KT (KT) 20-F 30 Apr 21 2020 FY Annual report (foreign) Financial data

Cover Page

Cover Page	12 Months Ended
	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	KT Corporation
Entity Central Index Key	0000892450
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	241,842,130
Entity Voluntary Filers	No
Entity Address, Country	KR
ICFR Auditor Attestation Flag	true
Document Shell Company Report	false
Entity Interactive Data Current	Yes
Document Transition Report	false
Document Annual Report	true
ADS [Member]
Document Information [Line Items]
Trading Symbol	KT
Title of 12(b) Security	American Depositary Shares
Security Exchange Name	NYSE
Ordinary shares [member]
Document Information [Line Items]
Trading Symbol	KT
Title of 12(b) Security	Ordinary share
Security Exchange Name	NYSE

Consolidated Statements of Fina

Consolidated Statements of Financial Position - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	₩ 2,634,624	₩ 2,305,894
Trade and other receivables, net	4,902,471	5,858,696
Other financial assets	1,202,840	868,388
Current income tax assets	2,059	68,120
Inventories, net	534,636	791,677
Assets held for sale	1,198	83,602
Other current assets	1,876,352	1,999,282
Total current assets	11,154,180	11,975,659
Non-current assets
Trade and other receivables, net	1,250,769	1,181,798
Other financial assets	544,347	821,658
Property and equipment, net	14,206,119	13,785,299
Right-of-use assets	1,217,179	1,268,329
Investment properties, net	1,368,453	1,387,430
Intangible assets, net	2,161,258	2,834,037
Investments in associates and joint ventures	557,881	267,660
Deferred income tax assets	433,698	424,856
Other non-current assets	768,661	685,488
Total non-current assets	22,508,365	22,656,555
Total assets	33,662,545	34,632,214
Current liabilities
Trade and other payables	6,210,099	7,597,478
Borrowings	1,418,114	1,185,725
Other financial liabilities	2,493	943
Current income tax liabilities	232,225	66,266
Provisions	165,990	175,612
Deferred revenue	60,252	53,473
Other current liabilities	1,103,299	1,068,557
Total current liabilities	9,192,472	10,148,054
Non-current liabilities
Trade and other payables	807,540	1,082,220
Borrowings	5,898,184	6,113,142
Other financial liabilities	260,676	149,136
Defined benefit liabilities, net	378,087	365,663
Provisions	86,202	78,550
Deferred revenue	149,050	99,180
Deferred income tax liabilities	429,331	425,468
Other non-current liabilities	909,570	1,030,117
Total non-current liabilities	8,918,640	9,343,476
Total liabilities	18,111,112	19,491,530
Equity
Share capital	1,564,499	1,564,499
Share premium	1,440,258	1,440,258
Retained earnings	12,155,420	11,590,916
Accumulated other comprehensive income	86,051	194,934
Other components of equity	(1,234,784)	(1,170,083)
Equity attributable to owners of the Controlling Company	14,011,444	13,620,524
Non-controlling interest	1,539,989	1,520,160
Total equity	15,551,433	15,140,684
Total liabilities and equity	₩ 33,662,545	₩ 34,632,214

Consolidated Statements of Oper

Consolidated Statements of Operations - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Profit or loss [abstract]
Operating revenue	₩ 24,440,647	₩ 24,899,189	₩ 23,436,050
Revenue	24,099,394	24,639,758	23,220,052
Others	341,253	259,431	215,998
Operating expenses	23,418,314	23,872,219	22,335,190
Operating profit	1,022,333	1,026,970	1,100,860
Finance income	498,614	424,395	374,243
Finance costs	(507,383)	(432,133)	(435,659)
Share of net profits of associates and joint ventures	18,041	(3,304)	(5,467)
Profit before income tax	1,031,605	1,015,928	1,033,977
Income tax expense	285,349	320,060	314,565
Profit for the year	746,256	695,868	719,412
Profit for the year attributable to:
Profit (loss) for the year attributable to Owners of the Controlling Company	700,889	645,703	645,571
Profit (loss) for the year attributable to Non-controlling interest	₩ 45,367	₩ 50,165	₩ 73,841
Earnings per share attributable to the equity holders of the Controlling Company during the year (in Korean won):
Basic earnings per share	₩ 2,858	₩ 2,634	₩ 2,634
Diluted earnings per share	₩ 2,858	₩ 2,632	₩ 2,634

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of comprehensive income [abstract]
Profit for the year	₩ 746,256	₩ 695,868	₩ 719,412
Other comprehensive income Items that will not be reclassified to profit or loss:
Remeasurements of the net defined benefit liability	(60,181)	(25,777)	(73,511)
Shares of remeasurement gain (loss) of associates and joint ventures	786	649	(816)
Gain on valuation of equity instruments at fair value through other comprehensive income	51,696	155,319	43,077
Other comprehensive income, Items that may be subsequently reclassified to profit or loss:
Gain on valuation of debt instruments at fair value through other comprehensive income	(9,699)	11,833	734
Valuation gain (loss) on cash flow hedge	(84,044)	67,548	17,268
Other comprehensive income (loss) from cash flow hedges reclassified to profit (loss)	111,431	(44,684)	(44,279)
Share of other comprehensive income (loss) from associates and joint ventures	15,932	2,517	(41)
Exchange differences on translation of foreign operations	(2,666)	4,933	2,940
Total other comprehensive income (loss)	23,255	172,338	(54,628)
Total comprehensive income for the year	769,511	868,206	664,784
Total comprehensive income for the year attributable to:
Owners of the Controlling Company	727,077	768,341	589,179
Non-controlling interest	₩ 42,434	₩ 99,865	₩ 75,605

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - KRW (₩) ₩ in Millions	Total	Share capital [member]	Share premium [member]	Retained earnings [member]	Accumulated other comprehensive income [member]	Other components of equity [member]	Total attributable to owners of the Controlling Company [member]	Non-controlling interest [member]
Beginning balance (Adjusted [member]) at Dec. 31, 2017	₩ 14,232,276	₩ 1,564,499	₩ 1,440,258	₩ 10,915,203	₩ 48,726	₩ (1,205,302)	₩ 12,763,384	₩ 1,468,892
Beginning balance at Dec. 31, 2017	13,183,354	1,564,499	1,440,258	9,961,150	30,985	(1,205,302)	11,791,590	1,391,764
Changes in value of available-for-sale financial assets | Increase (decrease) due to changes in accounting policy required by IFRSs [member]	1,048,922			954,053	17,741		971,794	77,128
Comprehensive income
Profit for the year	719,412			645,571			645,571	73,841
Remeasurements of net defined benefit liabilities	(73,511)			(61,449)			(61,449)	(12,062)
Share of gain on remeasurements of associates and joint ventures	(816)			(816)			(816)
Share of other comprehensive income of associates and joint ventures	(41)				(136)		(136)	95
Valuation gains (losses) on cashflow hedge	(27,011)				(27,011)		(27,011)
Gain(loss) on disposal of equity instruments at fair value through other comprehensive income				4,441	(4,441)
Gain on valuation of financial instruments at fair value through other comprehensive income	43,811				30,731		30,731	13,080
Exchange differences on translation of foreign operations	2,940				2,289		2,289	651
Total comprehensive income for the year	664,784			587,747	1,432		589,179	75,605
Transactions with equity holders
Dividends paid by the Controlling Company	(245,097)			(245,097)			(245,097)
Dividends paid to non-controlling interest of subsidiaries	(53,535)							(53,535)
Changes in consolidation scope	(1,701)					(1,803)	(1,803)	102
Changes in ownership interest in subsidiaries	48,589					11,118	11,118	37,471
Appropriation of loss on disposal of treasury stock				(2,046)		2,046
Disposal of treasury stock	9,547					9,547	9,547
Others	3,627			262		3,311	3,573	54
Subtotal	(238,570)			(246,881)		24,219	(222,662)	(15,908)
Ending balance (Adjusted [member]) at Dec. 31, 2018	14,654,600	1,564,499	1,440,258	11,252,179	50,158	(1,181,083)	13,126,011	1,528,589
Ending balance at Dec. 31, 2018	14,658,490	1,564,499	1,440,258	11,256,069	50,158	(1,181,083)	13,129,901	1,528,589
Changes in value of available-for-sale financial assets | Increase (decrease) due to changes in accounting policy required by IFRSs [member]	(3,890)			(3,890)			(3,890)
Comprehensive income
Profit for the year	695,868			645,703			645,703	50,165
Remeasurements of net defined benefit liabilities	(25,777)			(22,774)			(22,774)	(3,003)
Share of gain on remeasurements of associates and joint ventures	649			636			636	13
Share of other comprehensive income of associates and joint ventures	2,517				2,427		2,427	90
Valuation gains (losses) on cashflow hedge	22,864				22,850		22,850	14
Gain on valuation of financial instruments at fair value through other comprehensive income	167,152				114,869		114,869	52,283
Exchange differences on translation of foreign operations	4,933				4,630		4,630	303
Total comprehensive income for the year	868,206			623,565	144,776		768,341	99,865
Transactions with equity holders
Dividends paid by the Controlling Company	(269,659)			(269,659)			(269,659)
Dividends paid to non-controlling interest of subsidiaries	(35,500)							(35,500)
Changes in consolidation scope	1,539					(245)	(245)	1,784
Changes in ownership interest in subsidiaries	(83,660)					(9,082)	(9,082)	(74,578)
Appropriation of loss on disposal of treasury stock				(15,169)		15,169
Disposal of treasury stock	3,346					3,346	3,346
Others	1,812					1,812	1,812
Subtotal	(382,122)			(284,828)		11,000	(273,828)	(108,294)
Ending balance at Dec. 31, 2019	15,140,684	1,564,499	1,440,258	11,590,916	194,934	(1,170,083)	13,620,524	1,520,160
Comprehensive income
Profit for the year	746,256			700,889			700,889	45,367
Remeasurements of net defined benefit liabilities	(60,181)			(49,554)			(49,554)	(10,627)
Share of gain on remeasurements of associates and joint ventures	786			410			410	376
Share of other comprehensive income of associates and joint ventures	15,932				14,701		14,701	1,231
Valuation gains (losses) on cashflow hedge	27,387				27,433		27,433	(46)
Gain on valuation of financial instruments at fair value through other comprehensive income	41,997			184,215	(150,135)		34,080	7,917
Exchange differences on translation of foreign operations	(2,666)				(882)		(882)	(1,784)
Total comprehensive income for the year	769,511			835,960	(108,883)		727,077	42,434
Transactions with equity holders
Dividends paid by the Controlling Company	(269,766)			(269,766)			(269,766)
Dividends paid to non-controlling interest of subsidiaries	(40,802)							(40,802)
Changes in ownership interest in subsidiaries	29,825					11,628	11,628	18,197
Appropriation of loss on disposal of treasury stock				(1,690)		1,690
Acquisition of treasury stock	(110,097)					(110,097)	(110,097)
Disposal of treasury stock	33,213					33,213	33,213
Others	(1,135)					(1,135)	(1,135)
Subtotal	(358,762)			(271,456)		(64,701)	(336,157)	(22,605)
Ending balance at Dec. 31, 2020	₩ 15,551,433	₩ 1,564,499	₩ 1,440,258	₩ 12,155,420	₩ 86,051	₩ (1,234,784)	₩ 14,011,444	₩ 1,539,989

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Cash generated from operations	₩ 4,745,293	₩ 4,058,065	₩ 4,212,222
Interest paid	(254,852)	(255,908)	(304,428)
Interest received	259,836	276,349	242,951
Dividends received	19,623	18,922	14,074
Income tax paid	(30,073)	(352,255)	(154,355)
Net cash inflow from operating activities	4,739,827	3,745,173	4,010,464
Cash flows from investing activities
Collection of loans	63,435	63,517	64,023
Loans granted	(48,731)	(65,138)	(60,229)
Disposal of financial assets at fair value through profit or loss	528,655	720,148	397,224
Disposal of financial assets at amortized cost	528,746	422,637	255,290
Disposal of financial assets at fair value through other comprehensive income	351,065		2,474
Disposal of assets held-for-sale	83,241	28,834	9,842
Disposal of investments in associates and joint ventures	24	16,930	7,832
Acquisition of investments in associates and joint ventures	(273,411)	(29,980)	(34,420)
Disposal of property and equipment, and investment properties	49,832	42,554	90,992
Acquisition of property and equipment, and investment properties	(3,207,566)	(3,263,338)	(2,260,879)
Acquisition of financial assets at fair value through profit or loss	(521,142)	(793,977)	(158,787)
Acquisition of financial assets at amortized cost	(759,180)	(501,838)	(248,789)
Acquisition of financial assets at fair value through other comprehensive income	(14,092)	(14,277)	(16,239)
Disposal of intangible assets	13,362	12,097	20,037
Disposal of right-of-use assets	2,023	9,393
Discontinued operations	205	1,977
Acquisition of right-of-use assets	(5,824)	(6,236)
Acquisition of intangible assets	(511,094)	(530,775)	(746,213)
Decrease in cash due to business combination, etc.	(41,018)		(26,288)
Net cash outflow from investing activities	(3,761,470)	(3,887,472)	(2,704,130)
Cash flows from financing activities
Proceeds from borrowings and debentures	1,795,221	1,951,568	1,473,016
Repayments of borrowings and debentures	(1,627,354)	(1,377,394)	(1,612,731)
Settlement of derivative assets and liabilities, net	36,594	23,901	(3,461)
Cash outflow from consolidated capital transactions	(1,192)	(122,918)	(5,506)
Cash inflow from other financing activities	35,854	65,698	13,939
Dividends paid to shareholders	(310,567)	(305,159)	(298,632)
Acquisition of treasury stock	(114,683)		(24,415)
Decrease in finance leases liabilities	(447,784)	(485,444)	(73,885)
Decrease in other liabilities	(13,674)
Net cash outflow from financing activities	(647,585)	(249,748)	(531,675)
Effect of exchange rate change on cash and cash equivalents	(2,042)	(5,481)	581
Net increase (decrease) in cash and cash equivalents	328,730	(397,528)	775,240
Cash and cash equivalents at beginning of year	2,305,894	2,703,422	1,928,182
Cash and cash equivalents at end of year	₩ 2,634,624	₩ 2,305,894	₩ 2,703,422

General Information

General Information	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
General Information	1. General Information The consolidated financial statements as of December 31, 202 0 1.1 The Controlling Company KT Corporation (the “Controlling Company”) commenced operations on January 1, 1982, when it spun off from the Korea Communications Commission (formerly the Korean Ministry of Information and Communications) to provide telephone services and to engage in the development of advanced communications services under the Act of Telecommunications of Korea. The headquarters are located in Seongnam City, Gyeonggi Province, Republic of Korea, and the address of its registered head office is 90, Buljeong-ro, Bundang-gu, On October 1, 1997, upon the announcement of the Government-Investment Enterprises Management Basic Act and the Privatization Law, the Controlling Company became a government-funded institution under the Commercial Code of Korea. On December 23, 1998, the Controlling Company’s shares were listed on the Korea Exchange. On May 29, 1999, the Controlling Company issued 24,282,195 additional shares and issued American Depository Shares (ADS), representing new shares and 20,813,311 government-owned shares, at the New York Stock Exchange. On July 2, 2001, the additional ADS representing 55,502,161 government-owned shares were issued at the New York Stock Exchange. In 2002, the Controlling Company acquired the entire government-owned shares in accordance with the Korean government’s privatization plan. As at the end of the reporting period, the Korean government does not own any share in the Controlling Company. 1.2 Consolidated Subsidiaries The consolidated subsidiaries as at December 31, 2019 and 2020, are as follows: Controlling percentage 1 Subsidiary Type of business Location December 31, December 31, Closing month KT Powertel Co., Ltd. 2 Trunk Radio System (TRS) business Korea 44.8% 44.8% December KT Linkus Co., Ltd. Public telephone maintenance Korea 92.4% 92.4% December KT Submarine Co., Ltd. 2,4 Submarine cable construction and maintenance Korea 39.3% 39.3% December KT Telecop Co., Ltd. Security service Korea 86.8% 86.8% December KT Hitel Co., Ltd. Data communication Korea 67.1% 67.1% December KT Service Bukbu Co., Ltd. Opening services of fixed line Korea 67.3% 67.3% December KT Service Nambu Co., Ltd. Opening services of fixed line Korea 77.3% 77.3% December KT Commerce Inc. B2C, B2B service Korea 100.0% 100.0% December KT Strategic Investment Fund No.2 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.3 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.4 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.5 Investment fund Korea 100.0% 100.0% December BC-VP Investment fund Korea 100.0% 100.0% December BC Card Co., Ltd. Credit card business Korea 69.5% 69.5% December VP Inc. Payment security service for credit card, others Korea 50.9% 50.9% December H&C Network Call centre for financial sectors Korea 100.0% 100.0% December BC Card China Co., Ltd. Software development and data processing China 100.0% 100.0% December INITECH Co., Ltd. 4 Internet banking ASP and security solutions Korea 58.2% 58.2% December Smartro Co., Ltd. VAN (Value Added Network) business Korea 64.5% 64.5% December KTDS Co., Ltd. 4 System integration and maintenance Korea 95.5% 95.5% December KT M Hows Co., Ltd. Mobile marketing Korea 90.0% 90.0% December KT M&S Co., Ltd. PCS distribution Korea 100.0% 100.0% December GENIE Music Corporation (KT Music Corporation) 2,4 Online music production and distribution Korea 36.0% 36.2% December KT MOS Bukbu Co., Ltd. 4 Telecommunication facility maintenance Korea 100.0% 100.0% December KT MOS Nambu Co., Ltd. 4 Telecommunication facility maintenance Korea 98.4% 98.4% December KT Skylife Co., Ltd. 4 Satellite broadcasting business Korea 50.3% 50.3% December Skylife TV Co., Ltd. TV contents provider Korea 92.6% 92.6% December KT Estate Inc. Residential building development and supply Korea 100.0% 100.0% December KT AMC Co., Ltd. Asset management and consulting services Korea 100.0% 100.0% December NEXR Co., Ltd. Cloud system implementation Korea 100.0% 100.0% December KTGDH Co., Ltd. (KTSB Data Service) Data centre development and related service Korea 100.0% 100.0% December KT Sat Co., Ltd. Satellite communication business Korea 100.0% 100.0% December Nasmedia Co., Ltd. 3,4 Solution provider and IPTV advertisement sales business Korea 44.0% 44.0% December KT Sports Co., Ltd. Management of sports group Korea 100.0% 100.0% December KT Music Contents Fund No.1 Music contents investment business Korea 80.0% 80.0% December KT Music Contents Fund No.2 Music contents investment business Korea 100.0% 100.0% December KT-Michigan Content investment business Korea 88.6% 88.6% December Autopion Co., Ltd. Information and communication service Korea 100.0% 100.0% December KTCS Corporation 2,4 Database and online information provider Korea 30.9% 31.9% December KTIS Corporation 2,4 Database and online information provider Korea 30.1% 30.8% December KT M Mobile Co., Ltd. Special category telecommunications operator and sales of communication device Korea 100.0% 100.0% December KT Investment Co., Ltd. Technology business finance Korea 100.0% 100.0% December Whowho&Company Co., Ltd. Software development and supply Korea 100.0% 100.0% December PlayD Co., Ltd. (N Search Marketing Co., Ltd.) Advertising agency Korea 100.0% 70.4% December Next Connect PFV Residential building development and supply Korea 100.0% 100.0% December KT Rwanda Networks Ltd. Network installation and management Rwanda 51.0% 51.0% December AOS Ltd. System integration and maintenance Rwanda 51.0% 51.0% December KT Belgium Foreign investment business Belgium 100.0% 100.0% December Korea Telecom Japan Co., Ltd. Foreign telecommunication business Japan 100.0% 100.0% December KBTO sp.z o.o. Electronic communication business Poland 97.2% 97.4% December Korea Telecom China Co., Ltd. Foreign telecommunication business China 100.0% 100.0% December KT Dutch B.V. Super iMax and East Telecom management Netherlands 100.0% 100.0% December East Telecom LLC Fixed line telecommunication business Uzbekistan 91.0% 91.6% December Korea Telecom America, Inc. Foreign telecommunication business USA 100.0% 100.0% December PT. BC Card Asia Pacific Software development and supply Indonesia 99.9% 99.9% December KT Hong Kong Telecommunications Co., Ltd. Fixed line communication business Hong Kong 100.0% 100.0% December Korea Telecom Singapore Pte. Ltd. Foreign investment business Singapore 100.0% 100.0% December Texnoprosistem LLC Fixed line internet business Uzbekistan 100.0% 100.0% December Nasmedia Thailand Co., Ltd. Internet advertising solution provider Thailand 99.9% 99.9% December KT Huimangjieum Manufacturing Korea 100.0% 100.0% December GE Premier 1st Corporate Restructuring Real Estate Investment Trust Co. Residential building investment and rent Korea 63.5% 68.1% December K-REALTY Residential building Korea 100.0% 88.6% December Storywiz Co., Ltd Content and software development and supply Korea — 100.0% December KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) Telecommunication facility construction and maintenance Korea — 100.0% December 1 Sum of the ownership interests owned by the Controlling Company and subsidiaries. 2 Although the Controlling Company owns less than 50% ownership in this entity, this entity is consolidated as the Controlling Company can exercise the majority voting rights in its decision-making process at all times considering the historical voting pattern at the shareholders’ meetings. 3 Although the Controlling Company owns less than 50% ownership in this entity, this entity is consolidated as the Controlling Company holds the majority of voting right based on an agreement with other investors. 4 The number of subsidiaries’ treasury stock is deducted from the total number of shares when calculating the controlling percentage ownership. Changes in scope of consolidation in 2020 are as follows: Changes Location Name of Subsidiary Reason Included Korea Storywiz Co., Ltd Newly established Korea KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) Transferred Excluded Uzbekistan Super iMax LLC Merged Indonesia PT. KT Indonesia Liquidated Belgium KT ORS Belgium Liquidated Summarized information for consolidated subsidiaries as at and for the years ended December 31, 2018, 2019 and 2020, is as follows: (In millions of Korean won) 2018 Total Total Operating Profit (loss) for the year KT Powertel Co., Ltd. ￦ 124,064 ￦ 28,217 ￦ 65,620 ￦ (5,545 ) KT Linkus Co., Ltd. 54,147 44,895 106,337 1,216 KT Submarine Co., Ltd. 130,715 27,530 61,652 (4,286 ) KT Telecop Co., Ltd. 272,492 140,314 328,262 166 KT Hitel Co., Ltd. 272,708 66,043 279,117 657 KT Service Bukbu Co., Ltd. 30,599 23,964 195,961 (31 ) KT Service Nambu Co., Ltd. 37,452 27,939 230,088 160 BC Card Co., Ltd. 1 3,722,379 2,630,536 3,551,715 70,889 H&C Network 1 245,841 63,188 297,470 (15,944 ) Nasmedia Co., Ltd. 1 303,112 161,164 106,805 20,596 KTDS Co., Ltd. 1 148,675 95,834 434,302 8,586 KT M Hows Co., Ltd. 60,197 42,386 26,673 3,691 KT M&S Co., Ltd. 228,073 207,740 791,652 11,408 GENIE Music Corporation (KT Music Corporation) 221,559 75,827 171,314 6,374 KT MOS Bukbu Co., Ltd. 14,121 10,571 16,543 (782 ) KT MOS Nambu Co., Ltd. 14,313 8,927 14,941 (2,418 ) KT Skylife Co., Ltd. 1 816,001 149,841 694,059 52,010 KT Estate Inc. 1 1,695,995 304,712 569,269 51,854 KTGDH Co., Ltd. (KTSB Data service) 8,632 523 4,627 (9,576 ) KT Sat Co., Ltd. 685,926 173,513 137,186 4,921 KT Sports Co., Ltd. 9,560 6,376 55,565 (154 ) KT Music Contents Fund No.1 14,092 1,035 559 294 KT Music Contents Fund No.2 7,629 281 150 (142 ) KT-Michigan 12,741 — 869 (670 ) Autopion Co., Ltd. 8,838 5,801 12,035 453 KT M mobile Co., Ltd. 146,334 35,335 172,674 (10,085 ) KT Investment Co., Ltd. 1 74,580 58,040 8,095 247 KTCS Corporation 1 350,280 188,561 1,019,787 11,401 KTIS Corporation 229,246 68,997 451,532 7,900 Next connect PFV 385,769 34,370 143 (12,449 ) Korea Telecom Japan Co., Ltd. 1 1,326 2,910 1,965 (126 ) Korea Telecom China Co., Ltd. 661 22 681 10 KT Dutch B.V. 31,693 41 191 105 Super iMax LLC 4,150 4,528 4,845 (424 ) East Telecom LLC 1 16,590 14,263 15,087 2,639 Korea Telecom America, Inc. 4,218 832 7,554 350 PT. KT Indonesia 8 — — — KT Rwanda Networks Ltd. 2 144,129 162,801 15,150 (29,238 ) KT Belgium 90,172 1 29 (43 ) KT ORS Belgium 6,709 5 — (46 ) KBTO sp.zo.o. 1,364 217 202 (3,771 ) AOS Ltd. 2 14,018 4,952 6,300 (680 ) KT Hongkong Telecommunications Co., Ltd. 3,616 2,143 9,990 351 1 These companies are the intermediate controlling companies of other subsidiaries and the above financial information is from their consolidated financial statements. 2 At the end of the reporting period, convertible preferred stock issued by subsidiaries is included in liabilities. (In millions of Korean won) 2019 Total Total Operating Profit (loss) for the year KT Powertel Co., Ltd. ￦ 118,052 ￦ 19,766 ￦ 62,846 ￦ 3,085 KT Linkus Co., Ltd. 70,494 62,088 97,892 (2,258 ) KT Submarine Co., Ltd. 120,947 18,452 55,244 486 KT Telecop Co., Ltd. 279,878 153,841 332,063 (4,875 ) KT Hitel Co., Ltd. 279,818 74,769 323,065 1,426 KT Service Bukbu Co., Ltd. 64,802 58,984 219,427 (445 ) KT Service Nambu Co., Ltd. 63,917 55,548 266,148 280 BC Card Co., Ltd. 1 3,912,982 2,594,232 3,553,008 115,885 H&C Network 1 282,016 68,401 320,701 (1,593 ) Nasmedia Co., Ltd. 1 356,236 203,105 117,550 22,484 KTDS Co., Ltd. 1 158,153 105,462 428,758 9,027 KT M Hows Co., Ltd. 74,326 50,638 33,443 6,771 KT M&S Co., Ltd. 248,142 215,777 813,498 12,732 GENIE Music Corporation (KT Music Corporation) 234,131 80,952 230,480 7,658 KT MOS Bukbu Co., Ltd. 33,376 28,841 63,761 353 KT MOS Nambu Co., Ltd. 34,258 26,722 67,300 3,099 KT Skylife Co., Ltd. 1 848,276 142,839 704,996 56,008 KT Estate Inc. 1 1,686,000 295,706 485,686 48,552 KTGDH Co., Ltd. (KTSB Data service) 10,437 1,628 3,977 344 KT Sat Co., Ltd. 651,195 127,523 168,376 16,497 KT Sports Co., Ltd. 15,603 8,333 55,241 (464 ) KT Music Contents Fund No.1 10,579 1,677 521 345 KT Music Contents Fund No.2 7,675 279 331 48 KT-Michigan 11,688 61 248 (1,113 ) Autopion Co., Ltd. 7,460 4,894 5,604 (302 ) KT M mobile Co., Ltd. 135,917 30,603 161,720 (5,580 ) KT Investment Co., Ltd. 1 73,463 56,212 13,375 847 KTCS Corporation 1 378,171 213,983 944,778 7,597 KTIS Corporation 305,798 137,524 454,561 9,205 Next connect PFV 385,412 24,275 1,590 (5,898 ) Korea Telecom Japan Co., Ltd. 1 1,851 2,858 2,891 651 Korea Telecom China Co., Ltd. 879 39 844 192 KT Dutch B.V. 31,003 50 — (242 ) Super iMax LLC 3,568 5,304 4,604 (631 ) East Telecom LLC 1 20,857 16,302 17,186 2,140 Korea Telecom America, Inc. 4,611 537 6,808 572 PT. KT Indonesia 8 — — — KT Rwanda Networks Ltd. 2 132,461 183,164 18,013 (31,662 ) KT Belgium 93,321 11 — (64 ) KT ORS Belgium 6,913 14 — (43 ) KBTO sp.zo.o. 1,767 245 519 (3,457 ) AOS Ltd. 2 12,337 3,993 6,982 (591 ) KT Hongkong Telecommunications Co., Ltd. 5,126 2,923 13,321 586 KT Huimangjieum 2,129 1,019 1,027 (390 ) GE Premier 1st Corporate Restructuring Real Estate Investment Trust Co. 6,285 1,139 176 70 K-REALTY 300 — — — 1 These companies are the intermediate controlling companies of other subsidiaries and the above financial information is from their consolidated financial statements. 2 At the end of the reporting period, convertible preferred stock issued by subsidiaries is included in liabilities. ( I 2020 Total Total Operating Profit (loss) for the year KT Powertel Co., Ltd. ￦ 119,694 ￦ 18,833 ￦ 65,897 ￦ 3,809 KT Linkus Co., Ltd. 58,372 54,022 84,519 (3,212 ) KT Submarine Co., Ltd. 116,813 14,032 110,201 1,197 KT Telecop Co., Ltd. 318,456 193,737 392,489 212 KT Hitel Co., Ltd. 288,949 92,599 350,231 2,080 KT Service Bukbu Co., Ltd. 60,825 56,554 217,451 (871 ) KT Service Nambu Co., Ltd. 58,182 51,460 264,776 (456 ) BC Card Co., Ltd. 1 3,084,398 1,778,751 3,387,640 39,455 H&C Network 1 269,651 61,365 322,690 2,413 Nasmedia Co., Ltd. 1 422,039 221,371 113,136 23,134 KTDS Co., Ltd. 1 183,297 133,129 499,990 10,635 KT M Hows Co., Ltd. 104,704 76,315 44,860 6,935 KT M&S Co., Ltd. 231,260 197,306 661,533 (485 ) GENIE Music Corporation (KT Music Corporation) 250,538 88,488 247,237 9,472 KT MOS Bukbu Co., Ltd. 32,167 26,070 67,975 1,473 KT MOS Nambu Co., Ltd. 33,765 24,947 71,259 1,639 KT Skylife Co., Ltd. 1 919,476 175,039 706,631 58,190 KT Estate Inc. 1 1,689,601 325,429 365,335 14,370 KTGDH Co., Ltd. (KTSB Data Service) 11,003 1,669 4,282 538 KT Sat Co., Ltd. 630,740 92,791 173,693 14,753 KT Sports Co., Ltd. 26,572 14,940 46,608 (2,516 ) KT Music Contents Fund No.1 4,844 1,525 243 84 KT Music Contents Fund No.2 15,021 285 169 (116 ) KT-Michigan 10,382 175 111 (1,420 ) Autopion Co., Ltd. 4,903 4,961 6,174 (2,459 ) KT M Mobile Co., Ltd. 129,011 27,281 163,472 (3,617 ) KT Investment Co., Ltd. 1 115,627 93,695 47,801 4,680 KTCS Corporation 1 384,919 215,175 933,006 11,323 KTIS Corporation 294,289 126,894 454,172 7,387 Next Connect PFV 394,268 37,271 26 (7,101 ) Korea Telecom Japan Co., Ltd. 1 2,694 2,622 1,853 1 Korea Telecom China Co., Ltd. 381 21 618 (492 ) KT Dutch B.V. 1 29,585 10,109 26,782 6,061 Korea Telecom America, Inc. 4,498 125 6,808 712 KT Rwanda Networks Ltd. 2 114,768 191,781 17,870 (34,610 ) KT Belgium 87,608 — (81 ) (81 ) KBTO sp.z o.o. 438 117 490 (2,823 ) AOS Ltd. 2 11,812 3,875 5,719 296 KT Hong Kong Telecommunications Co., Ltd. 6,159 2,800 16,386 1,308 KT Huimangjieum 3,720 2,787 5,239 (13 ) GE Premier 1st Corporate Restructuring Real Estate Investment Trust Co. 5,703 1,165 333 83 Storywiz Co., Ltd 21,594 10,065 19,209 (1,954 ) KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) 138,220 102,963 346,040 (8,461 ) 1 These companies are the intermediate controlling companies of other subsidiaries and the above financial information is from their consolidated financial statements. 2 At the end of the reporting period, convertible preferred stock issued by subsidiaries is included in liabilities.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Significant Accounting Policies	2. Significant Accounting Policies The principal accounting policies applied in the preparation of these consolidated financial statements are set out below. These policies have been consistently applied to all the years presented, unless otherwise stated . 2.1 Basis of Preparation The consolidated financial statements of the Group have been prepared in accordance with International Financial Reporting Standards (“IFRS”) as issued by the International Accounting Standards Board (“IASB”). The financial statements have been prepared on a historical cost basis, except for the following: • Certain financial assets and liabilities (including derivative instruments) – measured at fair value • Assets held-for-sale • Defined benefit pension plans – plan assets measured at fair value The preparation of the consolidated financial statements requires the use of certain critical accounting estimates. It also requires management to exercise judgment in the process of applying the Group’s accounting policies. The areas involving a higher degree of judgment or complexity, or areas where assumptions and estimates are significant to the consolidated financial statements are disclosed in Note 3. 2.2 Changes in Accounting Policy and Disclosures (1) New and amended standards adopted by the Group The Group has applied the following standards and amendments for the first time for their annual reporting period commencing January 1, 2020. - Amendments to IAS 1 Presentation of Financial Statements Accounting policies, changes in accounting estimates and errors – Definition of Material The amendments clarify the definition of material. Information is material if omitting, misstating or obscuring it could reasonably be expected to influence the decisions that the primary users of general-purpose financial statements make on the basis of those financial statements. The amendments do not have a significant impact on the consolidated financial statements. - Amendments to IFRS 3 Business Combination – Definition of a Business The amended definition of a business requires an acquisition to include an input and a substantive process that together significantly contribute to the ability to create outputs and the definition of output excludes the returns in the form of lower costs and other economic benefits. If substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets, an entity may elect to apply an optional concentration test that permits a simplified assessment of whether an acquired set of activities and assets is not a business. The amendments do not have a significant impact on the consolidated financial statements. - Amendments to IFRS 9 Financial Instruments Financial Instruments: Recognition and Measurement Financial Instruments: Disclosure – Interest Rate Benchmark Reform The amendments allow to apply the exceptions when forward-looking analysis is performed in relation the application of hedge accounting, while uncertainties arising from interest rate benchmark reform exist. The exceptions require the Group assumes that the interest rate benchmark, on which the hedged items and the hedging instruments are based on, is not altered as a result of interest rate benchmark reform, when determining whether the expected cash flows are highly probable, whether an economic relationship between the hedged item and the hedging instrument exists, and when assessing the hedging relationship is highly effective. The Group’s risk exposure, directly affected by the interest rate benchmark reform, is the variable rate borrowings of USD 519,598,989 and SGD 284,000,000 with maximum remaining maturity of four years. To hedge fluctuations in cash flows of borrowings resulting from the changes in USD LIBOR of 3 months and SGD SOR of 6 months—an interest rate benchmark, the Group entered into an interest rate swap contract for a nominal amount of USD 519,598,989 and SGD 284,000,000 and designated it as a hedging instrument of cash flow hedge. - Agenda Decision of the International Accounting Standards Interpretations Committee – Lease Period The IFRS Interpretations Committee (IFRS IC) announced on December 16, 2019 that all economic penalties resulting from the termination of a lease are taken into account when determining the enforceable period for ‘Lease Term and Useful Life of Leasehold Improvements’. The Group’s changes in accounting policy have been adopted retrospectively in accordance with IAS 8 Accounting Policies, Changes in Accounting Estimates and Errors (2) New standards and interpretations not yet adopted by the Group The following new accounting standards and interpretations have been published that are not mandatory for December 31, 2020 reporting periods and have not been early adopted by the Group. - Amendments to IFRS 16 Lease – Practical expedient for COVID-19—Related As a practical expedient, a lessee may elect not to assess whether a rent concession occurring as a direct consequence of the COVID-19 - Amendments to IFRS 9 Financial Instruments, Financial Instruments: Recognition and Measurement, Financial Instruments: Disclosure, Insurance Contracts Lease – Interest Rate Benchmark Reform In relation to interest rate benchmark reform, the amendments provide exceptions including adjust effective interest rate instead of book amounts when interest rate benchmark of financial instruments at amortized costs is replaced, and apply hedge accounting without discontinuance although the interest rate benchmark is replaced in hedging relationship. The amendments should be applied for annual periods beginning on or after January 1, 2021, and earlier application is permitted. The Group is in review for the impact of these amendments on the financial statements. - Amendments to IFRS 3 Business Combination – Reference to the Conceptual Framework The amendments update a reference of definition of assets and liabilities qualify for recognition in revised Conceptual Framework for Financial Reporting. However, the amendments add an exception for the recognition of liabilities and contingent liabilities within the scope of IAS 37 Provisions, Contingent Liabilities and Contingent Assets Levies - Amendments to IAS 16 Property, Plant and Equipment—Proceeds Before Intended Use The amendments prohibit an entity from deducting from the cost of an item of property, plant and equipment any proceeds from selling items produced while the entity is preparing the asset for its intended use. Instead, the entity will recognize the proceeds from selling such items, and the costs of producing those items, in profit or loss. The amendments should be applied for annual periods beginning on or after January 1, 2022, and earlier application is permitted. The Group is in review for the impact of these amendments on the financial statements. - Amendments to IAS 37 Provisions, Contingent Liabilities and Contingent Assets—Onerous Contracts: Cost of Fulfilling a Contract The amendments clarify that the direct costs of fulfilling a contract include both the incremental costs of fulfilling the contract and an allocation of other costs directly related to fulfilling contracts when assessing whether the contract is onerous. The amendments should be applied for annual periods beginning on or after January 1, 2022, and earlier application is permitted. The Group does not expect that these amendments have a significant impact on the financial statements. - Annual improvements to IFRS 2018-2020 Annual improvements of IFRS 2018-2020 Cycle should be applied for annual periods beginning on or after January 1, 2022, and earlier application is permitted. The Group does not expect that these amendments have a significant impact on the financial statements. • IFRS 1 First time Adoption of Korean International Financial Reporting Standards • IFRS 9 Financial Instruments • IFRS 16 Leases • IAS 41 Agricultur - Amendments to IAS 1 Presentation of Financial Statements—Classification of Liabilities as Current or Non-Current The amendments clarify that liabilities are classified as either current or non-current, 2.3 Consolidation The Group has prepared the consolidated financial statements in accordance with IFRS 10 Consolidated Financial Statements (1) Subsidiaries Subsidiaries are all entities (including special purpose entities (“SPEs”)) over which the Group has control. The Group controls an entity when the Group is exposed to, or has rights to, variable returns from its involvement with the entity and has the ability to affect those returns through its power to direct the activities of the entity. Subsidiaries are fully consolidated from the date on which control is transferred to the Group. They are deconsolidated from the date that control ceases. The acquisition method of accounting is used to account for business combinations by the Group. The consideration transferred is measured at the fair values of the assets transferred, and identifiable assets acquired and liabilities and contingent liabilities assumed in a business combination are measured initially at their fair values at the acquisition date. The Group recognizes any non-controlling acquisition-by-acquisition non-controlling non-controlling The excess of consideration transferred, amount of any non-controlling Intercompany transactions, balances and unrealized gains on transactions between group companies are eliminated. Unrealized losses are also eliminated unless the transaction provides evidence of an impairment of the transferred asset. Accounting policies of subsidiaries have been changed where necessary to ensure consistency with the policies adopted by the Group. (2) Changes in ownership interests in subsidiaries without change of control Any difference between the amount of the adjustment to non-controlling (3) Disposal of subsidiaries When the Group ceases to consolidate for a subsidiary because of a loss of control, any retained interest in the subsidiary is remeasured to its fair value with the change in carrying amount recognized in profit or loss. (4) Associates Associates are entities over which the Group has significant influence but does not possess control or joint control. Investments in associates are accounted for using the equity method of accounting, after initially being recognized at cost. Unrealized gains on transactions between the Group and its associates are eliminated to the extent of the Group’s interest in the associates. If the Group’s share of losses of an associate equals or exceeds its interest in the associate (including long-term interests that, in substance, form part of the Group’s net investment in the associate), the Group discontinues recognizing its share of further losses. After the Group’s interest is reduced to zero, additional losses are provided for, and a liability is recognized, only to the extent that the Group has incurred legal or constructive obligations or made payments on behalf of the associate. If there is an objective evidence of impairment for the investment in the associate, the Group recognizes the difference between the recoverable amount of the associate and its book amount as impairment loss. If an associate uses accounting policies other than those of the Group for transactions and events in similar circumstances, if necessary, adjustments shall be made to make the associate’s accounting policies conform to those of the Group when the associate’s financial statements are used by the Group in applying the equity method. (5) Joint arrangement A joint arrangement, wherein two or more parties have joint control, is classified as either a joint operation or a joint venture. A joint operator recognizes its direct right to the assets, liabilities, revenues and expenses of joint operations and its share of any jointly held or incurred assets, liabilities, revenues and expenses. A joint venture has rights to the net assets relating to the joint venture and accounts for that investment using the equity method. 2.4 Segment Reporting Information of each operating segment is reported in a manner consistent with the business segment reporting provided to the chief operating decision-maker (Note 34). The chief operating decision-maker is responsible for allocating resources and assessing performance of the operating segments. 2.5 Foreign Currency Translation (1) Functional and presentation currency Items included in the financial statements of each of the Group’s entities are measured using the currency of the primary economic environment in which each entity operates (the “functional currency”). The consolidated financial statements are presented in Korean won, which is the Parent Company’s functional and presentation currency. (2) Transactions and balances Foreign currency transactions are translated into the functional currency using the exchange rates at the dates of the transactions. Foreign exchange gains and losses resulting from the settlement of such transactions and from the translation of monetary assets and liabilities denominated in foreign currencies at year end exchange rates are generally recognized in profit or loss. They are deferred in other comprehensive income if they relate to qualifying cash flow hedges and qualifying effective portion of net investment hedges, or are attributable to monetary part of the net investment in a foreign operation. Foreign exchange gains and losses that relate to borrowings are presented in the consolidated statements of operations, within finance costs. All other foreign exchange gains and losses are presented in the consolidated statements of operations within operating revenue or operating expenses. Non-monetary non-monetary non-monetary (3) Translation to the presentation currency The results and financial position of foreign operations that have a functional currency different from the presentation currency are translated into the presentation currency as follows: • assets and liabilities for each statement of financial position presented are translated at the closing rate at the end of the reporting period, • income and expenses for each consolidated statements of operations are translated at average exchange rates for the period, • equity is translated at the historical exchange rate, and • all resulting exchange differences are recognized in other comprehensive income. 2.6 Cash and cash equivalents Cash and cash equivalents comprise cash balances, call deposits and investment securities with maturities of three months or less from the acquisition date that are easily convertible to cash and subject to an insignificant risk of changes in their fair value. 2.7 Financial Assets The Group has applied IFRS 9 Financial Instruments, on January 1, 2018, the date of initial application. In accordance with the transitional provisions in IFRS 9, the Group recorded the cumulative effect as at the date of the initial application of the standards as an adjustment to the initial balance in the retained earnings. (1) Classification The Group classifies its financial assets in the following measurement categories: • those to be measured at fair value through profit or loss • those to be measured at fair value through other comprehensive income, and • those to be measured at amortized cost. The classification depends on the Group’s business model for managing the financial assets and the contractual terms of the cash flows. For financial assets measured at fair value, gains and losses will either be recorded in profit or loss or other comprehensive income. For investments in debt instruments, this will depend on the business model in which the investment is held. The Group reclassifies debt investments when, and only when its business model for managing those assets changes. For investments in equity instruments that are not held for trading, this will depend on whether the Group has made an irrevocable election at the time of initial recognition to account for the equity investment at fair value through other comprehensive income. Changes in fair value of the investments in equity instruments that are not accounted for as other comprehensive income are recognized in profit or loss. (2) Measurement At initial recognition, the Group measures a financial asset at its fair value plus, in the case of a financial asset not at fair value through profit or loss, transaction costs that are directly attributable to the acquisition of the financial asset. Transaction costs of financial assets carried at fair value through profit or loss are expensed in profit or loss. Hybrid (combined) contracts with embedded derivatives are considered in their entirety when determining whether their cash flows are solely payment of principal and interest. A. Debt instruments Subsequent measurement of debt instruments depends on the Group’s business model for managing the asset and the cash flow characteristics of the asset. The Group classifies its debt instruments into one of the following three measurement categories: • Amortized cost: Assets that are held for collection of contractual cash flows where those cash flows represent solely payments of principal and interest are measured at amortized cost. A gain or loss on a debt investment that is subsequently measured at amortized cost and is not part of a hedging relationship is recognized in profit or loss when the asset is derecognized or impaired. Interest income from these financial assets is included in ‘finance income’ using the effective interest rate method. • Fair value through other comprehensive income: Assets that are held for collection of contractual cash flows and for selling the financial assets, where the assets’ cash flows represent solely payments of principal and interest, are measured at fair value through other comprehensive income. Movements in the carrying amount are taken through other comprehensive income, except for the recognition of impairment loss (and reversal of impairment loss), interest income and foreign exchange gains and losses which are recognized in profit or loss. When the financial asset is derecognized, the cumulative gain or loss previously recognized in other comprehensive income is reclassified from equity to profit or loss. Interest income from these financial assets is included in ‘finance income’ using the effective interest rate method. Foreign exchange gains and losses are presented in ‘finance income or finance costs’ and impairment loss in ‘finance costs or operating expenses’. • Fair value through profit or loss: Assets that do not meet the criteria for amortized cost or fair value through other comprehensive income are measured at fair value through profit or loss. A gain or loss on a debt investment that is subsequently measured at fair value through profit or loss and is not part of a hedging relationship is recognized in profit or loss and presented net in the consolidated statements of operations within ‘finance income or finance costs’ in the period in which it arises. B. Equity instruments The Group subsequently measures all equity investments at fair value. Where the Group’s management has elected to present fair value gains and losses on equity investments in other comprehensive income, there is no subsequent reclassification of fair value gains and losses to profit or loss following the derecognition of the investment. Dividends from such investments continue to be recognized in profit or loss as ‘finance income’ when the Group’s right to receive payments is established. Changes in the fair value of financial assets at fair value through profit or loss are recognized in ‘finance income or finance costs’ in the consolidated statements of operations as applicable. Impairment loss (and reversal of impairment loss) on equity investments measured at fair value through other comprehensive income are not reported separately from other changes in fair value. (3) Impairment The Group assesses on a forward looking basis the expected credit losses associated with its debt instruments carried at amortized cost and fair value through other comprehensive income. The impairment methodology applied depends on whether there has been a significant increase in credit risk. For trade receivables and lease receivables, the Group applies the simplified approach, which requires expected lifetime credit losses to be recognized from initial recognition of the receivables. (4) Recognition and Derecognition Regular way purchases and sales of financial assets are recognized or derecognized on trade-date, the date on which the Group commits to purchase or sell the asset. Financial assets are derecognized when the rights to receive cash flows from the financial assets have expired or have been transferred and the Group has transferred substantially all the risks and rewards of ownership. If a transfer does not result in derecognition because the Group has retained substantially all the risks and rewards of ownership of the transferred asset, the Group continues to recognize the transferred asset in its entirety and recognizes a financial liability for the consideration received. (5) Offsetting of financial instruments Financial assets and liabilities are offset and the net amount reported in the statements of financial position where there is a legally enforceable right to offset the recognized amounts and there is an intention to settle on a net basis or realize the assets and settle the liability simultaneously. The legally enforceable right must not be contingent on future events and must be enforceable in the normal course of business and in the event of default, insolvency or bankruptcy of the Group or the counterparty. 2.8 Derivative Instruments Derivatives are initially recognized at fair value on the date a derivative contract is entered into and are subsequently remeasured to their fair value at the end of each reporting period. The accounting for subsequent changes in fair value depends on whether the derivative is designated as a hedging instrument, and if so, the nature of the item being hedged. The Group has hedge relationships and designates certain derivatives as: • hedges of a particular risk associated with the cash flows of recognized assets and liabilities and highly probable forecast transactions (cash flow hedges) At inception of the hedge relationship, the Group documents the economic relationship between hedging instruments and hedged items including whether changes in the cash flows of the hedging instruments are expected to offset changes in the cash flows of hedged items. The fair values of derivative financial instruments designated in hedge relationships are disclosed in Note 37. The full fair value of a hedging derivative is classified as a non-current non-derivative non-derivative non-current The effective portion of changes in fair value of derivatives that are designated and qualify as cash flow hedges is recognized in the cash flow hedge reserve within equity, and the ineffective portion is recognized in ‘finance income (costs)’. Amounts of changes in fair value of effective hedging instruments accumulated in equity are recognized as ‘finance income (costs)’ for the periods when the corresponding transactions affect profit or loss. When a hedging instrument expires, or is sold, terminated, exercised, or when a hedge no longer meets the criteria for hedge accounting, any accumulated cash flow hedge reserve at that time remains in equity until the forecast transaction occurs, resulting in the recognition of a non-financial 2.9 Trade Receivable s Trade receivables are recognized initially at the amount of consideration that is unconditional, unless they contain significant financing components when they are recognized at fair value. Trade receivables are subsequently measured at amortized cost using the effective interest method, less loss allowance. See Note 6 for further information about the Group’s accounting for trade receivables and Note 2. 7 2.10 Inventories Inventories are stated at the lower of cost and net realizable value. Cost is determined using the moving average method, except for inventories in-tran s . 2.1 1 Assets (or Disposal Group) Held-for-sale Assets(or disposal group) are classified as assets held for sale when their carrying amount will be recovered principally through a sale transaction rather than through continued use and when a sale is considered highly probable. The assets are measured at the lower amount between their carrying amount and the fair value less selling costs. 2.1 2 Property and Equipment Property and equipment are stated at historical cost less accumulated depreciation and accumulated impairment losses. Historical cost includes expenditures that are directly attributable to the acquisition of the items. Depreciation of all property and equipment, except for land, is calculated using the straight-line method to allocate their cost, net of their residual values, over their estimated useful lives as follows: Estimated Useful Life Buildings 5 – 40 years Structures 5 – 40 years Machinery and equipment (Telecommunications equipment and others) 2 – 40 years Others Vehicles 4 – 6 years Tools 4 – 6 years Office equipment 2 – 6 years The depreciation method, residual values and useful lives of property and equipment are reviewed at the end of each reporting period and, if appropriate, accounted for as changes in accounting estimates. 2.13 Investment Property Investment property is a property held to earn rentals or for capital appreciation. An investment property is measured initially at its cost. After recognition as an asset, investment property is carried at cost less accumulated depreciation and impairment losses. Investment property, except for land, is depreciated using the straight-line method over their useful lives from 10 to 40 years. 2.14 Intangible Assets (1) Goodwill Goodwill is measured as explained in Note 2.3 (1) and goodwill arising from acquisition of subsidiaries and business are included in intangible assets. Goodwill is tested at least annually for impairment and carried at cost less accumulated impairment losses. Gains and losses on the disposal of subsidiaries and business include the carrying amount of goodwill relating to the subsidiaries and business sold. For the purpose of impairment testing, goodwill acquired in a business combination is allocated to each of the CGUs, or group of CGUs, that is expected to benefit from the synergies of the combination. Goodwill is monitored at the operating segment level. Goodwill impairment reviews are undertaken at least annually or more frequently if events or changes in circumstances indicate a potential impairment. The carrying amount of goodwill is compared to the recoverable amount, which is the higher of value in use and the fair value less costs to sell. Any impairment is recognized immediately as an expense and is not subsequently reversed. (2) Intangible assets except goodwill Intangible assets, except for goodwill, are initially recognized at its historical cost, and carried at cost less accumulated amortization and accumulated impairment losses. Membership rights (condominium membership and golf membership) that have an indefinite useful life are not subject to amortization because there is no foreseeable limit to the period over which the assets are expected to be utilized. The Group amortizes intangible assets with a limited useful life using the straight-line method over the following periods: Estimated Useful Life Development costs 5 – 6 years Software 4 – 6 years Frequency usage rights 5 – 10 years Others 1 1 – 50 years 1 Membership rights (condominium membership and golf membership) and broadcast license included in others are classified as intangible assets with indefinite useful life. 2.15 Borrowing Costs General and specific borrowing costs that are directly attributable to the acquisition, construction or production of a qualifying asset are capitalized during the period of time that is required to complete and prepare the asset for its intended use or sale. Investment income earned on the temporary investment of specific borrowings pending their expenditure on qualifying assets is deducted from the borrowing costs eligible for capitalization. Other borrowing costs are expensed in the period in which they are incurred. 2.16 Government Grants Grants from the government are recognized at their fair value where there is a reasonable assurance that the grant will be received and the Group will comply with all attached conditions. Government grants related to assets are presented in the statement of financial position by setting up the grant as deferred income that is recognized in profit or loss on a systematic basis over the useful life of the asset. Grants related to income are presented as a credit in the consolidated statements of operations. 2.17 Impairment of Non-Financial Goodwill and intangible assets with indefinite useful life are tested at least annually for impairment at the end of each reporting period. If certain assets are deemed to be impaired, their recoverable amount is estimated in order to determine the impairment loss. The Group estimates the recoverable amount for each asset, and in cases when the recoverable amount cannot be estimated for an asset, the recoverable amount of the cash generating unit to which the asset belongs is estimated. Corporate assets are allocated to individual cash generating units on a reasonable and consistent basis and if they cannot be allocated to individual cash generating units, they are allocated to the smallest group of cash generating units on a reasonable and consistent basis. An impairment loss is recognized for the amount by which the asset’s carrying amount exceeds its recoverable amount (higher of its fair value less costs of disposal and value in use). Impairment loss on non-financial 2.1 8 Trade and other payables These amounts represent liabilities for goods and services provided to the Group prior to the end of reporting period which are unpaid. Trade and other payables are presented as current liabilities, unless payment is not due within 12 months after the reporting period. They are recognized initially at their fair value and subsequently measured at amortized cost using the effective interest method. 2.1 9 Financial Liabilities (1) Classification and measurement The Group’s financial liabilities measured at fair value through profit or loss are financial instruments held for trading. A financial liability is held for trading if it is incurred principally for the purpose of repurchasing in the near term. Derivatives that are not designated as hedging instruments or derivatives separated from financial instruments containing embedded derivatives are also categorized as held for trading. All non-derivative • Financial liabilities at fair value through profit or loss • Financial guarantee contract • Financial liabilities arising when the transfer of financial assets does not meet the elimination conditions Financial liabilities measured at amortized cost are displayed in the statement of financial position as ‘Trade and other payables’, ‘Borrowings’ and ‘Other financial liabilities’. Preferred shares that require mandatory redemption at a particular date are classified as liabilities. Interest expenses on these preferred shares using the effective interest method are recognized in the consolidated statements of operations as ‘finance costs’, together with interest expenses recognized from other financial liabilities. (2) Derecognition Financial liabilities are removed from the statement of financial position when they are extinguished; for example, when the obligation specified in the contract is discharged or cancelled or expired or when the terms of an existing financial liability are substantially modified. The difference between the carrying amount of a financial liability extinguished or transferred to another party and the consideration paid (including any non-cash 2.20 Financial Guarantee Contracts Financial guarantee contracts are recognized as a financial liability at the time the guarantee is issued. The liability is initially measured at fair value, subsequently at the higher of following and recognized in the statement of financial position within ‘other financial liabilities’. • the amount determined in accordance with the expected credit loss model under IFRS 9 Financial Instruments • the amount initially recognized less, where appropriate, the cumulative amount of income recognized in accordance with IFRS 15 Revenue from Contracts with Customers 2. 21 Employee Benefits (1) Post-employment be

