				(7,292,000,000)
Miscellaneous equipment [Member] \| Accumulated depreciation, amortization and impairment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	(7,662,000,000)		(7,292,000,000)
Depreciation expenses	(666,000,000)		(688,000,000)
Effect of retrospective application of IFRS 16			0
Disposal	504,000,000		402,000,000
Impairment losses			(64,000,000)
Effect of foreign exchange differences	0		1,000,000
Acquired by business combinations (Note 14)	(54,000,000)
Others	(48,000,000)		(21,000,000)
Ending balance	(7,926,000,000)		(7,662,000,000)	(7,292,000,000)
Miscellaneous equipment [Member] \| Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(7,292,000,000)
Ending balance				(7,292,000,000)
Construction in progress and equipment to be accepted [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			18,645,000,000
Ending balance				18,645,000,000
Construction in progress and equipment to be accepted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	13,723,000,000
Ending balance	8,529,000,000		13,723,000,000
Construction in progress and equipment to be accepted [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			18,645,000,000	18,527,000,000
Additions				27,413,000,000
Disposal				0
Effect of foreign exchange differences				0
Others				(27,295,000,000)
Ending balance				18,645,000,000
Construction in progress and equipment to be accepted [Member] \| Carrying Amount [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	13,752,000,000		18,645,000,000
Effect of retrospective application of IFRS 16			0
Additions	24,786,000,000		21,612,000,000
Disposal	(29,000,000)		0
Effect of foreign exchange differences	(7,000,000)		(6,000,000)
Acquired by business combinations (Note 14)	0
Others	(29,973,000,000)		(26,499,000,000)
Ending balance	8,529,000,000		13,752,000,000	18,645,000,000
Construction in progress and equipment to be accepted [Member] \| Carrying Amount [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			18,645,000,000
Ending balance				18,645,000,000
Construction in progress and equipment to be accepted [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			0	0
Depreciation expenses				0
Disposal				0
Effect of foreign exchange differences				0
Others				0
Ending balance				0
Construction in progress and equipment to be accepted [Member] \| Accumulated depreciation, amortization and impairment [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	(29,000,000)		0
Depreciation expenses	0		0
Effect of retrospective application of IFRS 16			0
Disposal	29,000,000		0
Impairment losses			(29,000,000)
Effect of foreign exchange differences	0		0
Acquired by business combinations (Note 14)	0
Others	0		0
Ending balance	$ 0		(29,000,000)	0
Construction in progress and equipment to be accepted [Member] \| Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			$ 0
Ending balance				$ 0

Property, Plant and Equipment_5

Property, Plant and Equipment - Additional Information (Detail) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2020TWD ($)	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure Of Property Plant And Equipment [Line Items]
Impairment loss on property, plant and equipment		$ 0	$ 0	$ 93,000,000	$ 0
Land [Member] \| Assets Subject to Operating Leases [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Lease period		1 year	1 year
Land [Member] \| Assets Subject to Operating Leases [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Lease period		20 years	20 years
Buildings [Member] \| Assets Subject to Operating Leases [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Lease period		1 year	1 year
Buildings [Member] \| Assets Subject to Operating Leases [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Lease period		20 years	20 years
Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Impairment loss on property, plant and equipment		$ 0
Gain (loss) on disposals, property, plant and equipment		1,268,000,000
Assets Used by the Company [Member] \| Land [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Carrying amount of trade-out of land		37,000,000
Assets Used by the Company [Member] \| Buildings [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Fair value of property, plant and equipment materially different from carrying amount		$ 1,305,000,000
Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Recoverable amount of asset				0
Impairment loss on property, plant and equipment				89,000,000
Chunghwa System Integration Co., Ltd. (CHSI) [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Recoverable amount of asset				0
Impairment loss on property, plant and equipment				$ 4,000,000
MOTC [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Difference between assessed value and construction cost of land	$ 1,057,000,000

Property, Plant and Equipment_6

Property, Plant and Equipment - Estimated Service Lives of Property, Plant and Equipment - Asset Used by The Company (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Land improvements [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P8Y
Land improvements [Member] \| Bottom of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P10Y	P10Y
Land improvements [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P30Y
Land improvements [Member] \| Top of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P30Y	P30Y
Main buildings [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P35Y
Main buildings [Member] \| Bottom of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P20Y	P20Y
Main buildings [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P60Y
Main buildings [Member] \| Top of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P60Y	P60Y
Other building facilities [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P3Y
Other building facilities [Member] \| Bottom of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P3Y	P3Y
Other building facilities [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P20Y
Other building facilities [Member] \| Top of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P15Y	P15Y
Computer equipment [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P2Y
Computer equipment [Member] \| Bottom of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P2Y	P2Y
Computer equipment [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P8Y
Computer equipment [Member] \| Top of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P8Y	P8Y
Telecommunication circuits [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P2Y
Telecommunication circuits [Member] \| Bottom of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P2Y	P2Y
Telecommunication circuits [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P30Y
Telecommunication circuits [Member] \| Top of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P30Y	P30Y
Telecommunication machinery and antennas equipment [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P2Y
Telecommunication machinery and antennas equipment [Member] \| Bottom of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P2Y	P2Y
Telecommunication machinery and antennas equipment [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P30Y
Telecommunication machinery and antennas equipment [Member] \| Top of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P30Y	P30Y
Transportation equipment [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P3Y
Transportation equipment [Member] \| Bottom of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P3Y	P3Y
Transportation equipment [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P10Y
Transportation equipment [Member] \| Top of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P10Y	P10Y
Leasehold improvements [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P1Y
Leasehold improvements [Member] \| Bottom of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P1Y	P1Y
Leasehold improvements [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P6Y
Leasehold improvements [Member] \| Top of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P9Y	P9Y
Mechanical and air conditioner equipment [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P3Y
Mechanical and air conditioner equipment [Member] \| Bottom of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P3Y	P3Y
Mechanical and air conditioner equipment [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P16Y
Mechanical and air conditioner equipment [Member] \| Top of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P16Y	P16Y
Others [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P1Y
Others [Member] \| Bottom of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P1Y	P1Y
Others [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives			P10Y
Others [Member] \| Top of Range [Member] \| Assets Used by the Company [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated service lives	P15Y	P15Y

Property, Plant and Equipment_7

Property, Plant and Equipment - Summary of Property, Plant and Equipment - Assets Subject to Operating Leases (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	$ 283,694		$ 288,914
Depreciation expenses	(26,989)		(26,930)	$ (27,461)
Additions	25,195		23,164	27,979
Impairment losses	0	$ 0	93	0
Ending balance	281,416	$ 10,022	283,694	288,914
Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	7,324
Ending balance	7,593		7,324
As Adjusted [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			5,935
Ending balance				5,935
Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			940,891	946,460
Additions				27,979
Others				(258)
Ending balance				940,891
Carrying Amount [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	8,821		0
Effect of retrospective application of IFRS 16			7,201
Additions			4
Transferred from (to) assets used by the Company			1,616
Others	388
Ending balance	9,209		8,821	0
Carrying Amount [Member] \| As Adjusted [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			7,201
Ending balance				7,201
Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(651,977)	(657,752)
Depreciation expenses				(27,461)
Others				28
Ending balance				(651,977)
Accumulated depreciation, amortization and impairment [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	(1,497)		0
Depreciation expenses	(82)		(74)
Effect of retrospective application of IFRS 16			(1,266)
Transferred from (to) assets used by the Company			(157)
Others	(37)
Ending balance	(1,616)		(1,497)	0
Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(1,266)
Ending balance				(1,266)
Land [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			103,972
Ending balance				103,972
Land [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	4,979
Ending balance	4,973		4,979
Land [Member] \| As Adjusted [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			3,617
Ending balance				3,617
Land [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			103,972	104,079
Additions				0
Others				(36)
Ending balance				103,972
Land [Member] \| Carrying Amount [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	4,979		0
Effect of retrospective application of IFRS 16			3,617
Additions			0
Transferred from (to) assets used by the Company			1,362
Others	(6)
Ending balance	4,973		4,979	0
Land [Member] \| Carrying Amount [Member] \| As Adjusted [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			3,617
Ending balance				3,617
Land [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			0	0
Depreciation expenses				0
Others				0
Ending balance				0
Land [Member] \| Accumulated depreciation, amortization and impairment [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	0		0
Depreciation expenses	0		0
Effect of retrospective application of IFRS 16			0
Transferred from (to) assets used by the Company			0
Others	0
Ending balance	0		0	0
Land [Member] \| Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			0
Ending balance				0
Land improvements [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			263
Ending balance				263
Land improvements [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	0
Ending balance	0		0
Land improvements [Member] \| As Adjusted [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			0
Ending balance				0
Land improvements [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			1,601	1,595
Additions				0
Others				6
Ending balance				1,601
Land improvements [Member] \| Carrying Amount [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	0		0
Effect of retrospective application of IFRS 16			1
Additions			0
Transferred from (to) assets used by the Company			(1)
Others	0
Ending balance	0		0	0
Land improvements [Member] \| Carrying Amount [Member] \| As Adjusted [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			1
Ending balance				1
Land improvements [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(1,338)	(1,293)
Depreciation expenses				(45)
Others				0
Ending balance				(1,338)
Land improvements [Member] \| Accumulated depreciation, amortization and impairment [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	0		0
Depreciation expenses	0		0
Effect of retrospective application of IFRS 16			(1)
Transferred from (to) assets used by the Company			1
Others	0
Ending balance	0		0	0
Land improvements [Member] \| Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(1)
Ending balance				(1)
Buildings [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			44,784
Ending balance				44,784
Buildings [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	2,345
Ending balance	2,620		2,345
Buildings [Member] \| As Adjusted [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			2,318
Ending balance				2,318
Buildings [Member] \| Carrying Amount [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			72,911	72,694
Additions				21
Others				196
Ending balance				72,911
Buildings [Member] \| Carrying Amount [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	3,842		0
Effect of retrospective application of IFRS 16			3,583
Additions			4
Transferred from (to) assets used by the Company			255
Others	394
Ending balance	4,236		3,842	0
Buildings [Member] \| Carrying Amount [Member] \| As Adjusted [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			3,583
Ending balance				3,583
Buildings [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			(28,127)	(26,799)
Depreciation expenses				(1,356)
Others				28
Ending balance				(28,127)
Buildings [Member] \| Accumulated depreciation, amortization and impairment [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance	(1,497)		0
Depreciation expenses	(82)		(74)
Effect of retrospective application of IFRS 16			(1,265)
Transferred from (to) assets used by the Company			(158)
Others	(37)
Ending balance	$ (1,616)		(1,497)	0
Buildings [Member] \| Accumulated depreciation, amortization and impairment [Member] \| As Adjusted [Member] \| Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning balance			$ (1,265)
Ending balance				$ (1,265)

Property, Plant and Equipment_8

Property, Plant and Equipment - Summary of Future Aggregate Lease Collection under Operating Lease for Freehold Plant, Property and Equipment - Assets Subject to Operating Leases (Detail) - TWD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	$ 434	$ 471
Year 1 [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	115	113
Year 2 [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	95	91
Year 3 [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	75	71
Year 4 [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	53	61
Year 5 [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	38	39
Onwards [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	58	96
Assets Subject to Operating Leases [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	2,335	2,354
Assets Subject to Operating Leases [Member] \| Year 1 [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	347	302
Assets Subject to Operating Leases [Member] \| Year 2 [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	288	273
Assets Subject to Operating Leases [Member] \| Year 3 [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	231	234
Assets Subject to Operating Leases [Member] \| Year 4 [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	164	191
Assets Subject to Operating Leases [Member] \| Year 5 [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	125	130
Assets Subject to Operating Leases [Member] \| Onwards [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Future aggregate lease collection under operating lease for freehold plant, property and equipment	$ 1,180	$ 1,224

Property, Plant and Equipment_9

Property, Plant and Equipment - Estimated Service Lives of Property, Plant and Equipment - Assets Subject to Operating Leases (Detail) - Assets Subject to Operating Leases [Member]	12 Months Ended
	Dec. 31, 2020
Land improvements [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated useful lives	10 years
Land improvements [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated useful lives	30 years
Main buildings [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated useful lives	35 years
Main buildings [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated useful lives	60 years
Other building facilities [Member] \| Bottom of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated useful lives	3 years
Other building facilities [Member] \| Top of Range [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Estimated useful lives	15 years

Lease Arrangements - Summary of

Lease Arrangements - Summary of Right-of-use Assets (Details) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2020USD ($)
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Right-of-use assets	$ 11,009	$ 11,364		$ 392
Additions to right-of-use assets	3,796	3,803
Depreciation charge for right-of-use assets
Depreciation, right-of-use assets	3,931	3,968	$ 0
Handsets Base Stations [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Right-of-use assets	7,096	6,845
Depreciation charge for right-of-use assets
Depreciation, right-of-use assets	2,729	2,728
Others [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Right-of-use assets	1,708	1,916
Depreciation charge for right-of-use assets
Depreciation, right-of-use assets	786	821
Equipment [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Right-of-use assets	2,205	2,603
Depreciation charge for right-of-use assets
Depreciation, right-of-use assets	$ 416	$ 419

Lease Arrangements - Additional

Lease Arrangements - Additional Information (Details) - TWD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Sublease	$ 0	$ 0
Impairment of right-of-use assets	$ 0	$ 0
Taiwan [Member] \| Bottom of Range [Member] \| Handsets Base Stations [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Lease Term	1 year
Taiwan [Member] \| Bottom of Range [Member] \| Offices, Server rooms and Stores [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Lease Term	1 year
Taiwan [Member] \| Top of Range [Member] \| Handsets Base Stations [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Lease Term	20 years
Taiwan [Member] \| Top of Range [Member] \| Offices, Server rooms and Stores [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Lease Term	30 years

Lease Arrangements - Summary _2

Lease Arrangements - Summary of Lease Liabilities (Details) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure Of Quantitative Information About Leases For Lessee [Abstract]
Lease liabilities - current	$ 3,382	$ 120	$ 3,291
Lease liabilities - noncurrent	6,215	$ 221	6,467
Lease liabilities	$ 9,597		$ 9,758

Lease Arrangements - Summary _3

Lease Arrangements - Summary of Range of Discount Rate for Lease Liabilities (Details) - Discount Rate [Member] - Lease Liabilities [Member]	Dec. 31, 2020	Dec. 31, 2019
Bottom of Range [Member] \| Handsets Base Stations [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Range of discount rate	0.46	0.58
Bottom of Range [Member] \| Others [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Range of discount rate	0.46	0.58
Bottom of Range [Member] \| Equipment [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Range of discount rate	0.46	0.58
Top of Range [Member] \| Handsets Base Stations [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Range of discount rate	1.18	1.18
Top of Range [Member] \| Others [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Range of discount rate	9	9
Top of Range [Member] \| Equipment [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Range of discount rate	2.99	4.50

Lease Arrangements - Summary _4

Lease Arrangements - Summary of Total Cash Outflow for Leases (Details) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Quantitative Information About Leases For Lessee [Abstract]
Expenses relating to low-value asset leases	$ 8	$ 7
Expenses relating to variable lease payments not included in the measurement of lease liabilities	5	6
Total cash outflow for leases	$ 3,776	$ 3,826

Investment Properties - Summary

Investment Properties - Summary of Investment Properties (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of detailed information about investment property [Line Items]
Beginning balance	$ 8,169
Depreciation expense	(22)		$ (25)	$ (21)
Reversal of impairment loss	27	$ 1	57	19
Ending balance	9,621	$ 343	8,169
Carrying Amount [Member]
Disclosure of detailed information about investment property [Line Items]
Beginning balance	9,214		9,392	9,135
Additions	1,359		1	6
Disposal	(37)		(6)
Reclassification	126		(173)	251
Ending balance	10,662		9,214	9,392
Accumulated depreciation, amortization and impairment [Member]
Disclosure of detailed information about investment property [Line Items]
Beginning balance	(1,045)		(1,105)	(1,087)
Depreciation expense	(22)		(25)	(21)
Disposal			6
Reclassification	(1)		22	(16)
Reversal of impairment loss	27		57	19
Ending balance	$ (1,041)		$ (1,045)	$ (1,105)

Investment Properties - Additio

Investment Properties - Additional Information (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure Of Investment Property [Abstract]
Reversal of impairment loss	$ 27	$ 1	$ 57	$ 19

Investment Properties - Estimat

Investment Properties - Estimated Service Lives of Investment Properties (Detail)	12 Months Ended
	Dec. 31, 2020
Land improvements [Member] \| Bottom of range [Member]
Disclosure of detailed information about investment property [Line Items]
Estimated service lives	10 years
Land improvements [Member] \| Top of Range [Member]
Disclosure of detailed information about investment property [Line Items]
Estimated service lives	30 years
Main buildings [Member] \| Bottom of range [Member]
Disclosure of detailed information about investment property [Line Items]
Estimated service lives	35 years
Main buildings [Member] \| Top of Range [Member]
Disclosure of detailed information about investment property [Line Items]
Estimated service lives	60 years
Other building facilities [Member] \| Bottom of range [Member]
Disclosure of detailed information about investment property [Line Items]
Estimated service lives	4 years
Other building facilities [Member] \| Top of Range [Member]
Disclosure of detailed information about investment property [Line Items]
Estimated service lives	10 years

Investment Properties - Key Ass

Investment Properties - Key Assumptions and Fair Values of Investment Properties (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about investment property [Line Items]
Investment properties	$ 9,621	$ 343	$ 8,169
Bottom of Range [Member]
Disclosure of detailed information about investment property [Line Items]
Overall capital interest rate	0.93%	0.93%	1.03%
Profit margin ratio	12.00%	12.00%	12.00%
Capitalization rate	0.73%	0.73%	0.79%
Top of Range [Member]
Disclosure of detailed information about investment property [Line Items]
Overall capital interest rate	3.03%	3.03%	4.04%
Profit margin ratio	20.00%	20.00%	20.00%
Capitalization rate	2.20%	2.20%	1.74%
At fair value [Member]
Disclosure of detailed information about investment property [Line Items]
Investment properties	$ 22,644		$ 18,701

Investment Properties - Schedul

Investment Properties - Schedule of Future Aggregate Lease Collection Under Operating Lease for Investment Properties (Detail) - TWD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Aggregate lease collection under operating lease	$ 434	$ 471
Year 1 [Member]
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Aggregate lease collection under operating lease	115	113
Year 2 [Member]
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Aggregate lease collection under operating lease	95	91
Year 3 [Member]
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Aggregate lease collection under operating lease	75	71
Year 4 [Member]
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Aggregate lease collection under operating lease	53	61
Year 5 [Member]
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Aggregate lease collection under operating lease	38	39
Onwards [Member]
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Aggregate lease collection under operating lease	$ 58	$ 96

Intangible Assets - Summary of

Intangible Assets - Summary of Intangible Assets (Detail) $ in Millions, $ in Millions	1 Months Ended	12 Months Ended
	Feb. 29, 2020TWD ($)	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		$ 47,047		$ 50,944
Additions-acquired separately	$ 48,373
Amortization expenses		(5,424)		(4,253)	$ (4,386)
Impairment losses		(9)	$ 0	(9)	(51)
Ending balance		90,285	$ 3,214	47,047	50,944
Carrying Amount [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		64,009		74,179	74,110
Additions-acquired separately		48,605		363	498
Disposal		(341)		(10,535)	(429)
Effect of foreign exchange difference		0		0	0
Acquired by business combinations		67
Others		1		2
Ending balance		112,341		64,009	74,179
Accumulated depreciation, amortization and impairment [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		(16,962)		(23,235)	(19,227)
Amortization expenses		(5,424)		(4,253)	(4,386)
Disposal		339		10,535	429
Impairment losses		(9)		(9)	(51)
Effect of foreign exchange difference		0		0	0
Acquired by business combinations		0
Ending balance		(22,056)		(16,962)	(23,235)
Mobile Broadband Concession [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		45,672		49,512
Ending balance		89,019		45,672	49,512
Mobile Broadband Concession [Member] \| Carrying Amount [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		59,965		70,144	70,144
Additions-acquired separately		48,373		0	0
Disposal		0		(10,179)	0
Effect of foreign exchange difference		0		0	0
Acquired by business combinations		0
Others		0		0
Ending balance		108,338		59,965	70,144
Mobile Broadband Concession [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		(14,293)		(20,632)	(16,675)
Amortization expenses		(5,026)		(3,840)	(3,957)
Disposal		0		10,179	0
Impairment losses		0		0	0
Effect of foreign exchange difference		0		0	0
Acquired by business combinations		0
Ending balance		(19,319)		(14,293)	(20,632)
Computer software [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		931		959
Ending balance		788		931	959
Computer software [Member] \| Carrying Amount [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		3,430		3,426	3,312
Additions-acquired separately		226		358	485
Disposal		(338)		(356)	(371)
Effect of foreign exchange difference		0		0	0
Acquired by business combinations		1
Others		1		2
Ending balance		3,320		3,430	3,426
Computer software [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		(2,499)		(2,467)	(2,432)
Amortization expenses		(371)		(388)	(406)
Disposal		338		356	371
Impairment losses		0		0	0
Effect of foreign exchange difference		0		0	0
Acquired by business combinations		0
Ending balance		(2,532)		(2,499)	(2,467)
Goodwill [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		200		209
Ending balance		246		200	209
Goodwill [Member] \| Carrying Amount [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		236		236	236
Additions-acquired separately		0		0	0
Disposal		0		0	0
Effect of foreign exchange difference		0		0	0
Acquired by business combinations		55
Others		0		0
Ending balance		291		236	236
Goodwill [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		(36)		(27)	(27)
Amortization expenses		0		0	0
Disposal		0		0	0
Impairment losses		(9)		(9)	0
Effect of foreign exchange difference		0		0	0
Acquired by business combinations		0
Ending balance		(45)		(36)	(27)
Others [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		244		264
Ending balance		232		244	264
Others [Member] \| Carrying Amount [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		378		373	418
Additions-acquired separately		6		5	13
Disposal		(3)		0	(58)
Effect of foreign exchange difference		0		0	0
Acquired by business combinations		11
Others		0		0
Ending balance		392		378	373
Others [Member] \| Accumulated depreciation, amortization and impairment [Member]
Disclosure of detailed information about intangible assets [Line Items]
Beginning balance		(134)		(109)	(93)
Amortization expenses		(27)		(25)	(23)
Disposal		1		0	58
Impairment losses		0		0	(51)
Effect of foreign exchange difference		0		0	0
Acquired by business combinations		0
Ending balance		$ (160)		$ (134)	$ (109)

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - TWD ($) $ in Millions	1 Months Ended		12 Months Ended
	Feb. 29, 2020	Oct. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of detailed information about intangible assets [Line Items]
5G spectrum bidding amount		$ 1,000
Additions-acquired separately	$ 48,373
Senao Networks, Inc. ("SNI") [Member]
Disclosure of detailed information about intangible assets [Line Items]
Discount rate			12.10%	12.30%	13.70%
Senao Networks, Inc. ("SNI") [Member] \| Goodwill [Member]
Disclosure of detailed information about intangible assets [Line Items]
Impairment loss			$ 9	$ 9	$ 0
Senao Networks, Inc. ("SNI") [Member] \| Certain licensed contract [Member]
Disclosure of detailed information about intangible assets [Line Items]
Impairment loss					$ 51
Bottom of range [Member] \| Computer software [Member]
Disclosure of detailed information about intangible assets [Line Items]
Estimated useful lives			1 year
Bottom of range [Member] \| Others [Member]
Disclosure of detailed information about intangible assets [Line Items]
Estimated useful lives			1 year
Top of Range [Member] \| Computer software [Member]
Disclosure of detailed information about intangible assets [Line Items]
Estimated useful lives			10 years
Top of Range [Member] \| Others [Member]
Disclosure of detailed information about intangible assets [Line Items]
Estimated useful lives			20 years

Other Assets - Summary of Other

Other Assets - Summary of Other Assets (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Miscellaneous Assets [Abstract]
Spare parts	$ 2,156		$ 2,336
Refundable deposits	2,009		1,879
Other financial assets	1,000		1,000
Deposit for mobile broadband license bidding (Note 19)	0		1,000
Others	2,450		2,316
Other assets	7,615		8,531
Others	193		94
Other current assets	2,349	$ 84	2,430
Others	2,257		2,222
Other noncurrent assets	$ 5,266	$ 188	$ 6,101

Other Assets - Additional Infor

Other Assets - Additional Information (Detail $ in Millions	12 Months Ended
Other Assets - Additional Information (Detail $ in Millions	Dec. 31, 2019TWD ($)
Disclosure Of Other Assets [Abstract]
Impairment loss on other assets	$ 44

Hedging Financial Instruments -

Hedging Financial Instruments - Summary of Hedging Instrument (Details) - Forecast Purchases - forward Exchange Contract [Member] - Cash flow hedges [member] € in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2020EUR (€)	Dec. 31, 2019EUR (€)	Dec. 31, 2018EUR (€)
Disclosure Of Detailed Information About Hedging Instruments [Line Items]
Change in Value of Hedged Item Used for Calculating Hedge Ineffectiveness	$ (2)	$ 1	$ (2)
Accumulated Gain or Loss on Hedging Instruments in Other Equity Continuing Hedges	2	0	1
Accumulated Gain or Loss on Hedging Instruments in Other Equity Hedge Accounting No Longer Applied	$ 0	$ 0	$ 0
Foreign currency risk [Member]
Disclosure Of Detailed Information About Hedging Instruments [Line Items]
Currency	NT$/EUR	NT$/EUR	NT$/EUR
Contract Amount	$ 201	$ 84	$ 172	€ 6	€ 2	€ 5
Maturity Period	2021.03	2020.03	2019.03
Forward Rate	34.45	33.66	34.98
Carrying Amount of Asset	$ 2	$ 0	$ 1
Carrying Amount of Liability	0	0	0
Change in Fair Values of Hedging Instruments Used for Calculating Hedge Ineffectiveness	$ 2	$ (1)	$ 2

Hedging Financial Instruments_2

Hedging Financial Instruments - Summary of Hedging Transaction and Reclassification Affected Comprehensive Income (Details) - Forecast Purchases - forward Exchange Contract [Member] - Cash flow hedges [member] - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Reclassification Of Financial Assets [Line Items]
Hedging Gain or Loss Recognized in OCI	$ 2	$ (1)	$ 2
Amount of Hedge Ineffectiveness Recognized in Profit or Loss	0	0	0
Line item in which hedge ineffectiveness is included	0	0	0
Amount Reclassified to P/L and the Adjusted Line Item	21	(2)	(4)
Due to Hedged Future Cash Flows No Longer Expected to Occur	$ 0	$ 0	$ 0

Short Term Loans - Summary of S

Short Term Loans - Summary of Short-term Loans (Detail) - Short-term loans [Member] - TWD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about borrowings [Line Items]
Unsecured bank loans	$ 67	$ 90
Unsecured loans [Member] \| Bottom of Range [Member]
Disclosure of detailed information about borrowings [Line Items]
Interest rates of bank loans	1.12%	1.20%
Unsecured loans [Member] \| Top of Range [Member]
Disclosure of detailed information about borrowings [Line Items]
Interest rates of bank loans	2.33%	2.50%

Short-term Bills Payable - Summ

Short-term Bills Payable - Summary of Short-term Bills Payable (Detail) $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Short Term Bills Payable [Abstract]
Commercial paper payable	$ 7,000,000,000		$ 0
Less: Discounts on commercial paper payable	(1,000,000)		0
Short-term bills payable	$ 6,999,000,000	$ 249	$ 0

Short-term Bills Payable - Su_2

Short-term Bills Payable - Summary of Annual Interest Rates of Commercial Paper Payable (Detail)	Dec. 31, 2020
Bottom of Range [Member]
Short Term Bills Payable [Line Items]
Commercial paper payable	0.34%
Top of Range [Member]
Short Term Bills Payable [Line Items]
Commercial paper payable	0.36%

Long Term Loans - Summary of Lo

Long Term Loans - Summary of Long-term Loans (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about borrowings [Line Items]
Less: Current portion	$ (1,600)	$ (57)	$ 0
Non-current portion of non-current borrowings	0	$ 0	1,600
Long-term loans [Member]
Disclosure of detailed information about borrowings [Line Items]
Secured loans	1,600		1,600
Less: Current portion	$ (1,600)
Non-current portion of non-current borrowings			$ 1,600
Long-term loans [Member] \| Secured loans [Member]
Disclosure of detailed information about borrowings [Line Items]
Interest rates of loans	0.72%	0.72%	0.92%

Long Term Loans - Additional In

Long Term Loans - Additional Information (Detail) - Light Era Development Co., Ltd. ("LED") [Member] - Chang Hwa Bank Secured Loan [Member] - TWD ($) $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2015	Dec. 31, 2020	Dec. 31, 2017	Sep. 30, 2010
Disclosure of detailed information about borrowings [Line Items]
Early repayment of secured loan	$ 50
Extended Due September 2021 [Member]
Disclosure of detailed information about borrowings [Line Items]
Loan due date			September 2021
Due December 2014 [Member]
Disclosure of detailed information about borrowings [Line Items]
Secured loan				$ 300
Loan due date		December 2014
Due September 2015 [Member]
Disclosure of detailed information about borrowings [Line Items]
Secured loan				$ 1,350
Loan due date		September 2015

Bonds Payable - Summary of Bond

Bonds Payable - Summary of Bonds Payable (Detail) $ in Millions	Dec. 31, 2020TWD ($)
Disclosure Of Detailed Information About Bonds Payable [Abstract]
Unsecured domestic bonds	$ 20,000
Less: Discounts on bonds payable	(20)
Bonds payable	$ 19,980

Bonds Payable - Summary of Majo

Bonds Payable - Summary of Major Terms of Unsecured Domestic Bonds Issued (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)
Disclosure Of Detailed Information About Bonds Payable [Line Items]
Total Amount	$ 20,000
Unsecured Domestic Bonds [Member] \| Tranche A [Member]
Disclosure Of Detailed Information About Bonds Payable [Line Items]
Issuance	2020-1
Issuance Period	July 2020 to July 2025
Total Amount	$ 8,800
Interest rates of loans	0.50%
Repayment and Interest Payment	One-time repayment upon maturity; interest payable annually
Unsecured Domestic Bonds [Member] \| Tranche B [Member]
Disclosure Of Detailed Information About Bonds Payable [Line Items]
Issuance Period	July 2020 to July 2027
Total Amount	$ 7,500
Interest rates of loans	0.54%
Repayment and Interest Payment	The same as above
Unsecured Domestic Bonds [Member] \| Tranche C [Member]
Disclosure Of Detailed Information About Bonds Payable [Line Items]
Issuance Period	July 2020 to July 2030
Total Amount	$ 3,700
Interest rates of loans	0.59%
Repayment and Interest Payment	The same as above

Trade Notes and Accounts Paya_3

Trade Notes and Accounts Payable - Summary of Trade Notes and Accounts Payable (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Trade And Other Current Payables [Abstract]
Trade notes and accounts payable	$ 15,591	$ 555	$ 15,312