Critical Accounting Estimates a

Critical Accounting Estimates and Assumptions	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Critical Accounting Estimates and Assumptions	3. Critical Accounting Estimates and Assumptions The Group makes estimates and assumptions concerning the future. The estimates and assumptions are continuously evaluated and are based on historical experience and other factors, including expectations of future events that are believed to be reasonable under the current circumstances. Actual results may differ from these estimates. During 2020, the spread of Coronavirus disease 2019 (“COVID-19”) Significant accounting estimates and assumptions applied in the preparation of the consolidated financial statements can be adjusted depending on changes in the uncertainty from COVID-19. COVID-19 The estimates and assumptions that have a significant risk of causing a material adjustment to the carrying amounts of assets and liabilities within the next financial year are discussed below. Additional information of significant judgement and assumptions of certain items are included in relevant notes. 3.1 Impairment of Non-Financial The Group determines the recoverable amount of a cash generating unit (CGU) based on fair value or value-in-use non-financial 3.2 Income Taxes The Group’s taxable income generated from these operations are subject to income taxes based on tax laws and interpretations of tax authorities in numerous jurisdictions. There are many transactions and calculations for which the ultimate tax determination is uncertain (Note 29). If certain portion of the taxable income is not used for investments or increase in wages or dividends in accordance with the Tax System For Recirculation of Corporate Income, the Group is liable to pay additional income tax calculated based on the tax laws. Accordingly, the measurement of current and deferred income tax is affected by the tax effects from the new tax system. As the Group’s income tax is dependent on the investments, increase in wages and dividends, there is an uncertainty measuring the final tax effects. 3.3 Fair Value of Derivatives and Financial Instruments The fair value of financial instruments that are not traded in an active market is determined by using valuation techniques. The Group uses its judgment to select a variety of methods and make assumptions that are mainly based on market conditions existing at the end of each reporting period (Note 37). 3.4 Impairment of Financial Assets The provision for impairment for financial assets are based on assumptions about risk of default and expected loss rates. The Group uses judgement in making these assumptions and selecting the inputs to the impairment calculation based on the Group’s past history, existing market conditions as well as forward looking estimates at the end of each reporting period (Note 36). 3.5 Net Defined Benefit Liability The present value of net defined benefit liability depends on a number of factors that are determined on an actuarial basis using a number of assumptions including the discount rate (Note 18). 3.6 Amortization of Contract Assets, Contract Liabilities and Contract Cost Assets Contract assets, contract liabilities and contract cost assets recognized under the application of IFRS 15 are amortized over the expected periods of customer relationships. The estimate of the expected terms of customer relationship is based on the historical data. If management’s estimate changes, it may cause significant differences in the timing of revenue recognition and amounts recognized. 3.7 Provisions As described in Note 17, the Group records provisions for litigation and assets retirement obligations at the end of the reporting period. The provisions are estimated based on the factors such as the historical experiences. 3.8 Useful Lives of Property and Equipment and Investment Property The property and equipment, intangible assets, and investment properties, excluding land, goodwill, condominium memberships and golf club memberships are depreciated using the straight-line method over their useful lives. The estimated useful lives are determined based on expected usage of the assets and the estimates can be materially affected by technical changes and other factors. The Group will increase depreciation expenses if the useful lives are considered shorter than the previously estimated useful lives. 3.9 Lease Term In determining the lease term, management considers the facts and circumstances that create an economic incentive to exercise an extension option, or not exercise a termination option. Extension options (or periods after termination options) are only included in the lease term if the lease is reasonably certain to be extended (or not terminated). For leases of property, machinery and communication line facilities, the following factors are normally the most relevant: • If there are significant penalties to terminate (or not extend), the Group is typically reasonably certain to extend (or not terminate). • If any leasehold improvements are expected to have a significant remaining value, the Group is typically reasonably certain to extend (or not terminate). • Otherwise, the Group considers other factors including historical lease durations and the costs and business disruption required to replace the leased asset. Most extension options in offices, retail stores and vehicles leases have not been included in the lease liability, because the Group could replace the assets without significant cost or business disruption. The lease term is reassessed if an option is actually exercised (or not exercised) or the Group becomes obliged to exercise (or not exercise) it. The assessment of reasonable certainty is only revised if a significant event or a significant change in circumstances occurs, which affects this assessment, and that is within the control of the lessee. Details on the current period’s financial impact from changes in accounting policies, to reflect exercising extension and termination options, are disclosed in Note 41.

Financial Instruments by Catego

Financial Instruments by Category	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Financial Instruments by Category	4. Financial Instruments by Category Financial instruments by category as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 Financial assets Financial assets at cost Financial Financial Derivatives Total Cash and cash equivalents ￦ 2,305,894 ￦ — ￦ — ￦ — ￦ 2,305,894 Trade and other receivables 1 5,748,459 — 1,256,266 — 7,004,725 Other financial assets 441,804 632,324 557,342 58,576 1,690,046 1 Lease receivables and others which are not applied to financial instruments by category are excluded. (In millions of Korean won) December 31, 2019 Financial liabilities Financial Financial Derivatives Total Trade and other payables ￦ 8,679,698 ￦ — ￦ — ￦ 8,679,698 Borrowings 7,298,867 — — 7,298,867 Other financial liabilities 129,945 38 20,096 150,079 (In millions of Korean won) December 31, 2020 Financial assets Financial Financial Financial Derivatives Total Cash and cash equivalents ￦ 2,634,624 ￦ — ￦ — ￦ — ￦ 2,634,624 Trade and other receivables 1 4,976,423 — 1,118,619 — 6,095,042 Other financial assets 671,068 809,919 258,516 7,684 1,747,187 1 Lease receivables and others which are not applied to financial instruments by category are excluded. (In millions of Korean won) December 31, 2020 Financial liabilities Financial Financial liabilities Derivatives Total Trade and other payables ￦ 7,017,639 ￦ — ￦ — ￦ 7,017,639 Borrowings 7,316,298 — — 7,316,298 Other financial liabilities 132,558 2,682 127,929 263,169 Gains or losses arising from financial instruments by category for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Financial assets at amortized cost Interest income 1,5 ￦ 93,233 ￦ 79,838 ￦ 55,742 Gain(loss) on foreign currency transaction 4 19,396 32,293 (19,244 ) Loss on foreign currency translation 4 (2,901 ) (474 ) (3,895 ) Gain(loss) on disposal 44 (43 ) 138 Loss on valuation (110,544 ) (59,947 ) (140,474 ) Financial assets at fair value through profit or loss Interest income 1 9,194 5,634 6,548 Dividend income 6 1,207 1,096 4,379 Gain on valuation 7 10,768 4,334 59,044 Gain on disposal 1,713 5,115 (329 ) Loss on foreign currency transaction 4 — — (38 ) Loss on foreign currency translation 4 — (27 ) — Financial assets at fair value through other comprehensive income Interest income 1 163,390 217,355 227,736 Dividend income 6 1,704 2,312 56 Impairment loss (2,416 ) (304 ) — Loss on disposal (13,818 ) (11,247 ) (8,152 ) Other comprehensive income for the year 2 43,811 167,152 41,997 Derivative assets used for hedging Gain on transaction 7,272 6,332 6,050 Gain(loss) on valuation 22,065 56,537 (2,707 ) Other comprehensive income(loss) for the year 2 20,078 46,806 (2,373 ) Reclassified to profit or loss from other comprehensive income for the year 2,3 (15,891 ) (39,604 ) 3,645 Financial liabilities at fair value through profit or loss Gain on disposal — 2,664 799 Gain(loss) on valuation (2,708 ) (1,936 ) 119 Derivative liabilities used for hedging Gain on transactions 20,678 — 1,141 Gain(loss) on valuation 42,195 4,949 (161,003 ) Other comprehensive income for the year 2 (2,810 ) 20,742 (81,671 ) Reclassified to profit or loss from other comprehensive income for the year 2,3 (28,388 ) (5,080 ) 107,786 Financial liabilities at amortized cost Interest expense 1,5 (296,894 ) (223,974 ) (220,945 ) Loss on repayment (15 ) — — Loss on foreign currency transaction 4 (30,956 ) (20,958 ) (10,717 ) Gain(loss) on foreign currency translation 4 (66,050 ) (75,502 ) 141,849 Total ￦ (116,643 ) ￦ 214,063 ￦ 5,481 1 BC Card, a subsidiary of the Group, recognized interest income and expense as operating revenue and expense, respectively. Related interest income recognized as operating revenue is ￦ ￦ ￦ ￦ ￦ ￦ 2 The amounts directly reflected in equity after adjustments of deferred income tax. 3 During the year, certain derivatives of the Group were settled and the related gain or loss on valuation of cash flow hedge in other comprehensive income was reclassified to profit or loss for the year. 4 BC Card Co., Ltd., a subsidiary of the Group recognized foreign currency translation/transaction gain and loss and as operating income and expenses. In relation to this, foreign currency translation gain and loss recognized as operating revenue and expense amount to ￦ ￦ ￦ ￦ ￦ ￦ 5 Interest income (interest expense) from lease receivables (lease liabilities) is excluded as it is not subject to classification of financial instruments (Note 21). 6 BC Card Co., Ltd., a subsidiary of the Group, recognized dividend income as operating revenue. Related dividend income recognized as operating revenue is ￦ ￦ ￦ 7 KT Investment Co., Ltd., etc., subsidiaries of the Group, recognized financial instruments measured at fair value through profit or loss as operating income and expenses. In relation to this, valuation gain and loss recognized as operating revenue and expense amount to ￦ 40,822 million (2018: ￦ (-) 5 million, 2019: ￦ 15,429 million), for the year ended December 31, 2020.

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Cash and Cash Equivalents	5. Cash and Cash Equivalents Restricted cash and cash equivalents as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, December 31, Description Bank deposits ￦ ￦ Deposit restricted for government project and others Cash and cash equivalents in the statement of financial position equal to cash and cash equivalents in the statement of cash flows.

Trade and Other Receivables

Trade and Other Receivables	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Trade and Other Receivables	6. Trade and Other Receivable s Trade and other receivables as at December 31, 2019 and 2020, are as follows: December 31, 2019 (In millions of Korean won) Total Provision Present value Carrying amount Current assets Trade receivables ￦ 3,451,107 ￦ (291,202 ) ￦ (9,510 ) ￦ 3,150,395 Other receivables 2,787,144 (78,572 ) (271 ) 2,708,301 ￦ 6,238,251 ￦ (369,774 ) ￦ (9,781 ) ￦ 5,858,696 Non-current Trade receivables ￦ 874,860 ￦ (4,117 ) ￦ (43,597 ) ￦ 827,146 Other receivables 382,468 (5,108 ) (22,708 ) 354,652 ￦ 1,257,328 ￦ (9,225 ) ￦ (66,305 ) ￦ 1,181,798 December 31, 2020 (In millions of Korean won) Total Provision Present value Carrying amount Current assets Trade receivables ￦ 3,388,099 ￦ (322,992 ) ￦ (8,977 ) ￦ 3,056,130 Other receivables 1,948,108 (101,619 ) (148 ) 1,846,341 ￦ 5,336,207 ￦ (424,611 ) ￦ (9,125 ) ￦ 4,902,471 Non-current Trade receivables ￦ 892,992 ￦ (4,323 ) ￦ (34,716 ) ￦ 853,953 Other receivables 513,926 (102,985 ) (14,125 ) 396,816 ￦ 1,406,918 ￦ (107,308 ) ￦ (48,841 ) ￦ 1,250,769 The fair values of trade and other receivables with original maturities less than one year equal to their carrying amounts because the discounting effect is immaterial. The fair value of trade and other receivables with original maturities longer than one year, which are mainly from sales of goods, is determined discounting the expected future cash flow at the weighted average interest rate. Details of changes in provision for impairment for the years ended December 31, 2019 and 2020, are as follows: 2019 2020 (In millions of Korean won) Trade Other Trade Other Beginning balance ￦ 359,924 ￦ 93,822 ￦ 295,319 ￦ 83,680 Provision 24,596 35,597 89,097 50,860 Reversal — (475 ) — (890 ) Written-off (90,513 ) (44,108 ) (60,598 ) (25,067 ) Change in consolidation scope — — 3,211 87,614 Others 1,312 (1,156 ) 286 8,407 Ending balance ￦ 295,319 ￦ 83,680 ￦ 327,315 ￦ 204,604 Provisions for impairment on trade and other receivables are recognized as operating expenses and finance costs. Details of other receivables as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, December 31, Loans ￦ 84,148 ￦ 116,082 Receivables 1 2,540,315 1,699,608 Accrued income 8,630 6,901 Refundable deposits 352,293 350,180 Loans receivable 105,961 150,527 Finance lease receivables 39,726 64,047 Others 15,560 60,416 Less: Provision for impairment (83,680 ) (204,604 ) ￦ 3,062,953 ￦ 2,243,157 1 Settlement receivables of BC Card Co., Ltd., a subsidiary of the Group, of ￦ ￦ The maximum exposure of trade and other receivables to credit risk is the carrying amount of each class of receivables mentioned above as at December 31, 2020. A portion of the trade receivables is classified as financial assets at fair value through other comprehensive income considering the trade receivables business model for managing the asset and the cash flow characteristics of the contract.

Other Financial Assets and Liab

Other Financial Assets and Liabilities	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Other Financial Assets and Liabilities	7. Other Financial Assets and Liabilitie s Details of other financial assets and liabilities as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Other financial assets Financial assets at amortized cost 1 ￦ 441,804 ￦ 671,068 Financial assets at fair value through profit or loss 1,2,3 632,324 809,919 Financial assets at fair value through other comprehensive income 1,3 557,342 258,516 Derivative used for hedging 58,576 7,684 Less: Non-current (821,658 ) (544,347 ) Current ￦ 868,388 ￦ 1,202,840 Other financial liabilities Financial liabilities at amortized cost ￦ 129,945 ￦ 132,558 Financial liabilities at fair value through profit or loss 38 2,682 Derivatives used for hedging 20,096 127,929 Less: Non-current (149,136 ) (260,676 ) Current ￦ 943 ￦ 2,493 1 As at December 31, 2020, the Group’s other financial assets amounting to ￦ ￦ 2 As at December 31, 2020, MMW (Money Market Wrap) and MMT (Money Market Trust) amounting to ￦ ￦ 3 As at December 31, 2020, the Group provided investments in Korea Software Financial Cooperative amounting to ￦ ￦ Details of financial assets at fair value through profit or loss as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Equity Instruments (Listed) ￦ 232 ￦ 46,449 Equity Instruments (Unlisted) 90,357 83,017 Debt securities 541,657 680,453 Derivatives held for trading 78 — Total 632,324 809,919 Less: non-current (219,026 ) (276,109 ) Current ￦ 413,298 ￦ 533,810 The maximum exposure of debt instruments of financial assets recognized at fair value through profit or loss to credit risk is the carrying amount as at December 31, 2020. Details of financial assets at fair value through other comprehensive income as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Equity Instruments (Listed) ￦ 6,738 ￦ 6,216 Equity Instruments (Unlisted) 543,518 245,730 Debt securities 7,086 6,570 Total 557,342 258,516 Less: non-current (556,147 ) (258,516 ) Current ￦ 1,195 ￦ — Upon disposal of these equity investments, any balance within the accumulated other comprehensive income for these equity investments is not classified to profit or loss, but to retained earnings. Upon disposal of debt investments, remaining balance of the accumulated other comprehensive income of debt instruments is reclassified to profit or loss. In 2020, the Group disposed shares of Mastercard Inc. amounting to ￦ ￦ ￦ Derivatives used for hedg ing December 31, 2019 December 31, 2020 (In millions of Korean won) Assets Liabilities Assets Liabilities Interest rate swap 1 ￦ — ￦ 1,464 ￦ — ￦ 1,078 Currency swap 2 55,569 18,632 7,684 126,189 Currency forwards 3 3,007 — — 662 Total 58,576 20,096 7,684 127,929 Less: non-current (28,304 ) (19,177 ) (2,111 ) (126,408 ) Current ￦ 30,272 ￦ 919 ￦ 5,573 ￦ 1,521 1 The interest rate swap contract is to hedge the risk of variability in future fair value of the borrowings. 2 The currency swap contract is to hedge the risk of variability in cash flow from the borrowings. In applying the cash flow hedge accounting, the Group hedges its exposures to cash flow fluctuation until September 7, 2034. 3 The currency forward contract is to hedge the risk of variability in cash flow from transactions in foreign currencies due to changes in foreign exchange rate. The full value of a hedging derivative is classified as a non-current The valuation gains and losses on the derivatives contracts for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of 2018 2019 2020 Type of Valuation gain Valuation loss Other comprehensive income 1 Valuation gain Valuation loss Other comprehensive income 1 Valuation gain Valuation Loss Other comprehensive income 1 Interest rate swap ￦ 192 ￦ — ￦ (488) ￦ — ￦ 45 ￦ (963) ￦ — ￦ — ￦ (567) Currency swap 58,912 2,045 22,139 72,417 15,784 87,626 — 161,661 (113,175 ) Currency forwards 7,201 — — 4,858 — 4,858 — 2,049 — Total ￦ 66,305 ￦ 2,045 ￦ 21,651 ￦ 77,275 ￦ 15,829 ￦ 91,521 ￦ — ￦ 163,710 ￦ (113,742) 1 The amounts before adjustments of deferred income tax directly reflected in equity and allocation to the non-controlling The ineffective portion recognized in profit or loss on the cash flow hedge is valuation loss of ￦ ￦ ￦ The unsettled amount of derivative instruments for the years ended December 31, 2020 and 2019, are as follows: (i) Hedging instruments (In millions of Korean won and thousands of foreign currencies) 2019 Book value of hedging Changes in fair Currency Foreign Contract Assets Liabilities USD 1,574,068 ￦ 1,788,831 ￦ 30,175 ￦ 10,692 ￦ 49,480 JPY 80,000,000 827,292 28,401 9,404 15,396 Total ￦ 2,616,123 ￦ 58,576 ￦ 20,096 ￦ 64,876 (In millions of Korean won and thousands of 2020 Book value of hedging Changes in fair Currency Foreign Contract Assets Liabilities USD 1,768,912 ￦ 2,037,568 ￦ 2,111 ￦ 100,623 ￦ (136,852 ) JPY 46,000,000 488,924 5,573 13,839 (4,065 ) SGD 284,000 245,208 — 13,467 (13,611 ) Total ￦ 2,771,700 ￦ 7,684 ￦ 127,929 ￦ (154,528 ) (ii) Hedged item (In millions of Korean won) 2019 2020 Currency Book value of hedged Changes in fair Cash flow 1 Book value of hedged Changes in fair Cash flow 1 USD ￦ 1,822,477 ￦ (45,855 ) ￦ (5,214 ) ￦ 1,924,576 ￦ 133,978 ￦ 19,641 JPY 850,776 (14,841 ) (2,395 ) 484,960 4,228 (2,569 ) SGD — — — 233,510 13,611 2,707 Total ￦ 2,673,253 ￦ (60,696 ) ￦ (7,609 ) ￦ 2,643,046 ￦ 151,817 ￦ 19,779 1 The amounts after adjustments of deferred income tax directly reflected in equity. Details of financial liabilities at fair value through profit or loss as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Financial liabilities at fair value through profit or loss Derivative liabilities held for trading ￦ 38 ￦ 45 Conversion Rights and Redemption Rights — 2,637 Total ￦ 38 ￦ 2,682 The valuation gain and loss on financial liabilities at fair value through profit or loss for the years ended December 31, 2018, 2019 and 2020, are as follows: 2018 2019 2020 (In millions of Korean won) Valuation gain Valuation loss Valuation gain Valuation loss Valuation gain Valuation loss Derivative liabilities held for trading ￦ — ￦ 2,707 ￦ 78 ￦ 2,014 ￦ 10 ￦ 53 Conversion Rights and Redemption Rights — — — — 162 — Total ￦ — ￦ 2,707 ￦ 78 ￦ 2,014 ￦ 172 ￦ 53

Inventories

Inventories	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Inventories	8. Inventories Inventories as at December 31, 2019 and 2020, are as follows: December 31, 2019 December 31, 2020 (In millions of Korean won) Acquisition Valuation Book amount Acquisition cost Valuation allowance Book amount Merchandise ￦ 805,691 ￦ (144,438 ) ￦ 661,253 ￦ 650,856 ￦ (133,224 ) ￦ 517,632 Others 130,424 — 130,424 17,004 — 17,004 Total ￦ 936,115 ￦ (144,438 ) ￦ 791,677 ￦ 667,860 ￦ (133,224 ) ￦ 534,636 Cost of inventories recognized as expenses for year ended December 31, 2020, amounts to ￦ ￦ ￦ ￦ ￦ ￦ .

Other Assets and Liabilities

Other Assets and Liabilities	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Other Assets and Liabilities	9. Other Assets and Liabilities Other assets and liabilities as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Other assets Advance payments ￦ 179,475 ￦ 168,302 Prepaid expenses 84,768 66,578 Contract cost 1 1,849,243 1,804,948 Contract assets 1 557,041 586,438 Others 14,243 18,747 Less: Non-current (685,488 ) (768,661 ) Current ￦ 1,999,282 ￦ 1,876,352 Other liabilities Advances received 1 ￦ 333,342 ￦ 328,491 Withholdings 99,844 105,415 Unearned revenue 1 65,228 29,593 Lease liabilities 1,211,352 1,143,640 Contract liabilities 1 365,610 384,133 Others 23,298 21,597 Less: Non-current (1,030,117 ) (909,570 ) Current ￦ 1,068,557 ￦ 1,103,299 1 The amounts include adjustments arising from adoption of IFRS 15 (Note 26).

Assets Held for Sale

Assets Held for Sale	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Assets Held for Sale	10. Assets Held for Sale For the year ended December 31, 2020, the Group decided to sell certain real estate and classified it as assets held for sale. Details of assets held for sale are as follows: (In millions of Korean won) Amount Land ￦ 172 Buildings and Other 1,026 Total ￦ 1,198 Consideration for sale is expected to exceed the carrying amount of net assets, and as a result, no impairment was recognized for the segment classified as held for sale. During the prior period, the Group decided to sell some real estate, in which the amount of ￦ .

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Property and Equipment	11. Property and Equipmen t Changes in property and equipment for the years ended December 31, 2019 and 2020, are as follows: 2019 (In millions of Korean won) Land Buildings Machinery Others Construction- in-progress Total Acquisition cost ￦ 1,281,319 ￦ 3,873,074 ￦ 36,327,007 ￦ 1,981,646 ￦ 826,583 ￦ 44,289,629 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,865,389 ) (27,851,991 ) (1,503,265 ) (595 ) (31,221,372 ) Beginning, net 1,281,187 2,007,685 8,475,016 478,381 825,988 13,068,257 Changes in accounting policy 1 — (149 ) (12,947 ) (196,932 ) — (210,028 ) Acquisition and capital expenditure 338 4,523 205,359 64,072 3,419,136 3,693,428 Disposal and termination (1,352 ) (4,213 ) (76,457 ) (4,109 ) (1,362 ) (87,493 ) Depreciation — (134,350 ) (2,278,286 ) (89,940 ) — (2,502,576 ) Impairment — (32 ) (41,450 ) (1,751 ) (27 ) (43,260 ) Transfer in (out) 126,066 270,980 2,742,671 16,218 (3,217,044 ) (61,109 ) Transfer to investment properties (33,254 ) (8,081 ) — — — (41,335 ) Transfer to assets held-for-sale (89,330 ) (1,121 ) — — — (90,451 ) Others (21,474 ) 26,822 79,345 1,596 (26,423 ) 59,866 Ending, net ￦ 1,262,181 ￦ 2,162,064 ￦ 9,093,251 ￦ 267,535 ￦ 1,000,268 ￦ 13,785,299 Acquisition cost ￦ 1,262,313 ￦ 4,125,229 ￦ 37,654,635 ￦ 1,612,108 ￦ 1,001,171 ￦ 45,655,456 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,963,165 ) (28,561,384 ) (1,344,573 ) (903 ) (31,870,157 ) 1 With the application of IFRS 16, property and equipment were reclassified to right-of-use 2020 (In millions of Korean won) Land Buildings Machinery Others Construction- in-progress Total Acquisition cost ￦ 1,262,313 ￦ 4,125,229 ￦ 37,654,635 ￦ 1,612,108 ￦ 1,001,171 ￦ 45,655,456 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,963,165 ) (28,561,384 ) (1,344,573 ) (903 ) (31,870,157 ) Beginning, net 1,262,181 2,162,064 9,093,251 267,535 1,000,268 13,785,299 Acquisition and capital expenditure 25,156 7,249 112,085 47,669 2,959,690 3,151,849 Disposal and termination (1,756 ) (3,367 ) (69,401 ) (3,385 ) (1,027 ) (78,936 ) Depreciation — (135,646 ) (2,343,965 ) (91,164 ) — (2,570,775 ) Impairment — (36 ) (35,271 ) (44,468 ) — (79,775 ) Transfer in (out) 53,238 283,937 2,489,138 28,024 (2,899,197 ) (44,860 ) Transfer to investment properties 6,792 (8,848 ) — — — (2,056 ) Changes in scope of consolidation 56 494 225 43 — 818 Others (11,040 ) 2,175 68,921 1,398 (16,899 ) 44,555 Ending, net ￦ 1,334,627 ￦ 2,308,022 ￦ 9,314,983 ￦ 205,652 ￦ 1,042,835 ￦ 14,206,119 Acquisition cost ￦ 1,334,759 ￦ 4,402,691 ￦ 39,182,265 ￦ 1,619,822 ￦ 1,046,795 ￦ 47,586,332 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (2,094,669 ) (29,867,282 ) (1,414,170 ) (3,960 ) (33,380,213 ) Details of property and equipment provided as collateral as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 Carrying Secured Related line Related Secured party Land and Buildings ￦ 17,097 ￦ 18,705 Borrowings ￦ 4,347 Industrial Bank , K Bank, Inc. Others ￦ 45,851 ￦ 41,681 Borrowings ￦ 3,473 Shinhan (In millions of Korean won) December 31, 2020 Carrying Secured Related line Related Secured party Land and Buildings ￦ 11,644 ￦ 15,502 Borrowings ￦ 3,072 Industrial Korea Bank ￦ 4,142 ￦ 249 Deposits ￦ 249 K Bank, Inc. The borrowing costs capitalized for qualifying assets amount to ￦ ￦

Investment Properties

Investment Properties	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Investment Properties	12. Investment Propertie s Changes in investment properties for the years ended December 31, 2019 and 2020, are as follows: (In millions of Korean won) 2019 Land Buildings Construction- in-progress Total Acquisition cost ￦ 350,417 ￦ 1,168,379 ￦ 121 ￦ 1,518,917 Less: Accumulated depreciation (1,569 ) (426,264 ) — (427,833 ) Beginning, net ￦ 348,848 ￦ 742,115 ￦ 121 ￦ 1,091,084 Changes in accounting policy 1 — 46,666 — 46,666 Acquisition 148,511 103,774 1,781 254,066 Disposal and termination (285 ) (1,408 ) — (1,693 ) Depreciation — (65,178 ) — (65,178 ) Transfer from property and equipment 33,254 8,081 — 41,335 Transfer and others 23,268 (2,118 ) — 21,150 Ending, net ￦ 553,596 ￦ 831,932 ￦ 1,902 ￦ 1,387,430 Acquisition cost ￦ 555,164 ￦ 1,323,518 ￦ 1,902 ￦ 1,880,584 Less: Accumulated depreciation (including accumulated impairment loss and others) (1,568 ) (491,586 ) — (493,154 ) 1 With the application of IFRS 16, right-of-use-assets (In millions of Korean won) 2020 Land Buildings Construction- in-progress Total Acquisition cost ￦ 555,164 ￦ 1,323,518 ￦ 1,902 ￦ 1,880,584 Less: Accumulated depreciation (1,568 ) (491,586 ) — (493,154 ) Beginning, net ￦ 553,596 ￦ 831,932 ￦ 1,902 ￦ 1,387,430 Acquisition 11,723 7,096 34,243 53,062 Disposal and termination (1,536 ) (243 ) — (1,779 ) Depreciation — (64,531 ) — (64,531 ) Transfer from property and equipment (6,792 ) 8,848 — 2,056 Transfer and others (18,656 ) 469 10,402 (7,785 ) Ending, net ￦ 538,335 ￦ 783,571 ￦ 46,547 ￦ 1,368,453 Acquisition cost ￦ 539,903 ￦ 1,341,326 ￦ 46,547 ￦ 1,927,776 Less: Accumulated depreciation (including accumulated impairment loss and others) (1,568 ) (557,755 ) — (559,323 ) The fair value of investment properties is ￦ ￦ Rental income from investment properties is ￦ ￦ As at December 31, 2020, the Group (Lessor) has entered into a non-cancellable ￦ ￦ ￦ ￦ Details of investment properties provided as collateral as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 Carrying Secured Related Related Land and Buildings ￦ 854,874 ￦ 62,896 Deposits ￦ 56,831 Land and Buildings ￦ 1,915 ￦ 3,044 Borrowings ￦ 1,903 (In millions of Korean won) December 31, 2020 Carrying Secured Related Related Land and Buildings ￦ 790,414 ￦ 62,968 Deposits ￦ 56,247 Land and Buildings ￦ 2,861 ￦ 3,434 Borrowings ￦ 2,928

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Intangible Assets	13. Intangible Asset s Changes in intangible assets for the years ended December 31, 2019 and 2020, are as follows: 2019 (In millions of Korean won) Goodwill Development Software Frequency usage rights Others Total Acquisition cost 542,074 1,680,372 947,312 3,641,231 1,253,281 8,064,270 Less: Accumulated amortization (including accumulated impairment loss and others) (306,016 ) (1,345,262 ) (781,368 ) (1,484,731 ) (739,769 ) (4,657,146 ) Beginning, net ￦ 236,058 ￦ 335,110 ￦ 65,944 ￦ 2,156,500 ￦ 513,512 ￦ 3,407,124 Changes in accounting policy 1 — — — — (26,207 ) (26,207 ) Acquisition and capital expenditure — 47,903 30,965 — 99,826 178,694 Disposal and termination — (3,019 ) (1,267 ) (284 ) (11,109 ) (15,679 ) Amortization — (115,839 ) (68,222 ) (399,382 ) (77,262 ) (660,705 ) Impairment (605 ) (1,333 ) (1,807 ) (3,035 ) (55,118 ) (61,898 ) Others 117 9,812 11,768 142 (9,131 ) 12,708 Ending, net ￦ 235,570 ￦ 272,634 ￦ 137,381 ￦ 1,753,941 ￦ 434,511 ￦ 2,834,037 Acquisition cost 541,596 1,661,372 978,139 3,622,327 1,193,048 7,996,482 Less: Accumulated amortization (including accumulated impairment loss and others) (306,026 ) (1,388,738 ) (840,758 ) (1,868,386 ) (758,537 ) (5,162,445 ) 1 With the application of IFRS 16, intangible assets were reclassified to right-of-use 2020 (In millions of Korean won) Goodwill Development Software Frequency usage rights Others 1 Total Acquisition cost 541,596 1,661,372 978,139 3,622,327 1,193,048 7,996,482 Less: Accumulated amortization (including accumulated impairment loss and others) (306,026 ) (1,388,738 ) (840,758 ) (1,868,386 ) (758,537 ) (5,162,445 ) Beginning, net ￦ 235,570 ￦ 272,634 ￦ 137,381 ￦ 1,753,941 ￦ 434,511 ￦ 2,834,037 Acquisition and capital expenditure — 26,990 37,077 — 101,563 165,630 Disposal and termination — (1,849 ) (105 ) — (11,866 ) (13,820 ) Amortization — (104,938 ) (54,191 ) (399,348 ) (69,677 ) (628,154 ) Impairment — — (1,776 ) (193,194 ) (16,667 ) (211,637 ) Changes in scope of consolidation — 575 77 — 3,690 4,342 Others (5,485 ) 87,587 27,537 (736 ) (98,043 ) 10,860 Ending, net ￦ 230,085 ￦ 280,999 ￦ 146,000 ￦ 1,160,663 ￦ 343,511 ￦ 2,161,258 Acquisition cost 536,093 1,767,422 1,053,980 3,373,095 1,167,735 7,898,325 Less: Accumulated amortization (including accumulated impairment loss and others) (306,008 ) (1,486,423 ) (907,980 ) (2,212,432 ) (824,224 ) (5,737,067 ) 1 The carrying amount of membership rights and others, excluding goodwill, with indefinite useful life not subject to amortization is ￦ ￦ Due to the change in its business environment, the Group expects that it is no longer probable that its 28GHz frequency usage rights will be in the condition necessary for it to be capable of operating in the manner intended by management. As a result, the ￦ ￦ In relation to KT Skylife TV Co., Ltd., the Group recognized impairment loss of ￦ Goodwill is allocated to the Group’s cash-generating unit which is identified by operating segments. As at December 31, 2020, goodwill allocated to each cash-generating unit is as follows: (In millions of Korean won) Operating Segment Cash generating Unit Amount ICT 6 Mobile services 1 ￦ 65,057 Finance BC Card Co., Ltd. 2 41,234 Others GENIE Music Corporation (KT Music Corporation) 3 50,214 PlayD Co., Ltd. (N SEARCH MARKETING Co., Ltd.) 4 42,745 KT Telecop Co., Ltd. 5 15,418 KT MOS Bukbu Co., Ltd and others 15,417 Total ￦ 230,085 1 The recoverable amounts of mobile services business are calculated based on value-in 2 The recoverable amounts of BC Card Co., Ltd. are calculated based on value-in 3 The recoverable amount of GENIE Music Corporation (KT Music Corporation) is calculated based on fair value less cost to sell. 4 The recoverable amount of PlayD Co., Ltd. (N SEARCH MARKETING Co., Ltd.) is calculated based on fair value less cost to sell. 5 The recoverable amounts of KT Telecop Co., Ltd. are calculated based on value-in 6 The Group performed its impairment assessment for long-lived assets attributed to the Information and Communication Technology (“ICT”) reporting segment, which includes the Cash-Generating Units of Mobile, Fixed line, and Corporate Services (the “CGUs”). The Group compared the carrying value of each CGU to the estimated recoverable amount. The recoverable amounts of ICT reporting segment are calculated based on value-in

Investments in Associates and J

Investments in Associates and Joint Ventures	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Investments in Associates and Joint Ventures	14. Investments in Associates and Joint Venture s Details of associates as at December 31, 2019 and 2020, are as follows: Percentage of ownership (%) Location Closing month 2019 2020 Korea Information & Technology Fund 33.3 % 33.3 % Korea December 31, 2019, KT-IBKC 1 50.0 % 50.0 % Korea December 31, 2019, KT-CKP 49.7 % — Korea December 31, 2019, K Bank Inc. 10.0 % 34.0 % Korea December 31, 2019, Hyundai Robotics Co., Ltd. 2 — 10.0 % Korea December 31, 2019, 1 At the end of the reporting period, although the Group owns 50% ownership, the equity method of accounting has been applied as the Group, which is a limited partner of the investment fund, because the Group cannot participate in determining the operating and financial policies. 2 At the end of the reporting period, although the Group has less than 20% ownership in ordinary share, this entity is included in investments in associates as the Group has a significant influence in determining the operating and financial policies. Changes in investments in associates and joint ventures for the years ended December 31, 2019 and 2020, are as follows: 2019 (In millions of Korean won) Beginning Acquisition (Disposal) Share of net profit 1 Others Ending Korea Information & Technology Fund ￦ 148,255 ￦ — ￦ 17,956 ￦ (2,236 ) ￦ 163,975 KT-SB 4,470 (4,470 ) — — — KT-IBKC 9,961 3,750 389 — 14,100 KT-CKP 281 (174 ) 27 — 134 K Bank Inc. 52,655 21,782 (28,865 ) (414 ) 45,158 Others 1 56,785 (7,867 ) 7,241 (11,866 ) 44,293 ￦ 272,407 ￦ 13,021 ￦ (3,252 ) ￦ (14,516 ) ￦ 267,660 2020 (In millions of Korean won) Beginning Acquisition (Disposal) Share of net profit 1 Others Ending Korea Information & Technology Fund ￦ 163,975 ￦ — ￦ 12,205 ￦ (6,025 ) ￦ 170,155 KT-IBKC 14,100 — 2,090 — 16,190 KT-CKP 134 (134 ) — — — K Bank Inc. 45,158 195,011 (30,209 ) (1,688 ) 208,272 Hyundai Robotics Co., Ltd. — 50,000 (64 ) 1,000 50,936 Others 1 44,293 28,400 34,298 5,337 112,328 ￦ 267,660 ￦ 273,277 ￦ 18,320 ￦ (1,376 ) ￦ 557,881 1 KT investment Co., Ltd., a subsidiary of the Group, recognized its share in net profit from associates and joint ventures as operating revenue and expense. These include its share in net gain from associates and joint ventures of ￦ ￦ ￦ Summarized financial information of associates and joint ventures as at and for the years ended December 31, 2019 and 2020, is as follows: (In millions of Korean won) December 31, 2019 Current Non-current assets Current Non-current liabilities Korea Information & Technology Fund ￦ 113,233 ￦ 378,691 ￦ — ￦ — KT-IBKC 28,200 — — — KT-CKP 3 267 — — K Bank Inc. 2,480,065 78,566 2,350,375 3,784 (In millions of Korean won) December 31, 2020 Current Non-current assets Current Non-current liabilities Korea Information & Technology Fund ￦ 107,652 ￦ 402,812 ￦ — ￦ — KT-IBKC Future Investment Fund 1 32,379 — — — K Bank Inc. 4,255,620 74,193 3,752,838 88,155 Hyundai Robotics Co., Ltd. 315,886 125,619 80,615 59,324 (In millions of Korean won) 2019 Operating Profit (loss) Other Total Dividends Korea Information & Technology Fund ￦ 70,577 ￦ 53,867 ￦ 6,132 ￦ 59,999 ￦ 4,280 KT-IBKC Future Investment Fund 1 1,694 779 — 779 — KT-CKP New Media Investment Fund 56 55 — 55 — K Bank Inc. 92,720 (100,773 ) (23 ) (100,796 ) — (In millions of Korean won) 2020 Operating Profit (loss) Other Total Dividends Korea Information & Technology Fund ￦ 54,473 ￦ 36,615 ￦ 9,647 ￦ 46,262 ￦ 9,241 KT-IBKC 6,551 4,179 — 4,179 — K Bank Inc. 80,301 (105,374 ) (1,126 ) (106,500 ) — Hyundai Robotics Co., Ltd. 195,311 (642 ) 11,573 10,931 — Details of a reconciliation of the summarized financial information to the carrying amount of interests in the associates and joint ventures as at and for the years end December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 Net assets (a) Percentage of Share in (c)=(a)x(b) Intercompany Book (c)+(d) Korea Information & Technology Fund ￦ 491,924 33.30 % ￦ 163,975 ￦ — ￦ 163,975 KT-IBKC Future Investment Fund 1 28,200 50.00 % 14,100 — 14,100 KT-CKP 270 49.70 % 134 — 134 K Bank Inc. 1 204,472 10.00 % 45,158 — 45,158 1 12.1% of non-voting (In millions of Korean won) December 31, 2020 Net assets (a) Percentage of Share in net (c)=(a)x(b) Intercompany Book amount (c)+(d) Korea Information & Technology Fund ￦ 510,464 33.30 % ￦ 170,155 ￦ — ￦ 170,155 KT-IBKC 32,379 50.00 % 16,190 — 16,190 K Bank Inc. 1 488,819 34.00 % 166,198 42,074 208,272 Hyundai Robotics Co., Ltd. 301,566 10.00 % 30,157 20,779 50,936 1 12.1% of non-voting Due to discontinuance of equity method of accounting, the Group has not recognized loss from associates and joint ventures of ￦ ￦ ￦ ￦

Trade and Other Payables

Trade and Other Payables	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Trade and Other Payables	15. Trade and Other Payable s Details of trade and other payables as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, December 31, Current liabilities Trade payables ￦ 1,304,795 ￦ 1,239,717 Other payables 6,292,683 4,970,382 Total ￦ 7,597,478 ￦ 6,210,099 Non-current Trade payables ￦ 1,733 ￦ 1,528 Other payables 1,080,487 806,012 Total ￦ 1,082,220 ￦ 807,540 Details of other payables as at December 31, 2019 and 2020 are as follows: (In millions of Korean won) December 31, December 31, Non-trade 1 ￦ 5,275,224 ￦ 3,841,227 Accrued expenses 987,624 933,978 Operating deposits 910,045 803,904 Others 200,277 197,285 Less: non-current (1,080,487 ) (806,012 ) Current ￦ 6,292,683 ￦ 4,970,382 1 Settlement payables of BC Card Co., Ltd., a subsidiary of the Group, of ￦ ￦

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Borrowings	16. Borrowing s Details of borrowings as at December 31, 2019 and 2020, are as follows: Debentures (In millions of Korean won and thousands of foreign currencies) December 31, 2019 December 31, 2020 Type Maturity Annual interest Foreign Korean Foreign Korean MTNP notes 1 Sept. 7, 2034 6.50% USD 100,000 ￦ 115,780 USD 100,000 ￦ 108,800 MTNP notes July 18, 2026 2.50% USD 400,000 463,120 USD 400,000 435,200 MTNP notes Aug. 7, 2022 2.63% USD 400,000 463,120 USD 400,000 435,200 FR notes Aug. 20, 2020 — USD 200,000 231,560 — — FR notes 2 Aug. 20, 2023 LIBOR(3M)+0.900% USD 100,000 115,780 USD 100,000 108,800 MTNP notes July 6, 2020 — JPY 4,000,000 42,539 — — MTNP notes July 6, 2021 0.38% JPY 16,000,000 170,155 JPY 16,000,000 168,682 MTNP notes Nov. 13, 2020 — JPY 30,000,000 319,041 — — MTNP notes July 19, 2022 0.22% JPY 29,600,000 314,787 JPY 29,600,000 312,061 MTNP notes July 19, 2024 0.33% JPY 400,000 4,254 JPY 400,000 4,217 FR notes 2 Nov. 1, 2024 LIBOR(3M)+0.980% USD 350,000 405,230 USD 350,000 380,800 FR notes 2 June 19, 2023 SOR(6M)+0.500% — — SGD 284,000 233,510 MTNP notes Sept. 1, 2025 1.00% — — USD 400,000 435,200 The 180-2rd Apr. 26, 2021 4.71% — 380,000 — 380,000 The 181-3rd Aug. 26, 2021 4.09% — 250,000 — 250,000 The 182-2nd Oct. 28, 2021 4.31% — 100,000 — 100,000 The 183-2nd Dec. 22, 2021 4.09% — 90,000 — 90,000 The 183-3rd Dec. 22, 2031 4.27% — 160,000 — 160,000 The 184-2nd Apr. 10, 2023 2.95% — 190,000 — 190,000 The 184-3rd Apr. 10, 2033 3.17% — 100,000 — 100,000 The 185-2nd Sept. 16, 2020 — — 300,000 — — The 186-3rd June 26, 2024 3.42% — 110,000 — 110,000 The 186-4th June 26, 2024 3.70% — 100,000 — 100,000 The 187-3rd Sept. 2, 2024 3.31% — 170,000 — 170,000 The 187-4th Sept. 2, 2034 3.55% — 100,000 — 100,000 The 188-1st Jan. 29, 2020 — — 160,000 — — The 188-2nd Jan. 29, 2025 2.45% — 240,000 — 240,000 The 188-3rd Jan. 29, 2035 2.71% — 50,000 — 50,000 The 189-2nd Jan. 28, 2021 1.95% — 130,000 — 130,000 The 189-3rd Jan. 28, 2026 2.20% — 100,000 — 100,000 The 189-4th Jan. 28, 2036 2.35% — 70,000 — 70,000 The 190-1st Jan. 29, 2021 2.55% — 110,000 — 110,000 The 190-2nd Jan. 30, 2023 2.75% — 150,000 — 150,000 The 190-3rd Jan. 30, 2028 2.95% — 170,000 — 170,000 The 190-4th Jan. 30, 2038 2.93% — 70,000 — 70,000 The 191-1st Jan. 14, 2022 2.05% — 220,000 — 220,000 The 191-2nd Jan. 15, 2024 2.09% — 80,000 — 80,000 The 191-3rd Jan. 15, 2029 2.16% — 110,000 — 110,000 The 191-4th Jan. 14, 2039 2.21% — 90,000 — 90,000 The 192-1st Oct. 11, 2022 1.55% — 340,000 — 340,000 The 192-2nd Oct. 11, 2024 1.58% — 100,000 — 100,000 The 192-3rd Oct. 11, 2029 1.62% — 50,000 — 50,000 The 192-4th Oct. 11, 2039 1.67% — 110,000 — 110,000 The 193-1st June 16, 2023 1.17% — — — 150,000 The 193-2nd June 17, 2025 1.43% — — — 70,000 The 193-3rd June 17, 2030 1.61% — — — 20,000 The 193-4th June 15, 2040 1.71% — — — 60,000 The 148th Won-denominated June 23, 2023 1.51% — — — 100,000 Subtotal 7,045,366 6,962,470 Less: Current portion (1,052,032 ) (1,228,283 ) Discount on bonds (20,780 ) (19,847 ) Total ￦ 5,972,554 ￦ 5,714,340 1 As at December 31, 2020, the Controlling Company has outstanding notes in the amount of USD 100 million with fixed interest rates under Medium Term Note Program (“MTNP”) registered in the Singapore Stock Exchange, which allowed issuance of notes of up to USD 2,000 million. However, the MTN Program has been suspended since 2007. 2 Libor (3M) and SOR (6M) are approximately 0.238% and 0.185%, respectively as at December 31, 2020. Convertible bonds (In millions of Korean won and thousands of foreign currencies) December 31, 2019 Type Issuance date Maturity Annual interest rate December 31, December 31, The 1st CB(Private) 1,2 Jun. 5, 2020 Jun. 5, 2025 0.00 % ￦ — ￦ 8,000 Redemption premium — 2,267 Bond discount issuance — (4,644 ) Subtotal ￦ — ￦ 5,623 Current portion ￦ — ￦ — Total ￦ — ￦ 5,623 1 Common shares of Storywiz are subject to conversion (appraisal period: June 5, 2021~ May 4, 2025). 2 Nominal interest rate and maturity yield is approximately 0% and 5% and will be settled on maturity Short-term borrowings (In millions of Korean won) December 31, December 31, Type Financial institution Annual interest rates Operational NongHyup Bank 1.740% ~ 2.360% ￦ 15,000 ￦ 40,189 Shinhan Bank 2.460% ~ 2.960% 57,500 22,500 Shinhan Bank CD91+1.431% — 10,000 Woori Bank 3.57% — 1,900 Korea Development Bank 3.34% 10,000 10,000 SooHyup Bank — 1,000 — Industrial Bank of Korea 1.74% — 200 Hana Bank 4.20% — 11,000 Total ￦ 83,500 ￦ 95,789 Long-term borrowings (In millions of Korean won and thousands of foreign currencies) December 31, 2019 December 31, 2020 Financial institution Type Annual interest rates Foreign currency Korean won Foreign currency Korean won Export-Import Bank of Korea Inter-Korean Cooperation Fund 1 1.50% — ￦ 3,454 — ￦ 2,961 Industrial Bank of Korea General loans 2.98% — 6,000 — 6,000 Shinhan Bank General loans 1.94% — 5,000 — 5,000 Facility loans 2 LIBOR(3M)+1.340% USD 25,918 30,008 USD 25,918 28,199 General loans 2 LIBOR(3M)+1.650% USD 3,000 3,473 USD 8,910 9,694 General loans 2 LIBOR(3M)+2.130% — — USD 25,000 27,200 CA-CIB Long-term CP 1.26% — — — 100,000 NongHyup Bank Facility loans 2.00% — 79 — 54 Korea Development Bank General loans 3.02% — 10,000 — 10,000 General loans 3.31% — 30,000 — 30,000 Others Kookmin Bank and other 2 LIBOR(3M)+1.850% USD 87,940 101,816 USD 48,855 53,155 — — 950 — — Subtotal ￦ 190,780 ￦ 272,263 Less: Current portion ￦ (50,192) ￦ (94,042) Total ￦ 140,588 ￦ 178,221 1 The above Inter-Korean Cooperation Fund is repayable in installments over 13 years after a seven-year grace period. 2 LIBOR(3M) is approximately 0.238% as at December 31, 2020. Repayment schedule of the Group’s borrowings including the portion of current liabilities as at December 31, 2020 is as follows: (In millions of Korean won) Debentures Borrowings Total In local In foreign Sub- total In local In foreign Sub- total Jan 1, 2021 ~ Dec 31, 2021 ￦ 1,060,000 ￦ 168,682 ￦ 1,228,682 ￦ 147,307 ￦ 42,524 ￦ 189,831 ￦ 1,418,513 Jan 1, 2022 ~ Dec 31, 2022 560,000 747,261 1,307,261 518 38,830 39,348 1,346,609 Jan 1, 2023 ~ Dec 31, 2023 590,000 342,310 932,310 100,500 36,894 137,394 1,069,704 Jan 1, 2024 ~ Dec 31, 2024 460,000 385,017 845,017 493 — 493 845,510 After Jan. 1, 2025 1,678,000 979,200 2,657,200 986 — 986 2,658,186 ￦ 4,348,000 ￦ 2,622,470 ￦ 6,970,470 ￦ 249,804 ￦ 118,248 ￦ 368,052 ￦ 7,338,522

Provisions

Provisions	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Provisions	17. Provision s Changes in provisions for the years ended December 31, 2019 and 2020, are as follows: 2019 (In millions of Korean won) Litigation Restoration cost Others Total Beginning balance ￦ 58,760 ￦ 118,828 ￦ 104,288 ￦ 281,876 Increase (Transfer) 42,684 6,591 17,328 66,603 Usage (35,640 ) (5,394 ) (15,851 ) (56,885 ) Reversal (1,563 ) (6,736 ) (29,133 ) (37,432 ) Ending balance ￦ 64,241 ￦ 113,289 ￦ 76,632 ￦ 254,162 Current ￦ 64,241 ￦ 37,906 ￦ 73,465 ￦ 175,612 Non-current — 75,383 3,167 78,550 2020 (In millions of Korean won) Litigation Restoration cost Others Total Beginning balance ￦ 64,241 ￦ 113,289 ￦ 76,632 ￦ 254,162 Increase (Transfer) 17,064 (1,933 ) 17,873 33,004 Usage (3,948 ) (2,990 ) (2,266 ) (9,204 ) Reversal (857 ) (3,023 ) (23,212 ) (27,092 ) Changes in scope of consolidation — 424 898 1,322 Ending balance ￦ 76,500 ￦ 105,767 ￦ 69,925 ￦ 252,192 Current ￦ 76,500 ￦ 22,343 ￦ 67,147 ￦ 165,990 Non-current — 83,424 2,778 86,202

Net Defined Benefit Liabilities

Net Defined Benefit Liabilities	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Net Defined Benefit Liabilities	18. Net Defined Benefit Liabilitie s The amounts recognized in the statements of financial position are determined as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Present value of defined benefit obligations ￦ 2,427,351 ￦ 2,556,712 Fair value of plan assets (2,069,710 ) (2,189,375 ) Liabilities ￦ 365,663 ￦ 378,087 Assets in the statement of financial position ￦ 8,022 ￦ 10,750 Changes in the defined benefit obligations for the years ended December 31, 2019 and 2020, are as follows: (In millions of Korean won) 2019 2020 Beginning ￦ 2,201,876 ￦ 2,427,351 Current service cost 243,598 248,047 Interest expense 47,403 45,083 Benefit paid (100,663 ) (258,866 ) Changes due to settlements of plan 910 1,075 Remeasurements: Actuarial gains and losses arising from changes in demographic assumptions 39 5,191 Actuarial gains and losses arising from changes in financial assumptions 11,773 17,077 Actuarial gains and losses arising from experience adjustments 19,465 57,703 Changes in scope of consolidation 2,950 14,051 Ending ￦ 2,427,351 ￦ 2,556,712 Changes in the fair value of plan assets for the years ended December 31, 2019 and 2020, are as follows: (In millions of Korean won) 2019 2020 Beginning ￦ 1,643,046 ￦ 2,069,710 Interest income 35,386 38,590 Remeasurements: Return on plan assets (excluding amounts included in interest income) (2,537 ) 2,589 Benefits paid (87,119 ) (213,953 ) Employer contributions 476,916 284,243 Changes in scope of consolidation 4,018 8,196 Ending ￦ 2,069,710 ￦ 2,189,375 Amounts recognized in the ‘Operating expenses’ of the consolidated statements of operations for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Current service cost ￦ 225,667 ￦ 243,598 ￦ 248,047 Net Interest cost 10,458 12,017 6,494 Past service cost 9,801 910 1,075 Transfer out (13,881 ) (16,215 ) (16,514 ) Total expenses ￦ 232,045 ￦ 240,310 ￦ 239,102 Principal actuarial assumptions used are as follows: December 31, December 31, December 31, Discount rate 2.32 % 1.97 % 1.93 % Future salary increase 5.08 % 4.92 % 4.88 % The sensitivity of the defined benefit obligations as at December 31, 2020, to changes in the principal assumptions is: (In percentage, in millions of Korean won) Effect on defined benefit obligation Changes in Increase in Decrease in Discount rate 0.5% point ￦ ￦ 93,254 Salary growth rate 0.5% point 85,344 (79,970 ) A decrease in corporate bond yields will increase plan liabilities, although this will be partially offset by an increase in the value of the plans’ bond holdings. The above sensitivity analyses are based on an assumption while holding all other assumptions constant. In practice, this is unlikely to occur, and changes in some of the assumptions may be correlated. The sensitivity of the defined benefit obligation to changes in principal actuarial assumptions is calculated using the projected unit credit method, the same method applied when calculating the defined benefit obligations recognized on the statement of financial position. The Group actively monitors how the duration and the expected yield of the investments match the expected cash outflows arising from the pension obligations. Expected contributions to post-employment benefit plans for the year ending December 31, 2021, are ￦ The expected maturity analysis of undiscounted pension benefits as at December 31, 2020, is as follows: (In millions of Korean won) Less than 1 year Between Between 2-5 Over 5 years Total Pension benefits ￦ 232,550 ￦ 271,366 ￦ 794,840 ￦ 2,284,517 ￦ 3,583,273 The weighted average duration of the defined benefit obligations is 6.7 years.