Other Payables - Summary of Oth

Other Payables - Summary of Other Payables (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Trade And Other Current Payables [Abstract]
Accrued salary and compensation	$ 9,450		$ 9,482
Payables to contractors	1,779		1,892
Accrued compensation to employees and remuneration to directors and supervisors	1,691		1,441
Amounts collected for others	1,308		1,279
Payable on land (Note 16)	1,057		0
Payables to equipment suppliers	1,049		296
Accrued maintenance costs	1,040		955
Accrued franchise fees	785		1,091
Others	5,829		6,517
Total	$ 23,988	$ 854	$ 22,953

Provisions - Summary of Provisi

Provisions - Summary of Provisions (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2017TWD ($)
Provisions [Abstract]
Warranties	$ 182		$ 173
Onerous contracts	171		67
Employee benefits	57		59
Others	5		5
Provisions	415		304	$ 207	$ 180
Current	314	$ 11	207
Noncurrent	$ 101	$ 4	$ 97

Provisions - Movements in Provi

Provisions - Movements in Provisions (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jul. 01, 2020
Disclosure of other provisions [Line Items]
Beginning balance	$ 304	$ 207	$ 180
Additional/(reversal of) provisions recognized	221	184	192
Used / forfeited during the year	(125)	(87)	(165)
Acquired by business combinations (Note 14)				$ 15
Ending balance	415	304	207
Warranties [Member]
Disclosure of other provisions [Line Items]
Beginning balance	173	132	132
Additional/(reversal of) provisions recognized	131	127	164
Used / forfeited during the year	(122)	(86)	(164)
Acquired by business combinations (Note 14)				0
Ending balance	182	173	132
Onerous Contracts [Member]
Disclosure of other provisions [Line Items]
Beginning balance	67	19	0
Additional/(reversal of) provisions recognized	92	48	19
Used / forfeited during the year	(3)	0	0
Acquired by business combinations (Note 14)				15
Ending balance	171	67	19
Employee benefits [Member]
Disclosure of other provisions [Line Items]
Beginning balance	59	51	43
Additional/(reversal of) provisions recognized	(2)	9	9
Used / forfeited during the year	0	(1)	(1)
Acquired by business combinations (Note 14)				0
Ending balance	57	59	51
Others [Member]
Disclosure of other provisions [Line Items]
Beginning balance	5	5	5
Additional/(reversal of) provisions recognized	0	0	0
Used / forfeited during the year	0	0	0
Acquired by business combinations (Note 14)				$ 0
Ending balance	$ 5	$ 5	$ 5

Retirement Benefit Plans - Addi

Retirement Benefit Plans - Additional Information (Detail)	12 Months Ended
Retirement Benefit Plans - Additional Information (Detail)	Dec. 31, 2020
Disclosure of Defined Retirement Plans
Percentage of monthly salaries and wages contributed to employees' individual pension accounts	6.00%
Top of range [Member]
Disclosure of Defined Retirement Plans
Defined benefit plan contribution, percentage	15.00%

Retirement Benefit Plans - Amou

Retirement Benefit Plans - Amounts Included in Consolidated Balance Sheets from Obligation in Respect of Defined Benefit Plans (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2017TWD ($)
Disclosure Of Defined Benefit Plans [Abstract]
Present value of funded defined benefit obligations	$ 39,536		$ 41,197
Fair value of plan assets	(39,494)		(39,820)
Funded status - deficit	42		1,377
Net defined benefit liabilities	3,415	$ 122	3,505
Net defined benefit assets	(3,373)	$ (120)	(2,128)
Defined benefit obligation	$ 42		$ 1,377	$ 2,370	$ 2,691

Retirement Benefit Plans - Move

Retirement Benefit Plans - Movements in Defined Benefit Obligation and Fair Value of Plan Assets (Detail) $ in Millions, $ in Millions	Jul. 01, 2020TWD ($)	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure Of Defined Plan [line items]
Net defined benefit liability (asset) at beginning of period		$ 1,377		$ 2,370	$ 2,691
Current service cost		2,052		2,927	3,024
Interest expense/interest income		1		10	6
Amounts recognized in profit or loss		2,053		2,937	3,030
Remeasurement on the net defined benefit liability
Return on plan assets (excluding amounts included in net interest)		(1,308)		(1,338)	(875)
Actuarial (gains) losses recognized from changes in demographic assumptions				6	4
Actuarial (gains) losses recognized from changes in financial assumptions		590		647	1,273
Actuarial (gains) losses recognized from experience adjustments		(475)		(842)	813
Amounts recognized in other comprehensive income		(1,193)	$ (43)	(1,527)	1,215
Contributions from employer		(1,964)		(2,099)	(4,374)
Benefits paid		0		0	0
Benefits paid directly by the Company		(263)		(304)	(192)
Acquired by business combinations (Note 14)	$ 32
Net defined benefit liability (asset) at end of period		42		1,377	2,370
Present value of funded defined benefit obligation [Member]
Disclosure Of Defined Plan [line items]
Net defined benefit liability (asset) at beginning of period		41,197		41,397	37,663
Current service cost		2,052		2,927	3,024
Interest expense/interest income		298		400	550
Amounts recognized in profit or loss		2,350		3,327	3,574
Remeasurement on the net defined benefit liability
Return on plan assets (excluding amounts included in net interest)		0		0	0
Actuarial (gains) losses recognized from changes in demographic assumptions				6	4
Actuarial (gains) losses recognized from changes in financial assumptions		590		647	1,273
Actuarial (gains) losses recognized from experience adjustments		(475)		(842)	813
Amounts recognized in other comprehensive income		115		(189)	2,090
Contributions from employer		0		0	0
Benefits paid		(3,919)		(3,034)	(1,738)
Benefits paid directly by the Company		(263)		(304)	(192)
Acquired by business combinations (Note 14)	56
Net defined benefit liability (asset) at end of period		39,536		41,197	41,397
Fair value of plan assets [Member]
Disclosure Of Defined Plan [line items]
Net defined benefit liability (asset) at beginning of period		39,820		39,027	34,972
Current service cost		0		0	0
Interest expense/interest income		297		390	544
Amounts recognized in profit or loss		297		390	544
Remeasurement on the net defined benefit liability
Return on plan assets (excluding amounts included in net interest)		1,308		1,338	875
Actuarial (gains) losses recognized from changes in demographic assumptions				0	0
Actuarial (gains) losses recognized from changes in financial assumptions		0		0	0
Actuarial (gains) losses recognized from experience adjustments		0		0	0
Amounts recognized in other comprehensive income		1,308		1,338	875
Contributions from employer		1,964		2,099	4,374
Benefits paid		(3,919)		(3,034)	(1,738)
Benefits paid directly by the Company		0		0	0
Acquired by business combinations (Note 14)	$ 24
Net defined benefit liability (asset) at end of period		$ 39,494		$ 39,820	$ 39,027

Retirement Benefit Plans - Pens

Retirement Benefit Plans - Pension Costs Recognized in Profit and Loss for Defined Benefit Plans (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Defined Plan [line items]
Defined benefit plans pension costs recognized in profit and loss	$ 2,001	$ 2,859	$ 2,953
Operating costs [Member]
Disclosure Of Defined Plan [line items]
Defined benefit plans pension costs recognized in profit and loss	1,205	1,726	1,796
Marketing expenses [Member]
Disclosure Of Defined Plan [line items]
Defined benefit plans pension costs recognized in profit and loss	603	866	886
General and administrative expenses [Member]
Disclosure Of Defined Plan [line items]
Defined benefit plans pension costs recognized in profit and loss	121	164	164
Research and development expenses [Member]
Disclosure Of Defined Plan [line items]
Defined benefit plans pension costs recognized in profit and loss	$ 72	$ 103	$ 107

Retirement Benefit Plans - Prin

Retirement Benefit Plans - Principal Assumptions Used for Actuarial Valuations (Detail)	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Defined Plan [line items]
Discount rates	0.50%	0.75%
Bottom of range [Member]
Disclosure Of Defined Plan [line items]
Expected rates of salary increase	1.00%	1.20%
Top of range [Member]
Disclosure Of Defined Plan [line items]
Expected rates of salary increase	2.00%	2.00%

Retirement Benefit Plans - Effe

Retirement Benefit Plans - Effect on Present Value of Defined Benefit Obligation Due to a Reasonably Possible Change of the Significant Actuarial Assumptions (Detail) - TWD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Discount rates [Member]
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]
0.5% increase	$ (1,208)	$ (1,275)
0.5% decrease	1,284	1,356
Expected rates of salary increases [Member]
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]
0.5% increase	1,372	1,448
0.5% decrease	$ (1,303)	$ (1,374)

Retirement Benefit Plans - Ef_2

Retirement Benefit Plans - Effect on Present Value of Defined Benefit Obligation Due to a Reasonably Possible Change of the Significant Actuarial Assumptions (Parenthetical) (Detail)	Dec. 31, 2020	Dec. 31, 2019
Discount rates [Member]
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]
Percentage increase in actuarial assumptions	0.50%	0.50%
Percentage decrease in actuarial assumptions	0.50%	0.50%
Expected rates of salary increases [Member]
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]
Percentage increase in actuarial assumptions	0.50%	0.50%
Percentage decrease in actuarial assumptions	0.50%	0.50%

Retirement Benefit Plans - Summ

Retirement Benefit Plans - Summary of Sensitivity Analysis (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]
The expected contributions to the plan for the next year	$ 1,932	$ 2,076
Bottom of range [Member]
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]
The average duration of the defined benefit obligations	6 years 4 months 24 days	6 years 6 months
Top of range [Member]
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]
The average duration of the defined benefit obligations	13 years	14 years

Retirement Benefit Plans - Matu

Retirement Benefit Plans - Maturity Analysis of Undiscounted Benefit Payments (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)
Disclosure Of Defined Benefit Plans [Abstract]
2021	$ 3,285
2022	7,056
2023	10,669
2024	11,799
2025 and thereafter	39,497
Total	$ 72,306

Equity - Summary of Common Stoc

Equity - Summary of Common Stocks (Detail) $ in Millions	Dec. 31, 2020TWD ($)shares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019TWD ($)shares
Disclosure Of Classes Of Share Capital [Abstract]
Number of authorized shares	12,000,000,000	12,000,000,000	12,000,000,000
Authorized shares \| $	$ 120,000,000,000		$ 120,000,000,000
Number of issued and paid shares	7,757,000,000	7,757,000,000	7,757,000,000
Issued and outstanding shares	$ 77,574,000,000	$ 2,763	$ 77,574,000,000

Equity - Additional Information

Equity - Additional Information (Detail) ADSs in Millions	12 Months Ended
Equity - Additional Information (Detail) ADSs in Millions	Dec. 31, 2020ADSs$ / sharesshares
Disclosure Of Classes Of Share Capital [Line Items]
Common stock par value \| $ / shares	$ 10
Percentage of American Depositary Shares as common stock outstanding	2.84%
Percentage of net income allocation toward legal reserve	10.00%
Bottom of range [Member]
Disclosure Of Classes Of Share Capital [Line Items]
Percentage of retained earnings distributed as dividend	50.00%
Dividend distributed per share threshold in the form of common stocks \| $ / shares	$ 0.10
Percentage of legal reserve on additional paid in capital	25.00%
American Depositary Shares [Member]
Disclosure Of Classes Of Share Capital [Line Items]
Number of common stocks represented by 1 ADS \| shares	10
Number of common stock outstanding \| shares	220,000,000
Number of units \| ADSs	22

Equity - Adjustments of Additio

Equity - Adjustments of Additional Paid-in Capital (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Beginning balance	$ 384,272		$ 384,529	$ 382,124
Unclaimed dividend	2		1	2
Partial disposal of interests in subsidiaries				1,175
Change in additional paid-in capital for not participating proportionately in the capital increase of subsidiaries	0			1,477
Share-based payment transactions of subsidiaries	89		21	53
Ending balance	387,273	$ 13,791	384,272	384,529
Share premium [Member]
Beginning balance	126,045		126,045	126,045
Partial disposal of interests in subsidiaries				0
Share-based payment transactions of subsidiaries	0		0	0
Ending balance	126,045		126,045	126,045
Movements Of Additional Paid-in Capital For Associates And Joint Ventures Accounted For Using Equity Method
Beginning balance	0		0	0
Partial disposal of interests in subsidiaries				0
Share-based payment transactions of subsidiaries	0		0	0
Ending balance	0		0	0
Movements of additional paid-in capital arising from changes in equities of subsidiaries [Member]
Beginning balance	2,063		2,064	1,221
Partial disposal of interests in subsidiaries				0
Change in additional paid-in capital for not participating proportionately in the capital increase of subsidiaries	0			777
Share-based payment transactions of subsidiaries	26		(1)	11
Treasury stock transfer of subsidiaries				55
Ending balance	2,089		2,063	2,064
Difference between consideration received and carrying amount of the subsidiaries' net assets upon disposal [Member]
Beginning balance	987		987	161
Partial disposal of interests in subsidiaries				826
Share-based payment transactions of subsidiaries	0		0	0
Ending balance	987		987	987
Donated capital [Member]
Beginning balance	19		18	16
Unclaimed dividend	2		1	2
Partial disposal of interests in subsidiaries				0
Share-based payment transactions of subsidiaries	0		0	0
Ending balance	21		19	18
Stockholders' contribution due to privatization [Member]
Beginning balance	20,648		20,648	20,648
Partial disposal of interests in subsidiaries				0
Share-based payment transactions of subsidiaries	0		0	0
Ending balance	20,648		20,648	20,648
Additional paid-in capital [Member]
Beginning balance	149,762		149,762	148,091
Unclaimed dividend	2		1	2
Partial disposal of interests in subsidiaries				826
Change in additional paid-in capital for not participating proportionately in the capital increase of subsidiaries	0			777
Share-based payment transactions of subsidiaries	26		(1)	11
Treasury stock transfer of subsidiaries				55
Ending balance	$ 149,790	$ 5,334	$ 149,762	$ 149,762

Equity - Appropriations of Earn

Equity - Appropriations of Earnings (Detail) - Cash dividends [Member] - TWD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Appropriations of earnings	$ 33,404	$ 32,783	$ 34,746
Cash dividends per share	$ 4.306	$ 4.226	$ 4.479

Equity - Unrealized Gain or Los

Equity - Unrealized Gain or Loss on Financial Assets at FVOCI (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Changes In Equity [Abstract]
Beginning balance	$ 735	$ 538	$ 883
Unrealized gain or loss for the year
Equity instruments	522	197	(345)
Transferred accumulated gain or loss to unappropriated earnings resulting from the disposal of equity instruments	(17)	0	0
Ending balance	$ 1,240	$ 735	$ 538

Equity - Noncontrolling Interes

Equity - Noncontrolling Interests (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Beginning balance	$ 384,272		$ 384,529	$ 382,124
Profit Allocated to Noncontrolling Interests	1,285	$ 46	974	1,024
Income tax relating to remeasurements of defined benefit pension plans	(239)		(305)	243
Cash dividends distributed by subsidiaries	(775)		(710)	(958)
Partial disposal of interests in subsidiaries				1,175
Share-based payment transactions of subsidiaries	89		21	53
Change in additional paid-in capital from investments in associates and joint ventures accounted for using equity method	(2)
Net increase (decrease) in noncontrolling interests	476		(1)	294
Ending balance	387,273	13,791	384,272	384,529
Noncontrolling interests [Member]
Beginning balance	10,115		9,857	8,470
Effect of retrospective application of IFRS 16			(20)
Profit Allocated to Noncontrolling Interests	1,285		974	1,024
Exchange differences arising from the translation of the net investment in foreign operations	(14)		8	(3)
Unrealized gain or loss on financial assets at FVOCI	(3)		(26)	(1)
Remeasurements of defined benefit pension plans	17		15	(9)
Income tax relating to remeasurements of defined benefit pension plans	(3)		(3)	3
Share of other comprehensive income (loss) of associates and joint ventures accounted for using equity method	(1)		(1)	1
Cash dividends distributed by subsidiaries	(775)		(710)	(958)
Partial disposal of interests in subsidiaries	0		0	349
Share-based payment transactions of subsidiaries	63		22	42
Change in additional paid-in capital for not proportionately participating in the capital increase of subsidiaries	0		0	700
Change in additional paid-in capital from investments in associates and joint ventures accounted for using equity method	(2)		0	0
Other changes in additional paid-in capital of subsidiaries	0		0	0
Net increase (decrease) in noncontrolling interests	476		(1)	239
Ending balance	11,158	$ 397	10,115	9,857
As Adjusted [Member] \| Noncontrolling interests [Member]
Beginning balance	$ 10,115		9,837	8,470
Ending balance			$ 10,115	$ 9,837

Revenue - Summary of Revenue (D

Revenue - Summary of Revenue (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Revenue [Abstract]
Revenue from contracts with customers	$ 206,396		$ 206,360	$ 214,461
Other revenues
Rental income	843		818	640
Others	370		342	382
Revenue other than from contracts with customers	1,213		1,160	1,022
Total	$ 207,609	$ 7,393	$ 207,520	$ 215,483

Revenue - Summary of Disaggrega

Revenue - Summary of Disaggregation of Revenue (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	$ 206,396	$ 206,360	$ 214,461
Domestic Fixed Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	68,804	65,066	66,103
Mobile Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	90,143	95,390	100,877
Internet Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	31,809	29,834	29,650
International Fixed Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	8,682	11,475	13,424
Other [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	6,958	4,595	4,407
Mobile services [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	56,724	58,703	63,906
Mobile services [Member] \| Mobile Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	56,724	58,703	63,906
Sales of product [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	39,391	41,593	41,289
Sales of product [Member] \| Domestic Fixed Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	2,214	1,957	1,731
Sales of product [Member] \| Mobile Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	32,112	35,545	35,702
Sales of product [Member] \| Internet Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	107	41	4
Sales of product [Member] \| International Fixed Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	313	265	251
Sales of product [Member] \| Other [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	4,645	3,785	3,601
Local telephone and domestic long distance telephone services [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	26,475	27,929	29,996
Local telephone and domestic long distance telephone services [Member] \| Domestic Fixed Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	26,475	27,929	29,996
Broadband access and domestic leased line services [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	22,420	22,116	22,453
Broadband access and domestic leased line services [Member] \| Domestic Fixed Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	22,420	22,116	22,453
Data communications internet services [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	21,447	21,003	21,137
Data communications internet services [Member] \| Internet Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	21,447	21,003	21,137
International network and leased line services
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	3,884	7,066	8,724
International network and leased line services \| International Fixed Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	3,884	7,066	8,724
Others [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	36,055	27,950	26,956
Others [Member] \| Domestic Fixed Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	17,695	13,064	11,923
Others [Member] \| Mobile Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	1,307	1,142	1,269
Others [Member] \| Internet Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	10,255	8,790	8,509
Others [Member] \| International Fixed Communications Business [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	4,485	4,144	4,449
Others [Member] \| Other [Member]
Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items]
Revenue from contracts with customers	$ 2,313	$ 810	$ 806

Revenue - Summary of Contract B

Revenue - Summary of Contract Balances (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Jan. 01, 2019TWD ($)
Disclosure Of Contract Balance [Abstract]
Trade notes and accounts receivable, net	$ 22,622	$ 806	$ 26,408	$ 30,076
Contract assets
Products and service bundling	7,232		6,943	7,123
Others	612		116	109
Less : Loss allowance	(18)		(17)	(19)
Contract assets	7,826		7,042	7,213
Current Contract Assets	5,331	190	4,441	4,869
Noncurrent Contract Assets	2,495	89	2,601	2,344
Contract liabilities
Telecommunications business	13,602		12,772	8,193
Project business	6,687		10,360	4,508
Products and service bundling	16		39	106
Others	421		510	476
Contract liabilities	20,726		23,681	13,283
Current Contract Liabilities	13,437	479	16,840	10,688
Noncurrent Contract Liabilities	7,289	$ 260	6,841	2,595
Contract liabilities	$ 20,726		$ 23,681	$ 13,283

Revenue - Summary of Changes in

Revenue - Summary of Changes in Contract Assets and Contract Liabilities (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Contract assets
Net increase of customer contracts	$ 5,972	$ 6,066	$ 4,126
Reclassified to trade receivables	(5,681)	(6,405)	(7,532)
Significant changes of contract assets	291	(339)	(3,406)
Contract liabilities
Net increase of customer contracts	7	22	16
Recognized as revenues	(30)	(89)	(194)
Significant changes of contract liabilities	$ (23)	$ (67)	$ (178)

Revenue - Summary of Revenue Re

Revenue - Summary of Revenue Recognized (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue [Abstract]
Telecommunications business	$ 5,492	$ 6,186	$ 7,157
Project business	6,092	3,973	627
Others	512	404	324
Contracts with customers revenue recognized	$ 12,096	$ 10,563	$ 8,108

Revenue - Summary of Incrementa

Revenue - Summary of Incremental Costs of Obtaining Contracts (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Revenue [Abstract]
Incremental costs of obtaining a contract	$ 1,000	$ 36	$ 943

Revenue - Additional Informatio

Revenue - Additional Information (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Revenue From Contract With Customer Line Item
Amortization of incremental costs of obtaining contracts	$ 772	$ 27	$ 1,173	$ 1,941
Telecommunications Business [Member]
Revenue From Contract With Customer Line Item
Transaction price allocated to performance obligations	$ 29,501
Remaining performance obligations, timing of satisfaction	The Company expects to recognize such revenue of $18,729 million, $9,082 million and $1,690 million in 2021, 2022 and 2023, respectively.	The Company expects to recognize such revenue of $18,729 million, $9,082 million and $1,690 million in 2021, 2022 and 2023, respectively.
Telecommunications Business [Member] \| Year 1 [Member]
Revenue From Contract With Customer Line Item
Transaction price allocated to performance obligations	$ 18,729
Telecommunications Business [Member] \| Later than one year and not later than two years [member]
Revenue From Contract With Customer Line Item
Transaction price allocated to performance obligations	9,082
Telecommunications Business [Member] \| Later than two years and not later than three years [member]
Revenue From Contract With Customer Line Item
Transaction price allocated to performance obligations	1,690
Project Business [Member]
Revenue From Contract With Customer Line Item
Transaction price allocated to performance obligations	$ 18,555
Remaining performance obligations, timing of satisfaction	The Company recognizes revenues when the project business contract is completed and accepted by customers. The Company expects to recognize such revenue of $7,977 million, $5,897 million and $4,681 million in 2021, 2022 and 2023, respectively.	The Company recognizes revenues when the project business contract is completed and accepted by customers. The Company expects to recognize such revenue of $7,977 million, $5,897 million and $4,681 million in 2021, 2022 and 2023, respectively.
Project Business [Member] \| Year 1 [Member]
Revenue From Contract With Customer Line Item
Transaction price allocated to performance obligations	$ 7,977
Project Business [Member] \| Later than one year and not later than two years [member]
Revenue From Contract With Customer Line Item
Transaction price allocated to performance obligations	5,897
Project Business [Member] \| Later than two years and not later than three years [member]
Revenue From Contract With Customer Line Item
Transaction price allocated to performance obligations	$ 4,681

Net Income - Other Income and E

Net Income - Other Income and Expenses (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Analysis Of Income And Expense [Abstract]
Gain (loss) on disposal of property, plant and equipment	$ 1,428	$ 51	$ (38)	$ 142
Impairment loss on property, plant and equipment	0	0	(93)	0
Gain on disposal of investment properties	151	5	0	0
Reversal of impairment loss on investment properties	27	1	57	19
Loss on disposal of intangible assets	(2)	0	0	0
Impairment loss on intangible assets	(9)	0	(9)	(51)
Impairment loss on other assets	0	0	(44)	0
Other income and expenses	$ 1,595	$ 57	$ (127)	$ 110

Net Income - Other Income (Deta

Net Income - Other Income (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Analysis Of Income And Expense [Abstract]
Dividend income	$ 246	$ 9	$ 296	$ 396
Rental income	70		85	70
Others	154		150	234
Other income	$ 470	$ 17	$ 531	$ 700

Net Income - Other Gains and Lo

Net Income - Other Gains and Losses (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Analysis Of Income And Expense [Abstract]
Foreign currency exchange gain or loss, net	$ (47)		$ 16	$ 37
Gain or loss on disposal of investments accounted for using equity method	10	$ 0	151	0
Gain (loss) on disposal of financial instruments	(2)	0	4	6
Valuation gain or loss on financial assets and liabilities at fair value through profit or loss, net	(99)	(4)	(38)	(21)
Others	(21)		(49)	(68)
Other gains and losses	$ (159)	$ (6)	$ 84	$ (46)

Net Income - Interest Expenses

Net Income - Interest Expenses (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Interest Costs [Abstract]
Interest paid to financial institutions	$ 79		$ 17	$ 16
Interest on lease liabilities	80		85	0
Interest on bonds payable	46		0	0
Others	1		2	2
Interest expenses	$ 206	$ 7	$ 104	$ 18

Net Income - Impairment Loss (R

Net Income - Impairment Loss (Reversal of Impairment Loss) on Financial Instruments and Non-financial Assets (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Abstract]
Contract assets	$ 1		$ (2)	$ 19
Trade notes and accounts receivable	49		(54)	805
Other receivables	(5)		(69)	96
Inventories	1,161	$ 41	475	365
Property, plant and equipment	0		93	0
Investment properties	(27)	(1)	(57)	(19)
Intangible assets	9	0	9	51
Other assets	$ 0	$ 0	$ 44	$ 0

Net Income - Depreciation and A

Net Income - Depreciation and Amortization Expenses (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure Of Depreciation And Amortization [Line Items]
Property, plant and equipment	$ 26,989		$ 26,930	$ 27,461
Right-of-use assets	3,931		3,968	0
Investment properties	22		25	21
Intangible assets	5,424		4,253	4,386
Incremental costs of obtaining contracts	772	$ 27	1,173	1,941
Total depreciation and amortization expenses	37,138		36,349	33,809
Depreciation expenses	30,942	$ 1,102	30,923	27,482
Amortization expenses	6,196		5,426	6,327
Operating costs [Member]
Disclosure Of Depreciation And Amortization [Line Items]
Depreciation expenses	29,056		28,957	25,996
Amortization expenses	5,971		5,196	6,085
Operating expenses [Member]
Disclosure Of Depreciation And Amortization [Line Items]
Depreciation expenses	1,886		1,966	1,486
Marketing expenses [Member]
Disclosure Of Depreciation And Amortization [Line Items]
Amortization expenses	100		96	113
General and administrative expenses [Member]
Disclosure Of Depreciation And Amortization [Line Items]
Amortization expenses	82		95	93
Research and development expenses [Member]
Disclosure Of Depreciation And Amortization [Line Items]
Amortization expenses	$ 43		$ 39	$ 36

Net Income - Employee Benefit E

Net Income - Employee Benefit Expenses (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure Of Employee Benefit Expenses [Line Items]
Defined contribution plans	$ 708		$ 654	$ 640
Defined benefit plans pension costs recognized in profit and loss	2,001		2,859	2,953
Post-employment benefit	2,709		3,513	3,593
Compensation cost of share-based payment transactions	8	$ 0	2	17
Salaries	26,630		25,464	26,204
Insurance	2,712		2,746	2,740
Others	12,904		14,430	14,470
Other employee benefit	42,246		42,640	43,414
Employee benefit expenses	44,963		46,155	47,024
Summary by functions
Compensation distributed to the employees			1,126	1,404
Remuneration paid to the directors			35	38
Operating costs [Member]
Disclosure Of Employee Benefit Expenses [Line Items]
Defined benefit plans pension costs recognized in profit and loss	1,205		1,726	1,796
Employee benefit expenses	23,005		23,587	24,367
Operating expenses [Member]
Disclosure Of Employee Benefit Expenses [Line Items]
Employee benefit expenses	$ 21,958		$ 22,568	$ 22,657

Net Income - Additional Informa

Net Income - Additional Information (Detail) $ in Millions	12 Months Ended
Net Income - Additional Information (Detail) $ in Millions	Dec. 31, 2020TWD ($)
Employee benefits expense [Line Items]
Employees' compensation payables	$ 1,202
Remuneration to directors payables	$ 36
Bottom of Range [Member]
Employee benefits expense [Line Items]
Employees' compensation distribution rate	1.70%
Top of Range [Member]
Employee benefits expense [Line Items]
Employees' compensation distribution rate	4.30%
Directors' remuneration distribution rate	0.17%

Income Tax - Major Components o

Income Tax - Major Components of Income Tax Expense (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Current tax
Current tax expenses recognized for the year	$ 8,172		$ 8,109	$ 8,271
Income tax on unappropriated earnings	8		(20)	(2,070)
Income tax adjustments on prior years	(22)		(91)	7
Others	19		12	8
Current tax	8,177		8,010	6,216
Deferred tax
Deferred tax expense (benefits) recognized for the year	(81)		(63)	208
Income tax adjustments on prior years	26		(1)	19
Change in tax rate	0		0	(38)
Deferred tax	(55)		(64)	189
Income tax expense recognized in profit or loss	$ 8,122	$ 289	$ 7,946	$ 6,405

Income Tax - Reconciliation of

Income Tax - Reconciliation of Accounting Profit and Income Tax Expense (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Reconciliation Of Accounting Profit Multiplied By Applicable Tax Rates [Abstract]
Income before income tax	$ 42,826	$ 1,525	$ 41,867	$ 44,986
Income tax expense calculated at the statutory rate	8,565		8,373	8,997
Nondeductible income and expenses in determining taxable income	15		18	227
Unrecognized deductible temporary differences	(5)		3	1
Unrecognized loss carryforwards	4		7	21
Tax-exempt income	(367)		(148)	(580)
Additional income tax under Alternative Minimum Tax Act	0		0	46
Income tax on unappropriated earnings	8		(20)	(2,070)
Investment credits	(131)		(203)	(204)
Change in tax rate	0		0	(38)
Effect of different tax rates of group entities operating in other jurisdictions	10		(9)	(15)
Income tax adjustments on prior years	4		(92)	26
Others	19		17	(6)
Income tax expense recognized in profit or loss	$ 8,122	$ 289	$ 7,946	$ 6,405

Income Tax - Additional Informa

Income Tax - Additional Information (Detail)	12 Months Ended
Income Tax - Additional Information (Detail)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income tax [Line Items]
Applicable tax rate	20.00%	20.00%	20.00%	17.00%
Unappropriated earnings [Member]
Income tax [Line Items]
Applicable tax rate			5.00%	10.00%
China [Member]
Income tax [Line Items]
Applicable tax rate	25.00%	25.00%	25.00%

Income Tax - Income Tax Recogni

Income Tax - Income Tax Recognized in Other Comprehensive Income (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax
Remeasurement on defined benefit pension plans	$ 239	$ 305	$ (243)
Change in tax rate - defined benefit pension plans	0	0	(207)
Total income tax expense (benefit) recognized in other comprehensive income	$ 239	$ 305	$ (450)

Income Tax - Current Tax Assets

Income Tax - Current Tax Assets and Liabilities (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Major Components Of Tax Expense Income [Abstract]
Tax refund receivable (included in other current assets - other)	$ 1		$ 1
Income tax payable	$ 6,157	$ 219	$ 5,812