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Defined Contribution Plan	19. Defined Contribution Plan Recognized expense related to the defined contribution plan for the year ended December 31, 2020, is ￦ ￦ ￦

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Commitments and Contingencies	20. Commitments and Contingencie s As at December 31, 2020, major commitments with local financial institutions are as follows: (In millions of Korean won and Financial institution Currency Limit Used Bank overdraft Kookmin Bank and others KRW 1,502,000 — Inter-Korean Cooperation Fund Export-Import Bank of Korea KRW 37,700 2,714 Insurance for Economic Cooperation project Export-Import Bank of Korea KRW 3,240 1,732 Collateralized loan on electronic accounts receivable-trade Kookmin Bank and others KRW 522,849 23,475 Plus electronic notes payable Industrial Bank of Korea KRW 50,000 331 Loans for working capital Korea Development Bank and others KRW 243,593 152,243 Facility loans Shinhan Bank and others KRW 100,123 55 Kookmin Bank and others USD 212,000 48,855 Derivatives transaction limit Korea Development Bank KRW 100,000 22,027 Woori Bank and others USD 69,054 44,616 Total KRW 2,559,505 202,577 USD 281,054 93,471 As at December 31, 2020, guarantees received from financial institutions are as follows: (In millions of Korean won and Financial institution Currency Limit Performance guarantee Seoul Guarantee Insurance and others KRW 208,386 Performance guarantee Korea Development Bank and others USD 8,569 Guarantee for import letters of credit Industrial Bank of Korea and others USD 5,000 Guarantee for payment in won currency Shinhan Bank and others KRW 70,962 Refund guarantee for advances received Korea Development Bank USD 8,536 Guarantee for payment in foreign currency KEB Hana Bank and others USD 40,840 Comprehensive credit line KEB Hana Bank and others KRW 41,100 Comprehensive credit line KEB Hana Bank and others USD 8,700 Bid guarantee KEB Hana Bank USD 400 Bid guarantee Korea Software Financial KRW 80,246 Performance guarantee /warranty guarantee KRW 393,019 Guarantee for advance payments/others KRW 388,656 Warranty guarantee Seoul Guarantee Insurance KRW 1,305 Performance guarantee KRW 9,690 Guarantees for licensing KRW 7,748 Guarantees for depositions KRW 3,792 Merchant business guarantee insurance KRW 237 Total KRW 1,205,141 USD 72,045 As at December 31, 2020, guarantees provided by the Group to a third party, are as follows: (In millions of Korean won) Subject to payment Creditor Limit Used Period KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) 1 Gasan Solar Power Plant Inc. Shinhan Bank 4,700 1,371 Jan. 08, 2025 KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) 1 SPP Inc. Suhyup Bank 3,250 932 Feb. 16, 2024 KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) 1 Korea Cell Inc. Suhyup Bank 3,250 880 Feb. 16, 2024 KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) 1 San-Ya Association Corporation Suhyup Bank 3,250 888 Feb. 16, 2024 KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) 1 Ciocanesti Korea Co., Ltd. NH Investment & 7,600 7,600 Jun. 8, 2017 KT Hitel Co., Ltd. Shinhan Bank Cash payers 700 — Apr. 17, 2020 ~ Apr. 16, 2021 Nasmedia Co., Ltd. Stockholders Association Members Korea Securities 5,654 2,735 — 1 According to the above payment guarantee, KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.), a subsidiary of the Group, will have an obligation of repayment if the principal borrower does not repay the borrowing. The Controlling Company is jointly and severally obligated with KT Sat Co., Ltd. to pay KT Sat Co., Ltd.’s liabilities incurred prior to spin-off. ￦ For the years ended December 31, 2019 and 2020, the Group made agreements with the Securitization Specialty Companies (2020: First 5G 49 th th rd th As at December 31, 2020, the Group is a defendant in 195 lawsuits with the total claimed amount of ￦ ￦ ￦ ￦ According to the financial and other covenants included in certain debentures and borrowings, the Group is required to maintain certain financial ratios such as debt-to-equity As at December 31, 2020, the Group participates in Algerie Sidi Abdela new town development consortium (percentage of ownership: 2.5%) and has joint liability with other consortium participants. As at December 31, 2020, contract amount of property and equipment acquisition agreement made but not yet recognized amounts to ￦ ￦

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Leases	21. Lease s Information on leases when the Group is a lessee is as follows: Information on leases when the Group is a lessor is provided in Note 12. (i) Amounts recognized in the consolidated statement of financial position The consolidated statement of financial position shows the following amounts relating to leases: (In millions of Korean won) December 31, December 31, Right-of-use Property and building ￦ 1,020,619 ￦ 1,073,207 Machinery and track facilities 140,296 42,127 Others 107,414 101,845 Total ￦ 1,268,329 ￦ 1,217,179 Investment property (buildings) 50,010 19,456 (In millions of Korean won) December 31, December 31, Lease liabilities 1 Current ￦ 392,433 ￦ 345,224 Non-Current 818,919 798,416 Total ￦ 1,211,352 ￦ 1,143,640 1 Included in the line items ‘Other current liabilities and other non-current For the year ended December 31, 2020, right-of-use ￦ (ii) Amounts recognized in the consolidated statements of profit or loss The consolidated statements of profit or loss show the following amounts relating to leases: (In millions of Korean won) December 31, December 31, Depreciation of Right-of-use Property and building ￦ 300,773 ￦ 290,168 Machinery and track facilities 89,452 58,419 Others 52,402 55,588 Total ￦ 442,627 ￦ 404,175 Depreciation of Investment Properties ￦ 21,809 ￦ 19,113 Interest expense relating to lease liabilities 55,001 44,091 Expense relating to short-term leases 14,718 10,998 Expense relating to leases of low-value 26,575 25,894 Expense relating to variable lease payments not included in lease liabilities 5,993 8,096 The total cash outflow for leases for December 31, 2020, was ￦ ￦ .

Share Capital

Share Capital	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Share Capital	22. Share Capita l As at December 31, 2019 and 2020, the Group’s number of authorized shares is one billion. December 31, 2019 December 31, 2020 Number of issued shares Par value per share (Korean won) Ordinary (in millions of Korean won) Number of issued Par value per share (Korean won) Ordinary (in millions of Korean won) Ordinary shares 1 261,111,808 ￦ ￦ 261,111,808 ￦ ￦ 1 The Group retired 51,787,959 treasury shares against retained earnings. Therefore, the ordinary shares amount differs from the amount resulting from multiplying the number of shares issued.

Retained Earnings

Retained Earnings	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Retained Earnings	23. Retained Earnings Details of retained earnings as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, December 31, Legal reserve 1 ￦ 782,249 ￦ 782,249 Voluntary reserves 2 4,651,362 4,651,362 Unappropriated retained earnings 6,157,305 6,721,809 Total ￦ 11,590,916 ￦ 12,155,420 1 The Commercial Code of the Republic of Korea requires the Controlling Company to appropriate, as a legal reserve, an amount equal to a minimum of 10% of cash dividends paid until such reserve equals 50% of its issued share capital. The reserve is not available for the payment of cash dividends, but may be transferred to share capital with the approval of the Controlling Company’s Board of Directors or used to reduce accumulated deficit, if any, with the ratification of the Controlling Company’s majority shareholders. 2 The provision of research and development of human resources is separately accumulated with tax reserve fund during earned surplus disposal by Tax Reduction and Exemption Control Act of Korea. Reversal of this provision can be paid out as dividends according to related tax law.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income and Other Components of Equity	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Accumulated Other Comprehensive Income and Other Components of Equity	24. Accumulated Other Comprehensive Income and Other Components of Equit y As at December 31, 2019 and 2020, the details of the Controlling Company’s accumulated other comprehensive income are as follows: (In millions of Korean won) December 31, December 31, Changes in investments in associates and joint ventures ￦ 1,556 ￦ 16,257 Loss on derivatives valuation (7,624 ) 19,809 Gain on valuation of financial assets at fair value through other comprehensive income 211,573 61,438 Exchange differences on translation for foreign operations (10,571 ) (11,453 ) Total ￦ 194,934 ￦ 86,051 Changes in accumulated other comprehensive income for the years ended December 31, 2019 and 2020, are as follows: 2019 (In millions of Korean won) Beginning Increase/ decrease Reclassification to gain or loss Ending Changes in investments in associates and joint ventures ￦ (871 ) ￦ 2,427 ￦ — ￦ 1,556 Gain or loss on derivatives valuation (30,474 ) 67,534 (44,684 ) (7,624 ) Gain on valuation of financial assets at fair value through other comprehensive income 96,704 114,869 — 211,573 Exchange differences on translation for foreign operations (15,201 ) 4,630 — (10,571 ) Total ￦ 50,158 ￦ 189,460 ￦ (44,684 ) ￦ 194,934 (In millions of Korean won) 2020 Beginning Increase/ decrease Reclassification to gain or loss Ending Changes in investments in associates and joint ventures ￦ 1,556 ￦ 14,701 ￦ — ￦ 16,257 Gain or loss on derivatives valuation (7,624 ) (83,998 ) 111,431 19,809 Gain on valuation of financial assets at fair value through other comprehensive income 211,573 (150,135 ) — 61,438 Exchange differences on translation for foreign operations (10,571 ) (882 ) — (11,453 ) Total ￦ 194,934 ￦ ) ￦ 111,431 ￦ 86,051 The Group’s other components of equity as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, December 31, Treasury stock 1 ￦ ￦ Gain or loss on disposal of treasury stock 2 1,229 (17,579 ) Share-based payments 7,769 5,901 Others 3 (353,243 ) (340,882 ) Total ￦ ) ￦ ) 1 During the year ended December 31, 2020, the Group acquired 4,550,000 treasury shares and granted 1,150,580 treasury shares as share-based payment. 2 The amount directly reflected in equity is ￦7,288 million (2019: ￦603 million) for the year ended December 31, 2020. 3 Profit or loss incurred from transactions with non-controlling As at December 31, 2019 and 2020 December 31, December 31, Number of shares (in shares) 15,870,258 19,269,678 Amounts (In millions of Korean won) ￦ 825,838 ￦ 882,224 Treasury stock is expected to be used for the stock compensation for the Group’s directors and employees and other purposes.

Share-based Payments

Share-based Payments	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Share-based Payments	25. Share-based Payments Details of share-based payments as at December 31, 2020, are as follows: (In share) 14th grant Grant date June 16, 2020 Grantee CEOs, internal directors, external directors, executives Vesting conditions Service condition: 1 year Non-market Fair value per option (in Korean won) ￦ Total compensation costs (in Korean won) ￦ Estimated exercise date (exercise date) During 2021 Valuation method Fair value method (In share) Employee wage negotiation Grant date September 21, 2020 Grantee All employees Vesting conditions Current employees as of September 21, 2020 Fair value per option (in Korean won) ￦ Total compensation costs (in Korean won) ￦ Estimated exercise date (exercise date) December 22, 2020 Valuation method Fair value method Changes in the number of stock options and the weighted-average exercise price as at December 31, 2019 and 2020, are as follows: 2019 Beginning Grant Expired Exercised 1 Ending Number of 12th grant 353,325 — 256,543 96,782 — — 13th grant — 372,023 — — 372,023 — Total 353,325 372,023 256,543 96,782 372,023 — 2020 Beginning Grant Expired Exercised 1 Ending Number of 13th grant 372,023 — 241,548 130,475 — — 14th grant — 398,856 — — 398,856 — Employee wage negotiation — 1,020,105 — 1,020,105 — — Total 372,023 1,418,961 241,548 1,150,580 398,856 — 1 The weighted average price of ordinary shares at the time of exercise in 2020 was ￦ ￦

Revenue from Contracts with Cus

Revenue from Contracts with Customers and Relevant Contract Assets and Liabilities	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Revenue from Contracts with Customers and Relevant Contract Assets and Liabilities	26. Revenue from Contracts with Customers and Relevant Contract Assets and Liabilities The Group has recognized the following amounts relating to revenue in the Consolidated Statements of Operations: (In millions of Korean won) 2018 2019 2020 Revenue from contracts with customers ￦ 23,012,257 ￦ 24,441,122 ￦ 23,895,631 Revenue from other sources 423,793 458,067 545,016 Total revenue ￦ 23,436,050 ￦ 24,899,189 ￦ 24,440,647 Operating revenues for the years ended December 31, 2018, 2019 and 2020 are as follows: (In millions of Korean won) 2018 2019 2020 Mobile services ￦ 6,827,685 ￦ 6,795,124 ￦ 6,805,218 Fixed-line services 4,869,253 4,866,698 4,827,015 Fixed-line and VoIP telephone services 1,708,319 1,578,546 1,463,553 Broadband Internet access services 2,112,763 2,177,447 2,256,188 Data communication services 1,048,171 1,110,705 1,107,274 Media and content 2,261,808 2,516,256 2,637,691 Financial services 3,444,917 3,641,655 3,493,920 Sale of goods 3,288,911 4,194,168 3,593,127 Others 2,743,476 2,885,288 3,083,676 Total ￦ 23,436,050 ￦ 24,899,189 ￦ 24,440,647 Mobile and fixed-line service Telecommunication service revenues include mobile and fixed-line(e.g., fixed-line and VoIP telephone, broadband internet access services and data communication services). These services represent a series of distinct services that are considered a separate performance obligations. Service revenue is recognized when services are provided, based upon either usage (e.g., minutes of traffic/bytes of data processed) or period of time (e.g., monthly service fees). Media and content services Revenue from media and content services primarily consists of installation fees and basic monthly charges of IPTV and satellite TV services, as well as revenue from digital content distribution, digital music streaming and downloading. Media and contents services revenue are recognized when services are provided, based upon either usage or period of time. Financial services Financial services primarily include commissions for merchant fees paid by merchants to credit card companies for processing transactions. Revenue from the commission is recognized when the service obligation is performed. Sale of goods Revenue from sale of goods, primarily handsets related to our mobile services is recognized when a performance obligation is satisfied by transferring promised goods to customers. The contract assets and liabilities recognized in relation to the revenues from contracts with customers are as follows: (In millions of Korean won) December 31, December 31, Contract assets 1 ￦ 655,329 ￦ 672,672 Contract liabilities 1 413,442 413,707 Deferred revenue 2 ￦ 92,557 ￦ 89,694 1 The Group recognized contract assets of ￦ ￦ ￦ ￦ 2 Deferred revenue recognized relating to government grant is excluded. The contract costs recognized as assets are as follows: (In millions of Korean won) December 31, December 31, Incremental cost of contract establishment ￦ 1,764,009 ￦ 1,726,191 Cost of Contract performance 85,234 78,757 As at December 31, 2020, the Group recognized ￦ ￦ The recognized revenue arising from carried-forward contract liabilities from prior year is as follows: (In millions of Korean won) 2018 2019 2020 Revenue recognized that was included in the contract liability balance at the beginning of the year Allocation of the transaction price ￦ 183,905 ￦ 266,478 ￦ 251,975 Deferred revenue of joining/installment fee 39,975 44,032 42,685 Others 1,536 — — Total ￦ 225,416 ￦ 310,510 ￦ 294,660

Operating Expenses

Operating Expenses	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Operating Expenses	27. Operating Expenses Operating expenses for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Salaries and wages ￦ 3,845,842 ￦ 3,974,233 ￦ 4,123,680 Depreciation 2,674,205 2,530,252 2,605,128 Depreciation of right-of-use — 442,629 404,175 Amortization of intangible assets 607,527 656,611 624,982 Commissions 1,080,168 1,115,477 965,461 Interconnection charges 579,613 534,025 500,081 International interconnection fee 226,627 240,254 172,529 Purchase of inventories 4,414,094 4,453,820 3,681,801 Changes of inventories (432,607 ) 282,957 257,041 Sales commission 1,942,841 2,315,731 2,337,127 Service cost 1,540,869 1,610,261 2,102,875 Utilities 323,411 332,816 360,797 Taxes and dues 285,131 277,742 283,197 Rent 460,377 193,357 136,355 Insurance premium 73,654 82,404 71,018 Installation fee 143,669 155,178 132,117 Advertising expenses 157,675 150,166 132,466 Research and development expenses 176,758 165,028 156,940 Card service cost 3,112,618 3,066,766 2,941,669 Others 1,122,718 1,292,512 1,428,875 Total ￦ 22,335,190 ￦ 23,872,219 ￦ 23,418,314 Details of salaries and wages for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Short-term employee benefits ￦ 3,505,214 ￦ 3,663,337 ￦ 3,770,786 Post-employment benefits(Defined benefit plan) 232,045 240,310 239,102 Post-employment benefits(Defined contribution plan) 48,210 57,170 61,912 Share-based payment 8,439 6,398 28,604 Others 51,934 7,018 23,276 Total ￦ 3,845,842 ￦ 3,974,233 ￦ 4,123,680

Financial Income and Costs

Financial Income and Costs	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Financial Income and Costs	28. Financial Income and Costs Details of financial income for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Interest income ￦ 244,796 ￦ 282,704 ￦ 270,571 Gain on foreign currency transactions 17,175 24,596 17,493 Gain on foreign currency translation 3,691 17,979 164,351 Gain on settlement of derivatives 27,950 9,016 9,397 Gain on valuation of derivatives 66,305 77,353 172 Others 14,326 12,747 36,630 Total ￦ 374,243 ￦ 424,395 ￦ 498,614 Details of financial costs for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Interest expenses ￦ 296,874 ￦ 278,427 ￦ 263,579 Loss on foreign currency transactions 49,156 30,267 27,805 Loss on foreign currency translation 72,642 93,977 26,340 Loss on settlement of derivatives — 20 1,406 Loss on valuation of derivatives 2,045 15,867 163,763 Loss on disposal of trade receivables 13,818 11,298 8,152 Others 1,124 2,277 16,338 Total ￦ 435,659 ￦ 432,133 ￦ 507,383

Deferred Income Tax and income

Deferred Income Tax and income Tax Expense	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Deferred Income Tax and income Tax Expense	29. Deferred Income Tax and income Tax Expens e The analysis of deferred tax assets and deferred tax liabilities as at December 31, 2019 and 2020, is as follows: (In millions of Korean won) December 31, December 31, Deferred tax assets Deferred tax assets to be recovered within 12 months ￦ 419,889 ￦ 404,434 Deferred tax assets to be recovered after more than 12 months 1,613,836 1,631,759 Deferred tax assets before offsetting 2,033,725 2,036,193 Deferred tax liabilities Deferred tax liability to be recovered within 12 months (538,578 ) (637,317 ) Deferred tax liability to be recovered after more than 12 months (1,495,759 ) (1,394,509 ) Deferred tax liabilities before offsetting (2,034,337 ) (2,031,826 ) Deferred tax assets after offsetting ￦ 424,856 ￦ 433,698 Deferred tax liabilities after offsetting ￦ 425,468 ￦ 429,331 The gross movements on the deferred income tax account for the years ended December 31, 2019 and 2020, are calculated as follows: (In millions of Korean won) 2019 2020 Beginning ￦ 260,584 ￦ (612 ) Changes to the statement of operations (199,527 ) (72,124 ) Changes to other comprehensive loss (income) (61,669 ) 77,103 Ending ￦ (612 ) ￦ 4,367 The movement in deferred income tax assets and liabilities during the year, without taking into consideration the offsetting of balances within the same tax jurisdiction, is as follows: (In millions of Korean won) 2019 Beginning Consolidated Other Ending Deferred tax liabilities Derivative instruments — (10,250 ) (648 ) (10,898 ) Investment in subsidiaries, associates, and joint ventures (93,604 ) (14,622 ) 35 (108,191 ) Depreciation (424 ) (11,182 ) — (11,606 ) Advanced depreciation provision (313,184 ) 63 — (313,121 ) Deposits for severance benefits (398,982 ) (99,126 ) 1,255 (496,853 ) Accrued income (1,558 ) 17 — (1,541 ) Reserve for technology and human resource development (204 ) — — (204 ) Contract cost (369,916 ) (40,947 ) — (410,863 ) Contract assets (11,505 ) (42,245 ) — (53,750 ) Financial assets at fair value through profit or loss (661 ) 338 — (323 ) Financial assets at fair value through other comprehensive income (41,798 ) (3,556 ) (58,483 ) (103,837 ) Others (284,255 ) (238,725 ) (170 ) (523,150 ) Total (1,516,091 ) (460,235 ) (58,011 ) (2,034,337 ) Deferred tax assets Derivative instruments 8,341 (850 ) (7,491 ) — Provision for impairment or trade receivables 99,887 (15,816 ) — 84,071 Inventory valuation 121 (98 ) — 23 Contribution for construction 16,800 (646 ) — 16,154 Unsettled expenses 127,897 32,539 — 160,436 Provisions 36,178 (3,354 ) — 32,824 Property and equipment 230,278 (1,623 ) — 228,655 Defined benefit liabilities 513,842 48,847 6,782 569,471 Withholding of facilities expenses 6,609 (426 ) — 6,183 Deduction of installment receivables 42 6 — 48 Assets retirement obligation 24,532 4,484 — 29,016 Gain or loss foreign currency translation 10,672 10,005 — 20,677 Deferred revenue 39,641 (3,841 ) — 35,800 Real-estate sales 21,728 (8,043 ) — 13,685 Others 537,209 174,177 (2,949 ) 708,437 Total 1,673,777 235,361 (3,658 ) 1,905,480 Temporary difference, net 157,686 (224,874 ) (61,669 ) (128,857 ) Tax credit carryforwards 102,898 25,347 — 128,245 Total net balance 260,584 (199,527 ) (61,669 ) (612 ) (In millions of Korean won) 2020 Beginning Consolidated Other Ending Deferred tax liabilities Derivative instruments (10,898 ) 10,055 — (843 ) Investment in subsidiaries, associates, and joint ventures (108,191 ) (64,553 ) (8,820 ) (181,564 ) Depreciation (11,606 ) 7,431 — (4,175 ) Advanced depreciation provision (313,121 ) 1,203 — (311,918 ) Deposits for severance benefits (496,853 ) (26,419 ) 2,015 (521,257 ) Accrued income (1,541 ) (212 ) — (1,753 ) Reserve for technology and human resource development (204 ) — — (204 ) Contract cost (410,863 ) 67,898 — (342,965 ) Contract assets (53,750 ) (112,794 ) — (166,544 ) Financial assets at fair value through profit or loss (323 ) (304 ) — (627 ) Financial assets at fair value through other comprehensive income (103,837 ) (4,420 ) 77,634 (30,623 ) Others (523,150 ) 53,797 — (469,353 ) Total (2,034,337 ) (68,318 ) 70,829 (2,031,826 ) Deferred tax assets Derivative instruments — 40,342 (9,860 ) 30,482 Provision for impairment or trade receivables 84,071 4,994 — 89,065 Inventory valuation 23 (259 ) — (236 ) Contribution for construction 16,154 246 — 16,400 Unsettled expenses 160,436 (24,358 ) — 136,078 Provisions 32,824 1,198 — 34,022 Property and equipment 228,655 (1,695 ) — 226,960 Defined benefit liabilities 569,471 13,707 15,186 598,364 Withholding of facilities expenses 6,183 (436 ) — 5,747 Deduction of installment receivables 48 (20 ) — 28 Assets retirement obligation 29,016 (883 ) — 28,133 Gain or loss foreign currency translation 20,677 (20,539 ) — 138 Deferred revenue 35,800 7,230 — 43,030 Contract assets — 97,464 — 97,464 Real-estate sales 13,685 (13,685 ) — — Others 708,437 (123,798 ) 948 585,587 Total 1,905,480 (20,492 ) 6,274 1,891,262 Temporary difference, net (128,857 ) (88,810 ) 77,103 (140,564 ) Tax credit carryforwards 128,245 16,686 — 144,931 Total net balance (612 ) (72,124 ) 77,103 4,367 The tax impacts recognized directly to equity as at December 31, 2018, 2019, and 2020, are as follows: 2018 2019 2020 (In millions of Korean won) Before recognition Tax effect After Before recognition Tax effect After Before recognition Tax effect After Gain on valuation of financial assets at fair value through other comprehensive income 59,384 (15,573 ) 43,811 225,635 (58,483 ) 167,152 54,969 (12,972 ) 41,997 Gain (loss) on valuation of hedge instruments (36,756 ) 9,745 (27,011 ) 31,003 (8,139 ) 22,864 37,247 (9,860 ) 27,387 Remeasurements of net defined benefit liabilities (116,324 ) 42,813 (73,511 ) (33,814 ) 8,037 (25,777 ) (77,382 ) 17,201 (60,181 ) Share of gain(loss) of associates and joint ventures, and others (1,036 ) 179 (857 ) 4,493 (1,327 ) 3,166 25,538 (8,820 ) 16,718 Exchange differences on translation for foreign operations 3,989 (1,049 ) 2,940 6,692 (1,759 ) 4,933 (3,614 ) 948 (2,666 ) Total ￦ (90,743 ) ￦ 36,115 ￦ (54,628 ) ￦ 234,009 ￦ (61,671 ) ￦ 172,338 ￦ 36,758 ￦ (13,503 ) ￦ 23,255 Details of income tax expense for the years ended December 31, 2018, 2019 and 2020, are calculated as follows: (In millions of Korean won) 2018 2019 2020 Current income tax expense ￦ 329,581 ￦ 120,533 ￦ 213,225 Impact of change in deferred taxes (15,016 ) 199,527 72,124 Income tax expense ￦ 314,565 ￦ 320,060 ￦ 285,349 The tax on the Group’s profit before tax differs from the theoretical amount that would arise using the weighted average tax rate applicable to profits of the entities as follows: (In millions of Korean won) 2018 2019 2020 Profit before income tax expense ￦ 1,033,977 ￦ 1,015,928 ￦ 1,031,605 Statutory income tax expense ￦ 273,982 ￦ 269,018 ￦ 273,329 Tax effect Income not taxable for taxation purposes (85,322 ) (1,265 ) (24,657 ) Non-deductible expenses 18,126 19,543 31,741 Tax credit (20,319 ) (39,190 ) (47,056 ) Additional payment of income taxes 11,439 3,832 429 Tax effect and adjustment on consolidation Goodwill impairment 137 159 — Eliminated dividend income form subsidiaries 31,966 21,917 20,682 Changes of out-side 618 13,539 38,552 Investment in-kind 82,820 — — Intangible Asset impairment and amortization — 14,052 3,790 Reversal expenses of contract cost assets — 11,213 (6,643 ) Others 1,118 7,242 (4,818 ) Income tax expense ￦ 314,565 ￦ 320,060 ￦ 285,349 Details of deferred tax assets and liabilities that are not recognized as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) 2019 2020 Deductible temporary differences Investment in subsidiaries, associates, and joint ventures ￦ 610,351 ￦ 583,890 Unused tax loss 31,257 28,115 Unused Tax credit — 2,654 Others 32,494 64,760 Total ￦ 674,102 ￦ 679,419 Taxable temporary differences Investment in subsidiaries, associates, and joint ventures ￦ 141,664 ￦ 132,848 Others 10,372 9,568 Total ￦ 152,036 ￦ 142,416 The expected period of expiry for unused tax losses not recognized in deferred tax assets as at December 31, 2019 and 2020, is as follows: (In millions of Korean won) 2019 2020 2021 ￦ 18,582 ￦ 2,140 2022 2,140 80,649 2023 80,649 5,848 2024 5,848 4,867 2025 4,867 2,847 2026 9,390 9,709 2027 7,888 8,389 2028 10,064 8,426 2029 2,030 2,579 2030 617 2,339 Total ￦ 142,075 ￦ 127,793

Earnings per Share

Earnings per Share	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Earnings per Share	30. Earnings per Share Basic earnings per share is calculated by dividing the profit from operations attributable to equity holders of the Group by the weighted average number of ordinary shares outstanding during the period, excluding ordinary shares purchased by the Group and held as treasury stock. Basic earnings per share from operations for the years ended December 31, 2018, 2019 and 2020, is calculated as follows: 2018 2019 2020 Profit attributable to ordinary shares (In millions of Korean won) ￦ 645,571 ￦ 645,703 ￦ 700,889 Weighted average number of ordinary shares outstanding (In number of shares) 245,049,466 245,171,283 245,207,307 Basic earnings per share (In Korean won) 2,634 2,634 2,858 Diluted earnings per share from operations is calculated by adjusting the weighted average number of ordinary shares outstanding to assume conversion of all dilutive potential ordinary shares. The Controlling Company has dilutive potential ordinary shares from convertible preferred stocks, stock options and other share-based payments. Diluted earnings per share from operations for the years ended December 31, 2018, 2019 and 2020 is calculated as follows: 2018 2019 2020 Profit attributable to ordinary shares (In millions of Korean won) ￦ 645,571 ￦ 645,703 ￦ 700,889 Adjustment to net income attributable to ordinary shares (In millions of Korean won) — (157 ) — Diluted profit attributable to ordinary shares (In millions of Korean won) 645,571 645,546 700,889 Number of dilutive potential ordinary shares outstanding (In number of shares) 1,163 70,267 69,598 Weighted average number of ordinary shares outstanding (In number of shares) 245,050,629 245,241,550 245,276,905 Diluted earnings per share (In Korean won) 2,634 2,632 2,858 Diluted earnings per share is earnings per outstanding of ordinary shares and dilutive potential ordinary shares. Diluted earnings per share is calculated by dividing adjusted profit for the year by the sum of the number of ordinary shares and dilutive potential ordinary shares.

Dividend

Dividend	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Dividend	31. Dividend The dividends paid by the Group in 2020, 2019 and 2018 were ￦ ￦ ￦ ￦ ￦ ￦ ￦ ￦

Cash Generated from Operations

Cash Generated from Operations	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Cash Generated from Operations	32. Cash Generated from Operations Cash flows from operating activities for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 1. Profit for the year ￦ 719,412 ￦ 695,868 ￦ 746,256 2. Adjustments to reconcile net income Income tax expense 314,565 320,060 285,349 Interest income (265,817 ) (303,722 ) (291,425 ) Interest expense 296,894 278,975 265,035 Dividends income (2,910 ) (3,408 ) (4,442 ) Depreciation 2,735,413 2,567,754 2,635,307 Amortization of intangible assets 629,526 660,705 628,154 Depreciation of right-of-use — 433,199 404,174 Provision for severance benefits 245,926 256,525 255,615 Impairment losses on trade receivables 113,064 60,193 139,957 Share of net profit or loss of associates and joint ventures 5,912 3,252 (18,041 ) Loss(gain) on disposal of associates and joint ventures (3,737 ) 30 111 Loss(gain) on disposal of right-of-use — 1,556 2,047 Impairment losses on assets held for sale — 7,586 — Loss on disposal of property and equipment and investment in properties 68,688 49,284 55,590 Loss(gain) on disposal of intangible assets (4,256 ) (1,248 ) 246 Loss on impairment of intangible assets 12,997 61,899 211,636 Loss(gain) on foreign currency translation 68,952 75,998 (138,011 ) Loss(gain) on valuation and settlement of derivatives, net (92,210 ) (70,482 ) 155,600 Loss(gain) on disposal of financial assets at fair value through profit or loss (1,712 ) (5,115 ) 329 Gain on valuation of financial assets at fair value through profit or loss (10,768 ) (4,335 ) (59,044 ) Loss(gain) on disposal of financial assets at amortized cost (44 ) 43 (138 ) Others (55,969 ) 143,500 127,949 3. Changes in operating assets and liabilities Decrease(increase) in trade receivables (81,217 ) (433,292 ) 66,462 Decrease(Increase) in other receivables 356,643 (79,130 ) 685,209 Decrease(increase) in other current assets (123,258 ) 984 9,089 Decrease(increase) in other non-current 19,556 (178,180 ) (86,039 ) Decrease(increase) in inventories (480,543 ) 240,488 288,507 Increase(decrease) in trade payables (167,841 ) 44,354 (135,760 ) Decrease in other payables (448,301 ) (102,375 ) (1,232,646 ) Increase in other current liabilities 291,548 43,384 127,076 Increase(decrease) in other non-current 144,072 (199,547 ) (56,319 ) Decrease(Increase) in provisions 85,946 (12,164 ) 2,264 Decrease(Increase) in deferred revenue 48,201 641 (1,948 ) Increase in plan assets (53,301 ) (375,499 ) (136,336 ) Payment of severance benefits (153,209 ) (119,716 ) (186,520 ) 4. Cash generated from operations (1+2+3) ￦ 4,212,222 ￦ 4,058,065 ￦ 4,745,293 The Group made agreements with securitization specialty companies and disposed of its trade receivables related to handset sales (Note 20). Cash flows from the disposals are presented in cash generated from operations. Significant transactions not affecting cash flows for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Reclassification of the current portion of borrowings ￦ 1,149,599 ￦ 1,030,056 ￦ 1,229,359 Reclassification of construction-in-progress 1,988,014 2,698,146 3,011,519 Reclassification of accounts payable from property and equipment 122,185 685,859 22,052 Reclassification of accounts payable from intangible assets 584,595 (356,911 ) (345,675 ) Reclassification of payable from defined benefit liability (31,838 ) (19,053 ) 72,346 Reclassification of payable from plan assets (9,497 ) (14,298 ) 66,046

Changes in Liabilities Arising

Changes in Liabilities Arising from Financing Activities	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Changes in Liabilities Arising from Financing Activities	33. Changes in Liabilities Arising from Financing Activities Changes in liabilities arising from financing activities, liabilities related to cashflow to be classified as future financing activities, for the years ended December 31, 2019 and 2020, are as follows: (In millions of 2019 Beginning Cash Non-cash Ending Changes in 1 Newly Exchange Fair Value Others Borrowing ￦ 6,648,294 ￦ 574,175 ￦ — ￦ — ￦ 64,398 ￦ — ￦ 12,000 ￦ 7,298,867 Lease liabilities 163,858 (485,444 ) 771,410 774,906 — — (13,379 ) 1,211,351 Derivative liabilities 65,067 (9,734 ) — — (4,234 ) (20,058 ) (10,945 ) 20,096 Derivative assets (29,843 ) 33,635 — — (53,729 ) (11,398 ) 2,759 (58,576 ) Total ￦ 6,847,376 ￦ 112,632 ￦ 771,410 ￦ 774,906 ￦ 6,435 ￦ (31,456 ) ￦ (9,565 ) ￦ 8,471,738 1 For information on the financial impacts due to change in accounting policy, see Note 41. (In millions of 2020 Beginning Cash Non-cash Ending Newly Exchange Fair Value Change in Others Borrowing ￦ 7,298,867 ￦ 167,867 ￦ 17,523 ￦ (157,985 ) ￦ — ￦ — ￦ (9,974 ) ￦ 7,316,298 Lease liabilities 1,211,351 (447,784 ) 473,477 (3 ) 40 3,564 (97,005 ) 1,143,640 — (13,674 ) 13,674 — — — — — Derivative liabilities 20,096 (943 ) 2,798 142,511 (23,669 ) — (10,220 ) 130,573 Derivative assets (58,576 ) 34,933 — 2,870 (3,456 ) — 16,623 (7,606 ) Total ￦ 8,471,738 ￦ (259,601 ) ￦ 507,472 ￦ (12,607 ) ￦ (27,085 ) ￦ 3,564 ￦ (100,576 ) ￦ 8,582,905

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Segment Information	34. Segment Information The Group’s operating segments are as follows: Details Business service ICT Mobile/fixed line telecommunication service and convergence business, B2B business and others Finance Credit card business and others Satellite TV Satellite TV business Others IT, facility security and global business, and others Details of each segment for the years ended December 31, 2018, 2019 and 2020, are as follows: 2018 (In millions of Korean won) Operating revenues Operating Income Depreciation and Amortization 1 ICT ￦ 17,724,320 ￦ 933,191 ￦ 2,917,163 Finance 3,771,681 148,440 22,580 Satellite TV 690,821 66,735 98,310 Others 5,159,459 53,316 236,715 27,346,281 1,201,682 3,274,768 Elimination (3,910,231 ) (100,822 ) 6,964 Consolidated amount ￦ 23,436,050 ￦ 1,100,860 ￦ 3,281,732 1 Sum of the amortization of tangible assets, intangible assets, investment properties, and right-of-use 2019 (In millions of Korean won) Operating revenues Operating Income Depreciation and Amortization 1 ICT ￦ 18,527,631 ￦ 634,046 ￦ 3,229,159 Finance 3,795,185 158,235 27,852 Satellite TV 694,637 69,357 94,992 Others 5,845,973 218,402 357,294 28,863,426 1,080,040 3,709,297 Elimination (3,964,237 ) (53,070 ) (79,805 ) Consolidated amount ￦ 24,899,189 ￦ 1,026,970 ￦ 3,629,492 1 Sum of the amortization of tangible assets, intangible assets, investment properties, and right-of-use 2020 (In millions of Korean won) Operating revenues Operating Income Depreciation and Amortization 1,2 ICT ￦ 18,275,765 ￦ 809,741 ￦ 3,233,878 Finance 3,686,430 85,008 53,098 Satellite TV 706,631 71,345 84,931 Others 5,944,093 209,078 346,215 28,612,919 1,175,172 3,718,122 Elimination (4,172,272 ) (152,839 ) (83,838 ) Consolidated amount ￦ 24,440,647 ￦ 1,022,333 ￦ 3,634,284 1 Sum of the amortization of tangible assets, intangible assets, investment properties, and right-of-use 2 Property and equipment and intangible assets associated with ICT reporting segment are ￦ Operating revenues for the years ended December 31, 2018, 2019 and 2020 and non-current (In millions of Korean won) Operating revenues Non-current 1 Location 2018 2019 2020 2019.12.31 2020.12.31 Domestic ￦ 23,376,218 ￦ 24,832,068 ￦ 24,368,729 ￦ 19,198,416 ￦ 18,934,766 Overseas 59,832 67,121 71,918 76,679 18,243 Total ￦ 23,436,050 ￦ 24,899,189 ￦ 24,440,647 ￦ 19,275,095 ￦ 18,953,009 1 Non-current right-of-use

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Related Party Transactions	35. Related Party Transaction s The list of related party of the Group as at December 31, 2020, is as follows: Relationship Name of Entry Associates and joint ventures Korea Information & Technology Investment Fund (KIF Investment Fund), K-Realty CR-REITs K-REALTY CR-REIT KT-DSC start-up K-REALTY KT-IBKC KT-Smart Outstanding balances of receivables and payables in relations to transactions with related parties as at December 31, 2019 and 2020, are as follows: December 31, 2019 Receivables Payables (In millions of Korean won) Trade Other Other Lease Associates and joint ventures K- CR-REITs ￦ 608 ￦ 23,100 ￦ — ￦ 57,907 K Bank, Inc. 583 13,664 557 — Others 434 1,177 711 — Total ￦ 1,625 ￦ 37,941 ￦ 1,268 ￦ 57,907 December 31, 2020 Receivables Payables (In millions of Korean won) Trade Other Other Lease Associates and joint ventures K- CR-REITs ￦ 457 ￦ 16,200 ￦ — ￦ 20,857 K Bank, Inc. 775 32,964 891 — Others 72 1,147 858 — Total ￦ 1,304 ￦ 50,311 ￦ 1,749 ￦ 20,857 Significant transactions with related parties for the years ended December 31, 2018, 2019 and 2020, are as follows: 2018 (In millions of Korean won) Sales Purchases 1 Dividend income Associates and joint ventures K- CR-REITs ￦ ￦ ￦ MOS GS Co., Ltd. 2 493 12,023 8 MOS Daegu Co., Ltd. 2 229 8,775 8 MOS Chungcheong Co., Ltd. 2 540 9,159 8 MOS Gangnam Co., Ltd. 2 333 11,549 10 MOS GB Co., Ltd. 2 1,378 16,519 12 MOS BS Co., Ltd. 2 324 11,193 10 MOS Honam Co., Ltd. 2 331 10,499 10 K Bank, Inc. 15,705 7,004 — NgeneBio 3 3 — — Others 2,888 9,547 2,148 Total ￦ ￦ ￦ 1 The amounts include acquisition of primarily property and equipment. 2 It is the amount before excluded from consolidation during the year. 3 It is the amount before excluded from associates during the year 2019 (In millions of Korean won) Sales Purchases 1 Associates and joint ventures K- CR-REITs ￦ 1,302 ￦ — K Bank, Inc. 17,815 8,524 Others 1,498 10,531 Others K-REALTY CR-REIT 1 2,801 — Total ￦ 23,416 ￦ 19,055 1 The amounts include acquisition of property and equipment and others. December 31, 2019 (In millions of Korean won) Acquisition Acquisition of right-of-use Interest Dividend Associates and joint ventures K- CR-REITs ￦ — ￦ 776 ￦ 2,225 ￦ 10,928 Korea Information & Technology Investment Fund (KIF Investment Fund) — — — 4,280 Others — — — 146 Total ￦ — ￦ 776 ￦ 2,225 ￦ 15,354 2020 (In millions of Korean won) Sales Purchases 1 Associates and joint ventures K- CR-REITs ￦ 2,298 ￦ — Korea Information & Technology Investment Fund (KIF Investment Fund) — — K Bank, Inc. 15,658 8,227 Others 809 10,272 Total ￦ 18,765 ￦ 18,499 1 December 31, 2020 (In millions of Korean won) Interest Interest Dividend Associates and joint ventures K- CR-REITs ￦ ￦ ￦ Korea Information & Technology Investment Fund (KIF Investment Fund) — — 9,241 K Bank, Inc. 14 — — Others — — 43 Total ￦ 14 ￦ 917 ￦ 17,345 Key management compensation for the years ended December 31, 2018, 2019 and 2020, consists of: (In millions of Korean won) 2018 2019 2020 Salaries and other short-term benefits ￦ 2,762 ￦ 2,955 ￦ 2,086 Post-employment benefits 751 321 390 Stock-based compensation 878 891 5,613 Total ￦ 4,391 ￦ 4,167 ￦ 8,089 Fund transactions with related parties for the years ended December 31, 2018, 2019 and 2020, are as follows: 2018 (In millions of Korean won) Equity Associates and joint ventures PHI Healthcare Inc. (HooH Healthcare Inc.) ￦ 1,000 KT-CKP (1,229 ) PT. Mitra Transaksi Indonesia 1 1,567 Gyeonggi-KT Yoojin Superman Fund 1,000 KT-DSC start-up (1,800 ) KT-IBKC (1,050 ) Korea Electronic Vehicle Charging Service 168 K Bank, Inc. 26,725 GE Premier 1st Corporate Restructuring Real Estate Investment Trust Company (3,423 ) JB Emerging Market Specialty Investment Private Equity Trust No.1 3,960 K-REALTY — Korea Information & Technology Investment Fund — MOS GS Co., Ltd. 2 (147 ) MOS Daegu Co., Ltd. 2 (147 ) MOS Chungcheong Co., Ltd. 2 (153 ) MOS Gangnam Co., Ltd. 2 (180 ) MOS GB Co., Ltd. 2 (203 ) MOS BS Co., Ltd. 2 (183 ) MOS Honam Co., Ltd. 2 (206 ) Daiwon Broadcasting Co., Ltd. — Boston Global Film & Contents Fund L.P. (986 ) Gyeonggi-KT Green Growth Fund — Total ￦ 24,713 1 It is the amount before reclassification to assets held for sale . 2 It is the amount before included in consolidation during the year. December 31, 2019 Borrowing transaction 1 Equity contributions (In millions of Korean won) Borrowing 2 Repayment KT-IBKC ￦ — ￦ — ￦ 3,750 KT Philippines co. Ltd. — — 99 Virtua Realm Sendirian Berhad — — 550 K-REALTY — 30,385 — K Bank, Inc — — 21,782 KIF Investment Fund — — — Daiwon Broadcasting Co.,Ltd. — — — JB Emerging Market Specialty Investment Private Equity Trust No.1 — — — Gyeonggi-KT Yoojin Superman Fund — — 1,000 KT-CKP — — (174 ) KT-DSC start-up — — (1,800 ) KT-Smart — — 2,800 KT-SB — — (2,404 ) Total ￦ — ￦ 30,385 ￦ 25,603 1 Borrowing transactions include lease transactions. 2 Conversion effect from the adoption of IFRS 16 Lease December 31, 2020 Borrowing transaction 1 Equity contributions (In millions of Korean won) Borrowing Repayment K- CR-REITs ￦ — ￦ 20,304 ￦ — Studio Discovery Co. Ltd. — — 3,000 KT Young Entrepreneurs DNA Investment Fund — — 3,600 KT-Smart — — 2,800 KT-CKP — — (109 ) K Bank Inc. — — 195,011 Gyeonggi-KT Yoojin Superman Fund — — 1,000 Hyundai Robotics Co. Ltd. — — 50,000 Total ￦ — ￦ 20,304 ￦ 255,302 1 Borrowing transactions include lease transactions. As at December 31, 2020, there is no collateral or payment guarantee provided to or from related parties.