Income Tax - Movements of Defer

Income Tax - Movements of Deferred Income Tax Assets and Liabilities (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income tax [Line Items]
Recognized in Profit or Loss	$ 81	$ 63	$ (208)
Recognized in Other Comprehensive Income	(239)	(305)	450
Deferred tax asset [Member]
Income tax [Line Items]
Beginning balance	3,259	3,554	2,730
Effect of Retrospective Application of IFRS 16		26
Acquired by business combinations (Note 14)	6
Recognized in Profit or Loss	107	(16)	374
Recognized in Other Comprehensive Income	(239)	(305)	450
Ending balance	3,133	3,259	3,554
Deferred tax asset [Member] \| Allowance for doubtful receivables over quota [Member]
Income tax [Line Items]
Beginning balance	404	435	289
Recognized in Profit or Loss	(39)	(31)	146
Ending balance	365	404	435
Deferred tax asset [Member] \| Share of profits of associates and joint ventures accounted for using equity method [Member]
Income tax [Line Items]
Beginning balance	402	389	331
Recognized in Profit or Loss	(1)	13	58
Ending balance	401	402	389
Deferred tax asset [Member] \| Defined benefit pension plans [Member]
Income tax [Line Items]
Beginning balance	2,034	2,307	1,723
Acquired by business combinations (Note 14)	1
Recognized in Profit or Loss	20	32	134
Recognized in Other Comprehensive Income	(239)	(305)	450
Ending balance	1,816	2,034	2,307
Deferred tax asset [Member] \| Valuation loss on inventory [Member]
Income tax [Line Items]
Beginning balance	141	88	23
Acquired by business combinations (Note 14)	3
Recognized in Profit or Loss	155	53	65
Ending balance	299	141	88
Deferred tax asset [Member] \| Deferred revenue [Member]
Income tax [Line Items]
Beginning balance	98	111	106
Recognized in Profit or Loss	(25)	(13)	5
Ending balance	73	98	111
Deferred tax asset [Member] \| Estimated warranty liabilities [Member]
Income tax [Line Items]
Beginning balance	34	26	22
Recognized in Profit or Loss	2	8	4
Ending balance	36	34	26
Deferred tax asset [Member] \| Accrued award credits liabilities [Member]
Income tax [Line Items]
Beginning balance	17	14	15
Recognized in Profit or Loss	1	3	(1)
Ending balance	18	17	14
Deferred tax asset [Member] \| Others [Member]
Income tax [Line Items]
Beginning balance	101	143	175
Effect of Retrospective Application of IFRS 16		26
Acquired by business combinations (Note 14)	2
Recognized in Profit or Loss	2	(68)	(32)
Ending balance	105	101	143
Deferred tax asset [Member] \| Temporary differences [Member]
Income tax [Line Items]
Beginning balance	3,231	3,513	2,684
Effect of Retrospective Application of IFRS 16		26
Acquired by business combinations (Note 14)	6
Recognized in Profit or Loss	115	(3)	379
Recognized in Other Comprehensive Income	(239)	(305)	450
Ending balance	3,113	3,231	3,513
Deferred tax asset [Member] \| Unused tax losses [Member]
Income tax [Line Items]
Beginning balance	28	41	46
Recognized in Profit or Loss	(8)	(13)	(5)
Ending balance	20	28	41
Deferred tax liability [Member]
Income tax [Line Items]
Beginning balance	(1,912)	(1,992)	(1,430)
Effect of Retrospective Application of IFRS 9			1
Acquired by business combinations (Note 14)	(3)
Recognized in Profit or Loss	(52)	80	(563)
Ending balance	(1,967)	(1,912)	(1,992)
Deferred tax liability [Member] \| Defined benefit pension plans [Member]
Income tax [Line Items]
Beginning balance	(1,758)	(1,832)	(1,265)
Recognized in Profit or Loss	(54)	74	(567)
Ending balance	(1,812)	(1,758)	(1,832)
Deferred tax liability [Member] \| Others [Member]
Income tax [Line Items]
Beginning balance	(1)	(2)	(2)
Effect of Retrospective Application of IFRS 9			1
Acquired by business combinations (Note 14)	(3)
Recognized in Profit or Loss	1	1	(1)
Ending balance	(3)	(1)	(2)
Deferred tax liability [Member] \| Land value incremental tax [Member]
Income tax [Line Items]
Beginning balance	(95)	(95)	(95)
Ending balance	(95)	(95)	(95)
Deferred tax liability [Member] \| Deferred revenue for award credits [Member]
Income tax [Line Items]
Beginning balance	(29)	(31)	(29)
Recognized in Profit or Loss	(1)	2	(2)
Ending balance	(30)	(29)	(31)
Deferred tax liability [Member] \| Intangible assets and goodwill [member]
Income tax [Line Items]
Beginning balance	(29)	(32)	(39)
Recognized in Profit or Loss	2	3	7
Ending balance	$ (27)	$ (29)	$ (32)

Income Tax - Items for Which No

Income Tax - Items for Which No Deferred Income Tax Assets Have Been Recognized (Detail) - TWD ($)	Dec. 31, 2020	Dec. 31, 2019
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Loss carryforwards	$ 70,000,000	$ 66,000,000
Deductible temporary differences	0	1,000,000
2021 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Loss carryforwards	12,000,000	13,000,000
2022 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Loss carryforwards	10,000,000	10,000,000
2023 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Loss carryforwards	8,000,000	8,000,000
2024 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Loss carryforwards	8,000,000	8,000,000
2025 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Loss carryforwards	19,000,000	15,000,000
2026 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Loss carryforwards	8,000,000	8,000,000
2027 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Loss carryforwards	3,000,000	3,000,000
2028 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Loss carryforwards	1,000,000	1,000,000
2029 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Loss carryforwards	1,000,000	0
2030 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Loss carryforwards	$ 0	$ 0

Income Tax - Information About

Income Tax - Information About Unused Loss Carryforwards (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Remaining creditable amount	$ 3,133	$ 112	$ 3,259
Unused tax losses [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Remaining creditable amount	91
Unused tax losses [Member] \| 2021 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Remaining creditable amount	14
Unused tax losses [Member] \| 2022 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Remaining creditable amount	11
Unused tax losses [Member] \| 2023 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Remaining creditable amount	9
Unused tax losses [Member] \| 2024 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Remaining creditable amount	8
Unused tax losses [Member] \| 2025 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Remaining creditable amount	22
Unused tax losses [Member] \| 2026 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Remaining creditable amount	16
Unused tax losses [Member] \| 2027 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Remaining creditable amount	3
Unused tax losses [Member] \| 2028 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Remaining creditable amount	4
Unused tax losses [Member] \| 2029 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Remaining creditable amount	2
Unused tax losses [Member] \| 2030 [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Remaining creditable amount	$ 2

Earnings Per Share - Net Income

Earnings Per Share - Net Income and Weighted Average Number of Common Stocks Used in Calculation of Earnings Per Share (Detail) shares in Millions, $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)shares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019TWD ($)shares	Dec. 31, 2018TWD ($)shares
Net income used to compute the basic earnings per share
Net income attributable to the parent	$ 33,419	$ 1,190	$ 32,947	$ 37,557
Assumed conversion of all dilutive potential common stocks
Employee stock options, employee compensation of subsidiaries \| $	(7)		(4)	(6)
Net income used to compute the diluted earnings per share \| $	$ 33,412		$ 32,943	$ 37,551
Weighted average number of common stocks used to compute the basic earnings per share	7,757	7,757	7,757	7,757
Assumed conversion of all dilutive potential common stocks
Employee compensation	8	8	8	9
Weighted average number of common stocks used to compute the diluted earnings per share	7,765	7,765	7,765	7,766

Share-based Payment Arrangeme_3

Share-based Payment Arrangement - SENAO Share-based Compensation Plan (Detail) - Senao International Co., Ltd. (SENAO) [Member]	12 Months Ended
	Dec. 31, 2020shares$ / shares	Jul. 31, 2018$ / shares	Jun. 30, 2018$ / shares
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Effective Date	2012.05.28
Grant Date	2013.05.07
Stock Options Units \| shares	10,000,000
Exercise Price	$ 66.20	$ 66.20	$ 70.70
Original price	$ 93

Share-based Payments Arrangemen

Share-based Payments Arrangement - Additional Information (Detail) $ / shares in Units, $ / shares in Units, $ in Millions	Dec. 20, 2019$ / sharesshares	Oct. 31, 2018$ / sharesshares	Dec. 19, 2017$ / sharesshares	Oct. 22, 2015shares	Jan. 31, 2014shares	Aug. 31, 2013shares	May 07, 2013shares	Mar. 31, 2018shares	Dec. 31, 2020TWD ($)$ / shares	Dec. 31, 2020TWD ($)$ / shares	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)$ / shares	Dec. 31, 2018TWD ($)$ / sharesshares	Dec. 31, 2020$ / shares	Jul. 31, 2020$ / shares	Jun. 30, 2019$ / shares	Aug. 31, 2018$ / shares	Jul. 31, 2018$ / shares	Jun. 30, 2018$ / shares	Dec. 31, 2017
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Compensation costs										$ 8,000,000	$ 0	$ 2,000,000	$ 17,000,000
Senao International Co., Ltd. (SENAO) [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of common share each option is eligible \| shares							1
Option expire period							six years
Exercise Price									$ 66.20	$ 66.20								$ 66.20	$ 70.70
Compensation costs \| $										$ 0		$ 0	$ 0
Outstanding stock options									0	0		0	5,318,000	0						5,926,000
Exercisable price												$ 0	$ 66.20
Senao International Co., Ltd. (SENAO) [Member] \| Stock Option Granted in April Member 2018 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Compensation costs \| $													$ 15,600,000
Number of treasury stock transfer to its specific employees \| shares													6,658,000
Senao International Co., Ltd. (SENAO) [Member] \| 2 years after grant date [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Vesting period							two years
Vesting percentage							50.00%
Senao International Co., Ltd. (SENAO) [Member] \| 3 years after grant date [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Vesting period							three years
Vesting percentage							25.00%
Senao International Co., Ltd. (SENAO) [Member] \| 4 years after grant date [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Vesting period							four years
Vesting percentage							25.00%
CHIEF Telecom Inc. (CHIEF) [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of common share each option is eligible \| shares		1,000	1,000	1,000
Compensation costs \| $													$ 0
Shares issued \| shares								7,842,000
Reserve for employee subscription \| shares								1,176,000
CHIEF Telecom Inc. (CHIEF) [Member] \| Granted on October 22, 2015 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Option expire period										five years	five years
Vesting period										two years	two years
Exercise Price									$ 34.40	$ 34.40		$ 34.40
Compensation costs \| $										$ 0		$ 300,000	$ 1,000,000
Outstanding stock options									0	0		314.25	882.75	0						1,936
Exercisable price									$ 0	$ 0		$ 34.40	$ 34.40
CHIEF Telecom Inc. (CHIEF) [Member] \| Granted on December 19, 2017 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Option expire period										five years	five years
Vesting period										two years	two years
Exercise Price			$ 147						$ 132.70	$ 132.70		$ 135.60			$ 132.70	$ 135.60	$ 140.60		$ 144.10
Compensation costs \| $										$ 200,000		$ 600,000	$ 600,000
Outstanding stock options									427.50	427.50		897	925	427.50						950
Exercisable price									$ 132.70	$ 132.70		$ 135.60	$ 0
CHIEF Telecom Inc. (CHIEF) [Member] \| Granted on October 31, 2018 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Option expire period										five years	five years
Vesting period										two years	two years
Exercise Price		$ 147							$ 138.70	$ 138.70		$ 141.70			$ 138.70	$ 141.70
Compensation costs \| $										$ 300,000		$ 600,000	$ 100,000
Outstanding stock options									21	21		46	50	21						0
Exercisable price									$ 0	$ 0		$ 0	$ 0
CHIEF Telecom Inc. (CHIEF) [Member] \| Granted on November 13, 2020 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Option expire period										five years	five years
Vesting period										two years	two years
Exercise Price									$ 206	$ 206
Compensation costs \| $										$ 1,000,000
Outstanding stock options									200	200		0		200
Exercisable price									$ 0	$ 0
CHT Security Co., Ltd. (CHTSC) [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of common share each option is eligible \| shares	1,000
Option expire period	five years
Vesting period	one year
Exercise Price									$ 19.085	$ 19.085		$ 19.085
Compensation costs \| $										$ 5,700,000		$ 200,000
Outstanding stock options									4,328	4,328		4,500		4,328
Shares issued \| shares	4,500,000
Exercisable price \| (per share)	$ 19.085								$ 19.085	$ 19.085		$ 0
IISI Plan [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of common share each option is eligible \| shares	1,000
Option expire period	seven years
Vesting period	two years
Exercise Price									$ 14	$ 14
Compensation costs \| $									$ 0
Outstanding stock options									530	530				530
Shares issued \| shares						1,335,000
Exercisable price \| (per share)									$ 14	$ 14				$ 14
Shares options \| shares					1,665,000

Share-based Payments Arrangem_2

Share-based Payments Arrangement - SENAO's Outstanding Stock Options (Detail) - Senao International Co., Ltd. (SENAO) [Member]	12 Months Ended
	Dec. 31, 2020$ / shares	Dec. 31, 2019$ / shares	Dec. 31, 2018$ / shares
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, Options outstanding at beginning of the year	0	5,318,000	5,926,000
Number of options, Options forfeited		(5,318,000)	(608,000)
Number of options, Options outstanding at end of the year	0	0	5,318,000
Number of options, Options exercisable at end of the year		0	5,318,000
Weighted-average exercise price, Options outstanding at beginning of the year	$ 0	$ 66.20	$ 70.70
Weighted-average exercise price, Options outstanding at end of the year		0	66.20
Weighted-average exercise price, Options exercisable at end of the year		$ 0	$ 66.20

Share-based Payments Arrangem_3

Share-based Payments Arrangement - Black-Scholes Model and Related Assumptions used to Evaluate Options and Fair Value of Options by SENAO (Detail) - Senao International Co., Ltd. (SENAO) [Member]	May 07, 2018TWD ($)d$ / shares	May 07, 2013TWD ($)yr$ / shares
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Grant-date share price	$ 51.60	$ 93
Exercise price	$ 49.28	$ 93
Dividend yield	0.00%	0.00%
Risk-free interest rate	0.59%	0.91%
Expected life	18	4.375
Expected volatility	8.78%	36.22%
Weighted-average fair value of grants \| $	$ 2.34	$ 28.72

Share-based Payments Arrangem_4

Share-based Payments Arrangement - CHIEF Share-based Compensation Plan (Detail) - CHIEF Telecom Inc. (CHIEF) [Member]	12 Months Ended
	Dec. 31, 2020$ / shares	Jul. 31, 2020$ / shares	Dec. 31, 2019$ / shares	Jun. 30, 2019$ / shares	Oct. 31, 2018$ / shares	Aug. 31, 2018$ / shares	Jun. 30, 2018$ / shares	Dec. 19, 2017$ / shares
Grant Date 2015.10.22 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Effective Date	2015.11.17
Grant Date	2015.10.22
Stock Options Units	2,000
Exercise Price	$ 34.40		$ 34.40
Original price	$ 43
Grant Date 2017.12.19 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Effective Date	2017.12.18
Grant Date	2017.12.19
Stock Options Units	950
Exercise Price	$ 132.70	$ 132.70	135.60	$ 135.60		$ 140.60	$ 144.10	$ 147
Original price	$ 147
Granted Date 2018.10.31 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Effective Date	2017.12.18
Grant Date	2018.10.31
Stock Options Units	50
Exercise Price	$ 138.70	$ 138.70	$ 141.70	$ 141.70	$ 147
Original price	$ 147
Granted Date 2020.11.13 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Effective Date	2020.09.16
Grant Date	2020.11.13
Stock Options Units	200
Exercise Price	$ 206