Financial Risk Management

Financial Risk Management	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Financial Risk Management	36. Financial Risk Managemen t (1) Financial Risk Factors The Group’s activities expose it to a variety of financial risks: market risk, credit risk and liquidity risk. The Group’s overall risk management program focuses on the unpredictability of financial markets and seeks to minimize potential adverse effects on the Group’s financial performance. The Group uses derivative financial instruments to hedge certain risk exposures such as cash flow risk. The Group’s financial policy is set up in the long-term perspective and annually reported to the Board of Directors. The financial risk management is carried out by the Value Management Office, which identifies, evaluates and hedges financial risks. The treasury department in the Value Management Office considers various finance market conditions to estimate the effect from the market changes. 1) Market risk The Group’s market risk management focuses on controlling the extent of exposure to the risk in order to minimize revenue volatility. Market risk is a risk that decreases value or profit of the Group’s portfolio due to changes in market interest rate, foreign exchange rate and other factors. (i) Sensitivity analysis Sensitivity analysis is performed for each type of market risk to which the Group is exposed. Reasonably possible changes in the relevant risk variable such as prevailing market interest rates, currency rates, equity prices or commodity prices are estimated and if the rate of change in the underlying risk variable is stable, the Group does not alter the chosen reasonably possible change in the risk variable. The reasonably possible change does not include remote or ‘worst case’ scenarios or ‘stress tests’. (ii) Foreign exchange risk The Group is exposed to foreign exchange risk arising from operating, investing and financing activities. Foreign exchange risk is managed within the range of the possible effect on the Group’s cash flows. Foreign exchange risk (i.e. foreign currency translation of overseas operating assets and liabilities) unaffecting the Group’s cash flows is not hedged but can be hedged at a particular situation. As at December 31, 2018, 2019 and 2020, if the foreign exchange rate had strengthened/weakened by 10% with all other variables held constant, the effects on profit before inc o (In millions of Ko r Fluctuation of Income before tax 1 Shareholders’ equity 2018.12.31 10 % ￦ 7,212 ￦ 10,196 -10 % (12,413 ) (9,625 ) 2019.12.31 10 % ￦ 45,149 ￦ 52,092 -10 % (45,149 ) (52,092 ) 2020.12.31 10 % ￦ 25,220 ￦ 36,961 -10 % (25,220 ) (36,961 ) 1 Computed with considering derivatives hedging effect applied by the Group to hedge foreign exchange risk of liabilities in foreign currencies. The above analysis is a simple sensitivity analysis which assumes that all the variables other than foreign exchange rates are held constant. Therefore, the analysis does not reflect any correlation between foreign exchange rates and other variables, nor the management’s decision to decrease the risk. Details of financial assets and liabilit i (In thousands of foreign currencies) 2018 2019 2020 Financial Financial Financial Financial Financial Financial US D 528,539 1,893,849 645,941 1,830,764 400,046 1,937,935 SDR 1 267 730 255 729 255 728 JPY 66,078 50,000,000 24,930 80,000,000 209,376 46,000,009 GBP — 256 — 56 — — EUR 2 6 1 6 316 162 DZD 2 618 — — — — — CNY 1,954 171 457 161 458 491 UZS 3 121,053 — — — — — RWF 4 857 — 706 — 646 — THB 5 — — — — 535 — MMK 6 84 — 84 — — — TZS 7 — 2,876 6,919 — 1,019 — BWP 8 897 — 911 — 212 — HKD — — — 268 — 198 BDT 9 39,494 — 18,897 — — — PLN 10 26 — — — 26 — VND 11 467,272 — 271,563 — 242,370 — XAF 12 666 — 97,411 — 16,229 — SGD — — — — 6 284,000 1 Special Drawing Rights. 2 Algeria Dinar. 3 Uzbekistan Sum. 4 Rwanda Franc. 5 Thailand Bhat. 6 Myanmar Kyat. 7 Tanzanian Shilling. 8 Botswana Pula. 9 Bangladesh Taka. 10 Polish Zloty. 11 Vietnam Dong. 12 Central African Franc. (iii) Price risk As at December 31, 2018, 2019 and 2020, the Group is exposed to equity securities price risk because the securities held by the Group are traded in active markets. If the market prices had increased/decreased by 10% with all other variables held constant, the effects on profit before income tax and shareholders’ equity would have been as follows: (In millions of Korean won) Fluctuation of price Income before tax Equity 2018.12.31 10% ￦ 12 ￦ 898 -10% (12 ) (898 ) 2019.12.31 10% ￦ 24 ￦ 613 -10% (24 ) (613 ) 2020.12.31 10% ￦ 2,811 ￦ 3,472 -10% (2,811 ) (3,472 ) The above analysis is based on the assumption that the equity index had increased/decreased by 10% with all other variables held constant and all the Group’s marketable equity instruments had moved according to the historical correlation with the index. Gain or loss on equity securities classified as financial assets at fair value through profit or loss and financial assets at fair value through other comprehensive income can increase or decrease equity. (iv) Cash flow and fair value interest rate risk The Group’s interest rate risk arises from liabilities in foreign currency such as foreign currency debentures. Debentures in foreign currency issued at variable rates expose the Group to cash flow interest rate risk which is partially offset by swap transactions. Debentures and borrowings issued at fixed rates expose the Group to fair value interest rate risk. The Group sets the policy and operates to minimize the uncertainty of the changes in interest rates and financial costs. As at December 31, 2018, 2019 and 2020, if the market interest rate had increased/decreased by 100 bp with other variables held constant, the effects on profit before income tax and shareholders’ equity would be as follows: (In millions of Korean won) Fluctuation of interest rate Income before tax Shareholders’ equity 2018.12.31 + 100 bp ￦ 1,059 ￦ 9,689 - 100 bp (1,958 ) (10,237 ) 2019.12.31 + 100 bp ￦ 425 ￦ 14,764 - 100 bp (482 ) (19,280 ) 2020.12.31 + 100 bp ￦ 973 ￦ 18,584 - 100 bp (973 ) (19,377 ) The above analysis is a simple sensitivity analysis which assumes that all the variables other than market interest rates are held constant. Therefore, the analysis does not reflect any correlation between market interest rates and other variables, nor the management’s decision to decrease the risk. 2) Credit risk Credit risk is the risk of financial loss to the Group if a customer or counterparty to a financial instrument fails to meet its contractual obligations, and arises principally from the Group’s trade receivables from customers, debt securities and others. - Risk management Credit risk is managed on the Group basis with the purpose of minimizing financial loss. Credit risk arises from the normal transactions and investing activities, where clients or other party fails to discharge an obligation on contract conditions. To manage credit risk, the Group considers the counterparty’s credit based on the counterparty’s financial conditions, default history and other important factors. Credit risk arises from cash and cash equivalents, derivative financial instruments and deposits with banks and financial institutions, as well as outstanding receivables. To minimize such risk, only the financial institutions with strong credit ratings are accepted. The Group’s investments in debt instruments are considered to be low risk investments. The credit ratings of the investments are monitored for credit deterioration . - Security For some trade receivables, the Group may obtain security in the form of guarantees or letters of credit, etc. which can be called upon if the counterparty is in default under the terms of the agreement. - Impairment of financial assets The Group has four types of financial assets that are subject to the expected credit loss model: • trade receivables for sales of goods and provision of services, • contract assets relating to provision of services, • debt investments carried at fair value through other comprehensive income, and • other financial assets carried at amortized cost. While cash equivalents are also subject to the impairment requirement, the identified impairment loss was immaterial. The maximum exposure to credit risk of the Group’s financial instruments without considering value of collaterals as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Cash and cash equivalents (except for cash on hand) ￦ 2,226,608 ￦ 2,625,581 Trade and other receivables Financial assets at amortized costs 5,784,228 5,034,621 Financial assets at fair value through other comprehensive income 1,256,266 1,118,619 Contract assets 557,041 586,438 Other financial assets Derivatives financial assets for hedging 58,576 7,684 Financial assets at fair value through profit or loss 541,657 680,453 Financial assets at fair value through other comprehensive income 7,086 6,570 Financial assets at amortized costs 441,804 671,068 Total ￦ 10,873,266 ￦ 10,731,034 (i) Trade receivables and contract assets The Group applies the simplified approach to measuring expected credit losses which uses a lifetime expected loss allowance for all trade receivables and contract assets. The Group measures the expected credit loss by considering the future irrecoverability rate of the remaining balance of trade receivables and other receivables at the end of the reporting period. Each trade receivables and other receivables are classified considering the credit risk characteristics and overdue periods in order to measure expected credit loss. The expected credit loss rate calculation is based on historical payment and credit loss information in relation to revenue for 36 months period up to December 31, 2020. Expected credit loss of 12 months was applied as the credit sales and other credit-related assets of BC Card Co., Ltd., a subsidiary of the Group, has been determined to have low credit risk. (ii) Cash equivalents (except for cash on hand) The Group is also exposed to credit risk in relation cash equivalents. The maximum exposure at the end of the reporting period is the carrying amount of these investments. (iii) Other financial assets at amortized costs Other financial assets at amortized cost include time deposits, other long-term financial instruments and others. All of the financial assets at amortized costs are considered to have low credit risk, and the loss allowance recognized during the period was, therefore, limited to 12 months expected losses. Management consider ‘low credit risk’ for other instruments when they have a low risk of default and the issuer has a strong capacity to meet its contractual cash flow obligations in the near term. (iv) Financial assets at fair value through other comprehensive income All of the debt investments at fair value through other comprehensive income are considered to have low credit risk, and the loss allowance recognized during the period was, therefore, limited to 12 months expected losses. Management consider ‘low credit risk’ for other instruments when they have a low risk of default and the issuer has a strong capacity to meet its contractual cash flow obligations in the near term. The maximum exposure at the end of the reporting period is the carrying amount of these investments. (v) Financial assets at fair value through profit or loss The Group is also exposed to credit risk in relation to financial assets that are measured at fair value through profit or loss. The maximum exposure at the end of the reporting period is the carrying amount of these investments. 3) Liquidity risk The Group manages its liquidity risk by liquidity strategy and plans. The Group considers the maturity of financial assets and financial liabilities and the estimated cash flows from operations. The table below analyzes the Group’s liabilities (including interest expenses) into relevant maturity groups based on the remaining period at the date of the end of each reporting period to the contractual maturity date. These amounts are contractual undiscounted cash flows and can differ from the amount in the consolidated financial statements. December 31, 2019 (In millions of Korean won) Less than 1 year 1-5 More than Total Trade and other payables ￦ 8,149,445 ￦ 805,241 ￦ 370,044 ￦ 9,324,730 Borrowings(including debentures) 1,304,936 4,417,639 2,493,637 8,216,212 Lease liabilities 397,609 688,518 221,255 1,307,382 Other non-derivative 1,749 175,764 18,962 196,475 Financial guarantee contracts 1 19,422 — — 19,422 Total ￦ 9,873,161 ￦ 6,087,162 ￦ 3,103,898 ￦ 19,064,221 1 It is total amount guaranteed by the Group according to guarantee contracts. Cash flow from financial guarantee contracts is classified as the maturity group in the earliest period when the financial guarantee contracts can be executed. December 31, 2020 (In millions of Korean won) Less than 1 year 1-5 More than Total Trade and other payables ￦ 6,587,796 ￦ 730,758 ￦ 258,255 ￦ 7,576,809 Borrowings(including debentures) 1,573,944 4,373,534 2,258,360 8,205,838 Lease liabilities 336,024 658,501 190,907 1,185,432 Other non-derivative 574 131,242 — 131,816 Financial guarantee contracts 1 22,422 — — 22,422 Total ￦ 8,520,760 ￦ 5,894,035 ￦ 2,707,522 ￦ 17,122,317 1 It is total amount guaranteed by the Group according to guarantee contracts. Cash flow from financial guarantee contracts is classified as the maturity group in the earliest period when the financial guarantee contracts can be executed. Cash outflow and inflow of derivatives settled gross or net are undiscounted contractual cash flow and can differ from the amount in the consolidated financial statements. December 31, 2018 (In millions of Korean won) Less than 1 year 1-5 More than Total Outflow ￦ 455,343 ￦ 1,466,915 ￦ 517,301 ￦ 2,439,559 Inflow 484,505 1,492,718 519,133 2,496,356 December 31, 2019 (In millions of Korean won) Less than 1 year 1-5 More than Total Outflow ￦ 650,497 ￦ 1,602,513 ￦ 507,947 ￦ 2,760,957 Inflow 684,720 1,648,746 524,483 2,857,949 December 31, 2020 (In millions of Korean won) Less than 1 year 1-5 More than Total Outflow ￦ 248,300 ￦ 2,179,046 ￦ 498,619 ￦ 2,925,965 Inflow 249,301 2,074,747 480,570 2,804,618 (2) Management of Capital Risk The Group’s objectives when managing capital are to safeguard the Group’s ability to continue as a going concern in order to provide returns for shareholders and benefits for other shareholders and to maintain an optimal capital structure to reduce the cost of capital. The Group’s capital structure consists of liabilities including borrowings, cash and cash equivalents, and shareholders’ equity. The treasury department monitors the Group’s capital structure and considers cost of capital and risks related each capital component. The debt-to-equity (In millions of Korean won) December 31, 2019 December 31, 2020 Total liabilities ￦ 19,491,530 ￦ 18,111,112 Total equity 15,140,684 15,551,433 Debt-to-equity 129 % 116 % The Group manages capital on the basis of the gearing ratio. This ratio is calculated as net debt divided by total capital. Net debt is calculated as total borrowings less cash and cash equivalents. Total capital is calculated as ‘equity’ in the statement of financial position plus net debt. The gearing ratios as at December 31, 2019 and 2020, are as follows: (In millions of Korean won, %) December 31, 2019 December 31, 2020 Total borrowings ￦ 7,298,867 ￦ 7,316,298 Less: cash and cash equivalents (2,305,894 ) (2,634,624 ) Net debt 4,992,973 4,681,674 Total equity 15,140,684 15,551,433 Total capital 20,133,657 20,233,107 Gearing ratio 25 % 23 % (3) Offsetting Financial Assets and Financial Liabilities Details of the Group’s recognized financial assets subject to enforceable master netting arrangements or similar agreements are as follows: (In millions of Korean won) December 31, 2019 Gross Gross Net amounts position Amounts not offset Net Financial Cash Trade receivables ￦ 66,487 ￦ (1 ) ￦ 66,486 ￦ (63,604 ) ￦ — ￦ 2,882 Other financial assets 18,571 (13 ) 18,558 (18,526 ) — 32 ￦ 85,058 ￦ (14 ) ￦ 85,044 ￦ (82,130 ) ￦ — ￦ 2,914 (In millions of Korean won) December 31, 2020 Gross Gross Net amounts position Amounts not offset Net Financial Cash Trade receivables ￦ 71,497 ￦ (1 ) ￦ 71,496 ￦ (67,421 ) ￦ — ￦ 4,075 Netting arrangements with reference to the offers of telecommunication facility interconnection, sharing data, and others among telecommunication companies. The Group’s recognized financial liabilities subject to enforceable master netting arrangements or similar agreements are as follows: (In millions of Korean won) December 31, 2019 Gross Gross offset Net amounts position Amounts not offset Net Financial Cash Trade payables ￦ 65,669 ￦ (13 ) ￦ 65,656 ￦ (63,628 ) ￦ — ￦ 2,028 Other financial liabilities 18,509 (1 ) 18,508 (18,502 ) — 6 ￦ 84,178 ￦ (14 ) ￦ 84,164 ￦ (82,130 ) ￦ — ￦ 2,034 (In millions of Korean won) December 31, 2020 Gross Gross offset Net amounts position Amounts not offset Net Financial Cash Trade payables ￦ 69,361 ￦ — ￦ 69,361 ￦ (67,421 ) ￦ — ￦ 1,940 Other financial liabilities 1 (1 ) — — — — ￦ 69,362 ￦ (1 ) ￦ 69,361 ￦ (67,421 ) ￦ — ￦ 1,940 Netting arrangements with reference to the offers of telecommunication facility interconnection, sharing data, and others among telecommunication companies.

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Fair Value	37. Fair Value 37.1 Fair Value of Financial Instruments by Categor y Carrying amount and fair value of financial instruments by category as at December 31, 2019 and 2020, are as follows: December 31, 2019 December 31, 2020 (In millions of Korean won) Carrying Fair value Carrying Fair value Financial assets Cash and cash equivalents ￦ 2,305,894 1 ￦ 2,634,624 1 Trade and other receivables Financial assets measured at amortized cost 2 5,748,459 1 4,976,423 1 Financial assets at fair value through other comprehensive income 1,256,266 1,256,266 1,118,619 1,118,619 Other financial assets Financial assets measured at amortized cost 441,804 1 671,068 1 Financial assets at fair value through profit or loss 632,324 632,324 809,919 809,919 Financial assets at fair value through other comprehensive income 557,342 557,342 258,516 258,516 Derivative financial assets for hedging 58,576 58,576 7,684 7,684 Total ￦ 11,000,665 ￦ 10,476,853 Financial liabilities Trade and other payables ￦ 8,679,698 1 ￦ 7,017,639 1 Borrowings 7,298,867 1 7,316,298 1 Other financial liabilities Financial liabilities at amortized cost 129,945 1 132,558 1 Financial liabilities at fair value through profit or loss 38 38 2,682 2,682 Derivative financial liabilities for hedging 20,096 20,096 127,929 127,929 Total ￦ 16,128,644 ￦ 14,597,106 1 The Group did not conduct fair value estimation since the book amount is a reasonable approximation of the fair value 2 With the application of IFRS 7, lease receivables are excluded from fair value disclosure. 37.2 Fair Value Hierarchy To provide an indication about the reliability of the inputs used in determining fair value, the Group classifies its financial instruments into the three levels prescribed under the accounting standards. Financial instruments that are measured at fair value are categorized by the fair value hierarchy, and the defined levels are as follows: • Level 1: The fair value of financial instruments traded in active markets is based on quoted market prices at the end of the reporting period. The quoted market price used for financial assets held by the Group is the current bid price. These instruments are included in level 1. • Level 2: The fair value of financial instruments that are not traded in an active market is determined using valuation techniques which maximize the use of observable market data and rely as little as possible on entity-specific estimates. If all significant inputs required to fair value an instrument are observable, the instrument is included in level 2. • Level 3: If one or more of the significant inputs is not based on observable market data, the instrument is included in level 3. Fair value hierarchy classifications of the financial assets and financial liabilities that are measured at fair value or its fair value is disclosed as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 Level 1 Level 2 Level 3 Total Assets Trade and other receivables Financial assets at fair value through other comprehensive income ￦ — ￦ 1,256,266 ￦ — ￦ 1,256,266 Other financial assets Financial assets at fair value through profit or loss 232 136,951 495,141 632,324 Financial assets at fair value through other comprehensive income 6,738 508,550 42,054 557,342 Derivative financial assets for hedging — 40,788 17,788 58,576 Disclosed fair value Investment properties — — 2,304,583 2,304,583 Total ￦ 6,970 ￦ 1,942,555 ￦ 2,859,566 ￦ 4,809,091 Liabilities Other financial liabilities Financial liabilities at fair value through profit or loss ￦ — ￦ 38 ￦ — ￦ 38 Derivative financial liabilities for hedging — 20,096 — 20,096 Total ￦ — ￦ 20,134 ￦ — ￦ 20,134 (In millions of Korean won) December 31, 2020 Level 1 Level 2 Level 3 Total Assets Trade and other receivables Financial assets at fair value through other comprehensive income ￦ — ￦ 1,118,619 ￦ — ￦ 1,118,619 Other financial assets Financial assets at fair value through profit or loss 46,449 330,961 432,509 809,919 Financial assets at fair value through other comprehensive income 5,606 202,121 50,789 258,516 Derivative financial assets for hedging — 7,684 — 7,684 Disclosed fair value Investment properties — — 2,645,482 2,645,482 Total ￦ 52,055 ￦ 1,659,385 ￦ 3,128,780 ￦ 4,840,220 Liabilities Other financial liabilities Financial liabilities at fair value through profit or loss ￦ — ￦ 45 ￦ 2,637 ￦ 2,682 Derivative financial liabilities for hedging — 123,735 4,194 127,929 Total ￦ — ￦ 123,780 ￦ 6,831 ￦ 130,611 37.3 Transfers Between Fair Value Hierarchy Levels of Recurring Fair Value Measurements There are no transfers between Level 1 and Level 2 of the fair value hierarchy for the recurring fair value measurements. Details of changes in Level 3 of the fair value hierarchy for the recurring fair value measurements as at December 31, 2019 and 2020, are as follows: 2019 Financial assets Financial liabilities (In millions of Korean won) Financial assets Financial assets Derivative Financial Beginning balance ￦ 163,600 ￦ 311,536 ￦ (10,183 ) ￦ 7,758 Purchases 584,671 6,081 — — Reclassification 225,873 (444,782 ) — — Disposal (485,419 ) (941 ) — (9,734 ) Amount recognized in profit or loss 1,2 6,416 — 14,462 1,976 Amount recognized in other comprehensive income 1 — 170,160 13,509 — Ending balance ￦ 495,141 ￦ 42,054 ￦ 17,788 ￦ — 1 Amount recognized in profit or loss and other comprehensive income with respect to derivative financial liabilities for hedging comprises loss on valuation of derivative instruments. 2 Amount recognized in profit or loss with respect to financial liabilities at fair value through profit or loss comprises loss on valuation of derivative instruments. 2020 Financial assets Financial liabilities (In millions of Korean won) Financial assets Financial assets Financial Derivative Beginning balance ￦ 495,141 ￦ 42,054 ￦ — ￦ (17,788 ) Purchases 374,259 13,142 2,798 — Reclassification 208 — — — Disposal (451,663 ) (571 ) — — Amount recognized in profit or loss 1,2 14,564 (428 ) (161 ) 29,345 Amount recognized in other comprehensive income 1 — (3,408 ) — (7,363 ) Ending balance ￦ 432,509 ￦ 50,789 ￦ 2,637 ￦ 4,194 1 Amount recognized in profit or loss and other comprehensive income with respect to derivative financial liabilities for hedging comprises loss on valuation of derivative instruments. 2 Amount recognized in profit or loss with respect to financial liabilities at fair value through profit or loss comprises loss on valuation of derivative instruments. 37.4 Valuation Technique and the Inputs Valuation techniques and inputs used in the recurring, non-recurring December 31, 2019 (In millions of Korean won) Fair value Level Valuation techniques Assets Trade and other receivables Financial assets at fair value through other comprehensive income ￦ 1,256,266 2 DCF Model Other financial assets Financial assets at fair value through profit or loss 632,092 2,3 DCF Model, Adjusted net asset model Financial assets at fair value through other comprehensive income 550,604 2,3 DCF Model, Comparable Company Analysis Derivative financial assets for hedging 58,576 2,3 Hull-White model, DCF Model Investment properties 2,304,583 3 DCF Model Liabilities Other financial liabilities Financial liabilities at fair value through profit or loss ￦ 38 2 DCF Model Derivative financial liabilities for hedging 20,096 2 DCF Model December 31, 2020 (In millions of Korean won) Fair value Level Valuation techniques Assets Trade and other receivables Financial assets at fair value through other comprehensive income ￦ 1,118,619 2 DCF Model Other financial assets Financial assets at fair value through profit or loss 763,470 2,3 DCF Model, Adjusted net asset model Financial assets at fair value through other comprehensive income 252,910 2,3 DCF Model, Comparable Company Analysis Derivative financial assets for hedging 7,684 2 DCF Model Investment properties 2,645,482 3 DCF Model Liabilities Other financial liabilities Financial liabilities at fair value through profit or loss ￦ 2,682 2,3 DCF Model, Binomial Option Pricing Derivative financial liabilities for hedging 127,929 2,3 Hull-White model, DCF Model 37.5 Valuation Processes for Fair Value Measurements Categorized Within Level 3 The Group uses external experts that perform the fair value measurements required for financial reporting purposes. External experts report directly to the chief financial officer (CFO), and discusses valuation processes and results with the CFO in line with the Group’s reporting dates. 37.6 Gains and losses on valuation at the transaction dat e In the case that the Group values derivative financial instruments using inputs not based on observable market data, and the fair value calculated by the said valuation technique differs from the transaction price, then the fair value of the financial instruments is recognized as the transaction price. The difference between the fair value at initial recognition and the transaction price is deferred and amortized using a straight-line method by maturity of the financial instruments. However, in the case that inputs of the valuation techniques become observable in markets, the remaining deferred difference is immediately recognized in full in profit for the year. In relation to this, details and changes of the total deferred difference for the years ended December 31, 2019 and 2020, are as follows: 2019 2020 (In millions of Korean won) Derivatives used Derivative held Derivatives used Derivative held I. Beginning balance ￦ 5,107 ￦ (2,824 ) ￦ 3,682 ￦ — II. New transactions — — — — III. Recognized at fair value through profit or loss (1,425 ) 2,824 (1,425 ) — IV. Ending balance (I+II+III) ￦ 3,682 ￦ — ￦ 2,257 ￦ —

Interests in Unconsolidated Str

Interests in Unconsolidated Structured Entities	12 Months Ended
	Dec. 31, 2020
Investments accounted for using equity method [abstract]
Interests in Unconsolidated Structured Entities	38. Interests in Unconsolidated Structured Entities Details of information about its interests in unconsolidated structured entities, which the Group does not have control over, including the nature, purpose and activities of the structured entity and how the structured entity is financed, are as follows: Classes of entities Nature, purpose, activities and others Real estate finance A structured entity incorporated for the purpose of real estate development is provided with funds by investors’ investments in equity and borrowings from financial institutions (including long-term and short-term loans and issuance of Asset Backed Commercial Paper (“ABCP”) due in three months), and based on these, the structured entity implements activities such as real estate acquisition, development and mortgage loans. The structured entity repays loan principals with funds incurred from instalment house sales after the completion of real estate development or with collection of the principal of mortgage loan. The remaining shares are distributed to investors. As at December 31, 2020, this entity is engaged in real estate finance structured entity, and generates revenues by receiving dividends from direct investments in or receiving interests on loans to the structured entity. Financial institutions, including the Entity, are provided with guarantees including joint guarantees or real estate collateral from investors and others. Consequently, the entity is a priority over other parties in the preservation of claim. However, when the credit rating of investors and others decreases or when the value of real estate decreases, the entity may be obliged to cover losses. PEF and investment funds Minority investors including managing members contribute to Private Equity Fund (“PEF”) and investment funds incorporated for the purpose of providing funds to the small, medium, or venture entities, and the managing member implements activities such as investments in equity or loans based on the contributions. As at December 31, 2020, the entity is engaged in PEF and investment funds structured entity, and after contributing to PEF and investment funds, the entity receives dividends for operating revenues from these contributions. The entity is provided with underlying assets of PEF and investment funds as collateral. However, when the value of the underlying assets decreases, the entity may be obliged to cover losses. Asset securitization The Group transfers accounts receivable for handset sales to its Special Purpose Company (“SPC”) for asset securitization. SPC issues the asset-backed securities with accounts receivable for handset sales as an underlying asset, and makes payment for the underlying asset acquired. Details of scale of unconsolidated structured entities and nature of the risks associated with an entity’s interests in unconsolidated structured entities as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 Real Estate PEF and Asset Total Total assets of unconsolidated structured entities ￦ 1,595,895 ￦ 4,060,992 ￦ 2,562,931 ￦ 8,219,818 Assets recognized in statement of financial position Other financial assets ￦ 15,816 ￦ 100,496 ￦ — ￦ 116,312 Joint ventures and associates 8,542 192,022 — 200,564 Total ￦ 24,358 ￦ 292,518 ￦ — ￦ 316,876 Maximum loss exposure 1 Investment assets ￦ 24,358 ￦ 292,518 ￦ — ￦ 316,876 Total ￦ 24,358 ￦ 292,518 ￦ — ￦ 316,876 1 It includes the investments recognized in the Group’s consolidated financial statements and the amounts which are probable to be determined when certain conditions are met by agreements including purchase agreements, credit granting and others. December 31, 2020 (In millions of Korean won) Real Estate PEF and Asset Total Total assets of unconsolidated structured entities ￦ 2,004,869 ￦ 4,380,534 ￦ 2,152,412 ￦ 8,537,815 Assets recognized in statement of financial position Other financial assets ￦ 29,874 ￦ 128,332 ￦ — ￦ 158,206 Joint ventures and associates 51,607 219,753 — 271,360 Total ￦ 81,481 ￦ 348,085 ￦ — ￦ 429,566 Maximum loss exposure 1 Investment assets ￦ 81,481 ￦ 348,085 ￦ — ￦ 429,566 Cash deficiency support — 29,130 — 29,130 Total ￦ 81,481 ￦ 377,215 ￦ — ￦ 458,696 1 It includes the investments recognized in the Group’s consolidated financial statements and the amounts which are probable to be determined when certain conditions are met by agreements including purchase agreements, credit granting and others.

Information About Non-controlli

Information About Non-controlling Interests	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Information About Non-controlling Interests	39. Information About Non-controlling 39.1 Changes in Accumulated Non-controlling Profit or loss allocated to non-controlling non-controlling (In millions of Korean won) December 31, 2018 Non- Accumulated non-controlling Profit or loss non-controlling Dividend paid to non- controlling Others Accumulated non-controlling KT Skylife Co., Ltd. 49.7 % ￦ 328,302 ￦ 23,405 ￦ (8,279 ) ￦ 30,722 ￦ 374,150 BC Card Co., Ltd. 30.5 % 339,067 28,418 (35,924 ) 13,986 345,547 KT Powertel Co., Ltd. 55.2 % 53,053 (3,058 ) — 2,870 52,865 KT Hitel Co.,Ltd. 32.9 % 53,146 454 — (1,264 ) 52,336 KT Telecop Co., Ltd. 13.2 % 103,468 59 — (170 ) 103,357 (In millions of Korean won) December 31, 2019 Non- Accumulated non-controlling Profit or loss non-controlling Dividend to non- Others Accumulated non-controlling KT Skylife Co., Ltd. 49.7 % ￦ 374,150 ￦ 10,029 ￦ (8,279 ) ￦ 6 ￦ 375,906 BC Card Co., Ltd. 30.5 % 345,547 37,795 (18,900 ) 53,033 417,475 KT Powertel Co., Ltd. 55.2 % 52,865 1,751 — (340 ) 54,276 KT Hitel Co., Ltd. 32.9 % 52,336 1,720 — 653 54,709 KT Telecop Co., Ltd. 13.2 % 103,357 (588 ) — (99,119 ) 3,650 (In millions of Korean won) December 31, 2020 Non- Accumulated non-controlling Profit or loss non-controlling Dividend non- Others Accumulated non-controlling KT Skylife Co., Ltd. 49.7 % ￦ 375,906 ￦ 22,171 ￦ (8,279 ) ￦ (898 ) ￦ 388,900 BC Card Co., Ltd. 30.5 % 417,475 9,899 (22,787 ) 7,239 411,826 KT Powertel Co., Ltd. 55.2 % 54,276 2,151 (478 ) (202 ) 55,747 KT Hitel Co., Ltd. 32.9 % 54,709 (1,840 ) — (2,563 ) 50,306 KT Telecop Co., Ltd. 13.2 % 3,650 152 — (208 ) 3,594 39.2 Summarized Financial Information on Subsidiaries The summarized financial information for each subsidiary with non-controlling Summarized consolidated statements of financial position as at December 31, 2018, 2019 and 2020, are as follows: December 31, 2018 (In millions of Korean won) KT Skylife BC Card Co., KT Powertel KT Hitel KT Telecop Co., Ltd. Non-controlling 49.7 % 30.5 % 55.2 % 32.9 % 13.2 % Current assets ￦ 301,739 ￦ 2,997,429 ￦ 84,785 ￦ 161,162 ￦ 52,367 Non-current 514,263 724,950 39,279 111,546 220,125 Current liabilities 112,411 2,520,050 27,187 63,231 85,648 Non-current 37,430 110,486 1,030 2,812 54,666 Equity 666,161 1,091,843 95,847 206,665 132,178 Operating revenue 694,059 3,551,715 65,620 279,117 328,262 Profit or loss for the year 52,010 70,889 (5,545 ) 657 166 Total comprehensive income (loss) 47,787 116,604 (5,792 ) 738 (1,517 ) Cash flows from operating activities 183,474 86,299 11,603 43,855 40,351 Cash flows from investing activities (139,846 ) 128,538 (2,580 ) (26,335 ) (76,969 ) Cash flows from financing activities (77,647 ) (117,561 ) — — 10,000 Net increase (decrease) in cash and cash equivalents (34,019 ) 97,276 9,023 17,520 (26,618 ) Cash and cash equivalents at beginning of year 65,747 177,826 6,626 21,647 32,326 Exchange differences — (13 ) — 19 — Cash and cash equivalents at end of year 31,728 275,089 15,649 39,186 5,708 December 31, 2019 (In millions of Korean won) KT Skylife BC Card Co., KT Powertel KT Hitel KT Telecop Co., Ltd. Non-controlling 49.7 % 30.5 % 55.2 % 32.9 % 13.2 % Current assets ￦ 459,077 ￦ 2,580,634 ￦ 86,465 ￦ 115,694 ￦ 55,908 Non-current 389,199 1,332,348 31,587 164,124 223,969 Current liabilities 123,506 2,452,219 17,757 62,378 64,218 Non-current 19,333 142,013 2,009 12,391 89,622 Equity 705,437 1,318,750 98,286 205,049 126,037 Operating revenue 704,996 3,553,008 62,846 323,065 332,063 Profit or loss for the year 56,008 115,885 3,085 1,426 (4,875 ) Total comprehensive income (loss) 55,936 289,122 2,469 (1,840 ) (6,558 ) Cash flows from operating activities 152,549 429,331 780 49,870 52,693 Cash flows from investing activities (101,594 ) (419,894 ) (9,525 ) (50,138 ) (44,393 ) Cash flows from financing activities (18,833 ) (5,744 ) (687 ) (1,860 ) (5,227 ) Net increase (decrease) in cash and cash equivalents 32,122 3,693 (9,432 ) (2,128 ) 3,073 Cash and cash equivalents at beginning of year 31,728 275,089 15,649 39,186 5,708 Exchange differences — 380 — (15 ) — Cash and cash equivalents at end of year 63,850 279,162 6,217 37,043 8,781 December 31, 2020 (In millions of Korean won) KT Skylife BC Card Co., KT Powertel KT Hitel KT Telecop Co., Ltd. Non-controlling 49.7 % 30.5 % 55.2 % 32.9 % 13.2 % Current assets ￦ 480,450 ￦ 1,785,914 ￦ 90,056 ￦ 140,948 ￦ 79,076 Non-current 439,026 1,298,484 29,638 148,001 239,380 Current liabilities 153,236 1,602,667 17,045 74,045 136,565 Non-current 21,803 176,083 1,788 18,554 57,172 Equity 744,437 1,305,648 100,861 196,350 124,719 Operating revenue 706,631 3,387,641 65,898 350,231 392,489 Profit or loss for the year 58,190 39,455 3,809 2,080 212 Total comprehensive income (loss) 55,647 61,796 3,442 (8,700 ) (1,319 ) Cash flows from operating activities 160,934 (119,163 ) 6,011 62,521 35,834 Cash flows from investing activities (105,293 ) 58,042 (3,353 ) (58,186 ) (57,976 ) Cash flows from financing activities (19,650 ) 22,790 (1,515 ) (1,856 ) 14,652 Net increase (decrease) in cash and cash equivalents 35,991 (38,331 ) 1,143 2,479 (7,490 ) Cash and cash equivalents at beginning of year 63,850 279,162 6,217 37,043 8,781 Exchange differences (7 ) (247 ) — (83 ) — Cash and cash equivalents at end of year 99,834 240,584 7,360 39,439 1,29 1 39.3 Transactions with Non-controlling The effect of changes in the ownership interest on the equity attributable to owners of the Group during 2018, 2019 and 2020 is summarized as follows: (In millions of Korean won) 2018 2019 2020 Carrying amount of non-controlling ￦ (194 ) ￦ (9,566 ) ￦ 1,750 Consideration paid to non-controlling 11,312 484 9,878 Excess of consideration paid recognized in parent’s equity ￦ 11,118 ￦ (9,082 ) ￦ 11,628

Business Combination

Business Combination	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Business Combination	40. Business Combination On April 30, 2020, the Controlling Company acquired 1,400,000 shares (59.8%) of KT Engineering Co., Ltd. (formerly KT ENG Core) and 940,000 shares (40.2%) of KT Estate, a subsidiary of the Group, to cultivate an engineering company in the group through early normalization and termination of corporate rehabilitation of KT Engineering Co., Ltd. (formerly KT ENG Core). Through these transactions, KT Engineering Co., Ltd. (formerly KT ENG Core Co., Ltd.) was included as a subsidiary, and it was accounted for in accordance with IFRS 3 Business Combinations . As a result of applying the acquisition method, identifiable intangible assets of ￦ ￦ As of the acquisition date of control, the total consideration transferred, the recognized amount of assets acquired and liabilities acquired by major types, and calculation details of goodwill are as follows: (In millions of Korean won) Amount Total transfer cost (a) ￦ 46,800 Recognized amount of assets acquired and liabilities assumed (b) 1 46,393 Cash and cash equivalents 57,845 Trade and other receivable 95,814 Other financial assets 3,110 Other assets 14,021 Inventories 1,521 Property and equipment 3,128 Intangible assets 410 Trade and other payables (105,964 ) Other liabilities (4,815 ) Current income tax liabilities (3,664 ) Other provisions (13,745 ) Retirement benefit liabilities (1,268 ) Goodwill (a-b) ￦ 407 1 Assets acquired and liabilities acquired in accordance with IFRS 3 Business Combinations As at December 31, 2020, goodwill is subject to change as the underwriting results of fair value valuation of identifiable asset liabilities for allocation of consideration has not been confirmed. After the acquisition of control, operating income included in the consolidated statement before the removal of intercompany transactions is ￦ ￦ ￦ ￦

Changes in Accounting Policies

Changes in Accounting Policies - Determination of Lease Term Considering Economic Penalty	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Changes in Accounting Policies - Determination of Lease Term Considering Economic Penalty	41. Changes in Accounting Policies – Determination of Lease Term Considering Economic Penalt y From January 1, 2020, the Group has changed its accounting policy by adopting accounting treatments in accordance with agenda decisions for ‘Lease Term and Useful Life of Leasehold Improvements’ issued by IFRS Interpretations Committee on December 16, 2019. The Group determines the lease term as the non-cancellable Accounting Policies, Changes in Accounting Estimates and Errors In relation to the changes in accounting policy, the adjusted amounts recognized in each line item in the consolidated financial statements are as follows: Consolidated Statements of Financial Position December 31, 2019 December 31, 2020 (In millions of Korean won) Previously Adjustment Adjusted Amount based Adjustment Amount based Current assets Prepaid expenses ￦ 76,036 ￦ (1,026 ) ￦ 75,010 ￦ 61,930 ￦ (2,119 ) ￦ 59,811 Non-current Right-of-use 788,497 479,832 1,268,329 585,034 632,145 1,217,179 Current liabilities Lease liabilities ￦ 355,833 ￦ 36,600 ￦ 392,433 ￦ 281,961 ￦ 63,263 ￦ 345,224 Non-current Lease liabilities 373,307 445,612 818,919 231,884 566,532 798,416 Total liabilities ￦ 729,140 ￦ 482,212 ￦ 1,211,352 ￦ 513,845 ￦ 629,795 ￦ 1,143,640 Net assets Retained earnings ￦ 11,594,322 ￦ (3,406 ) ￦ 11,590,916 ￦ 12,155,188 ￦ 232 ￦ 12,155,420 Total equity ￦ 11,594,322 ￦ (3,406 ) ￦ 11,590,916 ￦ 12,155,188 ￦ 232 ￦ 12,155,420 Consolidated Statements of Operations 2019 2020 (In millions of Korean won) Previously Adjustment Adjusted Amount Adjustment Amount Operating revenue ￦ 24,899,189 ￦ — ￦ 24,899,189 ￦ 24,434,851 ￦ 5,796 ￦ 24,440,647 Operating expenses 23,879,015 (6,796 ) 23,872,219 23,425,377 (7,063 ) 23,418,314 Finance income 424,395 — 424,395 498,614 — 498,614 Finance costs 421,931 10,202 432,133 498,161 9,222 507,383 Income tax expense 320,060 — 320,060 285,349 — 285,349 Profit for the year 699,274 (3,406 ) 695,868 742,619 3,637 746,256 Basic earnings per share 2,648 (14 ) 2,634 2,843 15 2,858 Diluted earnings per share 2,646 (14 ) 2,632 2,840 18 2,858 With the initial adoption of IFRS Lease , right-of-use assets and lease liabilities increased by ￦ million and ￦ million, respectively, as at January , . In consideration of the economic penalties to be incurred from the contractual obligations, changes in accounting policy in relation to lease term resulted in an additional increase to the beginning balance of right-of-use assets and lease liabilities, by the amount of ￦ million and ￦ million, respectively, for the year as at January , (Note .

Events after Reporting Period

Events after Reporting Period	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Events after Reporting Period	42. Events After Reporting Period The Group has issued the following bonds since the end of the reporting period . Type Issued date Face value (In millions Interest Redemption The 194-1st Jan. 27, 2021 ￦ 130,000 1.13 % Jan. 26, 2024 The 194-2nd Jan. 27, 2021 140,000 1.45 % Jan. 27, 2026 The 194-3rd Jan. 27, 2021 50,000 1.85 % Jan. 27, 2031 The 194-4th Jan. 27, 2021 80,000 1.98 % Jan. 25, 2041