Share-based Payments Arrangem_5

Share-based Payments Arrangement - CHIEF's Outstanding Stock Options (Detail) - CHIEF Telecom Inc. (CHIEF) [Member]	12 Months Ended
	Dec. 31, 2020$ / shares	Dec. 31, 2019$ / shares	Dec. 31, 2018$ / shares
Granted on December 19, 2017 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, Options outstanding at beginning of the year	897	925	950
Number of options, Options granted	0		0
Number of options, Options exercised	(448.50)	0	0
Number of options, Options forfeited	(21)	(28)	(25)
Number of options, Options outstanding at end of the year	427.50	897	925
Number of options, Option exercisable at end of the year	213.75	448.50	0
Weighted-average exercise price, Options outstanding at beginning of the year	$ 135.60	$ 140.60	$ 147
Weighted average exercise price, Options granted	0		0
Weighted average exercise price, Options exercised	135.60	0	0
Weighted average exercise price, Options forfeited	0	0	0
Weighted-average exercise price, Options outstanding at end of the year	132.70	135.60	140.60
Weighted average exercise price, Option exercisable at end of the year	$ 132.70	$ 135.60	$ 0
Granted on October 22, 2015 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, Options outstanding at beginning of the year	314.25	882.75	1,936
Number of options, Options granted	0		0
Number of options, Options exercised	(314.25)	(547.25)	(1,027.25)
Number of options, Options forfeited	0	(21.25)	(26)
Number of options, Options outstanding at end of the year	0	314.25	882.75
Number of options, Option exercisable at end of the year	0	314.25	416.50
Weighted-average exercise price, Options outstanding at beginning of the year	$ 34.40	$ 34.40	$ 34.40
Weighted average exercise price, Options granted	0		0
Weighted average exercise price, Options exercised	34.40	34.40	34.40
Weighted average exercise price, Options forfeited	0	0	0
Weighted-average exercise price, Options outstanding at end of the year	0	34.40	34.40
Weighted average exercise price, Option exercisable at end of the year	$ 0	$ 34.40	$ 34.40
Granted on October 31, 2018 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, Options outstanding at beginning of the year	46	50	0
Number of options, Options granted	0		50
Number of options, Options exercised	(21)	0	0
Number of options, Options forfeited	(4)	(4)	0
Number of options, Options outstanding at end of the year	21	46	50
Number of options, Option exercisable at end of the year	0	0	0
Weighted-average exercise price, Options outstanding at beginning of the year	$ 141.70	$ 147	$ 0
Weighted average exercise price, Options granted	0		147
Weighted average exercise price, Options exercised	138.70	0	0
Weighted average exercise price, Options forfeited	0	0	0
Weighted-average exercise price, Options outstanding at end of the year	138.70	141.70	147
Weighted average exercise price, Option exercisable at end of the year	$ 0	$ 0	$ 0
Granted on November 13, 2020 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, Options outstanding at beginning of the year	0
Number of options, Options granted	200
Number of options, Options exercised	0
Number of options, Options forfeited	0
Number of options, Options outstanding at end of the year	200	0
Number of options, Option exercisable at end of the year	0
Weighted-average exercise price, Options outstanding at beginning of the year	$ 0
Weighted average exercise price, Options granted	206
Weighted average exercise price, Options exercised	0
Weighted average exercise price, Options forfeited	0
Weighted-average exercise price, Options outstanding at end of the year	206	$ 0
Weighted average exercise price, Option exercisable at end of the year	$ 0

Share-based Payments Arrangem_6

Share-based Payments Arrangement - CHIEF's Employee Stock Options Outstanding (Detail) - CHIEF Telecom Inc. (CHIEF) [Member]	12 Months Ended
	Dec. 31, 2020$ / shares	Dec. 31, 2019$ / shares	Jul. 31, 2020$ / shares	Jun. 30, 2019$ / shares	Dec. 31, 2018$ / shares	Oct. 31, 2018$ / shares	Aug. 31, 2018$ / shares	Jun. 30, 2018$ / shares	Dec. 31, 2017$ / shares	Dec. 19, 2017$ / shares
Granted on October 22, 2015 [Member]
Disclosure Of Range Of Exercise Prices Of Outstanding Share Options [Line Items]
Range of Exercise Price	$ 34.40	$ 34.40
Number of Options Outstanding	0	314.25			882.75				1,936
Weighted-average Remaining Contractual Life (Years)		9 months 21 days
Weighted-average Exercise Price	$ 0	$ 34.40			$ 34.40				$ 34.40
Options Exercisable Number of Options	0	314.25			416.50
Option Exercisable Weighted-average Exercise Price	$ 0	$ 34.40			$ 34.40
Grant Date 2017.12.19 [Member]
Disclosure Of Range Of Exercise Prices Of Outstanding Share Options [Line Items]
Range of Exercise Price	$ 132.70	$ 135.60	$ 132.70	$ 135.60			$ 140.60	$ 144.10		$ 147
Number of Options Outstanding	427.50	897			925				950
Weighted-average Remaining Contractual Life (Years)	1 year 11 months 15 days	2 years 11 months 15 days
Weighted-average Exercise Price	$ 132.70	$ 135.60			$ 140.60				$ 147
Options Exercisable Number of Options	213.75	448.50			0
Option Exercisable Weighted-average Exercise Price	$ 132.70	$ 135.60			$ 0
Granted Date 2018.10.31 [Member]
Disclosure Of Range Of Exercise Prices Of Outstanding Share Options [Line Items]
Range of Exercise Price	$ 138.70	$ 141.70	$ 138.70	$ 141.70		$ 147
Number of Options Outstanding	21	46			50				0
Weighted-average Remaining Contractual Life (Years)	2 years 9 months 29 days	3 years 9 months 29 days
Weighted-average Exercise Price	$ 138.70	$ 141.70			$ 147				$ 0
Options Exercisable Number of Options	0	0			0
Option Exercisable Weighted-average Exercise Price	$ 0	$ 0			$ 0
Granted Date 2020.11.13 [Member]
Disclosure Of Range Of Exercise Prices Of Outstanding Share Options [Line Items]
Range of Exercise Price	$ 206
Number of Options Outstanding	200	0
Weighted-average Remaining Contractual Life (Years)	4 years 10 months 13 days
Weighted-average Exercise Price	$ 206	$ 0
Options Exercisable Number of Options	0
Option Exercisable Weighted-average Exercise Price	$ 0

Share-based Payments Arrangem_7

Share-based Payments Arrangement - Black-Scholes Model and Binomial Option Pricing Model and Related Assumptions used to Evaluate Options and Fair Value of Options by CHIEF (Detail) - CHIEF Telecom Inc. (CHIEF) [Member]	Nov. 13, 2020TWD ($)yr$ / shares	Oct. 31, 2018TWD ($)yr$ / shares	May 22, 2018TWD ($)d$ / shares	Dec. 19, 2017TWD ($)yr$ / shares	Oct. 22, 2015TWD ($)yr$ / shares
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Grant-date share price	$ 356	$ 166	$ 156.41	$ 95.92	$ 39.55
Exercise price	$ 206	$ 147	$ 170	$ 147	$ 43
Dividend yield	0.00%	0.00%	0.00%	0.00%	0.00%
Risk-free interest rate	0.18%	0.72%	0.34%	0.62%	0.86%
Expected life	5	5	7	5	5
Expected volatility	34.61%	16.60%	14.33%	17.35%	21.02%
Weighted average fair value of grants \| $	$ 173,893	$ 33,540	$ 0	$ 2,318	$ 4,863

Share-based Payments Arrangem_8

Share-based Payments Arrangement - Black-Scholes Model and Related Assumptions used to Evaluate Options and Fair Value of Options by CHIEF (Detail) - CHIEF Telecom Inc. (CHIEF) [Member]	Nov. 13, 2020TWD ($)yr$ / shares	Oct. 31, 2018TWD ($)yr$ / shares	May 22, 2018TWD ($)d$ / shares	Dec. 19, 2017TWD ($)yr$ / shares	Oct. 22, 2015TWD ($)yr$ / shares
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Grant-date share price	$ 356	$ 166	$ 156.41	$ 95.92	$ 39.55
Exercise price	$ 206	$ 147	$ 170	$ 147	$ 43
Dividend yield	0.00%	0.00%	0.00%	0.00%	0.00%
Risk-free interest rate	0.18%	0.72%	0.34%	0.62%	0.86%
Expected life	5	5	7	5	5
Expected volatility	34.61%	16.60%	14.33%	17.35%	21.02%
Weighted average fair value of grants \| $	$ 173,893	$ 33,540	$ 0	$ 2,318	$ 4,863

Share-based Payments Arrangem_9

Share-based Payments Arrangement - CHTSC's Outstanding Stock Options (Detail) - CHT Security Co., Ltd. (CHTSC) [Member]	12 Months Ended
	Dec. 31, 2020$ / shares	Dec. 31, 2019$ / shares
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, Options outstanding at beginning of the year	4,500
Number of options, Options outstanding at end of the year	4,328	4,500
Number of options, Options exercisable at end of the year	1,082	0
Weighted-average exercise price, Options outstanding at beginning of the year	$ 19.085
Weighted-average exercise price, Options outstanding at end of the year	19.085	$ 19.085
Weighted average exercise price, Option exercisable at end of the year	$ 19.085	$ 0
Granted on December 20, 2019 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, Options outstanding at beginning of the year	4,500	0
Number of options, Options granted	0	4,500
Number of options, Options forfeited	(172)	0
Number of options, Options outstanding at end of the year	4,328	4,500
Number of options, Options exercisable at end of the year	1,082	0
Weighted-average exercise price, Options outstanding at beginning of the year	$ 19.085	$ 0
Weighted average exercise price, Options granted	0	19.085
Weighted-average exercise price, Options forfeited	0	0
Weighted-average exercise price, Options outstanding at end of the year	19.085	19.085
Weighted average exercise price, Option exercisable at end of the year	$ 19.085	$ 0

Share-based Payments Arrange_10

Share-based Payments Arrangement - CHTSC's Employee Stock Options Outstanding (Detail) - CHT Security Co., Ltd. (CHTSC) [Member]	12 Months Ended
	Dec. 31, 2020$ / shares	Dec. 31, 2019$ / shares	Dec. 20, 2019$ / shares
Disclosure Of Range Of Exercise Prices Of Outstanding Share Options [Line Items]
Range of Exercise Price	$ 19.085	$ 19.085
Number of Options Outstanding	4,328	4,500
Weighted-average Remaining Contractual Life (Years)	3 years 11 months 19 days	4 years 11 months 19 days
Weighted-average Exercise Price	$ 19.085	$ 19.085
Options Exercisable Number of Options	1,082	0
Option Exercisable Weighted-average Exercise Price \| (per share)	$ 19.085	$ 0	$ 19.085

Share-based Payments Arrange_11

Share-based Payments Arrangement - Black-Scholes Model and Related Assumptions used to Evaluate Options and Fair Value of Options by CHTSC (Detail) - CHT Security Co., Ltd. (CHTSC) [Member]	Dec. 20, 2019TWD ($)yr$ / shares
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Grant-date share price	$ 20.17
Exercise price	$ 19.085
Dividend yield	12.49%
Risk-free interest rate	0.54%
Expected life \| yr	5
Expected volatility	42.41%
Weighted average fair value of grants \| $	$ 2,470

Share-based Payments Arrange_12

Share-based Payments Arrangement - IISI's Outstanding Stock Options (Detail) - IISI Plan [Member]	12 Months Ended
	Dec. 31, 2020$ / shares	Dec. 31, 2020$ / shares
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, Options outstanding at end of the year	530
Number of options, Options exercisable at end of the year	530	530
Weighted-average exercise price, Options outstanding at end of the year	$ 14
Weighted-average exercise price, Options exercisable at end of the year \| (per share)	$ 14	$ 14
Granted in August 2013 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, Options outstanding at beginning of the year	0
Options outstanding upon the date of business combination	1,022.96
Number of options, Options exercised	(432.50)
Number of options, Options forfeited	(590.46)
Number of options, Options outstanding at end of the year	0
Number of options, Options exercisable at end of the year	0	0
Weighted-average exercise price, Options outstanding at beginning of the year	$ 0
Options outstanding upon the date of business combination	14
Weighted average exercise price, Options exercised	14
Weighted-average exercise price, Options forfeited	0
Weighted-average exercise price, Options outstanding at end of the year	0
Weighted-average exercise price, Options exercisable at end of the year	$ 0
Granted in January 2014 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, Options outstanding at beginning of the year	0
Options outstanding upon the date of business combination	580
Number of options, Options exercised	(50)
Number of options, Options forfeited	0
Number of options, Options outstanding at end of the year	530
Number of options, Options exercisable at end of the year	530	530
Weighted-average exercise price, Options outstanding at beginning of the year	$ 0
Options outstanding upon the date of business combination	14
Weighted average exercise price, Options exercised	14
Weighted-average exercise price, Options forfeited	0
Weighted-average exercise price, Options outstanding at end of the year	14
Weighted-average exercise price, Options exercisable at end of the year	$ 14

Share-based Payments Arrange_13

Share-based Payments Arrangement - IISI's Employee Stock Options Outstanding (Detail) - IISI Plan [Member]	12 Months Ended
	Dec. 31, 2020$ / shares	Dec. 31, 2020$ / shares
Disclosure Of Range Of Exercise Prices Of Outstanding Share Options [Line Items]
Range of Exercise Price	$ 14
Number of Options Outstanding	530	530
Weighted-average Remaining Contractual Life (Years)	14 days
Weighted-average Exercise Price	$ 14
Options Exercisable Number of Options	530	530
Option Exercisable Weighted-average Exercise Price \| (per share)	$ 14	$ 14

Share-based Payments Arrange_14

Share-based Payments Arrangement - Black-Scholes Model and Related Assumptions used to Evaluate Options and Fair Value of Options by IISI (Detail) - IISI Plan [Member]	Jan. 31, 2014TWD ($)yr$ / shares	Aug. 31, 2013TWD ($)yr$ / shares
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Grant-date share price \| $ / shares	$ 14.51	$ 12.51
Exercise price \| $ / shares	$ 14	$ 14
Dividend yield	6.00%	6.00%
Weighted average fair value of grants \| $	$ 14.51	$ 12.51
Bottom of Range [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Risk-free interest rate	1.16%	1.20%
Expected life \| yr	4.5	4.5
Expected volatility	35.28%	36.01%
Top of Range [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Risk-free interest rate	1.32%	1.39%
Expected life \| yr	5.5	5.5
Expected volatility	35.97%	36.62%

Non-Cash Transactions - Non-cas

Non-Cash Transactions - Non-cash Investing Activities (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Noncash Investing Activities [Abstract]
Increase in property, plant and equipment	$ 25,195		$ 23,164	$ 27,979
Other payables	(1,684)		1,002	571
Acquisition of property, plant and equipment	23,511	$ 838	24,166	28,550
Increase in investment properties	1,359		1	6
Trade-in investment properties from asset exchange transaction (Note 16)	(1,305)		0	0
Acquisition of investment properties	54	2	1	6
Increase in intangible assets	48,605		363	498
Changes in other assets	(1,000)		0	0
Acquisition of intangible assets	47,605	1,695	363	498
Disposal of property, plant and equipment, net	307		86	122
Gain (loss) on disposal of property, plant and equipment	1,428	51	(38)	142
Trade-in investment properties from asset exchange transaction (Note 16)	(1,305)		0	0
Changes in other payables	(80)		0	0
Changes in other current monetary assets	(31)		0	0
Proceeds from disposal of property, plant and equipment	$ 319	$ 11	$ 48	$ 264

Non-Cash Transactions - Summary

Non-Cash Transactions - Summary of Changes in Liabilities Arising From Financing Activities Including Non-cash Transactions (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Reconciliation Of Liabilities Arising From Financing Activities [Abstract]
Beginning Balance	$ 9,758	$ 10,340
Cash Flows from Financing Activities	(3,683)	(3,728)
Changes in Non-Cash Transactions, New Leases	3,796	3,803
Changes in Non-Cash Transactions, Acquired by business combination	71
Changes in Non-Cash Transactions, Others	(265)	(572)
Cash Flows from Operation Activities - Interest Paid	(80)	(85)
Ending Balance	$ 9,597	$ 9,758

Financial Instruments - Categor

Financial Instruments - Categories of Financial Instruments (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Financial assets
Mandatorily measured at FVTPL	$ 687		$ 779
Hedging financial assets	2	$ 0	0
Financial assets at amortized cost (Note a)	62,405		71,852
Financial assets at FVOCI	7,193		7,154
Financial liabilities
Measured at FVTPL Held for trading	0		0
Measured at amortized cost (Note b)	$ 62,557		$ 34,434

Financial Instruments - Assets

Financial Instruments - Assets and Liabilities related to Foreign Currency Risk (Detail) - Foreign currency risk [Member] - TWD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
USD [Member]
Disclosure of detailed information about financial instruments [Line Items]
Foreign currency denominated monetary assets	$ 2,711	$ 5,782
Foreign currency denominated monetary liabilities	768	4,121
Derivatives assets	0	0
Derivatives liabilities	0	0
EUR [Member]
Disclosure of detailed information about financial instruments [Line Items]
Foreign currency denominated monetary assets	15	12
Foreign currency denominated monetary liabilities	957	206
Derivatives assets	4	0
Derivatives liabilities	0	0
SGD [Member]
Disclosure of detailed information about financial instruments [Line Items]
Foreign currency denominated monetary assets	170	225
Foreign currency denominated monetary liabilities	1,049	1,263
RMB [Member]
Disclosure of detailed information about financial instruments [Line Items]
Foreign currency denominated monetary assets	30	9
Foreign currency denominated monetary liabilities	0	0
JPY [Member]
Disclosure of detailed information about financial instruments [Line Items]
Foreign currency denominated monetary assets	22	17
Foreign currency denominated monetary liabilities	10	14
HKD [Member]
Disclosure of detailed information about financial instruments [Line Items]
Foreign currency denominated monetary assets	69	0
Foreign currency denominated monetary liabilities	$ 8	$ 15

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Foreign currency risk [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity rate	5.00%	5.00%	5.00%
Interest rate risk [member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity rate	0.25%	0.25%	0.25%
Increase decrease in pre-tax income due to sensitivity analysis	$ 19	$ 15	$ 19
Equity price risk [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity rate	5.00%	5.00%	5.00%
Equity price risk [Member] \| Pre-tax profit [Member]
Disclosure of detailed information about financial instruments [Line Items]
Increase decrease in pretax income of financial assets at FVTPL, FVOCI	$ 34	$ 39	$ 26
Equity price risk [Member] \| Pre-tax other comprehensive income [Member]
Disclosure of detailed information about financial instruments [Line Items]
Increase decrease in pretax income of financial assets at FVTPL, FVOCI	$ 360	$ 358	$ 347

Financial Instruments - Foreign

Financial Instruments - Foreign Currency Risk Sensitivity Analysis (Detail) - TWD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Profit and loss [Member] \| Financial instruments [Member] \| USD [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	$ 97	$ 83	$ (55)
Profit and loss [Member] \| Financial instruments [Member] \| EUR [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	(47)	(10)	(59)
Profit and loss [Member] \| Financial instruments [Member] \| SGD [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	(44)	(52)	4
Profit and loss [Member] \| Financial instruments [Member] \| RMB [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	1	0	0
Profit and loss [Member] \| Financial instruments [Member] \| JPY [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	1	0	0
Profit and loss [Member] \| Financial instruments [Member] \| HKD [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	3	(1)	0
Profit and loss [Member] \| Derivatives [Member] \| USD [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	(19)	1	3
Profit and loss [Member] \| Derivatives [Member] \| EUR [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	3	3	10
Equity [member] \| Derivatives [Member] \| EUR [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	$ 10	$ 4	$ 9

Financial Instruments - Remaini

Financial Instruments - Remaining Contractual Maturity for Non-derivative Financial Liabilities (Detail) - TWD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Non-derivative financial liabilities	$ 73,719	$ 45,357
Less Than 1 Month [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Non-derivative financial liabilities	44,749	36,437
1-3 Months [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Non-derivative financial liabilities	7	10
3 Months to 1 Year [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Non-derivative financial liabilities	4,136	2,562
1-5 Years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Non-derivative financial liabilities	13,627	6,348
More Than 5 Years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Non-derivative financial liabilities	11,200	0
Non-interest bearing [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	45,052	43,667
Non-interest bearing [Member] \| Less Than 1 Month [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	37,749	36,387
Non-interest bearing [Member] \| 1-3 Months [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	0	0
Non-interest bearing [Member] \| 3 Months to 1 Year [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	2,476	2,532
Non-interest bearing [Member] \| 1-5 Years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	4,827	4,748
Non-interest bearing [Member] \| More Than 5 Years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	0	0
Floating interest rate instruments [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	$ 1,667	$ 1,690
Floating interest rate instruments [Member] \| Weighted average [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Interest rates of bank loans	0.78%	0.98%
Floating interest rate instruments [Member] \| Less Than 1 Month [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	$ 0	$ 50
Floating interest rate instruments [Member] \| 1-3 Months [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	7	10
Floating interest rate instruments [Member] \| 3 Months to 1 Year [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	1,660	30
Floating interest rate instruments [Member] \| 1-5 Years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	0	1,600
Floating interest rate instruments [Member] \| More Than 5 Years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	0	0
Fixed interest rate instruments [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	$ 27,000
Fixed interest rate instruments [Member] \| Weighted average [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Interest rates of bank loans	0.50%
Fixed interest rate instruments [Member] \| Less Than 1 Month [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	$ 7,000
Fixed interest rate instruments [Member] \| 1-3 Months [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	0
Fixed interest rate instruments [Member] \| 3 Months to 1 Year [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	0
Fixed interest rate instruments [Member] \| 1-5 Years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	8,800
Fixed interest rate instruments [Member] \| More Than 5 Years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Loans	11,200
Fair value interest rate risk [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Financial assets	24,218	30,947
Financial liabilities	36,576	9,758
Cash flow interest rate risk [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Financial assets	9,306	7,681
Financial liabilities	$ 1,667	$ 1,690

Financial Instruments - Informa

Financial Instruments - Information About the Maturity Analysis for Lease Liabilities (Detail) - TWD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Lease liabilities	$ 9,737	$ 9,930
Less Than 1 Year [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Lease liabilities	3,397	3,310
1-3 Years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Lease liabilities	4,240	4,394
3-5 Years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Lease liabilities	1,691	1,581
More Than 5 Years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Lease liabilities	$ 409	$ 645

Financial Instruments - Liquidi

Financial Instruments - Liquidity Analysis for Derivative Financial Instruments (Detail) - TWD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross inflows (outflows) on derivatives	$ 4	$ 0
Forward exchange contracts inflows [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross inflows on derivatives	635	161
Forward exchange contracts outflows [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross outflows on derivatives	631	161
Less Than 1 Month [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross inflows (outflows) on derivatives	0	0
Less Than 1 Month [Member] \| Forward exchange contracts inflows [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross inflows on derivatives	0	26
Less Than 1 Month [Member] \| Forward exchange contracts outflows [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross outflows on derivatives	0	26
1-3 Months [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross inflows (outflows) on derivatives	4	0
1-3 Months [Member] \| Forward exchange contracts inflows [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross inflows on derivatives	635	135
1-3 Months [Member] \| Forward exchange contracts outflows [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross outflows on derivatives	631	135
3 Months to 1 Year [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross inflows (outflows) on derivatives	0	0
3 Months to 1 Year [Member] \| Forward exchange contracts inflows [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross inflows on derivatives	0	0
3 Months to 1 Year [Member] \| Forward exchange contracts outflows [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross outflows on derivatives	0	0
1-5 Years [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross inflows (outflows) on derivatives	0	0
1-5 Years [Member] \| Forward exchange contracts inflows [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross inflows on derivatives	0	0
1-5 Years [Member] \| Forward exchange contracts outflows [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Undiscounted gross outflows on derivatives	$ 0	$ 0

Financial Instruments - Financi

Financial Instruments - Financing Facilities (Detail) - TWD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Unsecured loans [Member]
Disclosure of detailed information about financial instruments [Line Items]
Unsecured bank loan facility, amount used	$ 7,068	$ 121
Bank loan facility, amount unused	59,277	46,109
Unsecured bank loan facility	66,345	46,230
Secured loans [Member]
Disclosure of detailed information about financial instruments [Line Items]
Bank loan facility, amount unused	20	1,340
Secured bank loan facility, amount used	1,600	1,600
Secured bank loan facility	$ 1,620	$ 2,940

Fair Value Information - Schedu

Fair Value Information - Schedule of Carrying Amounts of Financial Assets and Liabilities Not Measured at Fair Value (Detail) - Bonds Payable [Member] $ in Millions	Dec. 31, 2020TWD ($)
Disclosure of fair value measurement of assets and liabilities [Line Items]
Foreign currency denominated monetary liabilities	$ 19,980
Fair Value	$ 20,078

Fair Value Information - Financ

Fair Value Information - Financial Instruments Measured at Fair Value on a Recurring Basis (Detail) - TWD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial liabilities at FVTPL Derivative	$ 0	$ 0
Fair value on a recurring basis [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	687	779
Hedging financial assets	2	0
Financial assets at FVOCI	7,193	7,154
Financial liabilities at FVTPL Derivative	0	0
Fair value on a recurring basis [Member] \| Level 1 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	8	1
Hedging financial assets	0	0
Financial assets at FVOCI	2,754	2,454
Financial liabilities at FVTPL Derivative	0	0
Fair value on a recurring basis [Member] \| Level 2 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	2	0
Hedging financial assets	2	0
Financial assets at FVOCI	0	0
Financial liabilities at FVTPL Derivative	0	0
Fair value on a recurring basis [Member] \| Level 3 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	677	778
Hedging financial assets	0	0
Financial assets at FVOCI	4,439	4,700
Financial liabilities at FVTPL Derivative	0	0
Fair value on a recurring basis [Member] \| Non-listed stocks [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	677	778
Financial assets at FVOCI	4,439	4,700
Fair value on a recurring basis [Member] \| Non-listed stocks [Member] \| Level 1 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	0	0
Financial assets at FVOCI	0	0
Fair value on a recurring basis [Member] \| Non-listed stocks [Member] \| Level 2 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	0	0
Financial assets at FVOCI	0	0
Fair value on a recurring basis [Member] \| Non-listed stocks [Member] \| Level 3 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	677	778
Financial assets at FVOCI	4,439	4,700
Fair value on a recurring basis [Member] \| Derivatives [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	2	0
Fair value on a recurring basis [Member] \| Derivatives [Member] \| Level 1 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	0	0
Fair value on a recurring basis [Member] \| Derivatives [Member] \| Level 2 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	2	0
Fair value on a recurring basis [Member] \| Derivatives [Member] \| Level 3 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	0	0
Fair value on a recurring basis [Member] \| Listed stocks [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	8	1
Financial assets at FVOCI	2,754	2,454
Fair value on a recurring basis [Member] \| Listed stocks [Member] \| Level 1 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	8	1
Financial assets at FVOCI	2,754	2,454
Fair value on a recurring basis [Member] \| Listed stocks [Member] \| Level 2 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	0	0
Financial assets at FVOCI	0	0
Fair value on a recurring basis [Member] \| Listed stocks [Member] \| Level 3 [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Financial assets at FVTPL	0	0
Financial assets at FVOCI	$ 0	$ 0

Fair Value Information - Additi

Fair Value Information - Additional Information (Detail) - TWD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Fair Value Measurement Of Financial Instruments [Abstract]
Transfer between Level 1 and 2, assets	$ 0	$ 0	$ 0
Transfer between Level 2 and 1, assets	0	0	0
Transfer between Level 1 and 2, liabilities	0	0	0
Transfer between Level 2 and 1, liabilities	$ 0	$ 0	$ 0

Fair Value Information - Sche_2

Fair Value Information - Schedule of Reconciliations for Financial Assets (Detail) - Level 3 [Member] - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Fair Value Measurement Of Assets [Line Items]
Foreign currency denominated monetary assets	$ 5,116	$ 5,478	$ 4,550	$ 4,468
Acquisition		300	290
Recognized in profit or loss under “Other gains and losses”	(101)	(39)	(26)
Recognized in other comprehensive income under “Unrealized gain or loss on financial assets at fair value through other comprehensive income”	(263)	676	(175)
Proceeds from return of investees			(7)
Proceed from return of investments		(9)
Reclassified from investments accounted for using equity method	2
Measured at Fair Value Through Profit or Loss [Member]
Disclosure Of Fair Value Measurement Of Assets [Line Items]
Foreign currency denominated monetary assets	677	778	517	543
Acquisition		300
Recognized in profit or loss under “Other gains and losses”	(101)	(39)	(26)
Unrealized loss	(101)	(39)	(26)
FVOCI [Member]
Disclosure Of Fair Value Measurement Of Assets [Line Items]
Foreign currency denominated monetary assets	4,439	4,700	4,033	$ 3,925
Acquisition		0	290
Recognized in other comprehensive income under “Unrealized gain or loss on financial assets at fair value through other comprehensive income”	(263)	676	(175)
Proceeds from return of investees			$ (7)
Proceed from return of investments		$ (9)
Reclassified from investments accounted for using equity method	$ 2

Fair Value Information - Sche_3

Fair Value Information - Schedule of Percentage Decrease in Discount for Lack of Marketability or Noncontrolling Interests Discount (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Top of Range [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Discount for lack of marketability	20.00%	20.00%
Noncontrolling interests discount	25.00%	25.00%
Bottom of Range [Member]
Disclosure of fair value measurement of assets and liabilities [Line Items]
Discount for lack of marketability	14.73%	13.73%
Noncontrolling interests discount	17.29%	21.45%

Fair Value Information - Sche_4

Fair Value Information - Schedule of Impact of Decrease in Discount for Lack of Marketability or Noncontrolling Interests (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Fair Value Measurement Of Financial Instruments [Abstract]
Discount for lack of marketability 5% decrease	$ 320	$ 342
Noncontrolling interests discount 5% decrease	$ 47	$ 54