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Basis of Preparation	2.1 Basis of Preparation The consolidated financial statements of the Group have been prepared in accordance with International Financial Reporting Standards (“IFRS”) as issued by the International Accounting Standards Board (“IASB”). The financial statements have been prepared on a historical cost basis, except for the following: • Certain financial assets and liabilities (including derivative instruments) – measured at fair value • Assets held-for-sale • Defined benefit pension plans – plan assets measured at fair value The preparation of the consolidated financial statements requires the use of certain critical accounting estimates. It also requires management to exercise judgment in the process of applying the Group’s accounting policies. The areas involving a higher degree of judgment or complexity, or areas where assumptions and estimates are significant to the consolidated financial statements are disclosed in Note 3.
Changes in Accounting Policy and Disclosures	2.2 Changes in Accounting Policy and Disclosures (1) New and amended standards adopted by the Group The Group has applied the following standards and amendments for the first time for their annual reporting period commencing January 1, 2020. - Amendments to IAS 1 Presentation of Financial Statements Accounting policies, changes in accounting estimates and errors – Definition of Material The amendments clarify the definition of material. Information is material if omitting, misstating or obscuring it could reasonably be expected to influence the decisions that the primary users of general-purpose financial statements make on the basis of those financial statements. The amendments do not have a significant impact on the consolidated financial statements. - Amendments to IFRS 3 Business Combination – Definition of a Business The amended definition of a business requires an acquisition to include an input and a substantive process that together significantly contribute to the ability to create outputs and the definition of output excludes the returns in the form of lower costs and other economic benefits. If substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets, an entity may elect to apply an optional concentration test that permits a simplified assessment of whether an acquired set of activities and assets is not a business. The amendments do not have a significant impact on the consolidated financial statements. - Amendments to IFRS 9 Financial Instruments Financial Instruments: Recognition and Measurement Financial Instruments: Disclosure – Interest Rate Benchmark Reform The amendments allow to apply the exceptions when forward-looking analysis is performed in relation the application of hedge accounting, while uncertainties arising from interest rate benchmark reform exist. The exceptions require the Group assumes that the interest rate benchmark, on which the hedged items and the hedging instruments are based on, is not altered as a result of interest rate benchmark reform, when determining whether the expected cash flows are highly probable, whether an economic relationship between the hedged item and the hedging instrument exists, and when assessing the hedging relationship is highly effective. The Group’s risk exposure, directly affected by the interest rate benchmark reform, is the variable rate borrowings of USD 519,598,989 and SGD 284,000,000 with maximum remaining maturity of four years. To hedge fluctuations in cash flows of borrowings resulting from the changes in USD LIBOR of 3 months and SGD SOR of 6 months—an interest rate benchmark, the Group entered into an interest rate swap contract for a nominal amount of USD 519,598,989 and SGD 284,000,000 and designated it as a hedging instrument of cash flow hedge. - Agenda Decision of the International Accounting Standards Interpretations Committee – Lease Period The IFRS Interpretations Committee (IFRS IC) announced on December 16, 2019 that all economic penalties resulting from the termination of a lease are taken into account when determining the enforceable period for ‘Lease Term and Useful Life of Leasehold Improvements’. The Group’s changes in accounting policy have been adopted retrospectively in accordance with IAS 8 Accounting Policies, Changes in Accounting Estimates and Errors (2) New standards and interpretations not yet adopted by the Group The following new accounting standards and interpretations have been published that are not mandatory for December 31, 2020 reporting periods and have not been early adopted by the Group. - Amendments to IFRS 16 Lease – Practical expedient for COVID-19—Related As a practical expedient, a lessee may elect not to assess whether a rent concession occurring as a direct consequence of the COVID-19 - Amendments to IFRS 9 Financial Instruments, Financial Instruments: Recognition and Measurement, Financial Instruments: Disclosure, Insurance Contracts Lease – Interest Rate Benchmark Reform In relation to interest rate benchmark reform, the amendments provide exceptions including adjust effective interest rate instead of book amounts when interest rate benchmark of financial instruments at amortized costs is replaced, and apply hedge accounting without discontinuance although the interest rate benchmark is replaced in hedging relationship. The amendments should be applied for annual periods beginning on or after January 1, 2021, and earlier application is permitted. The Group is in review for the impact of these amendments on the financial statements. - Amendments to IFRS 3 Business Combination – Reference to the Conceptual Framework The amendments update a reference of definition of assets and liabilities qualify for recognition in revised Conceptual Framework for Financial Reporting. However, the amendments add an exception for the recognition of liabilities and contingent liabilities within the scope of IAS 37 Provisions, Contingent Liabilities and Contingent Assets Levies - Amendments to IAS 16 Property, Plant and Equipment—Proceeds Before Intended Use The amendments prohibit an entity from deducting from the cost of an item of property, plant and equipment any proceeds from selling items produced while the entity is preparing the asset for its intended use. Instead, the entity will recognize the proceeds from selling such items, and the costs of producing those items, in profit or loss. The amendments should be applied for annual periods beginning on or after January 1, 2022, and earlier application is permitted. The Group is in review for the impact of these amendments on the financial statements. - Amendments to IAS 37 Provisions, Contingent Liabilities and Contingent Assets—Onerous Contracts: Cost of Fulfilling a Contract The amendments clarify that the direct costs of fulfilling a contract include both the incremental costs of fulfilling the contract and an allocation of other costs directly related to fulfilling contracts when assessing whether the contract is onerous. The amendments should be applied for annual periods beginning on or after January 1, 2022, and earlier application is permitted. The Group does not expect that these amendments have a significant impact on the financial statements. - Annual improvements to IFRS 2018-2020 Annual improvements of IFRS 2018-2020 Cycle should be applied for annual periods beginning on or after January 1, 2022, and earlier application is permitted. The Group does not expect that these amendments have a significant impact on the financial statements. • IFRS 1 First time Adoption of Korean International Financial Reporting Standards • IFRS 9 Financial Instruments • IFRS 16 Leases • IAS 41 Agricultur - Amendments to IAS 1 Presentation of Financial Statements—Classification of Liabilities as Current or Non-Current The amendments clarify that liabilities are classified as either current or non-current,
Consolidation	2.3 Consolidation The Group has prepared the consolidated financial statements in accordance with IFRS 10 Consolidated Financial Statements (1) Subsidiaries Subsidiaries are all entities (including special purpose entities (“SPEs”)) over which the Group has control. The Group controls an entity when the Group is exposed to, or has rights to, variable returns from its involvement with the entity and has the ability to affect those returns through its power to direct the activities of the entity. Subsidiaries are fully consolidated from the date on which control is transferred to the Group. They are deconsolidated from the date that control ceases. The acquisition method of accounting is used to account for business combinations by the Group. The consideration transferred is measured at the fair values of the assets transferred, and identifiable assets acquired and liabilities and contingent liabilities assumed in a business combination are measured initially at their fair values at the acquisition date. The Group recognizes any non-controlling acquisition-by-acquisition non-controlling non-controlling The excess of consideration transferred, amount of any non-controlling Intercompany transactions, balances and unrealized gains on transactions between group companies are eliminated. Unrealized losses are also eliminated unless the transaction provides evidence of an impairment of the transferred asset. Accounting policies of subsidiaries have been changed where necessary to ensure consistency with the policies adopted by the Group. (2) Changes in ownership interests in subsidiaries without change of control Any difference between the amount of the adjustment to non-controlling (3) Disposal of subsidiaries When the Group ceases to consolidate for a subsidiary because of a loss of control, any retained interest in the subsidiary is remeasured to its fair value with the change in carrying amount recognized in profit or loss. (4) Associates Associates are entities over which the Group has significant influence but does not possess control or joint control. Investments in associates are accounted for using the equity method of accounting, after initially being recognized at cost. Unrealized gains on transactions between the Group and its associates are eliminated to the extent of the Group’s interest in the associates. If the Group’s share of losses of an associate equals or exceeds its interest in the associate (including long-term interests that, in substance, form part of the Group’s net investment in the associate), the Group discontinues recognizing its share of further losses. After the Group’s interest is reduced to zero, additional losses are provided for, and a liability is recognized, only to the extent that the Group has incurred legal or constructive obligations or made payments on behalf of the associate. If there is an objective evidence of impairment for the investment in the associate, the Group recognizes the difference between the recoverable amount of the associate and its book amount as impairment loss. If an associate uses accounting policies other than those of the Group for transactions and events in similar circumstances, if necessary, adjustments shall be made to make the associate’s accounting policies conform to those of the Group when the associate’s financial statements are used by the Group in applying the equity method. (5) Joint arrangement A joint arrangement, wherein two or more parties have joint control, is classified as either a joint operation or a joint venture. A joint operator recognizes its direct right to the assets, liabilities, revenues and expenses of joint operations and its share of any jointly held or incurred assets, liabilities, revenues and expenses. A joint venture has rights to the net assets relating to the joint venture and accounts for that investment using the equity method.
Segment Reporting	2.4 Segment Reporting Information of each operating segment is reported in a manner consistent with the business segment reporting provided to the chief operating decision-maker (Note 34). The chief operating decision-maker is responsible for allocating resources and assessing performance of the operating segments.
Foreign Currency Translation	2.5 Foreign Currency Translation (1) Functional and presentation currency Items included in the financial statements of each of the Group’s entities are measured using the currency of the primary economic environment in which each entity operates (the “functional currency”). The consolidated financial statements are presented in Korean won, which is the Parent Company’s functional and presentation currency. (2) Transactions and balances Foreign currency transactions are translated into the functional currency using the exchange rates at the dates of the transactions. Foreign exchange gains and losses resulting from the settlement of such transactions and from the translation of monetary assets and liabilities denominated in foreign currencies at year end exchange rates are generally recognized in profit or loss. They are deferred in other comprehensive income if they relate to qualifying cash flow hedges and qualifying effective portion of net investment hedges, or are attributable to monetary part of the net investment in a foreign operation. Foreign exchange gains and losses that relate to borrowings are presented in the consolidated statements of operations, within finance costs. All other foreign exchange gains and losses are presented in the consolidated statements of operations within operating revenue or operating expenses. Non-monetary non-monetary non-monetary (3) Translation to the presentation currency The results and financial position of foreign operations that have a functional currency different from the presentation currency are translated into the presentation currency as follows: • assets and liabilities for each statement of financial position presented are translated at the closing rate at the end of the reporting period, • income and expenses for each consolidated statements of operations are translated at average exchange rates for the period, • equity is translated at the historical exchange rate, and • all resulting exchange differences are recognized in other comprehensive income.
Cash and Cash Equivalents	2.6 Cash and cash equivalents Cash and cash equivalents comprise cash balances, call deposits and investment securities with maturities of three months or less from the acquisition date that are easily convertible to cash and subject to an insignificant risk of changes in their fair value.
Financial Assets	2.7 Financial Assets The Group has applied IFRS 9 Financial Instruments, on January 1, 2018, the date of initial application. In accordance with the transitional provisions in IFRS 9, the Group recorded the cumulative effect as at the date of the initial application of the standards as an adjustment to the initial balance in the retained earnings. (1) Classification The Group classifies its financial assets in the following measurement categories: • those to be measured at fair value through profit or loss • those to be measured at fair value through other comprehensive income, and • those to be measured at amortized cost. The classification depends on the Group’s business model for managing the financial assets and the contractual terms of the cash flows. For financial assets measured at fair value, gains and losses will either be recorded in profit or loss or other comprehensive income. For investments in debt instruments, this will depend on the business model in which the investment is held. The Group reclassifies debt investments when, and only when its business model for managing those assets changes. For investments in equity instruments that are not held for trading, this will depend on whether the Group has made an irrevocable election at the time of initial recognition to account for the equity investment at fair value through other comprehensive income. Changes in fair value of the investments in equity instruments that are not accounted for as other comprehensive income are recognized in profit or loss. (2) Measurement At initial recognition, the Group measures a financial asset at its fair value plus, in the case of a financial asset not at fair value through profit or loss, transaction costs that are directly attributable to the acquisition of the financial asset. Transaction costs of financial assets carried at fair value through profit or loss are expensed in profit or loss. Hybrid (combined) contracts with embedded derivatives are considered in their entirety when determining whether their cash flows are solely payment of principal and interest. A. Debt instruments Subsequent measurement of debt instruments depends on the Group’s business model for managing the asset and the cash flow characteristics of the asset. The Group classifies its debt instruments into one of the following three measurement categories: • Amortized cost: Assets that are held for collection of contractual cash flows where those cash flows represent solely payments of principal and interest are measured at amortized cost. A gain or loss on a debt investment that is subsequently measured at amortized cost and is not part of a hedging relationship is recognized in profit or loss when the asset is derecognized or impaired. Interest income from these financial assets is included in ‘finance income’ using the effective interest rate method. • Fair value through other comprehensive income: Assets that are held for collection of contractual cash flows and for selling the financial assets, where the assets’ cash flows represent solely payments of principal and interest, are measured at fair value through other comprehensive income. Movements in the carrying amount are taken through other comprehensive income, except for the recognition of impairment loss (and reversal of impairment loss), interest income and foreign exchange gains and losses which are recognized in profit or loss. When the financial asset is derecognized, the cumulative gain or loss previously recognized in other comprehensive income is reclassified from equity to profit or loss. Interest income from these financial assets is included in ‘finance income’ using the effective interest rate method. Foreign exchange gains and losses are presented in ‘finance income or finance costs’ and impairment loss in ‘finance costs or operating expenses’. • Fair value through profit or loss: Assets that do not meet the criteria for amortized cost or fair value through other comprehensive income are measured at fair value through profit or loss. A gain or loss on a debt investment that is subsequently measured at fair value through profit or loss and is not part of a hedging relationship is recognized in profit or loss and presented net in the consolidated statements of operations within ‘finance income or finance costs’ in the period in which it arises. B. Equity instruments The Group subsequently measures all equity investments at fair value. Where the Group’s management has elected to present fair value gains and losses on equity investments in other comprehensive income, there is no subsequent reclassification of fair value gains and losses to profit or loss following the derecognition of the investment. Dividends from such investments continue to be recognized in profit or loss as ‘finance income’ when the Group’s right to receive payments is established. Changes in the fair value of financial assets at fair value through profit or loss are recognized in ‘finance income or finance costs’ in the consolidated statements of operations as applicable. Impairment loss (and reversal of impairment loss) on equity investments measured at fair value through other comprehensive income are not reported separately from other changes in fair value. (3) Impairment The Group assesses on a forward looking basis the expected credit losses associated with its debt instruments carried at amortized cost and fair value through other comprehensive income. The impairment methodology applied depends on whether there has been a significant increase in credit risk. For trade receivables and lease receivables, the Group applies the simplified approach, which requires expected lifetime credit losses to be recognized from initial recognition of the receivables. (4) Recognition and Derecognition Regular way purchases and sales of financial assets are recognized or derecognized on trade-date, the date on which the Group commits to purchase or sell the asset. Financial assets are derecognized when the rights to receive cash flows from the financial assets have expired or have been transferred and the Group has transferred substantially all the risks and rewards of ownership. If a transfer does not result in derecognition because the Group has retained substantially all the risks and rewards of ownership of the transferred asset, the Group continues to recognize the transferred asset in its entirety and recognizes a financial liability for the consideration received. (5) Offsetting of financial instruments Financial assets and liabilities are offset and the net amount reported in the statements of financial position where there is a legally enforceable right to offset the recognized amounts and there is an intention to settle on a net basis or realize the assets and settle the liability simultaneously. The legally enforceable right must not be contingent on future events and must be enforceable in the normal course of business and in the event of default, insolvency or bankruptcy of the Group or the counterparty.
Derivative Instruments	2.8 Derivative Instruments Derivatives are initially recognized at fair value on the date a derivative contract is entered into and are subsequently remeasured to their fair value at the end of each reporting period. The accounting for subsequent changes in fair value depends on whether the derivative is designated as a hedging instrument, and if so, the nature of the item being hedged. The Group has hedge relationships and designates certain derivatives as: • hedges of a particular risk associated with the cash flows of recognized assets and liabilities and highly probable forecast transactions (cash flow hedges) At inception of the hedge relationship, the Group documents the economic relationship between hedging instruments and hedged items including whether changes in the cash flows of the hedging instruments are expected to offset changes in the cash flows of hedged items. The fair values of derivative financial instruments designated in hedge relationships are disclosed in Note 37. The full fair value of a hedging derivative is classified as a non-current non-derivative non-derivative non-current The effective portion of changes in fair value of derivatives that are designated and qualify as cash flow hedges is recognized in the cash flow hedge reserve within equity, and the ineffective portion is recognized in ‘finance income (costs)’. Amounts of changes in fair value of effective hedging instruments accumulated in equity are recognized as ‘finance income (costs)’ for the periods when the corresponding transactions affect profit or loss. When a hedging instrument expires, or is sold, terminated, exercised, or when a hedge no longer meets the criteria for hedge accounting, any accumulated cash flow hedge reserve at that time remains in equity until the forecast transaction occurs, resulting in the recognition of a non-financial
Trade Receivables	2.9 Trade Receivable s Trade receivables are recognized initially at the amount of consideration that is unconditional, unless they contain significant financing components when they are recognized at fair value. Trade receivables are subsequently measured at amortized cost using the effective interest method, less loss allowance. See Note 6 for further information about the Group’s accounting for trade receivables and Note 2. 7
Inventories	2.10 Inventories Inventories are stated at the lower of cost and net realizable value. Cost is determined using the moving average method, except for inventories in-tran s .
Assets (or Disposal Group) Held-for-sale	2.1 1 Assets (or Disposal Group) Held-for-sale Assets(or disposal group) are classified as assets held for sale when their carrying amount will be recovered principally through a sale transaction rather than through continued use and when a sale is considered highly probable. The assets are measured at the lower amount between their carrying amount and the fair value less selling costs.
Property and Equipment	2.1 2 Property and Equipment Property and equipment are stated at historical cost less accumulated depreciation and accumulated impairment losses. Historical cost includes expenditures that are directly attributable to the acquisition of the items. Depreciation of all property and equipment, except for land, is calculated using the straight-line method to allocate their cost, net of their residual values, over their estimated useful lives as follows: Estimated Useful Life Buildings 5 – 40 years Structures 5 – 40 years Machinery and equipment (Telecommunications equipment and others) 2 – 40 years Others Vehicles 4 – 6 years Tools 4 – 6 years Office equipment 2 – 6 years The depreciation method, residual values and useful lives of property and equipment are reviewed at the end of each reporting period and, if appropriate, accounted for as changes in accounting estimates.
Investment Property	2.13 Investment Property Investment property is a property held to earn rentals or for capital appreciation. An investment property is measured initially at its cost. After recognition as an asset, investment property is carried at cost less accumulated depreciation and impairment losses. Investment property, except for land, is depreciated using the straight-line method over their useful lives from 10 to 40 years.
Intangible Assets	2.14 Intangible Assets (1) Goodwill Goodwill is measured as explained in Note 2.3 (1) and goodwill arising from acquisition of subsidiaries and business are included in intangible assets. Goodwill is tested at least annually for impairment and carried at cost less accumulated impairment losses. Gains and losses on the disposal of subsidiaries and business include the carrying amount of goodwill relating to the subsidiaries and business sold. For the purpose of impairment testing, goodwill acquired in a business combination is allocated to each of the CGUs, or group of CGUs, that is expected to benefit from the synergies of the combination. Goodwill is monitored at the operating segment level. Goodwill impairment reviews are undertaken at least annually or more frequently if events or changes in circumstances indicate a potential impairment. The carrying amount of goodwill is compared to the recoverable amount, which is the higher of value in use and the fair value less costs to sell. Any impairment is recognized immediately as an expense and is not subsequently reversed. (2) Intangible assets except goodwill Intangible assets, except for goodwill, are initially recognized at its historical cost, and carried at cost less accumulated amortization and accumulated impairment losses. Membership rights (condominium membership and golf membership) that have an indefinite useful life are not subject to amortization because there is no foreseeable limit to the period over which the assets are expected to be utilized. The Group amortizes intangible assets with a limited useful life using the straight-line method over the following periods: Estimated Useful Life Development costs 5 – 6 years Software 4 – 6 years Frequency usage rights 5 – 10 years Others 1 1 – 50 years 1 Membership rights (condominium membership and golf membership) and broadcast license included in others are classified as intangible assets with indefinite useful life.
Borrowing Costs	2.15 Borrowing Costs General and specific borrowing costs that are directly attributable to the acquisition, construction or production of a qualifying asset are capitalized during the period of time that is required to complete and prepare the asset for its intended use or sale. Investment income earned on the temporary investment of specific borrowings pending their expenditure on qualifying assets is deducted from the borrowing costs eligible for capitalization. Other borrowing costs are expensed in the period in which they are incurred.
Government Grants	2.16 Government Grants Grants from the government are recognized at their fair value where there is a reasonable assurance that the grant will be received and the Group will comply with all attached conditions. Government grants related to assets are presented in the statement of financial position by setting up the grant as deferred income that is recognized in profit or loss on a systematic basis over the useful life of the asset. Grants related to income are presented as a credit in the consolidated statements of operations.
Impairment of Non-Financial Assets	2.17 Impairment of Non-Financial Goodwill and intangible assets with indefinite useful life are tested at least annually for impairment at the end of each reporting period. If certain assets are deemed to be impaired, their recoverable amount is estimated in order to determine the impairment loss. The Group estimates the recoverable amount for each asset, and in cases when the recoverable amount cannot be estimated for an asset, the recoverable amount of the cash generating unit to which the asset belongs is estimated. Corporate assets are allocated to individual cash generating units on a reasonable and consistent basis and if they cannot be allocated to individual cash generating units, they are allocated to the smallest group of cash generating units on a reasonable and consistent basis. An impairment loss is recognized for the amount by which the asset’s carrying amount exceeds its recoverable amount (higher of its fair value less costs of disposal and value in use). Impairment loss on non-financial
Trade and other payables	2.1 8 Trade and other payables These amounts represent liabilities for goods and services provided to the Group prior to the end of reporting period which are unpaid. Trade and other payables are presented as current liabilities, unless payment is not due within 12 months after the reporting period. They are recognized initially at their fair value and subsequently measured at amortized cost using the effective interest method.
Financial Liabilities	2.1 9 Financial Liabilities (1) Classification and measurement The Group’s financial liabilities measured at fair value through profit or loss are financial instruments held for trading. A financial liability is held for trading if it is incurred principally for the purpose of repurchasing in the near term. Derivatives that are not designated as hedging instruments or derivatives separated from financial instruments containing embedded derivatives are also categorized as held for trading. All non-derivative • Financial liabilities at fair value through profit or loss • Financial guarantee contract • Financial liabilities arising when the transfer of financial assets does not meet the elimination conditions Financial liabilities measured at amortized cost are displayed in the statement of financial position as ‘Trade and other payables’, ‘Borrowings’ and ‘Other financial liabilities’. Preferred shares that require mandatory redemption at a particular date are classified as liabilities. Interest expenses on these preferred shares using the effective interest method are recognized in the consolidated statements of operations as ‘finance costs’, together with interest expenses recognized from other financial liabilities. (2) Derecognition Financial liabilities are removed from the statement of financial position when they are extinguished; for example, when the obligation specified in the contract is discharged or cancelled or expired or when the terms of an existing financial liability are substantially modified. The difference between the carrying amount of a financial liability extinguished or transferred to another party and the consideration paid (including any non-cash
Financial Guarantee Contracts	2.20 Financial Guarantee Contracts Financial guarantee contracts are recognized as a financial liability at the time the guarantee is issued. The liability is initially measured at fair value, subsequently at the higher of following and recognized in the statement of financial position within ‘other financial liabilities’. • the amount determined in accordance with the expected credit loss model under IFRS 9 Financial Instruments • the amount initially recognized less, where appropriate, the cumulative amount of income recognized in accordance with IFRS 15 Revenue from Contracts with Customers
Employee Benefits	2. 21 Employee Benefits (1) Post-employment benefits The Group operates both defined contribution and defined benefit pension plans. A defined contribution plan is a pension plan under which the Group pays fixed contributions into a separate entity. The contributions are recognized as employee benefit expenses when an employee has rendered service. A defined benefit plan is a pension plan that is not a defined contribution plan. Generally, post-employment benefits are payable after the completion of employment, and the benefit amount depended on the employee’s age, periods of service or salary levels. The liability recognized in the statement of financial position in respect of defined benefit pension plans is the present value of the defined benefit obligation at the end of the reporting period less the fair value of plan assets. The defined benefit obligation is calculated at least annually by independent actuaries using the projected unit credit method. The present value of the defined benefit obligation is determined by discounting the estimated future cash outflows using interest rates of high-quality corporate bonds that are denominated in the currency in which the benefits will be paid, and that have terms approximating to the terms of the related obligation. Remeasurement gains and losses arising from experience adjustments and changes in actuarial assumptions are recognized in the period in which they occur, directly in other comprehensive income. Changes in the present value of the defined benefit obligation resulting from plan amendments or curtailments are recognized immediately in profit or loss as past service costs. (2) Termination benefits Termination benefits are payable when employment is terminated by the Group before the normal retirement date, or whenever an employee accepts voluntary redundancy in exchange for these benefits. The Group recognizes termination benefits at the earlier of the following dates: when the entity can no longer withdraw the offer of those benefits or when the entity recognizes costs for a restructuring. (3) Long-term employee benefits Certain entities within the Group provide long-term employee benefits that are entitled to employees with service period for ten years and above. The expected costs of these benefits are accrued over the period of employment using the same accounting methodology as used for defined benefit pension plans. The Group recognizes service cost, net interest on other long-term employee benefits and remeasurements as profit or loss for the year. These liabilities are valued at least annually by an independent qualified actuary.
Share-based payments	2.2 2 Share-based payments Equity-settled share-based payment is recognized at fair value of equity instruments granted, and employee benefit expense is recognized over the vesting period. At the end of each period, the Group revises its estimates of the number of options that are expected to vest based on the non-market
Provisions	2.2 3 Provisions Provisions for service warranties, recoveries, litigations and claims, and others are recognized when the Group presently hold legal or constructive obligation as a result of past events, and when it is probable that an outflow of resources will be required to settle the obligation and the amount can be reliably estimated. Provisions are measured at the present value of management’s best estimate of the expenditure required to settle the present obligation at the end of the reporting period, and the increase in the provision due to the passage of time is recognized as interest expense.
Leases	2.2 4 Leases As at January 1, 2019, with implementation of IFRS 16 Leases, the Group has changed accounting policy. The Group has adopted IFRS 16 modified retrospectively, as permitted under the specific transitional provisions in the standard, and recognized the cumulative impact of initially applying the standard as at January 1, 2019. As explained in “Note 2.2 (1)” above, the Group has changed its accounting policy for leases. The impact of the new accounting policies is disclosed in Note 41. (1) Lessee The Group leases various repeater server rack, offices, track facilities, machinery and cars. Contracts may contain both lease and non-lease non-lease non-lease Assets and liabilities arising from a lease are initially measured on a present value basis. Lease liabilities include the net present value of the following lease payments: • Fixed payments (including in-substance • Variable lease payment that are based on an index or a rate, initially measured using the index or rate as at the commencement date • Amounts expected to be payable by the Group (the lessee) under residual value guarantees • The exercise price of a purchase option if the Group (the lessee) is reasonably certain to exercise that option, and • Payments of penalties for terminating the lease, if the lease term reflects the Group (the lessee) exercising that option Lease liability measurement also include payments to be made in option periods if the lessee is reasonably certain in exercising an option to extend the lease. The Group determines the lease term as the non-cancellable The lease payments are discounted using the interest rate implicit in the lease. If that rate cannot be determined, the lessee’s incremental borrowing rate is used, which is the rate that the lessee would have to pay to borrow the funds necessary to obtain an asset of similar value in a similar economic environment with similar terms and conditions. The Group is exposed to potential future increases in variable lease payments based on an index or rate, which are not included in the lease liability until they take effect. When adjustments to lease payments based on an index or rate take effect, the lease liability is reassessed and adjusted against the right-of-use Each lease payment is allocated between the liability and finance cost. The finance cost is charged to profit or loss over the lease period in order to produce a constant periodic rate of interest on the remaining balance of the liability for each period. Right-of-use • amount of the initial measurement of lease liability • any lease payments made at or before the commencement date less any lease incentives received • any initial direct costs (leasehold deposits) • restoration costs, and • present value discount on leasehold deposit The right-of-use right-of-use Payments associated with short-term leases and leases of low-value Low-value (2) Lessor Lease income from operating leases where the Group is a lessor is recognized in income on a straight- line basis over the lease term. Initial direct costs incurred in obtaining an operating lease are added to the carrying amount of the underlying asset and recognized as expense over the lease term on the same basis as lease income. The respective leased assets are included in the statement of financial position based on their nature.
Share Capital	2. 25 Share Capital The Group classifies ordinary shares as equity. Where the Controlling Company purchases its own shares, the consideration paid, including any directly attributable incremental costs, is deducted from equity until the share are cancelled or reissued. When these treasury shares are reissued, any consideration received is including in equity attributable to the equity holders of the Controlling Company.
Revenue Recognition	2. 26 Revenue Recognition In May 2014, the IASB issued IFRS 15, which replaced IAS 18. This standard is applicable to years beginning on or after January 1, 2018. The Group adopted IFRS 15 modified retrospectively, with the cumulative effects of the initial application being recognized on the date of the initial application, on January 1, 2018. Accordingly, as provided for in this standard, the Group recorded the cumulative effect as at the date of the initial application of the standard as an adjustment to the initial balance in the retained earnings. In accordance with this transition method, the entity applied this pronouncement modified retrospectively only for contracts that are still in force as at the date of the initial application. (1) Identification of contracts The Group performed a comprehensive review of the commercial offers in force, in order to identify the principal contractual clauses and other contractual elements that may be significant regarding the adoption of the new accounting standard. (2) Identifying performance obligations With the application of IFRS 15, the Group identifies performance obligations with a customer such as Mobile and fixed-line service, Media and content services, financial services and sale of goods. Accordingly, the Group will recognize revenue when, or to the extent that, it satisfies the performance obligations by transferring the goods or services that were promised to the customer. Mobile and fixed-line service Telecommunication service revenues include mobile and fixed-line(e.g., fixed-line and VoIP telephone, broadband internet access services and data communication services). These services represent a series of distinct services that are considered a separate performance obligations. Service revenue is recognized when services are provided, based upon either usage (e.g., minutes of traffic/bytes of data processed) or period of time (e.g., monthly service fees). Media and content services Revenue from media and content services primarily consists of installation fees and basic monthly charges of IPTV and satellite TV services, as well as revenue from digital content distribution, digital music streaming and downloading. Media and contents services revenue are recognized when services are provided, based upon either usage or period of time. Financial services Financial services primarily include commissions for merchant fees paid by merchants to credit card companies for processing transactions. Revenue from the commission is recognized when the service obligation is performed. Sale of goods Revenue from sale of goods, primarily handsets related to our mobile services is recognized when a performance obligation is satisfied by transferring promised goods to customers. (3) Allocation the transaction price and Revenue recognition With the application of IFRS 15, the Group allocates the transaction price to each performance obligation identified in the contract based on a relative stand-alone selling prices of the goods or services being provided to the customer. The Group verified the existence of two main performance obligations: (i) telecommunication services; and (ii) selling handsets. To allocate the transaction price to each performance obligation on a relative stand-alone price basis, the Group determines the stand-alone selling price at contract inception of the distinct good or service underlying each performance obligation in the contract and allocate the transaction price in proportion to those stand-alone selling price. The standalone selling price is the price at which the Group would sell a promised good or service separately to the customer. The best evidence of a stand-alone selling price is the observable price of a good or service when the Group sells that good or service separately in similar circumstances and to similar customers. The Group recognizes the allocated amount as contract assets or contract liabilities, and amortizes it through the remaining period which is adjusted in operating profit. The adoption of the new revenue standard in some cases resulted in the early recognition of revenue from the sale of handsets, which are usually recognized upon the transfer of control to the customer, due to the allocation of discounts between the performance obligations arising from the sale of plans that include mobile services as well as handsets. The difference between the carrying value of sales of handsets, and the amount received from the customer is recorded as a contractual asset and/or liability at the beginning of the contract. Revenue from telecommunication services, in turn, will be recognized in the statement of income based on the allocation of the transaction price, and to the extent that services are being provided to customers in monthly basis. (4) Incremental contract acquisition costs The Group pays the commission fees to authorized dealers when new customer subscribe for telecommunication services. The incremental contract acquisition costs are those commission fees that the Group incurs to acquire a contract with a customer that it would not have incurred if the contract had not been acquired. According to IFRS 15, the Group recognizes as an asset the incremental contract acquisition costs and amortize it over the expected period of benefit. However, as a practical expedient, the Group may recognize the incremental contract acquisition costs as an expense when incurred if the amortization period of the asset is one year or less.
Current and Deferred Income Tax	2. 27 Current and Deferred Income Tax The tax expense for the period consists of current and deferred tax. Current and deferred tax is recognized in profit or loss, except to the extent that it relates to items recognized in other comprehensive income or directly in equity. In this case, the tax is also recognized in other comprehensive income or directly in equity, respectively. The tax expense is measured at the amount expected to be paid to the taxation authorities, using the tax rates (and tax laws) that have been enacted or substantively enacted by the end of the reporting period. Management periodically evaluates tax policies that are applied in tax returns in which applicable tax regulation is subject to interpretation. The Group recognizes current income tax on the basis of the amount expected to be paid to the tax authorities. Deferred income tax is provided in full, using the liability method, on temporary differences arising between the tax bases of assets and liabilities and their carrying amounts in the consolidated financial statements. However, deferred income tax is not accounted for if it arises from initial recognition of an asset or liability in a transaction other than a business combination that at the time of the transaction affects neither accounting nor taxable profit or loss. Deferred tax assets are recognized only if it is probable that future taxable amount will be available to utilize those temporary differences and losses. The Group recognizes a deferred tax liability for taxable temporary differences associated with investments in subsidiaries, associates, and interests in joint arrangements, except to the extent that the Group is able to control the timing of the reversal of the temporary difference and it is probable that the temporary difference will not reverse in the foreseeable future. In addition, The Group recognizes a deferred tax asset for all deductible temporary differences arising from such investments to the extent that it is probable the temporary difference will reverse in the foreseeable future and taxable profit will be available against which the temporary difference can be utilized. Deferred tax assets and liabilities are offset when there is a legally enforceable right to offset current tax assets and liabilities and when the deferred tax balances relate to the same taxation authority. Current tax assets and liabilities are offset when the Group has a legally enforceable right to offset and intends either to settle on a net basis, or to realize the assets and settle the liability simultaneously. The Group adopts the consolidated corporate tax return and calculates income tax expenses and income tax liabilities of the Group based on systematic and reasonable methods.
Dividend	2. 28 Dividend Dividend distribution to the Group’s shareholders is recognized as a liability in the consolidated financial statements in the period in which the dividends are approved by the Group’s shareholders.
Approval of the Consolidated Financial Statements	2.2 9 Approval of the Consolidated Financial Statements The consolidated financial statements for 2020 were approved for issuance by the Board of Directors on April 13, 2021.

General Information (Tables)

General Information (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Consolidated Subsidiaries	The consolidated subsidiaries as at December 31, 2019 and 2020, are as follows: Controlling percentage 1 Subsidiary Type of business Location December 31, December 31, Closing month KT Powertel Co., Ltd. 2 Trunk Radio System (TRS) business Korea 44.8% 44.8% December KT Linkus Co., Ltd. Public telephone maintenance Korea 92.4% 92.4% December KT Submarine Co., Ltd. 2,4 Submarine cable construction and maintenance Korea 39.3% 39.3% December KT Telecop Co., Ltd. Security service Korea 86.8% 86.8% December KT Hitel Co., Ltd. Data communication Korea 67.1% 67.1% December KT Service Bukbu Co., Ltd. Opening services of fixed line Korea 67.3% 67.3% December KT Service Nambu Co., Ltd. Opening services of fixed line Korea 77.3% 77.3% December KT Commerce Inc. B2C, B2B service Korea 100.0% 100.0% December KT Strategic Investment Fund No.2 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.3 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.4 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.5 Investment fund Korea 100.0% 100.0% December BC-VP Investment fund Korea 100.0% 100.0% December BC Card Co., Ltd. Credit card business Korea 69.5% 69.5% December VP Inc. Payment security service for credit card, others Korea 50.9% 50.9% December H&C Network Call centre for financial sectors Korea 100.0% 100.0% December BC Card China Co., Ltd. Software development and data processing China 100.0% 100.0% December INITECH Co., Ltd. 4 Internet banking ASP and security solutions Korea 58.2% 58.2% December Smartro Co., Ltd. VAN (Value Added Network) business Korea 64.5% 64.5% December KTDS Co., Ltd. 4 System integration and maintenance Korea 95.5% 95.5% December KT M Hows Co., Ltd. Mobile marketing Korea 90.0% 90.0% December KT M&S Co., Ltd. PCS distribution Korea 100.0% 100.0% December GENIE Music Corporation (KT Music Corporation) 2,4 Online music production and distribution Korea 36.0% 36.2% December KT MOS Bukbu Co., Ltd. 4 Telecommunication facility maintenance Korea 100.0% 100.0% December KT MOS Nambu Co., Ltd. 4 Telecommunication facility maintenance Korea 98.4% 98.4% December KT Skylife Co., Ltd. 4 Satellite broadcasting business Korea 50.3% 50.3% December Skylife TV Co., Ltd. TV contents provider Korea 92.6% 92.6% December KT Estate Inc. Residential building development and supply Korea 100.0% 100.0% December KT AMC Co., Ltd. Asset management and consulting services Korea 100.0% 100.0% December NEXR Co., Ltd. Cloud system implementation Korea 100.0% 100.0% December KTGDH Co., Ltd. (KTSB Data Service) Data centre development and related service Korea 100.0% 100.0% December KT Sat Co., Ltd. Satellite communication business Korea 100.0% 100.0% December Nasmedia Co., Ltd. 3,4 Solution provider and IPTV advertisement sales business Korea 44.0% 44.0% December KT Sports Co., Ltd. Management of sports group Korea 100.0% 100.0% December KT Music Contents Fund No.1 Music contents investment business Korea 80.0% 80.0% December KT Music Contents Fund No.2 Music contents investment business Korea 100.0% 100.0% December KT-Michigan Content investment business Korea 88.6% 88.6% December Autopion Co., Ltd. Information and communication service Korea 100.0% 100.0% December KTCS Corporation 2,4 Database and online information provider Korea 30.9% 31.9% December KTIS Corporation 2,4 Database and online information provider Korea 30.1% 30.8% December KT M Mobile Co., Ltd. Special category telecommunications operator and sales of communication device Korea 100.0% 100.0% December KT Investment Co., Ltd. Technology business finance Korea 100.0% 100.0% December Whowho&Company Co., Ltd. Software development and supply Korea 100.0% 100.0% December PlayD Co., Ltd. (N Search Marketing Co., Ltd.) Advertising agency Korea 100.0% 70.4% December Next Connect PFV Residential building development and supply Korea 100.0% 100.0% December KT Rwanda Networks Ltd. Network installation and management Rwanda 51.0% 51.0% December AOS Ltd. System integration and maintenance Rwanda 51.0% 51.0% December KT Belgium Foreign investment business Belgium 100.0% 100.0% December Korea Telecom Japan Co., Ltd. Foreign telecommunication business Japan 100.0% 100.0% December KBTO sp.z o.o. Electronic communication business Poland 97.2% 97.4% December Korea Telecom China Co., Ltd. Foreign telecommunication business China 100.0% 100.0% December KT Dutch B.V. Super iMax and East Telecom management Netherlands 100.0% 100.0% December East Telecom LLC Fixed line telecommunication business Uzbekistan 91.0% 91.6% December Korea Telecom America, Inc. Foreign telecommunication business USA 100.0% 100.0% December PT. BC Card Asia Pacific Software development and supply Indonesia 99.9% 99.9% December KT Hong Kong Telecommunications Co., Ltd. Fixed line communication business Hong Kong 100.0% 100.0% December Korea Telecom Singapore Pte. Ltd. Foreign investment business Singapore 100.0% 100.0% December Texnoprosistem LLC Fixed line internet business Uzbekistan 100.0% 100.0% December Nasmedia Thailand Co., Ltd. Internet advertising solution provider Thailand 99.9% 99.9% December KT Huimangjieum Manufacturing Korea 100.0% 100.0% December GE Premier 1st Corporate Restructuring Real Estate Investment Trust Co. Residential building investment and rent Korea 63.5% 68.1% December K-REALTY Residential building Korea 100.0% 88.6% December Storywiz Co., Ltd Content and software development and supply Korea — 100.0% December KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) Telecommunication facility construction and maintenance Korea — 100.0% December 1 Sum of the ownership interests owned by the Controlling Company and subsidiaries. 2 Although the Controlling Company owns less than 50% ownership in this entity, this entity is consolidated as the Controlling Company can exercise the majority voting rights in its decision-making process at all times considering the historical voting pattern at the shareholders’ meetings. 3 Although the Controlling Company owns less than 50% ownership in this entity, this entity is consolidated as the Controlling Company holds the majority of voting right based on an agreement with other investors. 4 The number of subsidiaries’ treasury stock is deducted from the total number of shares when calculating the controlling percentage ownership. Changes in scope of consolidation in 2020 are as follows: Changes Location Name of Subsidiary Reason Included Korea Storywiz Co., Ltd Newly established Korea KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) Transferred Excluded Uzbekistan Super iMax LLC Merged Indonesia PT. KT Indonesia Liquidated Belgium KT ORS Belgium Liquidated Summarized information for consolidated subsidiaries as at and for the years ended December 31, 2018, 2019 and 2020, is as follows: (In millions of Korean won) 2018 Total Total Operating Profit (loss) for the year KT Powertel Co., Ltd. ￦ 124,064 ￦ 28,217 ￦ 65,620 ￦ (5,545 ) KT Linkus Co., Ltd. 54,147 44,895 106,337 1,216 KT Submarine Co., Ltd. 130,715 27,530 61,652 (4,286 ) KT Telecop Co., Ltd. 272,492 140,314 328,262 166 KT Hitel Co., Ltd. 272,708 66,043 279,117 657 KT Service Bukbu Co., Ltd. 30,599 23,964 195,961 (31 ) KT Service Nambu Co., Ltd. 37,452 27,939 230,088 160 BC Card Co., Ltd. 1 3,722,379 2,630,536 3,551,715 70,889 H&C Network 1 245,841 63,188 297,470 (15,944 ) Nasmedia Co., Ltd. 1 303,112 161,164 106,805 20,596 KTDS Co., Ltd. 1 148,675 95,834 434,302 8,586 KT M Hows Co., Ltd. 60,197 42,386 26,673 3,691 KT M&S Co., Ltd. 228,073 207,740 791,652 11,408 GENIE Music Corporation (KT Music Corporation) 221,559 75,827 171,314 6,374 KT MOS Bukbu Co., Ltd. 14,121 10,571 16,543 (782 ) KT MOS Nambu Co., Ltd. 14,313 8,927 14,941 (2,418 ) KT Skylife Co., Ltd. 1 816,001 149,841 694,059 52,010 KT Estate Inc. 1 1,695,995 304,712 569,269 51,854 KTGDH Co., Ltd. (KTSB Data service) 8,632 523 4,627 (9,576 ) KT Sat Co., Ltd. 685,926 173,513 137,186 4,921 KT Sports Co., Ltd. 9,560 6,376 55,565 (154 ) KT Music Contents Fund No.1 14,092 1,035 559 294 KT Music Contents Fund No.2 7,629 281 150 (142 ) KT-Michigan 12,741 — 869 (670 ) Autopion Co., Ltd. 8,838 5,801 12,035 453 KT M mobile Co., Ltd. 146,334 35,335 172,674 (10,085 ) KT Investment Co., Ltd. 1 74,580 58,040 8,095 247 KTCS Corporation 1 350,280 188,561 1,019,787 11,401 KTIS Corporation 229,246 68,997 451,532 7,900 Next connect PFV 385,769 34,370 143 (12,449 ) Korea Telecom Japan Co., Ltd. 1 1,326 2,910 1,965 (126 ) Korea Telecom China Co., Ltd. 661 22 681 10 KT Dutch B.V. 31,693 41 191 105 Super iMax LLC 4,150 4,528 4,845 (424 ) East Telecom LLC 1 16,590 14,263 15,087 2,639 Korea Telecom America, Inc. 4,218 832 7,554 350 PT. KT Indonesia 8 — — — KT Rwanda Networks Ltd. 2 144,129 162,801 15,150 (29,238 ) KT Belgium 90,172 1 29 (43 ) KT ORS Belgium 6,709 5 — (46 ) KBTO sp.zo.o. 1,364 217 202 (3,771 ) AOS Ltd. 2 14,018 4,952 6,300 (680 ) KT Hongkong Telecommunications Co., Ltd. 3,616 2,143 9,990 351 1 These companies are the intermediate controlling companies of other subsidiaries and the above financial information is from their consolidated financial statements. 2 At the end of the reporting period, convertible preferred stock issued by subsidiaries is included in liabilities. (In millions of Korean won) 2019 Total Total Operating Profit (loss) for the year KT Powertel Co., Ltd. ￦ 118,052 ￦ 19,766 ￦ 62,846 ￦ 3,085 KT Linkus Co., Ltd. 70,494 62,088 97,892 (2,258 ) KT Submarine Co., Ltd. 120,947 18,452 55,244 486 KT Telecop Co., Ltd. 279,878 153,841 332,063 (4,875 ) KT Hitel Co., Ltd. 279,818 74,769 323,065 1,426 KT Service Bukbu Co., Ltd. 64,802 58,984 219,427 (445 ) KT Service Nambu Co., Ltd. 63,917 55,548 266,148 280 BC Card Co., Ltd. 1 3,912,982 2,594,232 3,553,008 115,885 H&C Network 1 282,016 68,401 320,701 (1,593 ) Nasmedia Co., Ltd. 1 356,236 203,105 117,550 22,484 KTDS Co., Ltd. 1 158,153 105,462 428,758 9,027 KT M Hows Co., Ltd. 74,326 50,638 33,443 6,771 KT M&S Co., Ltd. 248,142 215,777 813,498 12,732 GENIE Music Corporation (KT Music Corporation) 234,131 80,952 230,480 7,658 KT MOS Bukbu Co., Ltd. 33,376 28,841 63,761 353 KT MOS Nambu Co., Ltd. 34,258 26,722 67,300 3,099 KT Skylife Co., Ltd. 1 848,276 142,839 704,996 56,008 KT Estate Inc. 1 1,686,000 295,706 485,686 48,552 KTGDH Co., Ltd. (KTSB Data service) 10,437 1,628 3,977 344 KT Sat Co., Ltd. 651,195 127,523 168,376 16,497 KT Sports Co., Ltd. 15,603 8,333 55,241 (464 ) KT Music Contents Fund No.1 10,579 1,677 521 345 KT Music Contents Fund No.2 7,675 279 331 48 KT-Michigan 11,688 61 248 (1,113 ) Autopion Co., Ltd. 7,460 4,894 5,604 (302 ) KT M mobile Co., Ltd. 135,917 30,603 161,720 (5,580 ) KT Investment Co., Ltd. 1 73,463 56,212 13,375 847 KTCS Corporation 1 378,171 213,983 944,778 7,597 KTIS Corporation 305,798 137,524 454,561 9,205 Next connect PFV 385,412 24,275 1,590 (5,898 ) Korea Telecom Japan Co., Ltd. 1 1,851 2,858 2,891 651 Korea Telecom China Co., Ltd. 879 39 844 192 KT Dutch B.V. 31,003 50 — (242 ) Super iMax LLC 3,568 5,304 4,604 (631 ) East Telecom LLC 1 20,857 16,302 17,186 2,140 Korea Telecom America, Inc. 4,611 537 6,808 572 PT. KT Indonesia 8 — — — KT Rwanda Networks Ltd. 2 132,461 183,164 18,013 (31,662 ) KT Belgium 93,321 11 — (64 ) KT ORS Belgium 6,913 14 — (43 ) KBTO sp.zo.o. 1,767 245 519 (3,457 ) AOS Ltd. 2 12,337 3,993 6,982 (591 ) KT Hongkong Telecommunications Co., Ltd. 5,126 2,923 13,321 586 KT Huimangjieum 2,129 1,019 1,027 (390 ) GE Premier 1st Corporate Restructuring Real Estate Investment Trust Co. 6,285 1,139 176 70 K-REALTY 300 — — — 1 These companies are the intermediate controlling companies of other subsidiaries and the above financial information is from their consolidated financial statements. 2 At the end of the reporting period, convertible preferred stock issued by subsidiaries is included in liabilities. ( I 2020 Total Total Operating Profit (loss) for the year KT Powertel Co., Ltd. ￦ 119,694 ￦ 18,833 ￦ 65,897 ￦ 3,809 KT Linkus Co., Ltd. 58,372 54,022 84,519 (3,212 ) KT Submarine Co., Ltd. 116,813 14,032 110,201 1,197 KT Telecop Co., Ltd. 318,456 193,737 392,489 212 KT Hitel Co., Ltd. 288,949 92,599 350,231 2,080 KT Service Bukbu Co., Ltd. 60,825 56,554 217,451 (871 ) KT Service Nambu Co., Ltd. 58,182 51,460 264,776 (456 ) BC Card Co., Ltd. 1 3,084,398 1,778,751 3,387,640 39,455 H&C Network 1 269,651 61,365 322,690 2,413 Nasmedia Co., Ltd. 1 422,039 221,371 113,136 23,134 KTDS Co., Ltd. 1 183,297 133,129 499,990 10,635 KT M Hows Co., Ltd. 104,704 76,315 44,860 6,935 KT M&S Co., Ltd. 231,260 197,306 661,533 (485 ) GENIE Music Corporation (KT Music Corporation) 250,538 88,488 247,237 9,472 KT MOS Bukbu Co., Ltd. 32,167 26,070 67,975 1,473 KT MOS Nambu Co., Ltd. 33,765 24,947 71,259 1,639 KT Skylife Co., Ltd. 1 919,476 175,039 706,631 58,190 KT Estate Inc. 1 1,689,601 325,429 365,335 14,370 KTGDH Co., Ltd. (KTSB Data Service) 11,003 1,669 4,282 538 KT Sat Co., Ltd. 630,740 92,791 173,693 14,753 KT Sports Co., Ltd. 26,572 14,940 46,608 (2,516 ) KT Music Contents Fund No.1 4,844 1,525 243 84 KT Music Contents Fund No.2 15,021 285 169 (116 ) KT-Michigan 10,382 175 111 (1,420 ) Autopion Co., Ltd. 4,903 4,961 6,174 (2,459 ) KT M Mobile Co., Ltd. 129,011 27,281 163,472 (3,617 ) KT Investment Co., Ltd. 1 115,627 93,695 47,801 4,680 KTCS Corporation 1 384,919 215,175 933,006 11,323 KTIS Corporation 294,289 126,894 454,172 7,387 Next Connect PFV 394,268 37,271 26 (7,101 ) Korea Telecom Japan Co., Ltd. 1 2,694 2,622 1,853 1 Korea Telecom China Co., Ltd. 381 21 618 (492 ) KT Dutch B.V. 1 29,585 10,109 26,782 6,061 Korea Telecom America, Inc. 4,498 125 6,808 712 KT Rwanda Networks Ltd. 2 114,768 191,781 17,870 (34,610 ) KT Belgium 87,608 — (81 ) (81 ) KBTO sp.z o.o. 438 117 490 (2,823 ) AOS Ltd. 2 11,812 3,875 5,719 296 KT Hong Kong Telecommunications Co., Ltd. 6,159 2,800 16,386 1,308 KT Huimangjieum 3,720 2,787 5,239 (13 ) GE Premier 1st Corporate Restructuring Real Estate Investment Trust Co. 5,703 1,165 333 83 Storywiz Co., Ltd 21,594 10,065 19,209 (1,954 ) KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) 138,220 102,963 346,040 (8,461 ) 1 These companies are the intermediate controlling companies of other subsidiaries and the above financial information is from their consolidated financial statements. 2 At the end of the reporting period, convertible preferred stock issued by subsidiaries is included in liabilities.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Estimated Useful Lives of Property, Plant and Equipment	Depreciation of all property and equipment, except for land, is calculated using the straight-line method to allocate their cost, net of their residual values, over their estimated useful lives as follows: Estimated Useful Life Buildings 5 – 40 years Structures 5 – 40 years Machinery and equipment (Telecommunications equipment and others) 2 – 40 years Others Vehicles 4 – 6 years Tools 4 – 6 years Office equipment 2 – 6 years
Summary of Amortization of Intangible Assets With Limited Useful Life	The Group amortizes intangible assets with a limited useful life using the straight-line method over the following periods: Estimated Useful Life Development costs 5 – 6 years Software 4 – 6 years Frequency usage rights 5 – 10 years Others 1 1 – 50 years 1 Membership rights (condominium membership and golf membership) and broadcast license included in others are classified as intangible assets with indefinite useful life.

Financial Instruments by Cate_2

Financial Instruments by Category (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Financial Instruments by Category	Financial instruments by category as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 Financial assets Financial assets at cost Financial Financial Derivatives Total Cash and cash equivalents ￦ 2,305,894 ￦ — ￦ — ￦ — ￦ 2,305,894 Trade and other receivables 1 5,748,459 — 1,256,266 — 7,004,725 Other financial assets 441,804 632,324 557,342 58,576 1,690,046 1 Lease receivables and others which are not applied to financial instruments by category are excluded. (In millions of Korean won) December 31, 2019 Financial liabilities Financial Financial Derivatives Total Trade and other payables ￦ 8,679,698 ￦ — ￦ — ￦ 8,679,698 Borrowings 7,298,867 — — 7,298,867 Other financial liabilities 129,945 38 20,096 150,079 (In millions of Korean won) December 31, 2020 Financial assets Financial Financial Financial Derivatives Total Cash and cash equivalents ￦ 2,634,624 ￦ — ￦ — ￦ — ￦ 2,634,624 Trade and other receivables 1 4,976,423 — 1,118,619 — 6,095,042 Other financial assets 671,068 809,919 258,516 7,684 1,747,187 1 Lease receivables and others which are not applied to financial instruments by category are excluded. (In millions of Korean won) December 31, 2020 Financial liabilities Financial Financial liabilities Derivatives Total Trade and other payables ￦ 7,017,639 ￦ — ￦ — ￦ 7,017,639 Borrowings 7,316,298 — — 7,316,298 Other financial liabilities 132,558 2,682 127,929 263,169
Summary of Gains or Losses Arising From Financial Instruments by Category	Gains or losses arising from financial instruments by category for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Financial assets at amortized cost Interest income 1,5 ￦ 93,233 ￦ 79,838 ￦ 55,742 Gain(loss) on foreign currency transaction 4 19,396 32,293 (19,244 ) Loss on foreign currency translation 4 (2,901 ) (474 ) (3,895 ) Gain(loss) on disposal 44 (43 ) 138 Loss on valuation (110,544 ) (59,947 ) (140,474 ) Financial assets at fair value through profit or loss Interest income 1 9,194 5,634 6,548 Dividend income 6 1,207 1,096 4,379 Gain on valuation 7 10,768 4,334 59,044 Gain on disposal 1,713 5,115 (329 ) Loss on foreign currency transaction 4 — — (38 ) Loss on foreign currency translation 4 — (27 ) — Financial assets at fair value through other comprehensive income Interest income 1 163,390 217,355 227,736 Dividend income 6 1,704 2,312 56 Impairment loss (2,416 ) (304 ) — Loss on disposal (13,818 ) (11,247 ) (8,152 ) Other comprehensive income for the year 2 43,811 167,152 41,997 Derivative assets used for hedging Gain on transaction 7,272 6,332 6,050 Gain(loss) on valuation 22,065 56,537 (2,707 ) Other comprehensive income(loss) for the year 2 20,078 46,806 (2,373 ) Reclassified to profit or loss from other comprehensive income for the year 2,3 (15,891 ) (39,604 ) 3,645 Financial liabilities at fair value through profit or loss Gain on disposal — 2,664 799 Gain(loss) on valuation (2,708 ) (1,936 ) 119 Derivative liabilities used for hedging Gain on transactions 20,678 — 1,141 Gain(loss) on valuation 42,195 4,949 (161,003 ) Other comprehensive income for the year 2 (2,810 ) 20,742 (81,671 ) Reclassified to profit or loss from other comprehensive income for the year 2,3 (28,388 ) (5,080 ) 107,786 Financial liabilities at amortized cost Interest expense 1,5 (296,894 ) (223,974 ) (220,945 ) Loss on repayment (15 ) — — Loss on foreign currency transaction 4 (30,956 ) (20,958 ) (10,717 ) Gain(loss) on foreign currency translation 4 (66,050 ) (75,502 ) 141,849 Total ￦ (116,643 ) ￦ 214,063 ￦ 5,481 1 BC Card, a subsidiary of the Group, recognized interest income and expense as operating revenue and expense, respectively. Related interest income recognized as operating revenue is ￦ ￦ ￦ ￦ ￦ ￦ 2 The amounts directly reflected in equity after adjustments of deferred income tax. 3 During the year, certain derivatives of the Group were settled and the related gain or loss on valuation of cash flow hedge in other comprehensive income was reclassified to profit or loss for the year. 4 BC Card Co., Ltd., a subsidiary of the Group recognized foreign currency translation/transaction gain and loss and as operating income and expenses. In relation to this, foreign currency translation gain and loss recognized as operating revenue and expense amount to ￦ ￦ ￦ ￦ ￦ ￦ 5 Interest income (interest expense) from lease receivables (lease liabilities) is excluded as it is not subject to classification of financial instruments (Note 21). 6 BC Card Co., Ltd., a subsidiary of the Group, recognized dividend income as operating revenue. Related dividend income recognized as operating revenue is ￦ ￦ ￦ 7 KT Investment Co., Ltd., etc., subsidiaries of the Group, recognized financial instruments measured at fair value through profit or loss as operating income and expenses. In relation to this, valuation gain and loss recognized as operating revenue and expense amount to ￦ 40,822 million (2018: ￦ (-) 5 million, 2019: ￦ 15,429 million), for the year ended December 31, 2020.

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Restricted Cash and Cash Equivalents	Restricted cash and cash equivalents as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, December 31, Description Bank deposits ￦ ￦ Deposit restricted for government project and others

Trade and Other Receivables (Ta

Trade and Other Receivables (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Trade and Other Receivables	Trade and other receivables as at December 31, 2019 and 2020, are as follows: December 31, 2019 (In millions of Korean won) Total Provision Present value Carrying amount Current assets Trade receivables ￦ 3,451,107 ￦ (291,202 ) ￦ (9,510 ) ￦ 3,150,395 Other receivables 2,787,144 (78,572 ) (271 ) 2,708,301 ￦ 6,238,251 ￦ (369,774 ) ￦ (9,781 ) ￦ 5,858,696 Non-current Trade receivables ￦ 874,860 ￦ (4,117 ) ￦ (43,597 ) ￦ 827,146 Other receivables 382,468 (5,108 ) (22,708 ) 354,652 ￦ 1,257,328 ￦ (9,225 ) ￦ (66,305 ) ￦ 1,181,798 December 31, 2020 (In millions of Korean won) Total Provision Present value Carrying amount Current assets Trade receivables ￦ 3,388,099 ￦ (322,992 ) ￦ (8,977 ) ￦ 3,056,130 Other receivables 1,948,108 (101,619 ) (148 ) 1,846,341 ￦ 5,336,207 ￦ (424,611 ) ￦ (9,125 ) ￦ 4,902,471 Non-current Trade receivables ￦ 892,992 ￦ (4,323 ) ￦ (34,716 ) ￦ 853,953 Other receivables 513,926 (102,985 ) (14,125 ) 396,816 ￦ 1,406,918 ￦ (107,308 ) ￦ (48,841 ) ￦ 1,250,769
Summary of Changes in Provision for Impairment	Details of changes in provision for impairment for the years ended December 31, 2019 and 2020, are as follows: 2019 2020 (In millions of Korean won) Trade Other Trade Other Beginning balance ￦ 359,924 ￦ 93,822 ￦ 295,319 ￦ 83,680 Provision 24,596 35,597 89,097 50,860 Reversal — (475 ) — (890 ) Written-off (90,513 ) (44,108 ) (60,598 ) (25,067 ) Change in consolidation scope — — 3,211 87,614 Others 1,312 (1,156 ) 286 8,407 Ending balance ￦ 295,319 ￦ 83,680 ￦ 327,315 ￦ 204,604
Summary of Other Receivables	Details of other receivables as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, December 31, Loans ￦ 84,148 ￦ 116,082 Receivables 1 2,540,315 1,699,608 Accrued income 8,630 6,901 Refundable deposits 352,293 350,180 Loans receivable 105,961 150,527 Finance lease receivables 39,726 64,047 Others 15,560 60,416 Less: Provision for impairment (83,680 ) (204,604 ) ￦ 3,062,953 ￦ 2,243,157 1 Settlement receivables of BC Card Co., Ltd., a subsidiary of the Group, of ￦ ￦

Other Financial Assets and Li_2

Other Financial Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Other Financial Assets and Liabilities	Details of other financial assets and liabilities as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Other financial assets Financial assets at amortized cost 1 ￦ 441,804 ￦ 671,068 Financial assets at fair value through profit or loss 1,2,3 632,324 809,919 Financial assets at fair value through other comprehensive income 1,3 557,342 258,516 Derivative used for hedging 58,576 7,684 Less: Non-current (821,658 ) (544,347 ) Current ￦ 868,388 ￦ 1,202,840 Other financial liabilities Financial liabilities at amortized cost ￦ 129,945 ￦ 132,558 Financial liabilities at fair value through profit or loss 38 2,682 Derivatives used for hedging 20,096 127,929 Less: Non-current (149,136 ) (260,676 ) Current ￦ 943 ￦ 2,493 1 As at December 31, 2020, the Group’s other financial assets amounting to ￦ ￦ 2 As at December 31, 2020, MMW (Money Market Wrap) and MMT (Money Market Trust) amounting to ￦ ￦ 3 As at December 31, 2020, the Group provided investments in Korea Software Financial Cooperative amounting to ￦ ￦
Summary of Financial Assets at Fair Value Through Profit or Loss	Details of financial assets at fair value through profit or loss as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Equity Instruments (Listed) ￦ 232 ￦ 46,449 Equity Instruments (Unlisted) 90,357 83,017 Debt securities 541,657 680,453 Derivatives held for trading 78 — Total 632,324 809,919 Less: non-current (219,026 ) (276,109 ) Current ￦ 413,298 ￦ 533,810
Summary of Financial Assets at Fair Value Through Other Comprehensive Income	Details of financial assets at fair value through other comprehensive income as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Equity Instruments (Listed) ￦ 6,738 ￦ 6,216 Equity Instruments (Unlisted) 543,518 245,730 Debt securities 7,086 6,570 Total 557,342 258,516 Less: non-current (556,147 ) (258,516 ) Current ￦ 1,195 ￦ —
Summary of Derivative Financial Assets and Liabilities	Derivatives used for hedg ing December 31, 2019 December 31, 2020 (In millions of Korean won) Assets Liabilities Assets Liabilities Interest rate swap 1 ￦ — ￦ 1,464 ￦ — ￦ 1,078 Currency swap 2 55,569 18,632 7,684 126,189 Currency forwards 3 3,007 — — 662 Total 58,576 20,096 7,684 127,929 Less: non-current (28,304 ) (19,177 ) (2,111 ) (126,408 ) Current ￦ 30,272 ￦ 919 ￦ 5,573 ￦ 1,521 1 The interest rate swap contract is to hedge the risk of variability in future fair value of the borrowings. 2 The currency swap contract is to hedge the risk of variability in cash flow from the borrowings. In applying the cash flow hedge accounting, the Group hedges its exposures to cash flow fluctuation until September 7, 2034. 3 The currency forward contract is to hedge the risk of variability in cash flow from transactions in foreign currencies due to changes in foreign exchange rate. The full value of a hedging derivative is classified as a non-current
Summary of Valuation Gains and Losses on Derivatives Contracts	The valuation gains and losses on the derivatives contracts for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of 2018 2019 2020 Type of Valuation gain Valuation loss Other comprehensive income 1 Valuation gain Valuation loss Other comprehensive income 1 Valuation gain Valuation Loss Other comprehensive income 1 Interest rate swap ￦ 192 ￦ — ￦ (488) ￦ — ￦ 45 ￦ (963) ￦ — ￦ — ￦ (567) Currency swap 58,912 2,045 22,139 72,417 15,784 87,626 — 161,661 (113,175 ) Currency forwards 7,201 — — 4,858 — 4,858 — 2,049 — Total ￦ 66,305 ￦ 2,045 ￦ 21,651 ￦ 77,275 ￦ 15,829 ￦ 91,521 ￦ — ￦ 163,710 ￦ (113,742) 1 The amounts before adjustments of deferred income tax directly reflected in equity and allocation to the non-controlling The ineffective portion recognized in profit or loss on the cash flow hedge is valuation loss of ￦ ￦ ￦
Summary of Financial Liabilities at Fair Value Through Profit or Loss	Details of financial liabilities at fair value through profit or loss as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Financial liabilities at fair value through profit or loss Derivative liabilities held for trading ￦ 38 ￦ 45 Conversion Rights and Redemption Rights — 2,637 Total ￦ 38 ￦ 2,682
Summary of Valuation Gain and Loss on Financial Liabilities at Fair Value Through Profit or Loss	The valuation gain and loss on financial liabilities at fair value through profit or loss for the years ended December 31, 2018, 2019 and 2020, are as follows: 2018 2019 2020 (In millions of Korean won) Valuation gain Valuation loss Valuation gain Valuation loss Valuation gain Valuation loss Derivative liabilities held for trading ￦ — ￦ 2,707 ￦ 78 ￦ 2,014 ￦ 10 ￦ 53 Conversion Rights and Redemption Rights — — — — 162 — Total ￦ — ￦ 2,707 ￦ 78 ￦ 2,014 ￦ 172 ￦ 53
Summary of Hedging instruments	(i) Hedging instruments (In millions of Korean won and thousands of foreign currencies) 2019 Book value of hedging Changes in fair Currency Foreign Contract Assets Liabilities USD 1,574,068 ￦ 1,788,831 ￦ 30,175 ￦ 10,692 ￦ 49,480 JPY 80,000,000 827,292 28,401 9,404 15,396 Total ￦ 2,616,123 ￦ 58,576 ￦ 20,096 ￦ 64,876 (In millions of Korean won and thousands of 2020 Book value of hedging Changes in fair Currency Foreign Contract Assets Liabilities USD 1,768,912 ￦ 2,037,568 ￦ 2,111 ￦ 100,623 ￦ (136,852 ) JPY 46,000,000 488,924 5,573 13,839 (4,065 ) SGD 284,000 245,208 — 13,467 (13,611 ) Total ￦ 2,771,700 ￦ 7,684 ￦ 127,929 ￦ (154,528 )
Summary of Hedged items	(ii) Hedged item (In millions of Korean won) 2019 2020 Currency Book value of hedged Changes in fair Cash flow 1 Book value of hedged Changes in fair Cash flow 1 USD ￦ 1,822,477 ￦ (45,855 ) ￦ (5,214 ) ￦ 1,924,576 ￦ 133,978 ￦ 19,641 JPY 850,776 (14,841 ) (2,395 ) 484,960 4,228 (2,569 ) SGD — — — 233,510 13,611 2,707 Total ￦ 2,673,253 ￦ (60,696 ) ￦ (7,609 ) ￦ 2,643,046 ￦ 151,817 ￦ 19,779 1 The amounts after adjustments of deferred income tax directly reflected in equity.

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Inventories Net	Inventories as at December 31, 2019 and 2020, are as follows: December 31, 2019 December 31, 2020 (In millions of Korean won) Acquisition Valuation Book amount Acquisition cost Valuation allowance Book amount Merchandise ￦ 805,691 ￦ (144,438 ) ￦ 661,253 ￦ 650,856 ￦ (133,224 ) ￦ 517,632 Others 130,424 — 130,424 17,004 — 17,004 Total ￦ 936,115 ￦ (144,438 ) ￦ 791,677 ￦ 667,860 ￦ (133,224 ) ￦ 534,636

Other Assets and Liabilities (T

Other Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Other Assets and Liabilities	Other assets and liabilities as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Other assets Advance payments ￦ 179,475 ￦ 168,302 Prepaid expenses 84,768 66,578 Contract cost 1 1,849,243 1,804,948 Contract assets 1 557,041 586,438 Others 14,243 18,747 Less: Non-current (685,488 ) (768,661 ) Current ￦ 1,999,282 ￦ 1,876,352 Other liabilities Advances received 1 ￦ 333,342 ￦ 328,491 Withholdings 99,844 105,415 Unearned revenue 1 65,228 29,593 Lease liabilities 1,211,352 1,143,640 Contract liabilities 1 365,610 384,133 Others 23,298 21,597 Less: Non-current (1,030,117 ) (909,570 ) Current ￦ 1,068,557 ￦ 1,103,299 1 The amounts include adjustments arising from adoption of IFRS 15 (Note 26).

Assets Held for Sale (Tables)

Assets Held for Sale (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Assets Held for Sale	Details of assets held for sale are as follows: (In millions of Korean won) Amount Land ￦ 172 Buildings and Other 1,026 Total ￦ 1,198

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Changes in Property and Equipment	Changes in property and equipment for the years ended December 31, 2019 and 2020, are as follows: 2019 (In millions of Korean won) Land Buildings Machinery Others Construction- in-progress Total Acquisition cost ￦ 1,281,319 ￦ 3,873,074 ￦ 36,327,007 ￦ 1,981,646 ￦ 826,583 ￦ 44,289,629 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,865,389 ) (27,851,991 ) (1,503,265 ) (595 ) (31,221,372 ) Beginning, net 1,281,187 2,007,685 8,475,016 478,381 825,988 13,068,257 Changes in accounting policy 1 — (149 ) (12,947 ) (196,932 ) — (210,028 ) Acquisition and capital expenditure 338 4,523 205,359 64,072 3,419,136 3,693,428 Disposal and termination (1,352 ) (4,213 ) (76,457 ) (4,109 ) (1,362 ) (87,493 ) Depreciation — (134,350 ) (2,278,286 ) (89,940 ) — (2,502,576 ) Impairment — (32 ) (41,450 ) (1,751 ) (27 ) (43,260 ) Transfer in (out) 126,066 270,980 2,742,671 16,218 (3,217,044 ) (61,109 ) Transfer to investment properties (33,254 ) (8,081 ) — — — (41,335 ) Transfer to assets held-for-sale (89,330 ) (1,121 ) — — — (90,451 ) Others (21,474 ) 26,822 79,345 1,596 (26,423 ) 59,866 Ending, net ￦ 1,262,181 ￦ 2,162,064 ￦ 9,093,251 ￦ 267,535 ￦ 1,000,268 ￦ 13,785,299 Acquisition cost ￦ 1,262,313 ￦ 4,125,229 ￦ 37,654,635 ￦ 1,612,108 ￦ 1,001,171 ￦ 45,655,456 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,963,165 ) (28,561,384 ) (1,344,573 ) (903 ) (31,870,157 ) 1 With the application of IFRS 16, property and equipment were reclassified to right-of-use 2020 (In millions of Korean won) Land Buildings Machinery Others Construction- in-progress Total Acquisition cost ￦ 1,262,313 ￦ 4,125,229 ￦ 37,654,635 ￦ 1,612,108 ￦ 1,001,171 ￦ 45,655,456 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,963,165 ) (28,561,384 ) (1,344,573 ) (903 ) (31,870,157 ) Beginning, net 1,262,181 2,162,064 9,093,251 267,535 1,000,268 13,785,299 Acquisition and capital expenditure 25,156 7,249 112,085 47,669 2,959,690 3,151,849 Disposal and termination (1,756 ) (3,367 ) (69,401 ) (3,385 ) (1,027 ) (78,936 ) Depreciation — (135,646 ) (2,343,965 ) (91,164 ) — (2,570,775 ) Impairment — (36 ) (35,271 ) (44,468 ) — (79,775 ) Transfer in (out) 53,238 283,937 2,489,138 28,024 (2,899,197 ) (44,860 ) Transfer to investment properties 6,792 (8,848 ) — — — (2,056 ) Changes in scope of consolidation 56 494 225 43 — 818 Others (11,040 ) 2,175 68,921 1,398 (16,899 ) 44,555 Ending, net ￦ 1,334,627 ￦ 2,308,022 ￦ 9,314,983 ￦ 205,652 ￦ 1,042,835 ￦ 14,206,119 Acquisition cost ￦ 1,334,759 ￦ 4,402,691 ￦ 39,182,265 ￦ 1,619,822 ￦ 1,046,795 ￦ 47,586,332 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (2,094,669 ) (29,867,282 ) (1,414,170 ) (3,960 ) (33,380,213 )
Summary of the Details of Property and Equipment Provided	Details of property and equipment provided as collateral as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 Carrying Secured Related line Related Secured party Land and Buildings ￦ 17,097 ￦ 18,705 Borrowings ￦ 4,347 Industrial Bank , K Bank, Inc. Others ￦ 45,851 ￦ 41,681 Borrowings ￦ 3,473 Shinhan (In millions of Korean won) December 31, 2020 Carrying Secured Related line Related Secured party Land and Buildings ￦ 11,644 ￦ 15,502 Borrowings ￦ 3,072 Industrial Korea Bank ￦ 4,142 ￦ 249 Deposits ￦ 249 K Bank, Inc.

Investment Properties (Tables)

Investment Properties (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Investment Properties	Changes in investment properties for the years ended December 31, 2019 and 2020, are as follows: (In millions of Korean won) 2019 Land Buildings Construction- in-progress Total Acquisition cost ￦ 350,417 ￦ 1,168,379 ￦ 121 ￦ 1,518,917 Less: Accumulated depreciation (1,569 ) (426,264 ) — (427,833 ) Beginning, net ￦ 348,848 ￦ 742,115 ￦ 121 ￦ 1,091,084 Changes in accounting policy 1 — 46,666 — 46,666 Acquisition 148,511 103,774 1,781 254,066 Disposal and termination (285 ) (1,408 ) — (1,693 ) Depreciation — (65,178 ) — (65,178 ) Transfer from property and equipment 33,254 8,081 — 41,335 Transfer and others 23,268 (2,118 ) — 21,150 Ending, net ￦ 553,596 ￦ 831,932 ￦ 1,902 ￦ 1,387,430 Acquisition cost ￦ 555,164 ￦ 1,323,518 ￦ 1,902 ￦ 1,880,584 Less: Accumulated depreciation (including accumulated impairment loss and others) (1,568 ) (491,586 ) — (493,154 ) 1 With the application of IFRS 16, right-of-use-assets (In millions of Korean won) 2020 Land Buildings Construction- in-progress Total Acquisition cost ￦ 555,164 ￦ 1,323,518 ￦ 1,902 ￦ 1,880,584 Less: Accumulated depreciation (1,568 ) (491,586 ) — (493,154 ) Beginning, net ￦ 553,596 ￦ 831,932 ￦ 1,902 ￦ 1,387,430 Acquisition 11,723 7,096 34,243 53,062 Disposal and termination (1,536 ) (243 ) — (1,779 ) Depreciation — (64,531 ) — (64,531 ) Transfer from property and equipment (6,792 ) 8,848 — 2,056 Transfer and others (18,656 ) 469 10,402 (7,785 ) Ending, net ￦ 538,335 ￦ 783,571 ￦ 46,547 ￦ 1,368,453 Acquisition cost ￦ 539,903 ￦ 1,341,326 ￦ 46,547 ￦ 1,927,776 Less: Accumulated depreciation (including accumulated impairment loss and others) (1,568 ) (557,755 ) — (559,323 )
Summary of Investment Properties Provided as Collateral	Details of investment properties provided as collateral as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 Carrying Secured Related Related Land and Buildings ￦ 854,874 ￦ 62,896 Deposits ￦ 56,831 Land and Buildings ￦ 1,915 ￦ 3,044 Borrowings ￦ 1,903 (In millions of Korean won) December 31, 2020 Carrying Secured Related Related Land and Buildings ￦ 790,414 ￦ 62,968 Deposits ￦ 56,247 Land and Buildings ￦ 2,861 ￦ 3,434 Borrowings ￦ 2,928

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Intangible Assets	Changes in intangible assets for the years ended December 31, 2019 and 2020, are as follows: 2019 (In millions of Korean won) Goodwill Development Software Frequency usage rights Others Total Acquisition cost 542,074 1,680,372 947,312 3,641,231 1,253,281 8,064,270 Less: Accumulated amortization (including accumulated impairment loss and others) (306,016 ) (1,345,262 ) (781,368 ) (1,484,731 ) (739,769 ) (4,657,146 ) Beginning, net ￦ 236,058 ￦ 335,110 ￦ 65,944 ￦ 2,156,500 ￦ 513,512 ￦ 3,407,124 Changes in accounting policy 1 — — — — (26,207 ) (26,207 ) Acquisition and capital expenditure — 47,903 30,965 — 99,826 178,694 Disposal and termination — (3,019 ) (1,267 ) (284 ) (11,109 ) (15,679 ) Amortization — (115,839 ) (68,222 ) (399,382 ) (77,262 ) (660,705 ) Impairment (605 ) (1,333 ) (1,807 ) (3,035 ) (55,118 ) (61,898 ) Others 117 9,812 11,768 142 (9,131 ) 12,708 Ending, net ￦ 235,570 ￦ 272,634 ￦ 137,381 ￦ 1,753,941 ￦ 434,511 ￦ 2,834,037 Acquisition cost 541,596 1,661,372 978,139 3,622,327 1,193,048 7,996,482 Less: Accumulated amortization (including accumulated impairment loss and others) (306,026 ) (1,388,738 ) (840,758 ) (1,868,386 ) (758,537 ) (5,162,445 ) 1 With the application of IFRS 16, intangible assets were reclassified to right-of-use 2020 (In millions of Korean won) Goodwill Development Software Frequency usage rights Others 1 Total Acquisition cost 541,596 1,661,372 978,139 3,622,327 1,193,048 7,996,482 Less: Accumulated amortization (including accumulated impairment loss and others) (306,026 ) (1,388,738 ) (840,758 ) (1,868,386 ) (758,537 ) (5,162,445 ) Beginning, net ￦ 235,570 ￦ 272,634 ￦ 137,381 ￦ 1,753,941 ￦ 434,511 ￦ 2,834,037 Acquisition and capital expenditure — 26,990 37,077 — 101,563 165,630 Disposal and termination — (1,849 ) (105 ) — (11,866 ) (13,820 ) Amortization — (104,938 ) (54,191 ) (399,348 ) (69,677 ) (628,154 ) Impairment — — (1,776 ) (193,194 ) (16,667 ) (211,637 ) Changes in scope of consolidation — 575 77 — 3,690 4,342 Others (5,485 ) 87,587 27,537 (736 ) (98,043 ) 10,860 Ending, net ￦ 230,085 ￦ 280,999 ￦ 146,000 ￦ 1,160,663 ￦ 343,511 ￦ 2,161,258 Acquisition cost 536,093 1,767,422 1,053,980 3,373,095 1,167,735 7,898,325 Less: Accumulated amortization (including accumulated impairment loss and others) (306,008 ) (1,486,423 ) (907,980 ) (2,212,432 ) (824,224 ) (5,737,067 ) 1 The carrying amount of membership rights and others, excluding goodwill, with indefinite useful life not subject to amortization is ￦ ￦
Summary of Goodwill Allocated to Each Cash-Generation Unit	As at December 31, 2020, goodwill allocated to each cash-generating unit is as follows: (In millions of Korean won) Operating Segment Cash generating Unit Amount ICT 6 Mobile services 1 ￦ 65,057 Finance BC Card Co., Ltd. 2 41,234 Others GENIE Music Corporation (KT Music Corporation) 3 50,214 PlayD Co., Ltd. (N SEARCH MARKETING Co., Ltd.) 4 42,745 KT Telecop Co., Ltd. 5 15,418 KT MOS Bukbu Co., Ltd and others 15,417 Total ￦ 230,085 1 The recoverable amounts of mobile services business are calculated based on value-in 2 The recoverable amounts of BC Card Co., Ltd. are calculated based on value-in 3 The recoverable amount of GENIE Music Corporation (KT Music Corporation) is calculated based on fair value less cost to sell. 4 The recoverable amount of PlayD Co., Ltd. (N SEARCH MARKETING Co., Ltd.) is calculated based on fair value less cost to sell. 5 The recoverable amounts of KT Telecop Co., Ltd. are calculated based on value-in 6 The Group performed its impairment assessment for long-lived assets attributed to the Information and Communication Technology (“ICT”) reporting segment, which includes the Cash-Generating Units of Mobile, Fixed line, and Corporate Services (the “CGUs”). The Group compared the carrying value of each CGU to the estimated recoverable amount. The recoverable amounts of ICT reporting segment are calculated based on value-in

Investments in Associates and_2

Investments in Associates and Joint Ventures (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Details of Associates	Details of associates as at December 31, 2019 and 2020, are as follows: Percentage of ownership (%) Location Closing month 2019 2020 Korea Information & Technology Fund 33.3 % 33.3 % Korea December 31, 2019, KT-IBKC 1 50.0 % 50.0 % Korea December 31, 2019, KT-CKP 49.7 % — Korea December 31, 2019, K Bank Inc. 10.0 % 34.0 % Korea December 31, 2019, Hyundai Robotics Co., Ltd. 2 — 10.0 % Korea December 31, 2019, 1 At the end of the reporting period, although the Group owns 50% ownership, the equity method of accounting has been applied as the Group, which is a limited partner of the investment fund, because the Group cannot participate in determining the operating and financial policies. 2 At the end of the reporting period, although the Group has less than 20% ownership in ordinary share, this entity is included in investments in associates as the Group has a significant influence in determining the operating and financial policies.
Summary of Changes in Investments in Associates and Joint Ventures	Changes in investments in associates and joint ventures for the years ended December 31, 2019 and 2020, are as follows: 2019 (In millions of Korean won) Beginning Acquisition (Disposal) Share of net profit 1 Others Ending Korea Information & Technology Fund ￦ 148,255 ￦ — ￦ 17,956 ￦ (2,236 ) ￦ 163,975 KT-SB 4,470 (4,470 ) — — — KT-IBKC 9,961 3,750 389 — 14,100 KT-CKP 281 (174 ) 27 — 134 K Bank Inc. 52,655 21,782 (28,865 ) (414 ) 45,158 Others 1 56,785 (7,867 ) 7,241 (11,866 ) 44,293 ￦ 272,407 ￦ 13,021 ￦ (3,252 ) ￦ (14,516 ) ￦ 267,660 2020 (In millions of Korean won) Beginning Acquisition (Disposal) Share of net profit 1 Others Ending Korea Information & Technology Fund ￦ 163,975 ￦ — ￦ 12,205 ￦ (6,025 ) ￦ 170,155 KT-IBKC 14,100 — 2,090 — 16,190 KT-CKP 134 (134 ) — — — K Bank Inc. 45,158 195,011 (30,209 ) (1,688 ) 208,272 Hyundai Robotics Co., Ltd. — 50,000 (64 ) 1,000 50,936 Others 1 44,293 28,400 34,298 5,337 112,328 ￦ 267,660 ￦ 273,277 ￦ 18,320 ￦ (1,376 ) ￦ 557,881 1 KT investment Co., Ltd., a subsidiary of the Group, recognized its share in net profit from associates and joint ventures as operating revenue and expense. These include its share in net gain from associates and joint ventures of ￦ ￦ ￦
Summary of Financial Information of Associates and Joint Ventures	Summarized financial information of associates and joint ventures as at and for the years ended December 31, 2019 and 2020, is as follows: (In millions of Korean won) December 31, 2019 Current Non-current assets Current Non-current liabilities Korea Information & Technology Fund ￦ 113,233 ￦ 378,691 ￦ — ￦ — KT-IBKC 28,200 — — — KT-CKP 3 267 — — K Bank Inc. 2,480,065 78,566 2,350,375 3,784 (In millions of Korean won) December 31, 2020 Current Non-current assets Current Non-current liabilities Korea Information & Technology Fund ￦ 107,652 ￦ 402,812 ￦ — ￦ — KT-IBKC Future Investment Fund 1 32,379 — — — K Bank Inc. 4,255,620 74,193 3,752,838 88,155 Hyundai Robotics Co., Ltd. 315,886 125,619 80,615 59,324 (In millions of Korean won) 2019 Operating Profit (loss) Other Total Dividends Korea Information & Technology Fund ￦ 70,577 ￦ 53,867 ￦ 6,132 ￦ 59,999 ￦ 4,280 KT-IBKC Future Investment Fund 1 1,694 779 — 779 — KT-CKP New Media Investment Fund 56 55 — 55 — K Bank Inc. 92,720 (100,773 ) (23 ) (100,796 ) — (In millions of Korean won) 2020 Operating Profit (loss) Other Total Dividends Korea Information & Technology Fund ￦ 54,473 ￦ 36,615 ￦ 9,647 ￦ 46,262 ￦ 9,241 KT-IBKC 6,551 4,179 — 4,179 — K Bank Inc. 80,301 (105,374 ) (1,126 ) (106,500 ) — Hyundai Robotics Co., Ltd. 195,311 (642 ) 11,573 10,931 —
Summary of Reconciliation of Carrying Amount of Interests in the Associates and Joint Ventures	Details of a reconciliation of the summarized financial information to the carrying amount of interests in the associates and joint ventures as at and for the years end December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 Net assets (a) Percentage of Share in (c)=(a)x(b) Intercompany Book (c)+(d) Korea Information & Technology Fund ￦ 491,924 33.30 % ￦ 163,975 ￦ — ￦ 163,975 KT-IBKC Future Investment Fund 1 28,200 50.00 % 14,100 — 14,100 KT-CKP 270 49.70 % 134 — 134 K Bank Inc. 1 204,472 10.00 % 45,158 — 45,158 1 12.1% of non-voting (In millions of Korean won) December 31, 2020 Net assets (a) Percentage of Share in net (c)=(a)x(b) Intercompany Book amount (c)+(d) Korea Information & Technology Fund ￦ 510,464 33.30 % ￦ 170,155 ￦ — ￦ 170,155 KT-IBKC 32,379 50.00 % 16,190 — 16,190 K Bank Inc. 1 488,819 34.00 % 166,198 42,074 208,272 Hyundai Robotics Co., Ltd. 301,566 10.00 % 30,157 20,779 50,936 1 12.1% of non-voting

Trade and Other Payables (Table

Trade and Other Payables (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Trade and Other Payables	Details of trade and other payables as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, December 31, Current liabilities Trade payables ￦ 1,304,795 ￦ 1,239,717 Other payables 6,292,683 4,970,382 Total ￦ 7,597,478 ￦ 6,210,099 Non-current Trade payables ￦ 1,733 ￦ 1,528 Other payables 1,080,487 806,012 Total ￦ 1,082,220 ￦ 807,540
Summary of Other Payables	Details of other payables as at December 31, 2019 and 2020 are as follows: (In millions of Korean won) December 31, December 31, Non-trade 1 ￦ 5,275,224 ￦ 3,841,227 Accrued expenses 987,624 933,978 Operating deposits 910,045 803,904 Others 200,277 197,285 Less: non-current (1,080,487 ) (806,012 ) Current ￦ 6,292,683 ￦ 4,970,382 1 Settlement payables of BC Card Co., Ltd., a subsidiary of the Group, of ￦ ￦

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Borrowings	Debentures (In millions of Korean won and thousands of foreign currencies) December 31, 2019 December 31, 2020 Type Maturity Annual interest Foreign Korean Foreign Korean MTNP notes 1 Sept. 7, 2034 6.50% USD 100,000 ￦ 115,780 USD 100,000 ￦ 108,800 MTNP notes July 18, 2026 2.50% USD 400,000 463,120 USD 400,000 435,200 MTNP notes Aug. 7, 2022 2.63% USD 400,000 463,120 USD 400,000 435,200 FR notes Aug. 20, 2020 — USD 200,000 231,560 — — FR notes 2 Aug. 20, 2023 LIBOR(3M)+0.900% USD 100,000 115,780 USD 100,000 108,800 MTNP notes July 6, 2020 — JPY 4,000,000 42,539 — — MTNP notes July 6, 2021 0.38% JPY 16,000,000 170,155 JPY 16,000,000 168,682 MTNP notes Nov. 13, 2020 — JPY 30,000,000 319,041 — — MTNP notes July 19, 2022 0.22% JPY 29,600,000 314,787 JPY 29,600,000 312,061 MTNP notes July 19, 2024 0.33% JPY 400,000 4,254 JPY 400,000 4,217 FR notes 2 Nov. 1, 2024 LIBOR(3M)+0.980% USD 350,000 405,230 USD 350,000 380,800 FR notes 2 June 19, 2023 SOR(6M)+0.500% — — SGD 284,000 233,510 MTNP notes Sept. 1, 2025 1.00% — — USD 400,000 435,200 The 180-2rd Apr. 26, 2021 4.71% — 380,000 — 380,000 The 181-3rd Aug. 26, 2021 4.09% — 250,000 — 250,000 The 182-2nd Oct. 28, 2021 4.31% — 100,000 — 100,000 The 183-2nd Dec. 22, 2021 4.09% — 90,000 — 90,000 The 183-3rd Dec. 22, 2031 4.27% — 160,000 — 160,000 The 184-2nd Apr. 10, 2023 2.95% — 190,000 — 190,000 The 184-3rd Apr. 10, 2033 3.17% — 100,000 — 100,000 The 185-2nd Sept. 16, 2020 — — 300,000 — — The 186-3rd June 26, 2024 3.42% — 110,000 — 110,000 The 186-4th June 26, 2024 3.70% — 100,000 — 100,000 The 187-3rd Sept. 2, 2024 3.31% — 170,000 — 170,000 The 187-4th Sept. 2, 2034 3.55% — 100,000 — 100,000 The 188-1st Jan. 29, 2020 — — 160,000 — — The 188-2nd Jan. 29, 2025 2.45% — 240,000 — 240,000 The 188-3rd Jan. 29, 2035 2.71% — 50,000 — 50,000 The 189-2nd Jan. 28, 2021 1.95% — 130,000 — 130,000 The 189-3rd Jan. 28, 2026 2.20% — 100,000 — 100,000 The 189-4th Jan. 28, 2036 2.35% — 70,000 — 70,000 The 190-1st Jan. 29, 2021 2.55% — 110,000 — 110,000 The 190-2nd Jan. 30, 2023 2.75% — 150,000 — 150,000 The 190-3rd Jan. 30, 2028 2.95% — 170,000 — 170,000 The 190-4th Jan. 30, 2038 2.93% — 70,000 — 70,000 The 191-1st Jan. 14, 2022 2.05% — 220,000 — 220,000 The 191-2nd Jan. 15, 2024 2.09% — 80,000 — 80,000 The 191-3rd Jan. 15, 2029 2.16% — 110,000 — 110,000 The 191-4th Jan. 14, 2039 2.21% — 90,000 — 90,000 The 192-1st Oct. 11, 2022 1.55% — 340,000 — 340,000 The 192-2nd Oct. 11, 2024 1.58% — 100,000 — 100,000 The 192-3rd Oct. 11, 2029 1.62% — 50,000 — 50,000 The 192-4th Oct. 11, 2039 1.67% — 110,000 — 110,000 The 193-1st June 16, 2023 1.17% — — — 150,000 The 193-2nd June 17, 2025 1.43% — — — 70,000 The 193-3rd June 17, 2030 1.61% — — — 20,000 The 193-4th June 15, 2040 1.71% — — — 60,000 The 148th Won-denominated June 23, 2023 1.51% — — — 100,000 Subtotal 7,045,366 6,962,470 Less: Current portion (1,052,032 ) (1,228,283 ) Discount on bonds (20,780 ) (19,847 ) Total ￦ 5,972,554 ￦ 5,714,340 1 As at December 31, 2020, the Controlling Company has outstanding notes in the amount of USD 100 million with fixed interest rates under Medium Term Note Program (“MTNP”) registered in the Singapore Stock Exchange, which allowed issuance of notes of up to USD 2,000 million. However, the MTN Program has been suspended since 2007. 2 Libor (3M) and SOR (6M) are approximately 0.238% and 0.185%, respectively as at December 31, 2020.
Summary of Korean Won and Foreign Currency Borrowings	Convertible bonds (In millions of Korean won and thousands of foreign currencies) December 31, 2019 Type Issuance date Maturity Annual interest rate December 31, December 31, The 1st CB(Private) 1,2 Jun. 5, 2020 Jun. 5, 2025 0.00 % ￦ — ￦ 8,000 Redemption premium — 2,267 Bond discount issuance — (4,644 ) Subtotal ￦ — ￦ 5,623 Current portion ￦ — ￦ — Total ￦ — ￦ 5,623 1 Common shares of Storywiz are subject to conversion (appraisal period: June 5, 2021~ May 4, 2025). 2 Nominal interest rate and maturity yield is approximately 0% and 5% and will be settled on maturity
Summary of Short-term Borrowings	Short-term borrowings (In millions of Korean won) December 31, December 31, Type Financial institution Annual interest rates Operational NongHyup Bank 1.740% ~ 2.360% ￦ 15,000 ￦ 40,189 Shinhan Bank 2.460% ~ 2.960% 57,500 22,500 Shinhan Bank CD91+1.431% — 10,000 Woori Bank 3.57% — 1,900 Korea Development Bank 3.34% 10,000 10,000 SooHyup Bank — 1,000 — Industrial Bank of Korea 1.74% — 200 Hana Bank 4.20% — 11,000 Total ￦ 83,500 ￦ 95,789
Summary of Long-term Borrowings	Long-term borrowings (In millions of Korean won and thousands of foreign currencies) December 31, 2019 December 31, 2020 Financial institution Type Annual interest rates Foreign currency Korean won Foreign currency Korean won Export-Import Bank of Korea Inter-Korean Cooperation Fund 1 1.50% — ￦ 3,454 — ￦ 2,961 Industrial Bank of Korea General loans 2.98% — 6,000 — 6,000 Shinhan Bank General loans 1.94% — 5,000 — 5,000 Facility loans 2 LIBOR(3M)+1.340% USD 25,918 30,008 USD 25,918 28,199 General loans 2 LIBOR(3M)+1.650% USD 3,000 3,473 USD 8,910 9,694 General loans 2 LIBOR(3M)+2.130% — — USD 25,000 27,200 CA-CIB Long-term CP 1.26% — — — 100,000 NongHyup Bank Facility loans 2.00% — 79 — 54 Korea Development Bank General loans 3.02% — 10,000 — 10,000 General loans 3.31% — 30,000 — 30,000 Others Kookmin Bank and other 2 LIBOR(3M)+1.850% USD 87,940 101,816 USD 48,855 53,155 — — 950 — — Subtotal ￦ 190,780 ￦ 272,263 Less: Current portion ￦ (50,192) ￦ (94,042) Total ￦ 140,588 ￦ 178,221 1 The above Inter-Korean Cooperation Fund is repayable in installments over 13 years after a seven-year grace period. 2 LIBOR(3M) is approximately 0.238% as at December 31, 2020.
Summary of Repayment of Borrowings Including the Current Liabilities	Repayment schedule of the Group’s borrowings including the portion of current liabilities as at December 31, 2020 is as follows: (In millions of Korean won) Debentures Borrowings Total In local In foreign Sub- total In local In foreign Sub- total Jan 1, 2021 ~ Dec 31, 2021 ￦ 1,060,000 ￦ 168,682 ￦ 1,228,682 ￦ 147,307 ￦ 42,524 ￦ 189,831 ￦ 1,418,513 Jan 1, 2022 ~ Dec 31, 2022 560,000 747,261 1,307,261 518 38,830 39,348 1,346,609 Jan 1, 2023 ~ Dec 31, 2023 590,000 342,310 932,310 100,500 36,894 137,394 1,069,704 Jan 1, 2024 ~ Dec 31, 2024 460,000 385,017 845,017 493 — 493 845,510 After Jan. 1, 2025 1,678,000 979,200 2,657,200 986 — 986 2,658,186 ￦ 4,348,000 ￦ 2,622,470 ￦ 6,970,470 ￦ 249,804 ￦ 118,248 ￦ 368,052 ￦ 7,338,522

Provisions (Tables)

Provisions (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Changes in Provisions	Changes in provisions for the years ended December 31, 2019 and 2020, are as follows: 2019 (In millions of Korean won) Litigation Restoration cost Others Total Beginning balance ￦ 58,760 ￦ 118,828 ￦ 104,288 ￦ 281,876 Increase (Transfer) 42,684 6,591 17,328 66,603 Usage (35,640 ) (5,394 ) (15,851 ) (56,885 ) Reversal (1,563 ) (6,736 ) (29,133 ) (37,432 ) Ending balance ￦ 64,241 ￦ 113,289 ￦ 76,632 ￦ 254,162 Current ￦ 64,241 ￦ 37,906 ￦ 73,465 ￦ 175,612 Non-current — 75,383 3,167 78,550 2020 (In millions of Korean won) Litigation Restoration cost Others Total Beginning balance ￦ 64,241 ￦ 113,289 ￦ 76,632 ￦ 254,162 Increase (Transfer) 17,064 (1,933 ) 17,873 33,004 Usage (3,948 ) (2,990 ) (2,266 ) (9,204 ) Reversal (857 ) (3,023 ) (23,212 ) (27,092 ) Changes in scope of consolidation — 424 898 1,322 Ending balance ￦ 76,500 ￦ 105,767 ￦ 69,925 ￦ 252,192 Current ￦ 76,500 ￦ 22,343 ￦ 67,147 ￦ 165,990 Non-current — 83,424 2,778 86,202

Net Defined Benefit Liabiliti_2

Net Defined Benefit Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Statement [LineItems]
Summary of Amount Recognized in the Statements of Financial Position and Defined Benefit Obligations	The amounts recognized in the statements of financial position are determined as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Present value of defined benefit obligations ￦ 2,427,351 ￦ 2,556,712 Fair value of plan assets (2,069,710 ) (2,189,375 ) Liabilities ￦ 365,663 ￦ 378,087 Assets in the statement of financial position ￦ 8,022 ￦ 10,750
Summary of Changes in the Defined Benefit Obligations	Changes in the defined benefit obligations for the years ended December 31, 2019 and 2020, are as follows: (In millions of Korean won) 2019 2020 Beginning ￦ 2,201,876 ￦ 2,427,351 Current service cost 243,598 248,047 Interest expense 47,403 45,083 Benefit paid (100,663 ) (258,866 ) Changes due to settlements of plan 910 1,075 Remeasurements: Actuarial gains and losses arising from changes in demographic assumptions 39 5,191 Actuarial gains and losses arising from changes in financial assumptions 11,773 17,077 Actuarial gains and losses arising from experience adjustments 19,465 57,703 Changes in scope of consolidation 2,950 14,051 Ending ￦ 2,427,351 ￦ 2,556,712 Changes in the fair value of plan assets for the years ended December 31, 2019 and 2020, are as follows: (In millions of Korean won) 2019 2020 Beginning ￦ 1,643,046 ￦ 2,069,710 Interest income 35,386 38,590 Remeasurements: Return on plan assets (excluding amounts included in interest income) (2,537 ) 2,589 Benefits paid (87,119 ) (213,953 ) Employer contributions 476,916 284,243 Changes in scope of consolidation 4,018 8,196 Ending ￦ 2,069,710 ￦ 2,189,375
Summary of Amounts Recognized in the Operating expenses of the Consolidated Statements of Operations	Amounts recognized in the ‘Operating expenses’ of the consolidated statements of operations for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Current service cost ￦ 225,667 ￦ 243,598 ￦ 248,047 Net Interest cost 10,458 12,017 6,494 Past service cost 9,801 910 1,075 Transfer out (13,881 ) (16,215 ) (16,514 ) Total expenses ￦ 232,045 ￦ 240,310 ￦ 239,102
Summary of Principal Actuarial Assumptions	Principal actuarial assumptions used are as follows: December 31, December 31, December 31, Discount rate 2.32 % 1.97 % 1.93 % Future salary increase 5.08 % 4.92 % 4.88 %
Summary of Expected Maturity Analysis of Undiscounted Pension Benefits	The expected maturity analysis of undiscounted pension benefits as at December 31, 2020, is as follows: (In millions of Korean won) Less than 1 year Between Between 2-5 Over 5 years Total Pension benefits ￦ 232,550 ￦ 271,366 ￦ 794,840 ￦ 2,284,517 ￦ 3,583,273
Defined benefit obligations [member]
Statement [LineItems]
Summary of Sensitivity of the Defined Benefit Obligations	The sensitivity of the defined benefit obligations as at December 31, 2020, to changes in the principal assumptions is: (In percentage, in millions of Korean won) Effect on defined benefit obligation Changes in Increase in Decrease in Discount rate 0.5% point ￦ ￦ 93,254 Salary growth rate 0.5% point 85,344 (79,970 )

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary Of Major Commitments With Local Financial Institutions	As at December 31, 2020, major commitments with local financial institutions are as follows: (In millions of Korean won and Financial institution Currency Limit Used Bank overdraft Kookmin Bank and others KRW 1,502,000 — Inter-Korean Cooperation Fund Export-Import Bank of Korea KRW 37,700 2,714 Insurance for Economic Cooperation project Export-Import Bank of Korea KRW 3,240 1,732 Collateralized loan on electronic accounts receivable-trade Kookmin Bank and others KRW 522,849 23,475 Plus electronic notes payable Industrial Bank of Korea KRW 50,000 331 Loans for working capital Korea Development Bank and others KRW 243,593 152,243 Facility loans Shinhan Bank and others KRW 100,123 55 Kookmin Bank and others USD 212,000 48,855 Derivatives transaction limit Korea Development Bank KRW 100,000 22,027 Woori Bank and others USD 69,054 44,616 Total KRW 2,559,505 202,577 USD 281,054 93,471
Summary of Guarantees Received from Financial Institutions	As at December 31, 2020, guarantees received from financial institutions are as follows: (In millions of Korean won and Financial institution Currency Limit Performance guarantee Seoul Guarantee Insurance and others KRW 208,386 Performance guarantee Korea Development Bank and others USD 8,569 Guarantee for import letters of credit Industrial Bank of Korea and others USD 5,000 Guarantee for payment in won currency Shinhan Bank and others KRW 70,962 Refund guarantee for advances received Korea Development Bank USD 8,536 Guarantee for payment in foreign currency KEB Hana Bank and others USD 40,840 Comprehensive credit line KEB Hana Bank and others KRW 41,100 Comprehensive credit line KEB Hana Bank and others USD 8,700 Bid guarantee KEB Hana Bank USD 400 Bid guarantee Korea Software Financial KRW 80,246 Performance guarantee /warranty guarantee KRW 393,019 Guarantee for advance payments/others KRW 388,656 Warranty guarantee Seoul Guarantee Insurance KRW 1,305 Performance guarantee KRW 9,690 Guarantees for licensing KRW 7,748 Guarantees for depositions KRW 3,792 Merchant business guarantee insurance KRW 237 Total KRW 1,205,141 USD 72,045
Summary Of Guarantees Provided By The Group For Third Parties	As at December 31, 2020, guarantees provided by the Group to a third party, are as follows: (In millions of Korean won) Subject to payment Creditor Limit Used Period KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) 1 Gasan Solar Power Plant Inc. Shinhan Bank 4,700 1,371 Jan. 08, 2025 KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) 1 SPP Inc. Suhyup Bank 3,250 932 Feb. 16, 2024 KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) 1 Korea Cell Inc. Suhyup Bank 3,250 880 Feb. 16, 2024 KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) 1 San-Ya Association Corporation Suhyup Bank 3,250 888 Feb. 16, 2024 KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.) 1 Ciocanesti Korea Co., Ltd. NH Investment & 7,600 7,600 Jun. 8, 2017 KT Hitel Co., Ltd. Shinhan Bank Cash payers 700 — Apr. 17, 2020 ~ Apr. 16, 2021 Nasmedia Co., Ltd. Stockholders Association Members Korea Securities 5,654 2,735 — 1 According to the above payment guarantee, KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.), a subsidiary of the Group, will have an obligation of repayment if the principal borrower does not repay the borrowing.

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of balance sheet information about leases for lessee	The consolidated statement of financial position shows the following amounts relating to leases: (In millions of Korean won) December 31, December 31, Right-of-use Property and building ￦ 1,020,619 ￦ 1,073,207 Machinery and track facilities 140,296 42,127 Others 107,414 101,845 Total ￦ 1,268,329 ￦ 1,217,179 Investment property (buildings) 50,010 19,456 (In millions of Korean won) December 31, December 31, Lease liabilities 1 Current ￦ 392,433 ￦ 345,224 Non-Current 818,919 798,416 Total ￦ 1,211,352 ￦ 1,143,640 1 Included in the line items ‘Other current liabilities and other non-current
Summary of statement of profit or loss information about leases for lessee	The consolidated statements of profit or loss show the following amounts relating to leases: (In millions of Korean won) December 31, December 31, Depreciation of Right-of-use Property and building ￦ 300,773 ￦ 290,168 Machinery and track facilities 89,452 58,419 Others 52,402 55,588 Total ￦ 442,627 ￦ 404,175 Depreciation of Investment Properties ￦ 21,809 ￦ 19,113 Interest expense relating to lease liabilities 55,001 44,091 Expense relating to short-term leases 14,718 10,998 Expense relating to leases of low-value 26,575 25,894 Expense relating to variable lease payments not included in lease liabilities 5,993 8,096

Share Capital (Tables)

Share Capital (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Share Capital	As at December 31, 2019 and 2020, the Group’s number of authorized shares is one billion. December 31, 2019 December 31, 2020 Number of issued shares Par value per share (Korean won) Ordinary (in millions of Korean won) Number of issued Par value per share (Korean won) Ordinary (in millions of Korean won) Ordinary shares 1 261,111,808 ￦ ￦ 261,111,808 ￦ ￦ 1 The Group retired 51,787,959 treasury shares against retained earnings. Therefore, the ordinary shares amount differs from the amount resulting from multiplying the number of shares issued.

Retained Earnings (Tables)

Retained Earnings (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Retained Earnings	Details of retained earnings as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, December 31, Legal reserve 1 ￦ 782,249 ￦ 782,249 Voluntary reserves 2 4,651,362 4,651,362 Unappropriated retained earnings 6,157,305 6,721,809 Total ￦ 11,590,916 ￦ 12,155,420 1 The Commercial Code of the Republic of Korea requires the Controlling Company to appropriate, as a legal reserve, an amount equal to a minimum of 10% of cash dividends paid until such reserve equals 50% of its issued share capital. The reserve is not available for the payment of cash dividends, but may be transferred to share capital with the approval of the Controlling Company’s Board of Directors or used to reduce accumulated deficit, if any, with the ratification of the Controlling Company’s majority shareholders. 2 The provision of research and development of human resources is separately accumulated with tax reserve fund during earned surplus disposal by Tax Reduction and Exemption Control Act of Korea. Reversal of this provision can be paid out as dividends according to related tax law.