Related Parties Transactions -

Related Parties Transactions - Summary of Related Parties (Detail)	12 Months Ended
	Dec. 31, 2020
Taiwan International Standard Electronics Co., Ltd. ("TISE") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
So-net Entertainment Taiwan Limited ("So-net") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
KKBOX Taiwan Co., Ltd. ("KKBOXTW") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
KingwayTek Technology Co., Ltd. ("KWT") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
UUPON Inc. ("UUPON") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
Taiwan International Ports Logistics Corporation ("TIPL") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
International Integrated Systems, Inc. ("IISI") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Subsidiary
EnRack Tech. Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Subsidiary of the Company’s associate, Senao Networks, Inc.
Senao Networks, Inc. ("SNI") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
Emplus Technologies, Inc. [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Subsidiary of the Company’s associate, Senao Networks, Inc.
ST-2 Satellite Ventures Pte., Ltd. ("STS") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
Viettel-CHT Co., Ltd. ("Viettel-CHT") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
Chunghwa PChome Fund I Co., Ltd. ("CPFI") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
Click Force Co., Ltd. ("CF") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
Alliance Digital Tech Co., Ltd. ("ADT") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
Cornerstone Ventures Co., Ltd. ("CVC") [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
Next Commercial Bank Co., Ltd. (“NCB”) [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Associate
Chunghwa SEA Holdings (“CHT SEA”) [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Joint venture
Chunghwa Telecom Foundation [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	A nonprofit organization of which the funds donated by Chunghwa exceeds one third of its total funds
Senao Technical and Cultural Foundation [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	A nonprofit organization of which the funds donated by SENAO exceeds one third of its total funds
Sochamp Technology Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Investor of significant influence over CHST
E-Life Mall Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	One of the directors of E-Life Mall and a director of SENAO are members of an immediate family
Engenius Technologies Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Chairman of Engenius Technologies Co., Ltd. is a member of SENAO’s management
Cheng Keng Investment Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Relationship	Chairman of Cheng Keng Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family
Cheng Feng Investment Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Chairman of Cheng Feng Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family
All Oriented Investment Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Chairman of All Oriented Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family
Hwa Shun Investment Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Chairman of Hwa Shun Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family
Yu Yu Investment Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Chairman of Yu Yu Investment Co., Ltd. and SENAO’s chief executive officer are members of an immediate family
United Daily News Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Investor of significant influence over SFD
Shenzhen Century Communication Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Investor of significant influence over SCT
Chunghwa Post Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Relationship	Government-related entity as Chunghwa Telecom

Related Parties Transactions _2

Related Parties Transactions - Details of Transactions Between the Company and Other Related Parties (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2020USD ($)
Disclosure of transactions between related parties [Line Items]
Revenues	$ 1,574		$ 350	$ 438
Operating Costs and Expenses	783		1,040	1,379
Non-operating Income and Expenses	40		45	31
Receivables	230		17		$ 8
Payables	646		654		$ 24
Acquisition of property, plant and equipment	375		242	312
Proceeds from disposal of property, plant and equipment	319	$ 11	48	264
Prepaid rents - current				205
Prepaid rents - noncurrent				1,346
Prepaid rents				1,551
Associates [Member]
Disclosure of transactions between related parties [Line Items]
Revenues	1,508		274	344
Operating Costs and Expenses	715		964	1,304
Non-operating Income and Expenses	37		41	31
Receivables	229		10
Contract liabilities-current	183		0
Payables	643		651
Customers' deposits	5		8
Acquisition of property, plant and equipment	375		242	312
Others [Member]
Disclosure of transactions between related parties [Line Items]
Revenues	66		76	94
Operating Costs and Expenses	68		76	75
Non-operating Income and Expenses	3		4	$ 0
Receivables	1		7
Payables	3		3
Proceeds from disposal of property, plant and equipment	386		$ 0
Gain on Disposal	$ 310

Related Parties Transactions _3

Related Parties Transactions - Additional Information (Detail) $ in Millions, $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2011TWD ($)	Dec. 31, 2020TWD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Aug. 31, 2011SGD ($)
Disclosure of transactions between related parties [Line Items]
Lease contract value		$ 9,597	$ 9,758
Lease contract value, prepayment amount				$ 1,551
Interest on lease liabilities		80	85	0
ST-2 Satellite Ventures Pte., Ltd. ("STS") [Member]
Disclosure of transactions between related parties [Line Items]
Lease contract value		999	1,212
Interest on lease liabilities		$ 9	$ 11
ST-2 Satellite Ventures Pte., Ltd. ("STS") [Member]
Disclosure of transactions between related parties [Line Items]
Lease term	15 years
Lease contract value	$ 6,000				$ 261
Lease contract value, prepayment amount	$ 3,068
Rental expense				394
Rental expense, offsetting credit of the prepayment				204
Rental expense, additional accrual				$ 190

Related Parties Transactions _4

Related Parties Transactions - Summary of Lease Liabilities (Detail) $ in Millions, $ in Millions	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of transactions between related parties [Line Items]
Lease liabilities - current	$ 3,382	$ 120	$ 3,291
Lease liabilities - noncurrent	6,215	$ 221	6,467
Lease liabilities	9,597		9,758
ST-2 Satellite Ventures Pte., Ltd. ("STS") [Member]
Disclosure of transactions between related parties [Line Items]
Lease liabilities - current	182		188
Lease liabilities - noncurrent	817		1,024
Lease liabilities	$ 999		$ 1,212

Related Parties Transactions _5

Related Parties Transactions - Compensation of Directors and Other Key Management Personnel (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Transactions Between Related Parties [Abstract]
Short-term employee benefits	$ 290	$ 263	$ 282
Post-employment benefits	11	9	10
Share-based payment	0	0	9
Compensation of key management personnel	$ 301	$ 272	$ 301

Pledged Assets - Assets Pledged

Pledged Assets - Assets Pledged as Collaterals (Detail) - TWD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Subclassifications Of Assets Liabilities And Equities [Abstract]
Property, plant and equipment	$ 2,462	$ 2,491
Land held under development (included in inventories)	1,999	1,999
Restricted assets (included in other assets - others)	209	3
Assets pledged as collateral	$ 4,670	$ 4,493

Significant Contingent Liabil_2

Significant Contingent Liabilities and Unrecognized Commitments - Additional Information (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Aug. 15, 1996
Commitments And Contingencies [Line Items]
Unused letters of credit	$ 10
Top of Range [Member] \| Next Commercial Bank Co Ltd [Member]
Commitments And Contingencies [Line Items]
Ownership interest in associates	25.00%
Piping Fund [Member]
Commitments And Contingencies [Line Items]
Commitment amount		$ 2,000
Commitment to contribute to a Piping Fund, amount contributed		$ 1,000
Commitment to contribute to a Piping Fund, remaining amount	$ 1,000
Land and buildings [Member]
Commitments And Contingencies [Line Items]
Commitments for acquisitions of property, plant and equipment	119
Telecommunications equipment [Member]
Commitments And Contingencies [Line Items]
Commitments for acquisitions of property, plant and equipment	$ 26,815

Significant Events After the _2

Significant Events After the Reporting Period - Additional Information (Detail) - TWD ($) $ in Millions	1 Months Ended	12 Months Ended
	Feb. 28, 2021	Dec. 31, 2020
Disclosure Of Nonadjusting Events After Reporting Period [Line Items]
Investments at fair value		$ 568
Unrealized gain on investments in equity instruments at fair value through other comprehensive income		$ 17
Disposal of China Airlines, Ltd. [Member]
Disclosure Of Nonadjusting Events After Reporting Period [Line Items]
Investments at fair value	$ 2,635
Unrealized gain on investments in equity instruments at fair value through other comprehensive income	$ 94

Segment Information - Analysis

Segment Information - Analysis by Reportable Segment of Revenue and Operating Results of Continuing Operations (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of operating segments [Line Items]
Revenues	$ 207,609	$ 7,393	$ 207,520	$ 215,483
Income (loss) before income tax	42,826	$ 1,525	41,867	44,986
From External Customers [Member]
Disclosure of operating segments [Line Items]
Revenues	207,609		207,520	215,483
Intersegment [Member]
Disclosure of operating segments [Line Items]
Revenues	28,676		28,573	30,107
Segment [Member]
Disclosure of operating segments [Line Items]
Revenues	236,285		236,093	245,590
Intersegment Elimination [Member]
Disclosure of operating segments [Line Items]
Revenues	(28,676)		(28,573)	(30,107)
Consolidated [member]
Disclosure of operating segments [Line Items]
Revenues	207,609		207,520	215,483
Domestic Fixed Communications Business [Member]
Disclosure of operating segments [Line Items]
Income (loss) before income tax	22,504		19,537	18,243
Domestic Fixed Communications Business [Member] \| From External Customers [Member]
Disclosure of operating segments [Line Items]
Revenues	69,469		65,728	66,753
Domestic Fixed Communications Business [Member] \| Intersegment [Member]
Disclosure of operating segments [Line Items]
Revenues	15,930		16,065	17,125
Domestic Fixed Communications Business [Member] \| Segment [Member]
Disclosure of operating segments [Line Items]
Revenues	85,399		81,793	83,878
Mobile Communications Business [Member]
Disclosure of operating segments [Line Items]
Income (loss) before income tax	8,777		11,250	15,328
Mobile Communications Business [Member] \| From External Customers [Member]
Disclosure of operating segments [Line Items]
Revenues	90,230		95,469	100,937
Mobile Communications Business [Member] \| Intersegment [Member]
Disclosure of operating segments [Line Items]
Revenues	1,536		1,564	1,702
Mobile Communications Business [Member] \| Segment [Member]
Disclosure of operating segments [Line Items]
Revenues	91,766		97,033	102,639
Internet Business [Member]
Disclosure of operating segments [Line Items]
Income (loss) before income tax	13,120		12,515	11,944
Internet Business [Member] \| From External Customers [Member]
Disclosure of operating segments [Line Items]
Revenues	32,115		30,091	29,813
Internet Business [Member] \| Intersegment [Member]
Disclosure of operating segments [Line Items]
Revenues	3,966		3,951	4,038
Internet Business [Member] \| Segment [Member]
Disclosure of operating segments [Line Items]
Revenues	36,081		34,042	33,851
International Fixed Communications Business [Member]
Disclosure of operating segments [Line Items]
Income (loss) before income tax	829		799	1,024
International Fixed Communications Business [Member] \| From External Customers [Member]
Disclosure of operating segments [Line Items]
Revenues	8,695		11,485	13,435
International Fixed Communications Business [Member] \| Intersegment [Member]
Disclosure of operating segments [Line Items]
Revenues	1,875		2,079	2,234
International Fixed Communications Business [Member] \| Segment [Member]
Disclosure of operating segments [Line Items]
Revenues	10,570		13,564	15,669
Other [Member]
Disclosure of operating segments [Line Items]
Income (loss) before income tax	(2,404)		(2,234)	(1,553)
Other [Member] \| From External Customers [Member]
Disclosure of operating segments [Line Items]
Revenues	7,100		4,747	4,545
Other [Member] \| Intersegment [Member]
Disclosure of operating segments [Line Items]
Revenues	5,369		4,914	5,008
Other [Member] \| Segment [Member]
Disclosure of operating segments [Line Items]
Revenues	$ 12,469		$ 9,661	$ 9,553

Segment Information - Other Seg

Segment Information - Other Segment Information (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of operating segments [Line Items]
Share of profits of associates and joint ventures accounted for using equity method	$ 244	$ 9	$ 459	$ 509
Interest income	116	4	251	197
Interest expenses	206	7	104	18
Operating costs and expenses	166,843		166,747	171,949
Depreciation and amortization	37,138		36,349	33,809
Capital expenditure	23,511	838	24,166	28,550
Gain (loss) on disposal of property, plant and equipment	1,428	51	(38)	142
Gain on disposal of investment properties	151	5	0	0
Impairment loss on property, plant and equipment	0	0	93	0
Reversal of impairment loss	27	1	57	19
Impairment loss on intangible assets	9		9	51
Impairment loss on other assets	0	$ 0	44	0
Domestic Fixed Communications Business [Member]
Disclosure of operating segments [Line Items]
Share of profits of associates and joint ventures accounted for using equity method	0		0	0
Interest income	13		15	18
Interest expenses	6		5	0
Operating costs and expenses	59,371		56,269	59,430
Depreciation and amortization	14,250		14,842	15,027
Capital expenditure	11,483		12,071	12,693
Gain (loss) on disposal of property, plant and equipment	1,442
Gain on disposal of investment properties	151
Impairment loss on property, plant and equipment			0
Reversal of impairment loss	27		57	19
Impairment loss on intangible assets	0		0	0
Impairment loss on other assets			13
Mobile Communications Business [Member]
Disclosure of operating segments [Line Items]
Share of profits of associates and joint ventures accounted for using equity method	0		0	0
Interest income	5		9	12
Interest expenses	56		58	0
Operating costs and expenses	69,211		72,952	73,901
Depreciation and amortization	17,800		16,254	13,788
Capital expenditure	8,827		7,773	10,664
Gain (loss) on disposal of property, plant and equipment	(3)
Gain on disposal of investment properties	0
Impairment loss on property, plant and equipment			0
Reversal of impairment loss	0		0	0
Impairment loss on intangible assets	9		9	51
Impairment loss on other assets			0
Internet Business [Member]
Disclosure of operating segments [Line Items]
Share of profits of associates and joint ventures accounted for using equity method	0		0	0
Interest income	17		20	19
Interest expenses	1		1	0
Operating costs and expenses	15,241		13,850	13,766
Depreciation and amortization	2,669		2,914	3,121
Capital expenditure	1,397		1,425	2,729
Gain (loss) on disposal of property, plant and equipment	0
Gain on disposal of investment properties	0
Impairment loss on property, plant and equipment			0
Reversal of impairment loss	0		0	0
Impairment loss on intangible assets	0		0	0
Impairment loss on other assets			13
International Fixed Communications Business [Member]
Disclosure of operating segments [Line Items]
Share of profits of associates and joint ventures accounted for using equity method	0		0	0
Interest income	22		41	28
Interest expenses	10		12	0
Operating costs and expenses	8,573		11,427	13,279
Depreciation and amortization	1,450		1,547	1,425
Capital expenditure	779		1,117	1,348
Gain (loss) on disposal of property, plant and equipment	0
Gain on disposal of investment properties	0
Impairment loss on property, plant and equipment			0
Reversal of impairment loss	0		0	0
Impairment loss on intangible assets	0		0	0
Impairment loss on other assets			0
Other [Member]
Disclosure of operating segments [Line Items]
Share of profits of associates and joint ventures accounted for using equity method	244		459	509
Interest income	59		166	120
Interest expenses	133		28	18
Operating costs and expenses	14,447		12,249	11,573
Depreciation and amortization	969		792	448
Capital expenditure	1,025		1,780	1,116
Gain (loss) on disposal of property, plant and equipment	(11)
Gain on disposal of investment properties	0
Impairment loss on property, plant and equipment			93
Reversal of impairment loss	0		0	0
Impairment loss on intangible assets	$ 0		0	$ 0
Impairment loss on other assets			$ 18

Segment Information - Main Prod

Segment Information - Main Products and Service Revenues (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of products and services [Line Items]
Revenues	$ 207,609	$ 7,393	$ 207,520	$ 215,483
Mobile services [Member]
Disclosure of products and services [Line Items]
Revenues	56,724		58,703	63,906
Local telephone and domestic long distance telephone services [Member]
Disclosure of products and services [Line Items]
Revenues	26,475		27,929	29,996
Sales of products [Member]
Disclosure of products and services [Line Items]
Revenues	39,391		41,593	41,289
Broadband access and domestic leased line services [Member]
Disclosure of products and services [Line Items]
Revenues	22,420		22,116	22,453
Data communications internet services [Member]
Disclosure of products and services [Line Items]
Revenues	21,447		21,003	21,137
International network and leased line services revenue [Member]
Disclosure of products and services [Line Items]
Revenues	3,884		7,066	8,724
Others [Member]
Disclosure of products and services [Line Items]
Revenues	$ 37,268		$ 29,110	$ 27,978

Segment Information - Geographi

Segment Information - Geographic Information (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of geographical areas [Line Items]
Revenues	$ 207,609	$ 7,393	$ 207,520	$ 215,483
Taiwan, ROC [Member]
Disclosure of geographical areas [Line Items]
Revenues	200,881		197,895	205,696
Overseas [Member]
Disclosure of geographical areas [Line Items]
Revenues	$ 6,728		$ 9,625	$ 9,787

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019TWD ($)	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)
Disclosure of operating segments [Line Items]
Long-lived assets	$ 383,056	$ 424,377	$ 15,113
Information about major customers	Company did not have any single customer whose revenue exceeded 10% of the total revenues
Overseas [Member]
Disclosure of operating segments [Line Items]
Long-lived assets	$ 4,063	$ 3,746