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income and Other Components of Equity (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Accumulated Other Comprehensive Income	As at December 31, 2019 and 2020, the details of the Controlling Company’s accumulated other comprehensive income are as follows: (In millions of Korean won) December 31, December 31, Changes in investments in associates and joint ventures ￦ 1,556 ￦ 16,257 Loss on derivatives valuation (7,624 ) 19,809 Gain on valuation of financial assets at fair value through other comprehensive income 211,573 61,438 Exchange differences on translation for foreign operations (10,571 ) (11,453 ) Total ￦ 194,934 ￦ 86,051
Summary of Changes in Accumulated Other Comprehensive Income	Changes in accumulated other comprehensive income for the years ended December 31, 2019 and 2020, are as follows: 2019 (In millions of Korean won) Beginning Increase/ decrease Reclassification to gain or loss Ending Changes in investments in associates and joint ventures ￦ (871 ) ￦ 2,427 ￦ — ￦ 1,556 Gain or loss on derivatives valuation (30,474 ) 67,534 (44,684 ) (7,624 ) Gain on valuation of financial assets at fair value through other comprehensive income 96,704 114,869 — 211,573 Exchange differences on translation for foreign operations (15,201 ) 4,630 — (10,571 ) Total ￦ 50,158 ￦ 189,460 ￦ (44,684 ) ￦ 194,934 (In millions of Korean won) 2020 Beginning Increase/ decrease Reclassification to gain or loss Ending Changes in investments in associates and joint ventures ￦ 1,556 ￦ 14,701 ￦ — ￦ 16,257 Gain or loss on derivatives valuation (7,624 ) (83,998 ) 111,431 19,809 Gain on valuation of financial assets at fair value through other comprehensive income 211,573 (150,135 ) — 61,438 Exchange differences on translation for foreign operations (10,571 ) (882 ) — (11,453 ) Total ￦ 194,934 ￦ ) ￦ 111,431 ￦ 86,051
Summary of Other Components of Equity	The Group’s other components of equity as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, December 31, Treasury stock 1 ￦ ￦ Gain or loss on disposal of treasury stock 2 1,229 (17,579 ) Share-based payments 7,769 5,901 Others 3 (353,243 ) (340,882 ) Total ￦ ) ￦ ) 1 During the year ended December 31, 2020, the Group acquired 4,550,000 treasury shares and granted 1,150,580 treasury shares as share-based payment. 2 The amount directly reflected in equity is ￦7,288 million (2019: ￦603 million) for the year ended December 31, 2020. 3 Profit or loss incurred from transactions with non-controlling
Summary of Treasury Stock	As at December 31, 2019 and 2020 December 31, December 31, Number of shares (in shares) 15,870,258 19,269,678 Amounts (In millions of Korean won) ￦ 825,838 ￦ 882,224

Share-based Payments (Tables)

Share-based Payments (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Details of Share-Based Payments	Details of share-based payments as at December 31, 2020, are as follows: (In share) 14th grant Grant date June 16, 2020 Grantee CEOs, internal directors, external directors, executives Vesting conditions Service condition: 1 year Non-market Fair value per option (in Korean won) ￦ Total compensation costs (in Korean won) ￦ Estimated exercise date (exercise date) During 2021 Valuation method Fair value method (In share) Employee wage negotiation Grant date September 21, 2020 Grantee All employees Vesting conditions Current employees as of September 21, 2020 Fair value per option (in Korean won) ￦ Total compensation costs (in Korean won) ￦ Estimated exercise date (exercise date) December 22, 2020 Valuation method Fair value method
Summary of Changes in the Number of Stock Options and the Weighted-Average Exercise Price	Changes in the number of stock options and the weighted-average exercise price as at December 31, 2019 and 2020, are as follows: 2019 Beginning Grant Expired Exercised 1 Ending Number of 12th grant 353,325 — 256,543 96,782 — — 13th grant — 372,023 — — 372,023 — Total 353,325 372,023 256,543 96,782 372,023 — 2020 Beginning Grant Expired Exercised 1 Ending Number of 13th grant 372,023 — 241,548 130,475 — — 14th grant — 398,856 — — 398,856 — Employee wage negotiation — 1,020,105 — 1,020,105 — — Total 372,023 1,418,961 241,548 1,150,580 398,856 — 1 The weighted average price of ordinary shares at the time of exercise in 2020 was ￦ ￦

Revenue from Contracts with C_2

Revenue from Contracts with Customers and Relevant Contract Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Detail Explanation of Revenue in the consolidated Statement of operations	The Group has recognized the following amounts relating to revenue in the Consolidated Statements of Operations: (In millions of Korean won) 2018 2019 2020 Revenue from contracts with customers ￦ 23,012,257 ￦ 24,441,122 ￦ 23,895,631 Revenue from other sources 423,793 458,067 545,016 Total revenue ￦ 23,436,050 ￦ 24,899,189 ￦ 24,440,647
Detail Explanation of Operating Revenue	Operating revenues for the years ended December 31, 2018, 2019 and 2020 are as follows: (In millions of Korean won) 2018 2019 2020 Mobile services ￦ 6,827,685 ￦ 6,795,124 ￦ 6,805,218 Fixed-line services 4,869,253 4,866,698 4,827,015 Fixed-line and VoIP telephone services 1,708,319 1,578,546 1,463,553 Broadband Internet access services 2,112,763 2,177,447 2,256,188 Data communication services 1,048,171 1,110,705 1,107,274 Media and content 2,261,808 2,516,256 2,637,691 Financial services 3,444,917 3,641,655 3,493,920 Sale of goods 3,288,911 4,194,168 3,593,127 Others 2,743,476 2,885,288 3,083,676 Total ￦ 23,436,050 ￦ 24,899,189 ￦ 24,440,647
Detail Analysis of Contract with Customer Assets and Liabilities	The contract assets and liabilities recognized in relation to the revenues from contracts with customers are as follows: (In millions of Korean won) December 31, December 31, Contract assets 1 ￦ 655,329 ￦ 672,672 Contract liabilities 1 413,442 413,707 Deferred revenue 2 ￦ 92,557 ￦ 89,694 1 The Group recognized contract assets of ￦ ￦ ￦ ￦ 2 Deferred revenue recognized relating to government grant is excluded.
Detail Analysis of Contract Costs Recognized as Assets	The contract costs recognized as assets are as follows: (In millions of Korean won) December 31, December 31, Incremental cost of contract establishment ￦ 1,764,009 ￦ 1,726,191 Cost of Contract performance 85,234 78,757
Detail of Revenue Arising from Carried-Forward Contract Liabilities	The recognized revenue arising from carried-forward contract liabilities from prior year is as follows: (In millions of Korean won) 2018 2019 2020 Revenue recognized that was included in the contract liability balance at the beginning of the year Allocation of the transaction price ￦ 183,905 ￦ 266,478 ￦ 251,975 Deferred revenue of joining/installment fee 39,975 44,032 42,685 Others 1,536 — — Total ￦ 225,416 ￦ 310,510 ￦ 294,660

Operating Expenses (Tables)

Operating Expenses (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Operating Expenses	Operating expenses for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Salaries and wages ￦ 3,845,842 ￦ 3,974,233 ￦ 4,123,680 Depreciation 2,674,205 2,530,252 2,605,128 Depreciation of right-of-use — 442,629 404,175 Amortization of intangible assets 607,527 656,611 624,982 Commissions 1,080,168 1,115,477 965,461 Interconnection charges 579,613 534,025 500,081 International interconnection fee 226,627 240,254 172,529 Purchase of inventories 4,414,094 4,453,820 3,681,801 Changes of inventories (432,607 ) 282,957 257,041 Sales commission 1,942,841 2,315,731 2,337,127 Service cost 1,540,869 1,610,261 2,102,875 Utilities 323,411 332,816 360,797 Taxes and dues 285,131 277,742 283,197 Rent 460,377 193,357 136,355 Insurance premium 73,654 82,404 71,018 Installation fee 143,669 155,178 132,117 Advertising expenses 157,675 150,166 132,466 Research and development expenses 176,758 165,028 156,940 Card service cost 3,112,618 3,066,766 2,941,669 Others 1,122,718 1,292,512 1,428,875 Total ￦ 22,335,190 ￦ 23,872,219 ￦ 23,418,314
Summary of Details of Salaries and Wages	Details of salaries and wages for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Short-term employee benefits ￦ 3,505,214 ￦ 3,663,337 ￦ 3,770,786 Post-employment benefits(Defined benefit plan) 232,045 240,310 239,102 Post-employment benefits(Defined contribution plan) 48,210 57,170 61,912 Share-based payment 8,439 6,398 28,604 Others 51,934 7,018 23,276 Total ￦ 3,845,842 ￦ 3,974,233 ￦ 4,123,680

Financial Income and Costs (Tab

Financial Income and Costs (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Details of Financial Income	Details of financial income for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Interest income ￦ 244,796 ￦ 282,704 ￦ 270,571 Gain on foreign currency transactions 17,175 24,596 17,493 Gain on foreign currency translation 3,691 17,979 164,351 Gain on settlement of derivatives 27,950 9,016 9,397 Gain on valuation of derivatives 66,305 77,353 172 Others 14,326 12,747 36,630 Total ￦ 374,243 ￦ 424,395 ￦ 498,614
Summary of Details of Financial Costs	Details of financial costs for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Interest expenses ￦ 296,874 ￦ 278,427 ￦ 263,579 Loss on foreign currency transactions 49,156 30,267 27,805 Loss on foreign currency translation 72,642 93,977 26,340 Loss on settlement of derivatives — 20 1,406 Loss on valuation of derivatives 2,045 15,867 163,763 Loss on disposal of trade receivables 13,818 11,298 8,152 Others 1,124 2,277 16,338 Total ￦ 435,659 ￦ 432,133 ￦ 507,383

Deferred Income Tax and incom_2

Deferred Income Tax and income Tax Expense (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Analysis of Deferred Tax Assets and Deferred Tax Liabilities	The analysis of deferred tax assets and deferred tax liabilities as at December 31, 2019 and 2020, is as follows: (In millions of Korean won) December 31, December 31, Deferred tax assets Deferred tax assets to be recovered within 12 months ￦ 419,889 ￦ 404,434 Deferred tax assets to be recovered after more than 12 months 1,613,836 1,631,759 Deferred tax assets before offsetting 2,033,725 2,036,193 Deferred tax liabilities Deferred tax liability to be recovered within 12 months (538,578 ) (637,317 ) Deferred tax liability to be recovered after more than 12 months (1,495,759 ) (1,394,509 ) Deferred tax liabilities before offsetting (2,034,337 ) (2,031,826 ) Deferred tax assets after offsetting ￦ 424,856 ￦ 433,698 Deferred tax liabilities after offsetting ￦ 425,468 ￦ 429,331
Summary of Gross Movements on the Deferred Income Tax Account	The gross movements on the deferred income tax account for the years ended December 31, 2019 and 2020, are calculated as follows: (In millions of Korean won) 2019 2020 Beginning ￦ 260,584 ￦ (612 ) Changes to the statement of operations (199,527 ) (72,124 ) Changes to other comprehensive loss (income) (61,669 ) 77,103 Ending ￦ (612 ) ￦ 4,367
Summary of Movement in Deferred Income Tax Assets and Liabilities	The movement in deferred income tax assets and liabilities during the year, without taking into consideration the offsetting of balances within the same tax jurisdiction, is as follows: (In millions of Korean won) 2019 Beginning Consolidated Other Ending Deferred tax liabilities Derivative instruments — (10,250 ) (648 ) (10,898 ) Investment in subsidiaries, associates, and joint ventures (93,604 ) (14,622 ) 35 (108,191 ) Depreciation (424 ) (11,182 ) — (11,606 ) Advanced depreciation provision (313,184 ) 63 — (313,121 ) Deposits for severance benefits (398,982 ) (99,126 ) 1,255 (496,853 ) Accrued income (1,558 ) 17 — (1,541 ) Reserve for technology and human resource development (204 ) — — (204 ) Contract cost (369,916 ) (40,947 ) — (410,863 ) Contract assets (11,505 ) (42,245 ) — (53,750 ) Financial assets at fair value through profit or loss (661 ) 338 — (323 ) Financial assets at fair value through other comprehensive income (41,798 ) (3,556 ) (58,483 ) (103,837 ) Others (284,255 ) (238,725 ) (170 ) (523,150 ) Total (1,516,091 ) (460,235 ) (58,011 ) (2,034,337 ) Deferred tax assets Derivative instruments 8,341 (850 ) (7,491 ) — Provision for impairment or trade receivables 99,887 (15,816 ) — 84,071 Inventory valuation 121 (98 ) — 23 Contribution for construction 16,800 (646 ) — 16,154 Unsettled expenses 127,897 32,539 — 160,436 Provisions 36,178 (3,354 ) — 32,824 Property and equipment 230,278 (1,623 ) — 228,655 Defined benefit liabilities 513,842 48,847 6,782 569,471 Withholding of facilities expenses 6,609 (426 ) — 6,183 Deduction of installment receivables 42 6 — 48 Assets retirement obligation 24,532 4,484 — 29,016 Gain or loss foreign currency translation 10,672 10,005 — 20,677 Deferred revenue 39,641 (3,841 ) — 35,800 Real-estate sales 21,728 (8,043 ) — 13,685 Others 537,209 174,177 (2,949 ) 708,437 Total 1,673,777 235,361 (3,658 ) 1,905,480 Temporary difference, net 157,686 (224,874 ) (61,669 ) (128,857 ) Tax credit carryforwards 102,898 25,347 — 128,245 Total net balance 260,584 (199,527 ) (61,669 ) (612 ) (In millions of Korean won) 2020 Beginning Consolidated Other Ending Deferred tax liabilities Derivative instruments (10,898 ) 10,055 — (843 ) Investment in subsidiaries, associates, and joint ventures (108,191 ) (64,553 ) (8,820 ) (181,564 ) Depreciation (11,606 ) 7,431 — (4,175 ) Advanced depreciation provision (313,121 ) 1,203 — (311,918 ) Deposits for severance benefits (496,853 ) (26,419 ) 2,015 (521,257 ) Accrued income (1,541 ) (212 ) — (1,753 ) Reserve for technology and human resource development (204 ) — — (204 ) Contract cost (410,863 ) 67,898 — (342,965 ) Contract assets (53,750 ) (112,794 ) — (166,544 ) Financial assets at fair value through profit or loss (323 ) (304 ) — (627 ) Financial assets at fair value through other comprehensive income (103,837 ) (4,420 ) 77,634 (30,623 ) Others (523,150 ) 53,797 — (469,353 ) Total (2,034,337 ) (68,318 ) 70,829 (2,031,826 ) Deferred tax assets Derivative instruments — 40,342 (9,860 ) 30,482 Provision for impairment or trade receivables 84,071 4,994 — 89,065 Inventory valuation 23 (259 ) — (236 ) Contribution for construction 16,154 246 — 16,400 Unsettled expenses 160,436 (24,358 ) — 136,078 Provisions 32,824 1,198 — 34,022 Property and equipment 228,655 (1,695 ) — 226,960 Defined benefit liabilities 569,471 13,707 15,186 598,364 Withholding of facilities expenses 6,183 (436 ) — 5,747 Deduction of installment receivables 48 (20 ) — 28 Assets retirement obligation 29,016 (883 ) — 28,133 Gain or loss foreign currency translation 20,677 (20,539 ) — 138 Deferred revenue 35,800 7,230 — 43,030 Contract assets — 97,464 — 97,464 Real-estate sales 13,685 (13,685 ) — — Others 708,437 (123,798 ) 948 585,587 Total 1,905,480 (20,492 ) 6,274 1,891,262 Temporary difference, net (128,857 ) (88,810 ) 77,103 (140,564 ) Tax credit carryforwards 128,245 16,686 — 144,931 Total net balance (612 ) (72,124 ) 77,103 4,367
Summary of Tax Impacts Recognized Directly To Equity	The tax impacts recognized directly to equity as at December 31, 2018, 2019, and 2020, are as follows: 2018 2019 2020 (In millions of Korean won) Before recognition Tax effect After Before recognition Tax effect After Before recognition Tax effect After Gain on valuation of financial assets at fair value through other comprehensive income 59,384 (15,573 ) 43,811 225,635 (58,483 ) 167,152 54,969 (12,972 ) 41,997 Gain (loss) on valuation of hedge instruments (36,756 ) 9,745 (27,011 ) 31,003 (8,139 ) 22,864 37,247 (9,860 ) 27,387 Remeasurements of net defined benefit liabilities (116,324 ) 42,813 (73,511 ) (33,814 ) 8,037 (25,777 ) (77,382 ) 17,201 (60,181 ) Share of gain(loss) of associates and joint ventures, and others (1,036 ) 179 (857 ) 4,493 (1,327 ) 3,166 25,538 (8,820 ) 16,718 Exchange differences on translation for foreign operations 3,989 (1,049 ) 2,940 6,692 (1,759 ) 4,933 (3,614 ) 948 (2,666 ) Total ￦ (90,743 ) ￦ 36,115 ￦ (54,628 ) ￦ 234,009 ￦ (61,671 ) ￦ 172,338 ￦ 36,758 ￦ (13,503 ) ￦ 23,255
Summary of Details of Income Tax Expense	Details of income tax expense for the years ended December 31, 2018, 2019 and 2020, are calculated as follows: (In millions of Korean won) 2018 2019 2020 Current income tax expense ￦ 329,581 ￦ 120,533 ￦ 213,225 Impact of change in deferred taxes (15,016 ) 199,527 72,124 Income tax expense ￦ 314,565 ￦ 320,060 ￦ 285,349
Summary of Tax on the Group's Profit Before Tax	The tax on the Group’s profit before tax differs from the theoretical amount that would arise using the weighted average tax rate applicable to profits of the entities as follows: (In millions of Korean won) 2018 2019 2020 Profit before income tax expense ￦ 1,033,977 ￦ 1,015,928 ￦ 1,031,605 Statutory income tax expense ￦ 273,982 ￦ 269,018 ￦ 273,329 Tax effect Income not taxable for taxation purposes (85,322 ) (1,265 ) (24,657 ) Non-deductible expenses 18,126 19,543 31,741 Tax credit (20,319 ) (39,190 ) (47,056 ) Additional payment of income taxes 11,439 3,832 429 Tax effect and adjustment on consolidation Goodwill impairment 137 159 — Eliminated dividend income form subsidiaries 31,966 21,917 20,682 Changes of out-side 618 13,539 38,552 Investment in-kind 82,820 — — Intangible Asset impairment and amortization — 14,052 3,790 Reversal expenses of contract cost assets — 11,213 (6,643 ) Others 1,118 7,242 (4,818 ) Income tax expense ￦ 314,565 ￦ 320,060 ￦ 285,349
Summary of deferred tax assets and liabilities that are not recognized	Details of deferred tax assets and liabilities that are not recognized as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) 2019 2020 Deductible temporary differences Investment in subsidiaries, associates, and joint ventures ￦ 610,351 ￦ 583,890 Unused tax loss 31,257 28,115 Unused Tax credit — 2,654 Others 32,494 64,760 Total ￦ 674,102 ￦ 679,419 Taxable temporary differences Investment in subsidiaries, associates, and joint ventures ￦ 141,664 ￦ 132,848 Others 10,372 9,568 Total ￦ 152,036 ￦ 142,416
Summary of expected period of expiry for unused tax losses not recognized in deferred tax assets	The expected period of expiry for unused tax losses not recognized in deferred tax assets as at December 31, 2019 and 2020, is as follows: (In millions of Korean won) 2019 2020 2021 ￦ 18,582 ￦ 2,140 2022 2,140 80,649 2023 80,649 5,848 2024 5,848 4,867 2025 4,867 2,847 2026 9,390 9,709 2027 7,888 8,389 2028 10,064 8,426 2029 2,030 2,579 2030 617 2,339 Total ￦ 142,075 ￦ 127,793

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Basic and Diluted Earnings per Share From Operations	Basic earnings per share from operations for the years ended December 31, 2018, 2019 and 2020, is calculated as follows: 2018 2019 2020 Profit attributable to ordinary shares (In millions of Korean won) ￦ 645,571 ￦ 645,703 ￦ 700,889 Weighted average number of ordinary shares outstanding (In number of shares) 245,049,466 245,171,283 245,207,307 Basic earnings per share (In Korean won) 2,634 2,634 2,858 Diluted earnings per share from operations is calculated by adjusting the weighted average number of ordinary shares outstanding to assume conversion of all dilutive potential ordinary shares. The Controlling Company has dilutive potential ordinary shares from convertible preferred stocks, stock options and other share-based payments. Diluted earnings per share from operations for the years ended December 31, 2018, 2019 and 2020 is calculated as follows: 2018 2019 2020 Profit attributable to ordinary shares (In millions of Korean won) ￦ 645,571 ￦ 645,703 ￦ 700,889 Adjustment to net income attributable to ordinary shares (In millions of Korean won) — (157 ) — Diluted profit attributable to ordinary shares (In millions of Korean won) 645,571 645,546 700,889 Number of dilutive potential ordinary shares outstanding (In number of shares) 1,163 70,267 69,598 Weighted average number of ordinary shares outstanding (In number of shares) 245,050,629 245,241,550 245,276,905 Diluted earnings per share (In Korean won) 2,634 2,632 2,858

Cash Generated from Operations

Cash Generated from Operations (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Cash Flows from Operating Activities	Cash flows from operating activities for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 1. Profit for the year ￦ 719,412 ￦ 695,868 ￦ 746,256 2. Adjustments to reconcile net income Income tax expense 314,565 320,060 285,349 Interest income (265,817 ) (303,722 ) (291,425 ) Interest expense 296,894 278,975 265,035 Dividends income (2,910 ) (3,408 ) (4,442 ) Depreciation 2,735,413 2,567,754 2,635,307 Amortization of intangible assets 629,526 660,705 628,154 Depreciation of right-of-use — 433,199 404,174 Provision for severance benefits 245,926 256,525 255,615 Impairment losses on trade receivables 113,064 60,193 139,957 Share of net profit or loss of associates and joint ventures 5,912 3,252 (18,041 ) Loss(gain) on disposal of associates and joint ventures (3,737 ) 30 111 Loss(gain) on disposal of right-of-use — 1,556 2,047 Impairment losses on assets held for sale — 7,586 — Loss on disposal of property and equipment and investment in properties 68,688 49,284 55,590 Loss(gain) on disposal of intangible assets (4,256 ) (1,248 ) 246 Loss on impairment of intangible assets 12,997 61,899 211,636 Loss(gain) on foreign currency translation 68,952 75,998 (138,011 ) Loss(gain) on valuation and settlement of derivatives, net (92,210 ) (70,482 ) 155,600 Loss(gain) on disposal of financial assets at fair value through profit or loss (1,712 ) (5,115 ) 329 Gain on valuation of financial assets at fair value through profit or loss (10,768 ) (4,335 ) (59,044 ) Loss(gain) on disposal of financial assets at amortized cost (44 ) 43 (138 ) Others (55,969 ) 143,500 127,949 3. Changes in operating assets and liabilities Decrease(increase) in trade receivables (81,217 ) (433,292 ) 66,462 Decrease(Increase) in other receivables 356,643 (79,130 ) 685,209 Decrease(increase) in other current assets (123,258 ) 984 9,089 Decrease(increase) in other non-current 19,556 (178,180 ) (86,039 ) Decrease(increase) in inventories (480,543 ) 240,488 288,507 Increase(decrease) in trade payables (167,841 ) 44,354 (135,760 ) Decrease in other payables (448,301 ) (102,375 ) (1,232,646 ) Increase in other current liabilities 291,548 43,384 127,076 Increase(decrease) in other non-current 144,072 (199,547 ) (56,319 ) Decrease(Increase) in provisions 85,946 (12,164 ) 2,264 Decrease(Increase) in deferred revenue 48,201 641 (1,948 ) Increase in plan assets (53,301 ) (375,499 ) (136,336 ) Payment of severance benefits (153,209 ) (119,716 ) (186,520 ) 4. Cash generated from operations (1+2+3) ￦ 4,212,222 ￦ 4,058,065 ￦ 4,745,293
Summary of Significant Transactions not Affecting Cash Flows	Significant transactions not affecting cash flows for the years ended December 31, 2018, 2019 and 2020, are as follows: (In millions of Korean won) 2018 2019 2020 Reclassification of the current portion of borrowings ￦ 1,149,599 ￦ 1,030,056 ￦ 1,229,359 Reclassification of construction-in-progress 1,988,014 2,698,146 3,011,519 Reclassification of accounts payable from property and equipment 122,185 685,859 22,052 Reclassification of accounts payable from intangible assets 584,595 (356,911 ) (345,675 ) Reclassification of payable from defined benefit liability (31,838 ) (19,053 ) 72,346 Reclassification of payable from plan assets (9,497 ) (14,298 ) 66,046

Changes in Liabilities Arisin_2

Changes in Liabilities Arising from Financing Activities (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Changes in Liabilities Arising from Financial Activities	Changes in liabilities arising from financing activities, liabilities related to cashflow to be classified as future financing activities, for the years ended December 31, 2019 and 2020, are as follows: (In millions of 2019 Beginning Cash Non-cash Ending Changes in 1 Newly Exchange Fair Value Others Borrowing ￦ 6,648,294 ￦ 574,175 ￦ — ￦ — ￦ 64,398 ￦ — ￦ 12,000 ￦ 7,298,867 Lease liabilities 163,858 (485,444 ) 771,410 774,906 — — (13,379 ) 1,211,351 Derivative liabilities 65,067 (9,734 ) — — (4,234 ) (20,058 ) (10,945 ) 20,096 Derivative assets (29,843 ) 33,635 — — (53,729 ) (11,398 ) 2,759 (58,576 ) Total ￦ 6,847,376 ￦ 112,632 ￦ 771,410 ￦ 774,906 ￦ 6,435 ￦ (31,456 ) ￦ (9,565 ) ￦ 8,471,738 1 For information on the financial impacts due to change in accounting policy, see Note 41. (In millions of 2020 Beginning Cash Non-cash Ending Newly Exchange Fair Value Change in Others Borrowing ￦ 7,298,867 ￦ 167,867 ￦ 17,523 ￦ (157,985 ) ￦ — ￦ — ￦ (9,974 ) ￦ 7,316,298 Lease liabilities 1,211,351 (447,784 ) 473,477 (3 ) 40 3,564 (97,005 ) 1,143,640 — (13,674 ) 13,674 — — — — — Derivative liabilities 20,096 (943 ) 2,798 142,511 (23,669 ) — (10,220 ) 130,573 Derivative assets (58,576 ) 34,933 — 2,870 (3,456 ) — 16,623 (7,606 ) Total ￦ 8,471,738 ￦ (259,601 ) ￦ 507,472 ￦ (12,607 ) ￦ (27,085 ) ￦ 3,564 ￦ (100,576 ) ￦ 8,582,905

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Segment Information	Details of each segment for the years ended December 31, 2018, 2019 and 2020, are as follows: 2018 (In millions of Korean won) Operating revenues Operating Income Depreciation and Amortization 1 ICT ￦ 17,724,320 ￦ 933,191 ￦ 2,917,163 Finance 3,771,681 148,440 22,580 Satellite TV 690,821 66,735 98,310 Others 5,159,459 53,316 236,715 27,346,281 1,201,682 3,274,768 Elimination (3,910,231 ) (100,822 ) 6,964 Consolidated amount ￦ 23,436,050 ￦ 1,100,860 ￦ 3,281,732 1 Sum of the amortization of tangible assets, intangible assets, investment properties, and right-of-use 2019 (In millions of Korean won) Operating revenues Operating Income Depreciation and Amortization 1 ICT ￦ 18,527,631 ￦ 634,046 ￦ 3,229,159 Finance 3,795,185 158,235 27,852 Satellite TV 694,637 69,357 94,992 Others 5,845,973 218,402 357,294 28,863,426 1,080,040 3,709,297 Elimination (3,964,237 ) (53,070 ) (79,805 ) Consolidated amount ￦ 24,899,189 ￦ 1,026,970 ￦ 3,629,492 1 Sum of the amortization of tangible assets, intangible assets, investment properties, and right-of-use 2020 (In millions of Korean won) Operating revenues Operating Income Depreciation and Amortization 1,2 ICT ￦ 18,275,765 ￦ 809,741 ￦ 3,233,878 Finance 3,686,430 85,008 53,098 Satellite TV 706,631 71,345 84,931 Others 5,944,093 209,078 346,215 28,612,919 1,175,172 3,718,122 Elimination (4,172,272 ) (152,839 ) (83,838 ) Consolidated amount ￦ 24,440,647 ￦ 1,022,333 ￦ 3,634,284 1 Sum of the amortization of tangible assets, intangible assets, investment properties, and right-of-use 2 Property and equipment and intangible assets associated with ICT reporting segment are ￦
Summary of Operating Revenues and Non Current Assets by Geographical Regions	Operating revenues for the years ended December 31, 2018, 2019 and 2020 and non-current (In millions of Korean won) Operating revenues Non-current 1 Location 2018 2019 2020 2019.12.31 2020.12.31 Domestic ￦ 23,376,218 ￦ 24,832,068 ￦ 24,368,729 ￦ 19,198,416 ￦ 18,934,766 Overseas 59,832 67,121 71,918 76,679 18,243 Total ￦ 23,436,050 ￦ 24,899,189 ￦ 24,440,647 ￦ 19,275,095 ￦ 18,953,009 1 Non-current right-of-use

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Related Parties Outstanding Balances of Receivables and Payables	Outstanding balances of receivables and payables in relations to transactions with related parties as at December 31, 2019 and 2020, are as follows: December 31, 2019 Receivables Payables (In millions of Korean won) Trade Other Other Lease Associates and joint ventures K- CR-REITs ￦ 608 ￦ 23,100 ￦ — ￦ 57,907 K Bank, Inc. 583 13,664 557 — Others 434 1,177 711 — Total ￦ 1,625 ￦ 37,941 ￦ 1,268 ￦ 57,907 December 31, 2020 Receivables Payables (In millions of Korean won) Trade Other Other Lease Associates and joint ventures K- CR-REITs ￦ 457 ￦ 16,200 ￦ — ￦ 20,857 K Bank, Inc. 775 32,964 891 — Others 72 1,147 858 — Total ￦ 1,304 ￦ 50,311 ￦ 1,749 ￦ 20,857
Summary of Significant Transactions With Related Parties	Significant transactions with related parties for the years ended December 31, 2018, 2019 and 2020, are as follows: 2018 (In millions of Korean won) Sales Purchases 1 Dividend income Associates and joint ventures K- CR-REITs ￦ ￦ ￦ MOS GS Co., Ltd. 2 493 12,023 8 MOS Daegu Co., Ltd. 2 229 8,775 8 MOS Chungcheong Co., Ltd. 2 540 9,159 8 MOS Gangnam Co., Ltd. 2 333 11,549 10 MOS GB Co., Ltd. 2 1,378 16,519 12 MOS BS Co., Ltd. 2 324 11,193 10 MOS Honam Co., Ltd. 2 331 10,499 10 K Bank, Inc. 15,705 7,004 — NgeneBio 3 3 — — Others 2,888 9,547 2,148 Total ￦ ￦ ￦ 1 The amounts include acquisition of primarily property and equipment. 2 It is the amount before excluded from consolidation during the year. 3 It is the amount before excluded from associates during the year 2019 (In millions of Korean won) Sales Purchases 1 Associates and joint ventures K- CR-REITs ￦ 1,302 ￦ — K Bank, Inc. 17,815 8,524 Others 1,498 10,531 Others K-REALTY CR-REIT 1 2,801 — Total ￦ 23,416 ￦ 19,055 1 The amounts include acquisition of property and equipment and others. December 31, 2019 (In millions of Korean won) Acquisition Acquisition of right-of-use Interest Dividend Associates and joint ventures K- CR-REITs ￦ — ￦ 776 ￦ 2,225 ￦ 10,928 Korea Information & Technology Investment Fund (KIF Investment Fund) — — — 4,280 Others — — — 146 Total ￦ — ￦ 776 ￦ 2,225 ￦ 15,354 2020 (In millions of Korean won) Sales Purchases 1 Associates and joint ventures K- CR-REITs ￦ 2,298 ￦ — Korea Information & Technology Investment Fund (KIF Investment Fund) — — K Bank, Inc. 15,658 8,227 Others 809 10,272 Total ￦ 18,765 ￦ 18,499 1 December 31, 2020 (In millions of Korean won) Interest Interest Dividend Associates and joint ventures K- CR-REITs ￦ ￦ ￦ Korea Information & Technology Investment Fund (KIF Investment Fund) — — 9,241 K Bank, Inc. 14 — — Others — — 43 Total ￦ 14 ￦ 917 ￦ 17,345
Summary of Key Management Compensation	Key management compensation for the years ended December 31, 2018, 2019 and 2020, consists of: (In millions of Korean won) 2018 2019 2020 Salaries and other short-term benefits ￦ 2,762 ￦ 2,955 ￦ 2,086 Post-employment benefits 751 321 390 Stock-based compensation 878 891 5,613 Total ￦ 4,391 ￦ 4,167 ￦ 8,089
Summary of Fund Transactions With Related Parties	Fund transactions with related parties for the years ended December 31, 2018, 2019 and 2020, are as follows: 2018 (In millions of Korean won) Equity Associates and joint ventures PHI Healthcare Inc. (HooH Healthcare Inc.) ￦ 1,000 KT-CKP (1,229 ) PT. Mitra Transaksi Indonesia 1 1,567 Gyeonggi-KT Yoojin Superman Fund 1,000 KT-DSC start-up (1,800 ) KT-IBKC (1,050 ) Korea Electronic Vehicle Charging Service 168 K Bank, Inc. 26,725 GE Premier 1st Corporate Restructuring Real Estate Investment Trust Company (3,423 ) JB Emerging Market Specialty Investment Private Equity Trust No.1 3,960 K-REALTY — Korea Information & Technology Investment Fund — MOS GS Co., Ltd. 2 (147 ) MOS Daegu Co., Ltd. 2 (147 ) MOS Chungcheong Co., Ltd. 2 (153 ) MOS Gangnam Co., Ltd. 2 (180 ) MOS GB Co., Ltd. 2 (203 ) MOS BS Co., Ltd. 2 (183 ) MOS Honam Co., Ltd. 2 (206 ) Daiwon Broadcasting Co., Ltd. — Boston Global Film & Contents Fund L.P. (986 ) Gyeonggi-KT Green Growth Fund — Total ￦ 24,713 1 It is the amount before reclassification to assets held for sale . 2 It is the amount before included in consolidation during the year. December 31, 2019 Borrowing transaction 1 Equity contributions (In millions of Korean won) Borrowing 2 Repayment KT-IBKC ￦ — ￦ — ￦ 3,750 KT Philippines co. Ltd. — — 99 Virtua Realm Sendirian Berhad — — 550 K-REALTY — 30,385 — K Bank, Inc — — 21,782 KIF Investment Fund — — — Daiwon Broadcasting Co.,Ltd. — — — JB Emerging Market Specialty Investment Private Equity Trust No.1 — — — Gyeonggi-KT Yoojin Superman Fund — — 1,000 KT-CKP — — (174 ) KT-DSC start-up — — (1,800 ) KT-Smart — — 2,800 KT-SB — — (2,404 ) Total ￦ — ￦ 30,385 ￦ 25,603 1 Borrowing transactions include lease transactions. 2 Conversion effect from the adoption of IFRS 16 Lease December 31, 2020 Borrowing transaction 1 Equity contributions (In millions of Korean won) Borrowing Repayment K- CR-REITs ￦ — ￦ 20,304 ￦ — Studio Discovery Co. Ltd. — — 3,000 KT Young Entrepreneurs DNA Investment Fund — — 3,600 KT-Smart — — 2,800 KT-CKP — — (109 ) K Bank Inc. — — 195,011 Gyeonggi-KT Yoojin Superman Fund — — 1,000 Hyundai Robotics Co. Ltd. — — 50,000 Total ￦ — ￦ 20,304 ￦ 255,302 1 Borrowing transactions include lease transactions. As at December 31, 2020, there is no collateral or payment guarantee provided to or from related parties.

Financial Risk Management (Tabl

Financial Risk Management (Tables)	12 Months Ended
	Dec. 31, 2020
Statement [LineItems]
Summary of Maximum Exposure to Credit Risk	The maximum exposure to credit risk of the Group’s financial instruments without considering value of collaterals as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 December 31, 2020 Cash and cash equivalents (except for cash on hand) ￦ 2,226,608 ￦ 2,625,581 Trade and other receivables Financial assets at amortized costs 5,784,228 5,034,621 Financial assets at fair value through other comprehensive income 1,256,266 1,118,619 Contract assets 557,041 586,438 Other financial assets Derivatives financial assets for hedging 58,576 7,684 Financial assets at fair value through profit or loss 541,657 680,453 Financial assets at fair value through other comprehensive income 7,086 6,570 Financial assets at amortized costs 441,804 671,068 Total ￦ 10,873,266 ￦ 10,731,034
Summary of Contractual Undiscounted Cash Flows	The table below analyzes the Group’s liabilities (including interest expenses) into relevant maturity groups based on the remaining period at the date of the end of each reporting period to the contractual maturity date. These amounts are contractual undiscounted cash flows and can differ from the amount in the consolidated financial statements. December 31, 2019 (In millions of Korean won) Less than 1 year 1-5 More than Total Trade and other payables ￦ 8,149,445 ￦ 805,241 ￦ 370,044 ￦ 9,324,730 Borrowings(including debentures) 1,304,936 4,417,639 2,493,637 8,216,212 Lease liabilities 397,609 688,518 221,255 1,307,382 Other non-derivative 1,749 175,764 18,962 196,475 Financial guarantee contracts 1 19,422 — — 19,422 Total ￦ 9,873,161 ￦ 6,087,162 ￦ 3,103,898 ￦ 19,064,221 1 It is total amount guaranteed by the Group according to guarantee contracts. Cash flow from financial guarantee contracts is classified as the maturity group in the earliest period when the financial guarantee contracts can be executed. December 31, 2020 (In millions of Korean won) Less than 1 year 1-5 More than Total Trade and other payables ￦ 6,587,796 ￦ 730,758 ￦ 258,255 ￦ 7,576,809 Borrowings(including debentures) 1,573,944 4,373,534 2,258,360 8,205,838 Lease liabilities 336,024 658,501 190,907 1,185,432 Other non-derivative 574 131,242 — 131,816 Financial guarantee contracts 1 22,422 — — 22,422 Total ￦ 8,520,760 ￦ 5,894,035 ￦ 2,707,522 ￦ 17,122,317 1 It is total amount guaranteed by the Group according to guarantee contracts. Cash flow from financial guarantee contracts is classified as the maturity group in the earliest period when the financial guarantee contracts can be executed.
Summary of Cash Outflow and Inflow of Derivatives Settled Gross or Net are Undiscounted Contractual Cash Flow	Cash outflow and inflow of derivatives settled gross or net are undiscounted contractual cash flow and can differ from the amount in the consolidated financial statements. December 31, 2018 (In millions of Korean won) Less than 1 year 1-5 More than Total Outflow ￦ 455,343 ￦ 1,466,915 ￦ 517,301 ￦ 2,439,559 Inflow 484,505 1,492,718 519,133 2,496,356 December 31, 2019 (In millions of Korean won) Less than 1 year 1-5 More than Total Outflow ￦ 650,497 ￦ 1,602,513 ￦ 507,947 ￦ 2,760,957 Inflow 684,720 1,648,746 524,483 2,857,949 December 31, 2020 (In millions of Korean won) Less than 1 year 1-5 More than Total Outflow ￦ 248,300 ￦ 2,179,046 ￦ 498,619 ￦ 2,925,965 Inflow 249,301 2,074,747 480,570 2,804,618
Summary of Debt-to-equity Ratios	The debt-to-equity (In millions of Korean won) December 31, 2019 December 31, 2020 Total liabilities ￦ 19,491,530 ￦ 18,111,112 Total equity 15,140,684 15,551,433 Debt-to-equity 129 % 116 %
Summary of Gearing Ratios	The gearing ratios as at December 31, 2019 and 2020, are as follows: (In millions of Korean won, %) December 31, 2019 December 31, 2020 Total borrowings ￦ 7,298,867 ￦ 7,316,298 Less: cash and cash equivalents (2,305,894 ) (2,634,624 ) Net debt 4,992,973 4,681,674 Total equity 15,140,684 15,551,433 Total capital 20,133,657 20,233,107 Gearing ratio 25 % 23 %
Summary of Group's Recognized Financial Assets Subject to Enforceable Master Netting Arrangements or Similar Agreements	Details of the Group’s recognized financial assets subject to enforceable master netting arrangements or similar agreements are as follows: (In millions of Korean won) December 31, 2019 Gross Gross Net amounts position Amounts not offset Net Financial Cash Trade receivables ￦ 66,487 ￦ (1 ) ￦ 66,486 ￦ (63,604 ) ￦ — ￦ 2,882 Other financial assets 18,571 (13 ) 18,558 (18,526 ) — 32 ￦ 85,058 ￦ (14 ) ￦ 85,044 ￦ (82,130 ) ￦ — ￦ 2,914 (In millions of Korean won) December 31, 2020 Gross Gross Net amounts position Amounts not offset Net Financial Cash Trade receivables ￦ 71,497 ￦ (1 ) ￦ 71,496 ￦ (67,421 ) ￦ — ￦ 4,075
Summary of Group's Recognized Financial Liabilities Subject to Enforceable Master Netting Arrangements or Similar Agreements	The Group’s recognized financial liabilities subject to enforceable master netting arrangements or similar agreements are as follows: (In millions of Korean won) December 31, 2019 Gross Gross offset Net amounts position Amounts not offset Net Financial Cash Trade payables ￦ 65,669 ￦ (13 ) ￦ 65,656 ￦ (63,628 ) ￦ — ￦ 2,028 Other financial liabilities 18,509 (1 ) 18,508 (18,502 ) — 6 ￦ 84,178 ￦ (14 ) ￦ 84,164 ￦ (82,130 ) ￦ — ￦ 2,034 (In millions of Korean won) December 31, 2020 Gross Gross offset Net amounts position Amounts not offset Net Financial Cash Trade payables ￦ 69,361 ￦ — ￦ 69,361 ￦ (67,421 ) ￦ — ￦ 1,940 Other financial liabilities 1 (1 ) — — — — ￦ 69,362 ￦ (1 ) ￦ 69,361 ￦ (67,421 ) ￦ — ￦ 1,940
Currency risk [Member]
Statement [LineItems]
Summary of Exposures to Risks, Effects on Profit before Income Tax and Shareholders' Equity	As at December 31, 2018, 2019 and 2020, if the foreign exchange rate had strengthened/weakened by 10% with all other variables held constant, the effects on profit before inc o (In millions of Ko r Fluctuation of Income before tax 1 Shareholders’ equity 2018.12.31 10 % ￦ 7,212 ￦ 10,196 -10 % (12,413 ) (9,625 ) 2019.12.31 10 % ￦ 45,149 ￦ 52,092 -10 % (45,149 ) (52,092 ) 2020.12.31 10 % ￦ 25,220 ￦ 36,961 -10 % (25,220 ) (36,961 )
Summary of Details of Financial Assets and Liabilities in Foreign Currencies	Details of financial assets and liabilit i (In thousands of foreign currencies) 2018 2019 2020 Financial Financial Financial Financial Financial Financial US D 528,539 1,893,849 645,941 1,830,764 400,046 1,937,935 SDR 1 267 730 255 729 255 728 JPY 66,078 50,000,000 24,930 80,000,000 209,376 46,000,009 GBP — 256 — 56 — — EUR 2 6 1 6 316 162 DZD 2 618 — — — — — CNY 1,954 171 457 161 458 491 UZS 3 121,053 — — — — — RWF 4 857 — 706 — 646 — THB 5 — — — — 535 — MMK 6 84 — 84 — — — TZS 7 — 2,876 6,919 — 1,019 — BWP 8 897 — 911 — 212 — HKD — — — 268 — 198 BDT 9 39,494 — 18,897 — — — PLN 10 26 — — — 26 — VND 11 467,272 — 271,563 — 242,370 — XAF 12 666 — 97,411 — 16,229 — SGD — — — — 6 284,000 1 Special Drawing Rights. 2 Algeria Dinar. 3 Uzbekistan Sum. 4 Rwanda Franc. 5 Thailand Bhat. 6 Myanmar Kyat. 7 Tanzanian Shilling. 8 Botswana Pula. 9 Bangladesh Taka. 10 Polish Zloty. 11 Vietnam Dong. 12 Central African Franc.
Equity price risk [Member]
Statement [LineItems]
Summary of Exposures to Risks, Effects on Profit before Income Tax and Shareholders' Equity	As at December 31, 2018, 2019 and 2020, the Group is exposed to equity securities price risk because the securities held by the Group are traded in active markets. If the market prices had increased/decreased by 10% with all other variables held constant, the effects on profit before income tax and shareholders’ equity would have been as follows: (In millions of Korean won) Fluctuation of price Income before tax Equity 2018.12.31 10% ￦ 12 ￦ 898 -10% (12 ) (898 ) 2019.12.31 10% ￦ 24 ￦ 613 -10% (24 ) (613 ) 2020.12.31 10% ￦ 2,811 ￦ 3,472 -10% (2,811 ) (3,472 )
Interest rate risk [Member]
Statement [LineItems]
Summary of Exposures to Risks, Effects on Profit before Income Tax and Shareholders' Equity	As at December 31, 2018, 2019 and 2020, if the market interest rate had increased/decreased by 100 bp with other variables held constant, the effects on profit before income tax and shareholders’ equity would be as follows: (In millions of Korean won) Fluctuation of interest rate Income before tax Shareholders’ equity 2018.12.31 + 100 bp ￦ 1,059 ￦ 9,689 - 100 bp (1,958 ) (10,237 ) 2019.12.31 + 100 bp ￦ 425 ￦ 14,764 - 100 bp (482 ) (19,280 ) 2020.12.31 + 100 bp ￦ 973 ￦ 18,584 - 100 bp (973 ) (19,377 )

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Carrying Amount and Fair Value of Financial Instruments by Category	Carrying amount and fair value of financial instruments by category as at December 31, 2019 and 2020, are as follows: December 31, 2019 December 31, 2020 (In millions of Korean won) Carrying Fair value Carrying Fair value Financial assets Cash and cash equivalents ￦ 2,305,894 1 ￦ 2,634,624 1 Trade and other receivables Financial assets measured at amortized cost 2 5,748,459 1 4,976,423 1 Financial assets at fair value through other comprehensive income 1,256,266 1,256,266 1,118,619 1,118,619 Other financial assets Financial assets measured at amortized cost 441,804 1 671,068 1 Financial assets at fair value through profit or loss 632,324 632,324 809,919 809,919 Financial assets at fair value through other comprehensive income 557,342 557,342 258,516 258,516 Derivative financial assets for hedging 58,576 58,576 7,684 7,684 Total ￦ 11,000,665 ￦ 10,476,853 Financial liabilities Trade and other payables ￦ 8,679,698 1 ￦ 7,017,639 1 Borrowings 7,298,867 1 7,316,298 1 Other financial liabilities Financial liabilities at amortized cost 129,945 1 132,558 1 Financial liabilities at fair value through profit or loss 38 38 2,682 2,682 Derivative financial liabilities for hedging 20,096 20,096 127,929 127,929 Total ￦ 16,128,644 ￦ 14,597,106 1 The Group did not conduct fair value estimation since the book amount is a reasonable approximation of the fair value 2 With the application of IFRS 7, lease receivables are excluded from fair value disclosure.
Summary of Fair Value Hierarchy Classifications of Financial Assets and Financial Liabilities That are Measured at Fair Value	Fair value hierarchy classifications of the financial assets and financial liabilities that are measured at fair value or its fair value is disclosed as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 Level 1 Level 2 Level 3 Total Assets Trade and other receivables Financial assets at fair value through other comprehensive income ￦ — ￦ 1,256,266 ￦ — ￦ 1,256,266 Other financial assets Financial assets at fair value through profit or loss 232 136,951 495,141 632,324 Financial assets at fair value through other comprehensive income 6,738 508,550 42,054 557,342 Derivative financial assets for hedging — 40,788 17,788 58,576 Disclosed fair value Investment properties — — 2,304,583 2,304,583 Total ￦ 6,970 ￦ 1,942,555 ￦ 2,859,566 ￦ 4,809,091 Liabilities Other financial liabilities Financial liabilities at fair value through profit or loss ￦ — ￦ 38 ￦ — ￦ 38 Derivative financial liabilities for hedging — 20,096 — 20,096 Total ￦ — ￦ 20,134 ￦ — ￦ 20,134 (In millions of Korean won) December 31, 2020 Level 1 Level 2 Level 3 Total Assets Trade and other receivables Financial assets at fair value through other comprehensive income ￦ — ￦ 1,118,619 ￦ — ￦ 1,118,619 Other financial assets Financial assets at fair value through profit or loss 46,449 330,961 432,509 809,919 Financial assets at fair value through other comprehensive income 5,606 202,121 50,789 258,516 Derivative financial assets for hedging — 7,684 — 7,684 Disclosed fair value Investment properties — — 2,645,482 2,645,482 Total ￦ 52,055 ￦ 1,659,385 ￦ 3,128,780 ￦ 4,840,220 Liabilities Other financial liabilities Financial liabilities at fair value through profit or loss ￦ — ￦ 45 ￦ 2,637 ￦ 2,682 Derivative financial liabilities for hedging — 123,735 4,194 127,929 Total ￦ — ￦ 123,780 ￦ 6,831 ￦ 130,611
Summary of Changes in Level 3 of Fair Value Hierarchy for Recurring Fair Value Measurements	Details of changes in Level 3 of the fair value hierarchy for the recurring fair value measurements as at December 31, 2019 and 2020, are as follows: 2019 Financial assets Financial liabilities (In millions of Korean won) Financial assets Financial assets Derivative Financial Beginning balance ￦ 163,600 ￦ 311,536 ￦ (10,183 ) ￦ 7,758 Purchases 584,671 6,081 — — Reclassification 225,873 (444,782 ) — — Disposal (485,419 ) (941 ) — (9,734 ) Amount recognized in profit or loss 1,2 6,416 — 14,462 1,976 Amount recognized in other comprehensive income 1 — 170,160 13,509 — Ending balance ￦ 495,141 ￦ 42,054 ￦ 17,788 ￦ — 1 Amount recognized in profit or loss and other comprehensive income with respect to derivative financial liabilities for hedging comprises loss on valuation of derivative instruments. 2 Amount recognized in profit or loss with respect to financial liabilities at fair value through profit or loss comprises loss on valuation of derivative instruments. 2020 Financial assets Financial liabilities (In millions of Korean won) Financial assets Financial assets Financial Derivative Beginning balance ￦ 495,141 ￦ 42,054 ￦ — ￦ (17,788 ) Purchases 374,259 13,142 2,798 — Reclassification 208 — — — Disposal (451,663 ) (571 ) — — Amount recognized in profit or loss 1,2 14,564 (428 ) (161 ) 29,345 Amount recognized in other comprehensive income 1 — (3,408 ) — (7,363 ) Ending balance ￦ 432,509 ￦ 50,789 ￦ 2,637 ￦ 4,194 1 Amount recognized in profit or loss and other comprehensive income with respect to derivative financial liabilities for hedging comprises loss on valuation of derivative instruments. 2 Amount recognized in profit or loss with respect to financial liabilities at fair value through profit or loss comprises loss on valuation of derivative instruments.
Summary of Valuation Techniques and Inputs	Valuation techniques and inputs used in the recurring, non-recurring December 31, 2019 (In millions of Korean won) Fair value Level Valuation techniques Assets Trade and other receivables Financial assets at fair value through other comprehensive income ￦ 1,256,266 2 DCF Model Other financial assets Financial assets at fair value through profit or loss 632,092 2,3 DCF Model, Adjusted net asset model Financial assets at fair value through other comprehensive income 550,604 2,3 DCF Model, Comparable Company Analysis Derivative financial assets for hedging 58,576 2,3 Hull-White model, DCF Model Investment properties 2,304,583 3 DCF Model Liabilities Other financial liabilities Financial liabilities at fair value through profit or loss ￦ 38 2 DCF Model Derivative financial liabilities for hedging 20,096 2 DCF Model December 31, 2020 (In millions of Korean won) Fair value Level Valuation techniques Assets Trade and other receivables Financial assets at fair value through other comprehensive income ￦ 1,118,619 2 DCF Model Other financial assets Financial assets at fair value through profit or loss 763,470 2,3 DCF Model, Adjusted net asset model Financial assets at fair value through other comprehensive income 252,910 2,3 DCF Model, Comparable Company Analysis Derivative financial assets for hedging 7,684 2 DCF Model Investment properties 2,645,482 3 DCF Model Liabilities Other financial liabilities Financial liabilities at fair value through profit or loss ￦ 2,682 2,3 DCF Model, Binomial Option Pricing Derivative financial liabilities for hedging 127,929 2,3 Hull-White model, DCF Model
Summary of Details and Changes of Total Deferred Difference	In relation to this, details and changes of the total deferred difference for the years ended December 31, 2019 and 2020, are as follows: 2019 2020 (In millions of Korean won) Derivatives used Derivative held Derivatives used Derivative held I. Beginning balance ￦ 5,107 ￦ (2,824 ) ￦ 3,682 ￦ — II. New transactions — — — — III. Recognized at fair value through profit or loss (1,425 ) 2,824 (1,425 ) — IV. Ending balance (I+II+III) ￦ 3,682 ￦ — ￦ 2,257 ￦ —

Interests in Unconsolidated S_2

Interests in Unconsolidated Structured Entities (Tables)	12 Months Ended
	Dec. 31, 2020
Investments accounted for using equity method [abstract]
Summary of Unconsolidated Structured Entities and Nature of Risks	Details of scale of unconsolidated structured entities and nature of the risks associated with an entity’s interests in unconsolidated structured entities as at December 31, 2019 and 2020, are as follows: (In millions of Korean won) December 31, 2019 Real Estate PEF and Asset Total Total assets of unconsolidated structured entities ￦ 1,595,895 ￦ 4,060,992 ￦ 2,562,931 ￦ 8,219,818 Assets recognized in statement of financial position Other financial assets ￦ 15,816 ￦ 100,496 ￦ — ￦ 116,312 Joint ventures and associates 8,542 192,022 — 200,564 Total ￦ 24,358 ￦ 292,518 ￦ — ￦ 316,876 Maximum loss exposure 1 Investment assets ￦ 24,358 ￦ 292,518 ￦ — ￦ 316,876 Total ￦ 24,358 ￦ 292,518 ￦ — ￦ 316,876 1 It includes the investments recognized in the Group’s consolidated financial statements and the amounts which are probable to be determined when certain conditions are met by agreements including purchase agreements, credit granting and others. December 31, 2020 (In millions of Korean won) Real Estate PEF and Asset Total Total assets of unconsolidated structured entities ￦ 2,004,869 ￦ 4,380,534 ￦ 2,152,412 ￦ 8,537,815 Assets recognized in statement of financial position Other financial assets ￦ 29,874 ￦ 128,332 ￦ — ￦ 158,206 Joint ventures and associates 51,607 219,753 — 271,360 Total ￦ 81,481 ￦ 348,085 ￦ — ￦ 429,566 Maximum loss exposure 1 Investment assets ￦ 81,481 ￦ 348,085 ￦ — ￦ 429,566 Cash deficiency support — 29,130 — 29,130 Total ￦ 81,481 ￦ 377,215 ￦ — ￦ 458,696 1 It includes the investments recognized in the Group’s consolidated financial statements and the amounts which are probable to be determined when certain conditions are met by agreements including purchase agreements, credit granting and others.

Information About Non-control_2

Information About Non-controlling Interests (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Changes in Accumulated Non-controlling Interests	Profit or loss allocated to non-controlling non-controlling (In millions of Korean won) December 31, 2018 Non- Accumulated non-controlling Profit or loss non-controlling Dividend paid to non- controlling Others Accumulated non-controlling KT Skylife Co., Ltd. 49.7 % ￦ 328,302 ￦ 23,405 ￦ (8,279 ) ￦ 30,722 ￦ 374,150 BC Card Co., Ltd. 30.5 % 339,067 28,418 (35,924 ) 13,986 345,547 KT Powertel Co., Ltd. 55.2 % 53,053 (3,058 ) — 2,870 52,865 KT Hitel Co.,Ltd. 32.9 % 53,146 454 — (1,264 ) 52,336 KT Telecop Co., Ltd. 13.2 % 103,468 59 — (170 ) 103,357 (In millions of Korean won) December 31, 2019 Non- Accumulated non-controlling Profit or loss non-controlling Dividend to non- Others Accumulated non-controlling KT Skylife Co., Ltd. 49.7 % ￦ 374,150 ￦ 10,029 ￦ (8,279 ) ￦ 6 ￦ 375,906 BC Card Co., Ltd. 30.5 % 345,547 37,795 (18,900 ) 53,033 417,475 KT Powertel Co., Ltd. 55.2 % 52,865 1,751 — (340 ) 54,276 KT Hitel Co., Ltd. 32.9 % 52,336 1,720 — 653 54,709 KT Telecop Co., Ltd. 13.2 % 103,357 (588 ) — (99,119 ) 3,650 (In millions of Korean won) December 31, 2020 Non- Accumulated non-controlling Profit or loss non-controlling Dividend non- Others Accumulated non-controlling KT Skylife Co., Ltd. 49.7 % ￦ 375,906 ￦ 22,171 ￦ (8,279 ) ￦ (898 ) ￦ 388,900 BC Card Co., Ltd. 30.5 % 417,475 9,899 (22,787 ) 7,239 411,826 KT Powertel Co., Ltd. 55.2 % 54,276 2,151 (478 ) (202 ) 55,747 KT Hitel Co., Ltd. 32.9 % 54,709 (1,840 ) — (2,563 ) 50,306 KT Telecop Co., Ltd. 13.2 % 3,650 152 — (208 ) 3,594
Summary of Financial Information on Subsidiaries	Summarized consolidated statements of financial position as at December 31, 2018, 2019 and 2020, are as follows: December 31, 2018 (In millions of Korean won) KT Skylife BC Card Co., KT Powertel KT Hitel KT Telecop Co., Ltd. Non-controlling 49.7 % 30.5 % 55.2 % 32.9 % 13.2 % Current assets ￦ 301,739 ￦ 2,997,429 ￦ 84,785 ￦ 161,162 ￦ 52,367 Non-current 514,263 724,950 39,279 111,546 220,125 Current liabilities 112,411 2,520,050 27,187 63,231 85,648 Non-current 37,430 110,486 1,030 2,812 54,666 Equity 666,161 1,091,843 95,847 206,665 132,178 Operating revenue 694,059 3,551,715 65,620 279,117 328,262 Profit or loss for the year 52,010 70,889 (5,545 ) 657 166 Total comprehensive income (loss) 47,787 116,604 (5,792 ) 738 (1,517 ) Cash flows from operating activities 183,474 86,299 11,603 43,855 40,351 Cash flows from investing activities (139,846 ) 128,538 (2,580 ) (26,335 ) (76,969 ) Cash flows from financing activities (77,647 ) (117,561 ) — — 10,000 Net increase (decrease) in cash and cash equivalents (34,019 ) 97,276 9,023 17,520 (26,618 ) Cash and cash equivalents at beginning of year 65,747 177,826 6,626 21,647 32,326 Exchange differences — (13 ) — 19 — Cash and cash equivalents at end of year 31,728 275,089 15,649 39,186 5,708 December 31, 2019 (In millions of Korean won) KT Skylife BC Card Co., KT Powertel KT Hitel KT Telecop Co., Ltd. Non-controlling 49.7 % 30.5 % 55.2 % 32.9 % 13.2 % Current assets ￦ 459,077 ￦ 2,580,634 ￦ 86,465 ￦ 115,694 ￦ 55,908 Non-current 389,199 1,332,348 31,587 164,124 223,969 Current liabilities 123,506 2,452,219 17,757 62,378 64,218 Non-current 19,333 142,013 2,009 12,391 89,622 Equity 705,437 1,318,750 98,286 205,049 126,037 Operating revenue 704,996 3,553,008 62,846 323,065 332,063 Profit or loss for the year 56,008 115,885 3,085 1,426 (4,875 ) Total comprehensive income (loss) 55,936 289,122 2,469 (1,840 ) (6,558 ) Cash flows from operating activities 152,549 429,331 780 49,870 52,693 Cash flows from investing activities (101,594 ) (419,894 ) (9,525 ) (50,138 ) (44,393 ) Cash flows from financing activities (18,833 ) (5,744 ) (687 ) (1,860 ) (5,227 ) Net increase (decrease) in cash and cash equivalents 32,122 3,693 (9,432 ) (2,128 ) 3,073 Cash and cash equivalents at beginning of year 31,728 275,089 15,649 39,186 5,708 Exchange differences — 380 — (15 ) — Cash and cash equivalents at end of year 63,850 279,162 6,217 37,043 8,781 December 31, 2020 (In millions of Korean won) KT Skylife BC Card Co., KT Powertel KT Hitel KT Telecop Co., Ltd. Non-controlling 49.7 % 30.5 % 55.2 % 32.9 % 13.2 % Current assets ￦ 480,450 ￦ 1,785,914 ￦ 90,056 ￦ 140,948 ￦ 79,076 Non-current 439,026 1,298,484 29,638 148,001 239,380 Current liabilities 153,236 1,602,667 17,045 74,045 136,565 Non-current 21,803 176,083 1,788 18,554 57,172 Equity 744,437 1,305,648 100,861 196,350 124,719 Operating revenue 706,631 3,387,641 65,898 350,231 392,489 Profit or loss for the year 58,190 39,455 3,809 2,080 212 Total comprehensive income (loss) 55,647 61,796 3,442 (8,700 ) (1,319 ) Cash flows from operating activities 160,934 (119,163 ) 6,011 62,521 35,834 Cash flows from investing activities (105,293 ) 58,042 (3,353 ) (58,186 ) (57,976 ) Cash flows from financing activities (19,650 ) 22,790 (1,515 ) (1,856 ) 14,652 Net increase (decrease) in cash and cash equivalents 35,991 (38,331 ) 1,143 2,479 (7,490 ) Cash and cash equivalents at beginning of year 63,850 279,162 6,217 37,043 8,781 Exchange differences (7 ) (247 ) — (83 ) — Cash and cash equivalents at end of year 99,834 240,584 7,360 39,439 1,29 1
Summary of Changes in Ownership Interest on the Equity Attributable to Owners	The effect of changes in the ownership interest on the equity attributable to owners of the Group during 2018, 2019 and 2020 is summarized as follows: (In millions of Korean won) 2018 2019 2020 Carrying amount of non-controlling ￦ (194 ) ￦ (9,566 ) ￦ 1,750 Consideration paid to non-controlling 11,312 484 9,878 Excess of consideration paid recognized in parent’s equity ￦ 11,118 ￦ (9,082 ) ￦ 11,628

Business Combination (Tables)

Business Combination (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Business Combination	As of the acquisition date of control, the total consideration transferred, the recognized amount of assets acquired and liabilities acquired by major types, and calculation details of goodwill are as follows: (In millions of Korean won) Amount Total transfer cost (a) ￦ 46,800 Recognized amount of assets acquired and liabilities assumed (b) 1 46,393 Cash and cash equivalents 57,845 Trade and other receivable 95,814 Other financial assets 3,110 Other assets 14,021 Inventories 1,521 Property and equipment 3,128 Intangible assets 410 Trade and other payables (105,964 ) Other liabilities (4,815 ) Current income tax liabilities (3,664 ) Other provisions (13,745 ) Retirement benefit liabilities (1,268 ) Goodwill (a-b) ￦ 407 1 Assets acquired and liabilities acquired in accordance with IFRS 3 Business Combinations

Changes in Accounting Policie_2

Changes in Accounting Policies - Determination of Lease Term Considering Economic Penalty (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Disclosure Of Detailed Information About Impact On Consolidated Financial Statements Due to Application of Accounting Policy Explanatory	In relation to the changes in accounting policy, the adjusted amounts recognized in each line item in the consolidated financial statements are as follows: Consolidated Statements of Financial Position December 31, 2019 December 31, 2020 (In millions of Korean won) Previously Adjustment Adjusted Amount based Adjustment Amount based Current assets Prepaid expenses ￦ 76,036 ￦ (1,026 ) ￦ 75,010 ￦ 61,930 ￦ (2,119 ) ￦ 59,811 Non-current Right-of-use 788,497 479,832 1,268,329 585,034 632,145 1,217,179 Current liabilities Lease liabilities ￦ 355,833 ￦ 36,600 ￦ 392,433 ￦ 281,961 ￦ 63,263 ￦ 345,224 Non-current Lease liabilities 373,307 445,612 818,919 231,884 566,532 798,416 Total liabilities ￦ 729,140 ￦ 482,212 ￦ 1,211,352 ￦ 513,845 ￦ 629,795 ￦ 1,143,640 Net assets Retained earnings ￦ 11,594,322 ￦ (3,406 ) ￦ 11,590,916 ￦ 12,155,188 ￦ 232 ￦ 12,155,420 Total equity ￦ 11,594,322 ￦ (3,406 ) ￦ 11,590,916 ￦ 12,155,188 ￦ 232 ￦ 12,155,420 Consolidated Statements of Operations 2019 2020 (In millions of Korean won) Previously Adjustment Adjusted Amount Adjustment Amount Operating revenue ￦ 24,899,189 ￦ — ￦ 24,899,189 ￦ 24,434,851 ￦ 5,796 ￦ 24,440,647 Operating expenses 23,879,015 (6,796 ) 23,872,219 23,425,377 (7,063 ) 23,418,314 Finance income 424,395 — 424,395 498,614 — 498,614 Finance costs 421,931 10,202 432,133 498,161 9,222 507,383 Income tax expense 320,060 — 320,060 285,349 — 285,349 Profit for the year 699,274 (3,406 ) 695,868 742,619 3,637 746,256 Basic earnings per share 2,648 (14 ) 2,634 2,843 15 2,858 Diluted earnings per share 2,646 (14 ) 2,632 2,840 18 2,858

Events after Reporting Period (

Events after Reporting Period (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Public Bonds Issued After Reporting Period	The Group has issued the following bonds since the end of the reporting period . Type Issued date Face value (In millions Interest Redemption The 194-1st Jan. 27, 2021 ￦ 130,000 1.13 % Jan. 26, 2024 The 194-2nd Jan. 27, 2021 140,000 1.45 % Jan. 27, 2026 The 194-3rd Jan. 27, 2021 50,000 1.85 % Jan. 27, 2031 The 194-4th Jan. 27, 2021 80,000 1.98 % Jan. 25, 2041

General Information - Additiona

General Information - Additional Information (Detail) - shares	Jul. 02, 2001	May 09, 1999
Disclosure of general information [line items]
Number of additional shares issued	55,502,161	24,282,195
Government Owned shares [member]
Disclosure of general information [line items]
Number of additional shares issued		20,813,311

General Information - Summary o

General Information - Summary of Consolidated Subsidiaries (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of subsidiaries [line items]
Total assets	₩ 33,662,545	₩ 34,632,214
Total liabilities	18,111,112	19,491,530
Operating revenues	24,440,647	24,899,189	₩ 23,436,050
Profit (loss) for the year	₩ 746,256	₩ 695,868	₩ 719,412
KT Powertel Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Powertel Co., Ltd.	KT Powertel Co., Ltd.	KT Powertel Co., Ltd.
Total assets	₩ 119,694	₩ 118,052	₩ 124,064
Type of Business	Trunk Radio System (TRS) business
Total liabilities	₩ 18,833	19,766	28,217
Location	Korea
Operating revenues	₩ 65,897	₩ 62,846	65,620
Controlling percentage ownership	44.80%	44.80%
Profit (loss) for the year	₩ 3,809	₩ 3,085	₩ (5,545)
Closing month	December
KT Linkus Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Linkus Co., Ltd.	KT Linkus Co., Ltd.	KT Linkus Co., Ltd
Total assets	₩ 58,372	₩ 70,494	₩ 54,147
Type of Business	Public telephone maintenance
Total liabilities	₩ 54,022	62,088	44,895
Location	Korea
Operating revenues	₩ 84,519	₩ 97,892	106,337
Controlling percentage ownership	92.40%	92.40%
Profit (loss) for the year	₩ (3,212)	₩ (2,258)	₩ 1,216
Closing month	December
KT Submarine Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Submarine Co., Ltd.	KT Submarine Co., Ltd.	KT Submarine Co., Ltd.
Total assets	₩ 116,813	₩ 120,947	₩ 130,715
Type of Business	Submarine cable construction and maintenance
Total liabilities	₩ 14,032	18,452	27,530
Location	Korea
Operating revenues	₩ 110,201	₩ 55,244	61,652
Controlling percentage ownership	39.30%	39.30%
Profit (loss) for the year	₩ 1,197	₩ 486	₩ (4,286)
Closing month	December
KT Telecop Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Telecop Co., Ltd.	KT Telecop Co., Ltd.	KT Telecop Co., Ltd.
Total assets	₩ 318,456	₩ 279,878	₩ 272,492
Type of Business	Security service
Total liabilities	₩ 193,737	153,841	140,314
Location	Korea
Operating revenues	₩ 392,489	₩ 332,063	328,262
Controlling percentage ownership	86.80%	86.80%
Profit (loss) for the year	₩ 212	₩ (4,875)	₩ 166
Closing month	December
KT Hitel Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Hitel Co., Ltd.	KT Hitel Co., Ltd.	KT Hitel Co., Ltd.
Total assets	₩ 288,949	₩ 279,818	₩ 272,708
Type of Business	Data communication
Total liabilities	₩ 92,599	74,769	66,043
Location	Korea
Operating revenues	₩ 350,231	₩ 323,065	279,117
Controlling percentage ownership	67.10%	67.10%
Profit (loss) for the year	₩ 2,080	₩ 1,426	₩ 657
Closing month	December
KT service bukbu Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Service Bukbu Co., Ltd.	KT Service Bukbu Co., Ltd.	KT Service Bukbu Co., Ltd.
Total assets	₩ 60,825	₩ 64,802	₩ 30,599
Type of Business	Opening services of fixed line
Total liabilities	₩ 56,554	58,984	23,964
Location	Korea
Operating revenues	₩ 217,451	₩ 219,427	195,961
Controlling percentage ownership	67.30%	67.30%
Profit (loss) for the year	₩ (871)	₩ (445)	₩ (31)
Closing month	December
KT service nambu Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Service Nambu Co., Ltd.	KT Service Nambu Co., Ltd.	KT Service Nambu Co., Ltd.
Total assets	₩ 58,182	₩ 63,917	₩ 37,452
Type of Business	Opening services of fixed line
Total liabilities	₩ 51,460	55,548	27,939
Location	Korea
Operating revenues	₩ 264,776	₩ 266,148	230,088
Controlling percentage ownership	77.30%	77.30%
Profit (loss) for the year	₩ (456)	₩ 280	₩ 160
Closing month	December
KT Commerce Inc. [Member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Commerce Inc.
Type of Business	B2C, B2B service
Location	Korea
Controlling percentage ownership	100.00%	100.00%
Closing month	December
KT Strategic Investment Fund No.2 [Member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Strategic Investment Fund No.2
Type of Business	Investment fund
Location	Korea
Controlling percentage ownership	100.00%	100.00%
Closing month	December
KT Strategic Investment Fund No.3 [Member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Strategic Investment Fund No.3
Type of Business	Investment fund
Location	Korea
Controlling percentage ownership	100.00%	100.00%
Closing month	December
KT Strategic Investment Fund No.4 [Member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Strategic Investment Fund No.4
Type of Business	Investment fund
Location	Korea
Controlling percentage ownership	100.00%	100.00%
Closing month	December
KT Strategic Investment Fund No.5 [Member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Strategic Investment Fund No.5
Type of Business	Investment fund
Location	Korea
Controlling percentage ownership	100.00%	100.00%
Closing month	December
BCVP Strategic Investment Fund Number One [member]
Disclosure of subsidiaries [line items]
Subsidiary	BC-VP Strategic Investment Fund No.1
Type of Business	Investment fund
Location	Korea
Controlling percentage ownership	100.00%	100.00%
Closing month	December
BC Card Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	BC Card Co., Ltd.	BC Card Co., Ltd.	BC Card Co., Ltd.1
Total assets	₩ 3,084,398	₩ 3,912,982	₩ 3,722,379
Type of Business	Credit card business
Total liabilities	₩ 1,778,751	2,594,232	2,630,536
Location	Korea
Operating revenues	₩ 3,387,640	₩ 3,553,008	3,551,715
Controlling percentage ownership	69.50%	69.50%
Profit (loss) for the year	₩ 39,455	₩ 115,885	₩ 70,889
Closing month	December
VP Inc. [Member]
Disclosure of subsidiaries [line items]
Subsidiary	VP Inc.
Type of Business	Payment security service for credit card, others
Location	Korea
Controlling percentage ownership	50.90%	50.90%
Closing month	December
H&C Network [member]
Disclosure of subsidiaries [line items]
Subsidiary	H&C Network	H&C Network	H&C Network
Total assets	₩ 269,651	₩ 282,016	₩ 245,841
Type of Business	Call centre for financial sectors
Total liabilities	₩ 61,365	68,401	63,188
Location	Korea
Operating revenues	₩ 322,690	₩ 320,701	297,470
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 2,413	₩ (1,593)	₩ (15,944)
Closing month	December
BC Card China Co., Ltd. [Member]
Disclosure of subsidiaries [line items]
Subsidiary	BC Card China Co., Ltd.
Type of Business	Software development and data processing
Location	China
Controlling percentage ownership	100.00%	100.00%
Closing month	December
INITECH Co., Ltd. [Member]
Disclosure of subsidiaries [line items]
Subsidiary	INITECH Co., Ltd.
Type of Business	Internet banking ASP and security solutions
Location	Korea
Controlling percentage ownership	58.20%	58.20%
Closing month	December
Smartro Co., Ltd. [Member]
Disclosure of subsidiaries [line items]
Subsidiary	Smartro Co., Ltd.
Type of Business	VAN (Value Added Network) business
Location	Korea
Controlling percentage ownership	64.50%	64.50%
Closing month	December
KTDS Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KTDS Co., Ltd.	KTDS Co., Ltd.	KTDS Co., Ltd
Total assets	₩ 183,297	₩ 158,153	₩ 148,675
Type of Business	System integration and maintenance
Total liabilities	₩ 133,129	105,462	95,834
Location	Korea
Operating revenues	₩ 499,990	₩ 428,758	434,302
Controlling percentage ownership	95.50%	95.50%
Profit (loss) for the year	₩ 10,635	₩ 9,027	₩ 8,586
Closing month	December
KT M Hows Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT M Hows Co., Ltd.	KT M Hows Co., Ltd.	KT M Hows Co., Ltd.
Total assets	₩ 104,704	₩ 74,326	₩ 60,197
Type of Business	Mobile marketing
Total liabilities	₩ 76,315	50,638	42,386
Location	Korea
Operating revenues	₩ 44,860	₩ 33,443	26,673
Controlling percentage ownership	90.00%	90.00%
Profit (loss) for the year	₩ 6,935	₩ 6,771	₩ 3,691
Closing month	December
KT M&S Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT M&S Co., Ltd.	KT M&S Co., Ltd.	KT M&S Co., Ltd.
Total assets	₩ 231,260	₩ 248,142	₩ 228,073
Type of Business	PCS distribution
Total liabilities	₩ 197,306	215,777	207,740
Location	Korea
Operating revenues	₩ 661,533	₩ 813,498	791,652
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (485)	₩ 12,732	₩ 11,408
Closing month	December
GENIE Music Corporation K T Music Corporation [member]
Disclosure of subsidiaries [line items]
Subsidiary	GENIE Music Corporation (KT Music Corporation)	GENIE Music Corporation (KT Music Corporation)	GENIE Music Corporation (KT Music Corporation)
Total assets	₩ 250,538	₩ 234,131	₩ 221,559
Type of Business	Online music production and distribution
Total liabilities	₩ 88,488	80,952	75,827
Location	Korea
Operating revenues	₩ 247,237	₩ 230,480	171,314
Controlling percentage ownership	36.20%	36.00%
Profit (loss) for the year	₩ 9,472	₩ 7,658	₩ 6,374
Closing month	December
KT MOS Bukbu Co.,Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT MOS Bukbu Co., Ltd.	KT MOS Bukbu Co., Ltd.	KT MOS Bukbu Co., Ltd.
Total assets	₩ 32,167	₩ 33,376	₩ 14,121
Type of Business	Telecommunication facility maintenance
Total liabilities	₩ 26,070	28,841	10,571
Location	Korea
Operating revenues	₩ 67,975	₩ 63,761	16,543
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 1,473	₩ 353	₩ (782)
Closing month	December
KTMOS Nambu Co.,Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT MOS Nambu Co., Ltd.	KT MOS Nambu Co., Ltd.	KT MOS Nambu Co., Ltd.
Total assets	₩ 33,765	₩ 34,258	₩ 14,313
Type of Business	Telecommunication facility maintenance
Total liabilities	₩ 24,947	26,722	8,927
Location	Korea
Operating revenues	₩ 71,259	₩ 67,300	14,941
Controlling percentage ownership	98.40%	98.40%
Profit (loss) for the year	₩ 1,639	₩ 3,099	₩ (2,418)
Closing month	December
KT Skylife Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Skylife Co., Ltd.	KT Skylife Co., Ltd.	KT Skylife Co., Ltd.1
Total assets	₩ 919,476	₩ 848,276	₩ 816,001
Type of Business	Satellite broadcasting business
Total liabilities	₩ 175,039	142,839	149,841
Location	Korea
Operating revenues	₩ 706,631	₩ 704,996	694,059
Controlling percentage ownership	50.30%	50.30%
Profit (loss) for the year	₩ 58,190	₩ 56,008	₩ 52,010
Closing month	December
Skylife TV Co., Ltd. [Member]
Disclosure of subsidiaries [line items]
Subsidiary	Skylife TV Co., Ltd.
Type of Business	TV contents provider
Location	Korea
Controlling percentage ownership	92.60%	92.60%
Closing month	December
KT Estate Inc. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Estate Inc.	KT Estate Inc.	KT Estate Inc.1
Total assets	₩ 1,689,601	₩ 1,686,000	₩ 1,695,995
Type of Business	Residential building development and supply
Total liabilities	₩ 325,429	295,706	304,712
Location	Korea
Operating revenues	₩ 365,335	₩ 485,686	569,269
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 14,370	₩ 48,552	₩ 51,854
Closing month	December
KT AMC Co., Ltd. [Member]
Disclosure of subsidiaries [line items]
Subsidiary	KT AMC Co., Ltd.
Type of Business	Asset management and consulting services
Location	Korea
Controlling percentage ownership	100.00%	100.00%
Closing month	December
NEXR Co., Ltd. [Member]
Disclosure of subsidiaries [line items]
Subsidiary	NEXR Co., Ltd.
Type of Business	Cloud system implementation
Location	Korea
Controlling percentage ownership	100.00%	100.00%
Closing month	December
KTGDH Co., Ltd. (KTSB Data service) [member]
Disclosure of subsidiaries [line items]
Subsidiary	KTGDH Co., Ltd. (KTSB Data Service)	KTGDH Co., Ltd. (KTSB Data service)	KTGDH Co., Ltd. (KTSB Data service)
Total assets	₩ 11,003	₩ 10,437	₩ 8,632
Type of Business	Data centre development and related service
Total liabilities	₩ 1,669	1,628	523
Location	Korea
Operating revenues	₩ 4,282	₩ 3,977	4,627
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 538	₩ 344	₩ (9,576)
Closing month	December
KT Sat Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Sat Co., Ltd.	KT Sat Co., Ltd.	KT Sat Co., Ltd.
Total assets	₩ 630,740	₩ 651,195	₩ 685,926
Type of Business	Satellite communication business
Total liabilities	₩ 92,791	127,523	173,513
Location	Korea
Operating revenues	₩ 173,693	₩ 168,376	137,186
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 14,753	₩ 16,497	₩ 4,921
Closing month	December
Nasmedia Co Ltd [member]
Disclosure of subsidiaries [line items]
Subsidiary	Nasmedia Co., Ltd.	Nasmedia Co., Ltd.	Nasmedia Co., Ltd.
Total assets	₩ 422,039	₩ 356,236	₩ 303,112
Type of Business	Solution provider and IPTV advertisement sales business
Total liabilities	₩ 221,371	203,105	161,164
Location	Korea
Operating revenues	₩ 113,136	₩ 117,550	106,805
Controlling percentage ownership	44.00%	44.00%
Profit (loss) for the year	₩ 23,134	₩ 22,484	20,596
Closing month	December
KT sports [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Sports Co., Ltd.	KT Sports Co., Ltd.
Total assets			9,560
Type of Business	Management of sports group
Total liabilities			6,376
Operating revenues			55,565
Profit (loss) for the year			₩ (154)
KT Sports Co Ltd [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Sports Co., Ltd.		KT Sports Co., Ltd.
Total assets	₩ 26,572	₩ 15,603
Total liabilities	₩ 14,940	8,333
Location	Korea
Operating revenues	₩ 46,608	₩ 55,241
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (2,516)	₩ (464)
Closing month	December
KT music contents fund no.1 [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Music Contents Fund No.1	KT Music Contents Fund No.1	KT Music Contents Fund No.1
Total assets	₩ 4,844	₩ 10,579	₩ 14,092
Type of Business	Music contents investment business
Total liabilities	₩ 1,525	1,677	1,035
Location	Korea
Operating revenues	₩ 243	₩ 521	559
Controlling percentage ownership	80.00%	80.00%
Profit (loss) for the year	₩ 84	₩ 345	₩ 294
Closing month	December
K T Music Contents Fund No.2 [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Music Contents Fund No.2	KT Music Contents Fund No.2	KT Music Contents Fund No.2
Total assets	₩ 15,021	₩ 7,675	₩ 7,629
Type of Business	Music contents investment business
Total liabilities	₩ 285	279	281
Location	Korea
Operating revenues	₩ 169	₩ 331	150
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (116)	₩ 48	₩ (142)
Closing month	December
KT-Michigan global content fund [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT-Michigan Global Contents Fund	KT-Michigan Global Content Fund	KT-Michigan Global Content Fund
Total assets	₩ 10,382	₩ 11,688	₩ 12,741
Type of Business	Content investment business
Total liabilities	₩ 175	61	0
Location	Korea
Operating revenues	₩ 111	₩ 248	869
Controlling percentage ownership	88.60%	88.60%
Profit (loss) for the year	₩ (1,420)	₩ (1,113)	₩ (670)
Closing month	December
Autopion Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	Autopion Co., Ltd.	Autopion Co., Ltd.	Autopion Co., Ltd.
Total assets	₩ 4,903	₩ 7,460	₩ 8,838
Type of Business	Information and communication service
Total liabilities	₩ 4,961	4,894	5,801
Location	Korea
Operating revenues	₩ 6,174	₩ 5,604	12,035
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (2,459)	₩ (302)	₩ 453
Closing month	December
KTCS Corporation [member]
Disclosure of subsidiaries [line items]
Subsidiary	KTCS Corporation	KTCS Corporation	KTCS Corporation
Total assets	₩ 384,919	₩ 378,171	₩ 350,280
Type of Business	Database and online information provider
Total liabilities	₩ 215,175	213,983	188,561
Location	Korea
Operating revenues	₩ 933,006	₩ 944,778	1,019,787
Controlling percentage ownership	31.90%	30.90%
Profit (loss) for the year	₩ 11,323	₩ 7,597	₩ 11,401
Closing month	December
KTIS Corporation [member]
Disclosure of subsidiaries [line items]
Subsidiary	KTIS Corporation	KTIS Corporation	KTIS Corporation
Total assets	₩ 294,289	₩ 305,798	₩ 229,246
Type of Business	Database and online information provider
Total liabilities	₩ 126,894	137,524	68,997
Location	Korea
Operating revenues	₩ 454,172	₩ 454,561	451,532
Controlling percentage ownership	30.80%	30.10%
Profit (loss) for the year	₩ 7,387	₩ 9,205	₩ 7,900
Closing month	December
KT M mobile Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT M Mobile Co., Ltd.	KT M mobile Co., Ltd.	KT M mobile Co., Ltd.
Total assets	₩ 129,011	₩ 135,917	₩ 146,334
Type of Business	Special category telecommunications operator and sales of communication device
Total liabilities	₩ 27,281	30,603	35,335
Location	Korea
Operating revenues	₩ 163,472	₩ 161,720	172,674
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (3,617)	₩ (5,580)	₩ (10,085)
Closing month	December
KT Investment Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Investment Co., Ltd.	KT Investment Co., Ltd.	KT Investment Co., Ltd.
Total assets	₩ 115,627	₩ 73,463	₩ 74,580
Type of Business	Technology business finance
Total liabilities	₩ 93,695	56,212	58,040
Location	Korea
Operating revenues	₩ 47,801	₩ 13,375	8,095
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 4,680	₩ 847	₩ 247
Closing month	December
Whowho&Company Co., Ltd. [Member]
Disclosure of subsidiaries [line items]
Subsidiary	Whowho&Company Co., Ltd.
Type of Business	Software development and supply
Location	Korea
Controlling percentage ownership	100.00%	100.00%
Closing month	December
PlayD Co., Ltd. (N Search Marketing Co., Ltd.) [member]
Disclosure of subsidiaries [line items]
Subsidiary	PlayD Co., Ltd. (N Search Marketing Co., Ltd.)
Type of Business	Advertising agency
Location	Korea
Controlling percentage ownership	70.40%	100.00%
Closing month	December
Next Connect PFV [member]
Disclosure of subsidiaries [line items]
Subsidiary	Next Connect PFV	Next connect PFV	Next connect PFV
Total assets	₩ 394,268	₩ 385,412	₩ 385,769
Type of Business	Residential building development and supply
Total liabilities	₩ 37,271	24,275	34,370
Location	Korea
Operating revenues	₩ 26	₩ 1,590	143
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (7,101)	₩ (5,898)	₩ (12,449)
Closing month	December
KT Rwanda Networks Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Rwanda Networks Ltd.	KT Rwanda Networks Ltd.	KT Rwanda Networks Ltd.
Total assets	₩ 114,768	₩ 132,461	₩ 144,129
Type of Business	Network installation and management
Total liabilities	₩ 191,781	183,164	162,801
Location	Rwanda
Operating revenues	₩ 17,870	₩ 18,013	15,150
Controlling percentage ownership	51.00%	51.00%
Profit (loss) for the year	₩ (34,610)	₩ (31,662)	₩ (29,238)
Closing month	December
AOS Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	AOS Ltd.	AOS Ltd.	AOS Ltd.
Total assets	₩ 11,812	₩ 12,337	₩ 14,018
Type of Business	System integration and maintenance
Total liabilities	₩ 3,875	3,993	4,952
Location	Rwanda
Operating revenues	₩ 5,719	₩ 6,982	6,300
Controlling percentage ownership	51.00%	51.00%
Profit (loss) for the year	₩ 296	₩ (591)	₩ (680)
Closing month	December
KT Belgium [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Belgium	KT Belgium	KT Belgium
Total assets	₩ 87,608	₩ 93,321	₩ 90,172
Type of Business	Foreign investment business
Total liabilities		11	1
Location	Belgium
Operating revenues		₩ (81)	29
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (81)	₩ (64)	₩ (43)
Closing month	December
KT ORS Belgium [member]
Disclosure of subsidiaries [line items]
Subsidiary		KT ORS Belgium	KT ORS Belgium
Total assets		₩ 6,913	₩ 6,709
Total liabilities		14	5
Profit (loss) for the year		₩ (43)	₩ (46)
Korea Telecom Japan Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	Korea Telecom Japan Co., Ltd.	Korea Telecom Japan Co., Ltd.	Korea Telecom Japan Co., Ltd.
Total assets	₩ 2,694	₩ 1,851	₩ 1,326
Type of Business	Foreign telecommunication business
Total liabilities	₩ 2,622	2,858	2,910
Location	Japan
Operating revenues	₩ 1,853	₩ 2,891	1,965
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 1	₩ 651	₩ (126)
Closing month	December
KBTO sp.zo.o. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KBTO sp.z o.o.	KBTO sp.zo.o.	KBTO sp.zo.o.
Total assets	₩ 438	₩ 1,767	₩ 1,364
Type of Business	Electronic communication business
Total liabilities	₩ 117	245	217
Location	Poland
Operating revenues	₩ 490	₩ 519	202
Controlling percentage ownership	97.40%	97.20%
Profit (loss) for the year	₩ (2,823)	₩ (3,457)	₩ (3,771)
Closing month	December
Korea Telecom China Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	Korea Telecom China Co., Ltd.	Korea Telecom China Co., Ltd.	Korea Telecom China Co., Ltd.
Total assets	₩ 381	₩ 879	₩ 661
Type of Business	Foreign telecommunication business
Total liabilities	₩ 21	39	22
Location	China
Operating revenues	₩ 618	₩ 844	681
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (492)	₩ 192	₩ 10
Closing month	December
KT Dutch B.V. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Dutch B.V.	KT Dutch B.V.	KT Dutch B.V.
Total assets	₩ 29,585	₩ 31,003	₩ 31,693
Type of Business	Super iMax and East Telecom management
Total liabilities	₩ 10,109	50	41
Location	Netherlands
Operating revenues		₩ 26,782	191
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 6,061	₩ (242)	₩ 105
Closing month	December
Super iMax LLC [member]
Disclosure of subsidiaries [line items]
Subsidiary		Super iMax LLC	Super iMax LLC
Total assets		₩ 3,568	₩ 4,150
Total liabilities		5,304	4,528
Operating revenues		4,604	4,845
Profit (loss) for the year		₩ (631)	₩ (424)
East Telecom LLC [member]
Disclosure of subsidiaries [line items]
Subsidiary	East Telecom LLC	East Telecom LLC	East Telecom LLC1
Total assets		₩ 20,857	₩ 16,590
Type of Business	Fixed line telecommunication business
Total liabilities		16,302	14,263
Location	Uzbekistan
Operating revenues		₩ 17,186	15,087
Controlling percentage ownership	91.60%	91.00%
Profit (loss) for the year		₩ 2,140	₩ 2,639
Closing month	December
Korea Telecom America, Inc. [member]
Disclosure of subsidiaries [line items]
Subsidiary	Korea Telecom America, Inc.	Korea Telecom America, Inc.	Korea Telecom America, Inc.
Total assets	₩ 4,498	₩ 4,611	₩ 4,218
Type of Business	Foreign telecommunication business
Total liabilities	₩ 125	537	832
Location	USA
Operating revenues	₩ 6,808	₩ 6,808	7,554
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 712	₩ 572	₩ 350
Closing month	December
PT. KT Indonesia [member]
Disclosure of subsidiaries [line items]
Subsidiary		PT. KT Indonesia	PT. KT Indonesia
Total assets		₩ 8	₩ 8
PT BC card Asia Pacific [member]
Disclosure of subsidiaries [line items]
Subsidiary	PT. BC Card Asia Pacific
Type of Business	Software development and supply
Location	Indonesia
Controlling percentage ownership	99.90%	99.90%
Closing month	December
KT Hongkong Telecommunications Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Hong Kong Telecommunications Co., Ltd.	KT Hongkong Telecommunications Co., Ltd.	KT Hongkong Telecommunications Co., Ltd.
Total assets	₩ 6,159	₩ 5,126	₩ 3,616
Type of Business	Fixed line communication business
Total liabilities	₩ 2,800	2,923	2,143
Location	Hong Kong
Operating revenues	₩ 16,386	₩ 13,321	9,990
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 1,308	₩ 586	₩ 351
Closing month	December
Korea Telecom Singapore Pte.Ltd. [member]
Disclosure of subsidiaries [line items]
Subsidiary	Korea Telecom Singapore Pte. Ltd.
Type of Business	Foreign investment business
Location	Singapore
Controlling percentage ownership	100.00%	100.00%
Closing month	December
Texnoprosistem LLP [member]
Disclosure of subsidiaries [line items]
Subsidiary	Texnoprosistem LLC
Type of Business	Fixed line internet business
Location	Uzbekistan
Controlling percentage ownership	100.00%	100.00%
Closing month	December
Nasmedia Thailand Co Ltd [member]
Disclosure of subsidiaries [line items]
Subsidiary	Nasmedia Thailand Co., Ltd.
Type of Business	Internet advertising solution provider
Location	Thailand
Controlling percentage ownership	99.90%	99.90%
Closing month	December
KT Huimangjieum [member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Huimangjieum	KT Huimangjieum
Total assets	₩ 3,720	₩ 2,129
Type of Business	Manufacturing
Total liabilities	₩ 2,787	1,019
Location	Korea
Operating revenues	₩ 5,239	₩ 1,027
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (13)	₩ (390)
Closing month	December
GE Premier 1st Corporate Restructuring Real Estate Investment Trust Co. [member]
Disclosure of subsidiaries [line items]
Subsidiary	GE Premier 1st Corporate Restructuring Real Estate Investment Trust Co.	GE Premier 1st Corporate Restructuring Real Estate Investment Trust Co.
Total assets	₩ 5,703	₩ 6,285
Type of Business	Residential building investment and rent
Total liabilities	₩ 1,165	1,139
Location	Korea
Operating revenues	₩ 333	₩ 176
Controlling percentage ownership	68.10%	63.50%
Profit (loss) for the year	₩ 83	₩ 70
Closing month	December
K-REALTY RENTAL HOUSING REIT 3 [member]
Disclosure of subsidiaries [line items]
Subsidiary	K-REALTY RENTAL HOUSING REIT 3	K-REALTY RENTAL HOUSING REIT 3
Total assets		₩ 300
Type of Business	Residential building
Location	Korea
Controlling percentage ownership	88.60%	100.00%
Closing month	December
GENIE Music Corporation(KT Music Corporation) [member]
Disclosure of subsidiaries [line items]
Subsidiary	GENIE Music Corporation (KT Music Corporation)
Storywiz Co Ltd [Member]
Disclosure of subsidiaries [line items]
Subsidiary	Storywiz Co., Ltd
Total assets	₩ 21,594
Type of Business	Content and software development and supply
Total liabilities	₩ 10,065
Location	Korea
Operating revenues	₩ 19,209
Controlling percentage ownership	100.00%
Profit (loss) for the year	₩ (1,954)
Closing month	December
KT Engineering Co Ltd KT ENGCORE Co Ltd [Member]
Disclosure of subsidiaries [line items]
Subsidiary	KT Engineering Co., Ltd. (KT ENGCORE Co., Ltd.)
Total assets	₩ 138,220
Type of Business	Telecommunication facility construction and maintenance
Total liabilities	₩ 102,963
Location	Korea
Operating revenues	₩ 346,040
Controlling percentage ownership	100.00%
Profit (loss) for the year	₩ (8,461)
Closing month	December

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Detail) ₩ in Millions	12 Months Ended
	Dec. 31, 2020KRW (₩)	Dec. 31, 2020SGD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019KRW (₩)
Disclosure of significant accounting policies [line items]
Borrowing	₩ 7,316,298	$ 284,000,000	$ 519,598,989	₩ 7,298,867
Notional amount		$ 284,000,000	$ 519,598,989
Derecognition of financial liabilities, percent	10.00%
Bottom of range [member]
Disclosure of significant accounting policies [line items]
Useful lives of investment property, excluding land depreciated cost model	10 years
Top of range [member]
Disclosure of significant accounting policies [line items]
Useful lives of investment property, excluding land depreciated cost model	40 years

Significant Accounting Polici_5

Significant Accounting Policies - Summary of Estimated Useful Lives of Property, Plant and Equipment (Detail)	12 Months Ended
	Dec. 31, 2020
Buildings [member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	5 years
Buildings [member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	40 years
Structures [member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	5 years
Structures [member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	40 years
Machinery and equipment (Telecommunications equipment and others) [member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	2 years
Machinery and equipment (Telecommunications equipment and others) [member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	40 years
Vehicles [member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	4 years
Vehicles [member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	6 years
Tools [member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	4 years
Tools [member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	6 years
Office equipment [member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	2 years
Office equipment [member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	6 years

Significant Accounting Polici_6

Significant Accounting Policies - Summary of Amortization of Intangible Assets With Limited Useful Life (Detail)	12 Months Ended
	Dec. 31, 2020
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	3 years
Development costs [member] | Bottom of range [member]
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	5 years
Development costs [member] | Top of range [member]
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	6 years
Software [member] | Bottom of range [member]
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	4 years
Software [member] | Top of range [member]
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	6 years
Frequency usage rights [member] | Bottom of range [member]
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	5 years
Frequency usage rights [member] | Top of range [member]
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	10 years
Others [member] | Bottom of range [member]
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	1 year
Others [member] | Top of range [member]
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	50 years

Financial Instruments by Cate_3

Financial Instruments by Category - Summary of Financial Instruments by Category (Detail) ₩ in Millions	Dec. 31, 2020KRW (₩)	Dec. 31, 2020SGD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019KRW (₩)	Dec. 31, 2018KRW (₩)	Dec. 31, 2017KRW (₩)
Disclosure of detailed information about financial instruments [line items]
Trade and other payables	₩ 7,017,639			₩ 8,679,698
Borrowings	7,316,298	$ 284,000,000	$ 519,598,989	7,298,867
Other financial liabilities	263,169			150,079
Cash and cash equivalents	2,634,624			2,305,894	₩ 2,703,422	₩ 1,928,182
Trade and other receivables	6,095,042			7,004,725
Other financial assets	1,747,187			1,690,046
Loans and receivables [member]
Disclosure of detailed information about financial instruments [line items]
Cash and cash equivalents	2,634,624			2,305,894
Trade and other receivables	4,976,423			5,748,459
Other financial assets	671,068			441,804
Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Other financial assets	809,919			632,324
Derivative used for hedge [member]
Disclosure of detailed information about financial instruments [line items]
Other financial liabilities	127,929			20,096
Other financial assets	7,684			58,576
Financial liabilities designated as at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Other financial liabilities	2,682			38
Financial liabilities at amortized cost [member]
Disclosure of detailed information about financial instruments [line items]
Trade and other payables	7,017,639			8,679,698
Borrowings	7,316,298			7,298,867
Other financial liabilities	132,558			129,945
Financial assets at fair value through other comprehensive income [member]
Disclosure of detailed information about financial instruments [line items]
Trade and other receivables	1,118,619			1,256,266
Other financial assets	₩ 258,516			₩ 557,342

Financial Instruments by Cate_4

Financial Instruments by Category - Summary of Gains or Losses Arising From Financial Instruments by Category (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of detailed information about financial instruments [line items]
Interest income	₩ 270,571	₩ 282,704	₩ 244,796
Interest expense	(263,579)	(278,427)	(296,874)
Total		214,063	(116,643)
Gain (loss) on valuation	40,822	15,429	(5)
Other comprehensive income (loss) for the year	23,255	172,338	(54,628)
Reclassified to profit or loss from other comprehensive income for the year	111,431	(44,684)
Financial liabilities designated as at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Gain (loss) on disposal	799	2,664
Gain (loss) on valuation	119
Derivatives used for hedging [member]
Disclosure of detailed information about financial instruments [line items]
Gain on transactions	1,141		20,678
Gain (loss) on valuation	(161,003)	4,949	42,195
Other comprehensive income (loss) for the year	(81,671)	20,742	(2,810)
Reclassified to profit or loss from other comprehensive income for the year	107,786	(5,080)	(28,388)
Financial liabilities at amortized cost [member]
Disclosure of detailed information about financial instruments [line items]
Interest expense	(220,945)	(223,974)	(296,894)
Loss on repayment			(15)
Gain (loss) foreign currency transaction	(10,717)	(20,958)	(30,956)
Gain (loss) on foreign currency translation	141,849	(75,502)	(66,050)
Total	5,481
Financial assets at amortized cost [member]
Disclosure of detailed information about financial instruments [line items]
Interest income	55,742	79,838	93,233
Gain (loss) foreign currency transaction	(19,244)	32,293	19,396
Gain (loss) on foreign currency translation	(3,895)	(474)	(2,901)
Gain (loss) on disposal	138	(43)	44
Gain (loss) on valuation	(140,474)	(59,947)	(110,544)
Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Interest income	6,548	5,634	9,194
Dividend income	4,379	1,096	1,207
Gain (loss) foreign currency transaction	(38)	(27)
Gain (loss) on disposal	(329)	5,115	1,713
Gain (loss) on valuation	59,044	4,334	10,768
Financial assets at fair value through other comprehensive income [member]
Disclosure of detailed information about financial instruments [line items]
Interest income	227,736	217,355	163,390
Dividend income	56	2,312	1,704
Gain (loss) on disposal	(8,152)	(11,247)	(13,818)
Impairment loss		(304)	(2,416)
Other comprehensive income (loss) for the year	41,997	167,152	43,811
Derivative financial liabilities [member]
Disclosure of detailed information about financial instruments [line items]
Gain on transactions	6,050	6,332	7,272
Gain (loss) on valuation	(2,707)	56,537	22,065
Other comprehensive income (loss) for the year	(2,373)	46,806	20,078
Reclassified to profit or loss from other comprehensive income for the year	₩ 3,645	(39,604)	(15,891)
Held-to-maturity financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Gain (loss) on valuation		₩ (1,936)	₩ (2,708)

Financial Instruments by Cate_5

Financial Instruments by Category - Summary of Gains or Losses Arising From Financial Instruments by Category (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of detailed information about financial instruments [line items]
Interest income recognized as operating revenue	₩ 270,571	₩ 282,704	₩ 244,796
Interest expense recognized as operating expense	263,579	278,427	296,874
Profit and loss from foreign currency transaction	17,493	24,596	17,175
Gain (loss) on valuation	40,822	15,429	(5)
BC Card Co., Ltd. [member]
Disclosure of detailed information about financial instruments [line items]
Interest income recognized as operating revenue	21,018	21,021	20,854
Interest expense recognized as operating expense	548	21	1,456
Profit and loss from foreign currency transaction	17,006	20,422	19,687
Operating expenses from foreign currency translation	5	0	56
Dividend income	₩ 2,250	₩ 1,598	₩ 2,059

Cash and Cash Equivalents to Re

Cash and Cash Equivalents to Restricted Cash - Summary of Restricted Cash and Cash Equivalents (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Cash and cash equivalents [abstract]
Deposit restricted for governmental project and others	₩ 28,414	₩ 21,290

Trade and Other Receivables - S

Trade and Other Receivables - Summary of Trade and Other Receivables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of financial assets [line items]
Trade receivables	₩ 3,056,130	₩ 3,150,395
Other receivables	1,846,341	2,708,301
Trade and other receivables, net	4,902,471	5,858,696
Trade receivables	853,953	827,146
Other receivables	396,816	354,652
Trade and other receivables, net	1,250,769	1,181,798
Gross carrying amount [member]
Disclosure of financial assets [line items]
Trade receivables	3,388,099	3,451,107
Other receivables	1,948,108	2,787,144
Trade and other receivables, net	5,336,207	6,238,251
Trade receivables	892,992	874,860
Other receivables	513,926	382,468
Trade and other receivables, net	1,406,918	1,257,328
Accumulated depreciation, amortisation and impairment [member]
Disclosure of financial assets [line items]
Trade receivables	(322,992)	(291,202)
Other receivables	(101,619)	(78,572)
Trade and other receivables, net	(424,611)	(369,774)
Trade receivables	(4,323)	(4,117)
Other receivables	(102,985)	(5,108)
Trade and other receivables, net	(107,308)	(9,225)
Present value discount [member]
Disclosure of financial assets [line items]
Trade receivables	(8,977)	(9,510)
Other receivables	(148)	(271)
Trade and other receivables, net	(9,125)	(9,781)
Trade receivables	(34,716)	(43,597)
Other receivables	(14,125)	(22,708)
Trade and other receivables, net	₩ (48,841)	₩ (66,305)

Trade and Other Receivables -_2

Trade and Other Receivables - Summary of Changes in Summary of Changes in Provision for Impairment (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Trade receivables [member]
Disclosure of financial assets [line items]
Beginning balance	₩ 295,319	₩ 359,924
Provision	89,097	24,596
Write-off or transfer out	(60,598)	(90,513)
Changes in the scope of consolidation	3,211
Others	286	1,312
Ending balance	327,315	295,319
Other receivables [member]
Disclosure of financial assets [line items]
Beginning balance	83,680	93,822
Provision	50,860	35,597
Reversal	(890)	(475)
Write-off or transfer out	(25,067)	(44,108)
Changes in the scope of consolidation	87,614
Others	8,407	(1,156)
Ending balance	₩ 204,604	₩ 83,680

Trade and Other Receivables -_3

Trade and Other Receivables - Summary of Other Receivables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of financial assets [line items]
Receivables	₩ 6,095,042	₩ 7,004,725
Other receivables [member]
Disclosure of financial assets [line items]
Loans	116,082	84,148
Receivables	1,699,608	2,540,315
Accrued income	6,901	8,630
Refundable deposits	350,180	352,293
Loans receivable	150,527	105,961
Finance lease receivables	64,047	39,726
Others	60,416	15,560
Less Provision for impairment	(204,604)	(83,680)	₩ (93,822)
Other receivables	₩ 2,243,157	₩ 3,062,953

Trade and Other Receivables -_4

Trade and Other Receivables - Summary of Other Receivables (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
BC Card Co., Ltd. [member]
Disclosure of financial assets [line items]
Settlement receivable included in other receivables	₩ 986,384	₩ 1,786,610

Other Financial Assets and Li_3

Other Financial Assets and Liabilities - Summary of Other Financial Assets and Liabilities (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Other financial assets
Financial assets at amortized cost	₩ 671,068	₩ 441,804
Financial assets at fair value through profit or loss	809,919	632,324
Financial assets at fair value through other comprehensive income	258,516	557,342
Derivative used for hedging	7,684	58,576
Less: Non-current	544,347	821,658
Current	1,202,840	868,388
Other financial liabilities
Financial liabilities at amortized cost	132,558	129,945
Financial liabilities at fair value through profit or loss	2,682	38
Derivatives used for hedging	127,929	20,096
Less: Non-current	(260,676)	(149,136)
Current Other financial assets	₩ 2,493	₩ 943

Other Financial Assets and Li_4

Other Financial Assets and Liabilities - Summary of Other Financial Assets and Liabilities (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about financial instruments [line items]
Other financial assets	₩ 1,747,187	₩ 1,690,046
Korea software financial cooperative [member]
Disclosure of detailed information about financial instruments [line items]
Available-for-sale financial assets investment amount	5,491	1,849
Ustream Inc. [member]
Disclosure of detailed information about financial instruments [line items]
Proceeds from the disposal of Subsidiary	104,442	91,445
Money Market Wrap and Money Market Trust [member]
Disclosure of detailed information about financial instruments [line items]
Other financial assets	₩ 509,068	₩ 406,062

Other Financial Assets and Li_5

Other Financial Assets and Liabilities - Summary of Financial Assets at Fair Value Through Profit or Loss (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of financial assets [line items]
Equity Instruments	₩ 809,919	₩ 632,324
Less: non-current	(276,109)	(219,026)
Current	533,810	413,298
Equity Instruments Listed [member]
Disclosure of financial assets [line items]
Equity Instruments	46,449	232
Equity Instruments Unlisted [member]
Disclosure of financial assets [line items]
Equity Instruments	83,017	90,357
Debt securities [member]
Disclosure of financial assets [line items]
Equity Instruments	₩ 680,453	541,657
Derivatives held for trading [member]
Disclosure of financial assets [line items]
Equity Instruments		₩ 78

Other Financial Assets and Li_6

Other Financial Assets and Liabilities - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of detailed information about financial instruments [line items]
Ineffective portion recognized in profit or loss cash flow hedge valuation gain	₩ 2,711	₩ 4,181	₩ 263
Reclassified as accumulated other comprehensive income after tax	265,087
Retained earnings of attributable to owners	12,155,420	11,590,916
Disposal of investments in associates and joint ventures	24	₩ 16,930	₩ 7,832
Equity Instruments Listed [member]
Disclosure of detailed information about financial instruments [line items]
Retained earnings of attributable to owners	184,330
Disposal of investments in associates and joint ventures	₩ 350,777

Other Financial Assets and Li_7

Other Financial Assets and Liabilities - Summary of Financial Assets at Fair Value Through Other Comprehensive Income (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financial assets at fair value through other comprehensive income [line items]
Equity Instruments	₩ 258,516	₩ 557,342
Less: non-current	(258,516)	(556,147)
Current
Equity Instruments Listed [member]
Financial assets at fair value through other comprehensive income [line items]
Equity Instruments	6,216	6,738
Equity Instruments Unlisted [member]
Financial assets at fair value through other comprehensive income [line items]
Equity Instruments	245,730	543,518
Debt securities [member]
Financial assets at fair value through other comprehensive income [line items]
Equity Instruments	₩ 6,570	₩ 7,086

Other Financial Assets and Li_8

Other Financial Assets and Liabilities - Summary of Derivative Financial Assets and Liabilities (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about financial instruments [line items]
Assets, Total	₩ 7,684	₩ 58,576
Less: Assets, non-current	(2,111)	(28,304)
Assets, Current	5,573	30,272
Liabilities, Total	127,929	20,096
Less: Liabilities, non-current	(126,408)	(19,177)
Liabilities, Current	1,521	919
Interest rate swap [member]
Disclosure of detailed information about financial instruments [line items]
Liabilities, Total	1,078	1,464
Currency swap [member]
Disclosure of detailed information about financial instruments [line items]
Assets, Total	7,684	55,569
Liabilities, Total	126,189	18,632
Currency forwards [member]
Disclosure of detailed information about financial instruments [line items]
Assets, Total		₩ 3,007
Liabilities, Total	₩ 662

Other Financial Assets and Li_9

Other Financial Assets and Liabilities - Summary of Valuation Gains and Losses on Derivatives Contracts (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of detailed information about financial instruments [line items]
Valuation gain		₩ 77,275	₩ 66,305
Valuation loss	₩ 163,710	15,829	2,045
Other comprehensive income	(113,742)	91,521	21,651
Interest rate swap [member]
Disclosure of detailed information about financial instruments [line items]
Valuation gain			192
Valuation loss		45
Other comprehensive income	(567)	(963)	(488)
Currency swap [member]
Disclosure of detailed information about financial instruments [line items]
Valuation gain		72,417	58,912
Valuation loss	161,661	15,784	2,045
Other comprehensive income	(113,175)	87,626	22,139
Currency forwards [member]
Disclosure of detailed information about financial instruments [line items]
Valuation gain		4,858	₩ 7,201
Valuation loss	₩ 2,049
Other comprehensive income		₩ 4,858

Other Financial Assets and L_10

Other Financial Assets and Liabilities - Summary of Hedged items (Detail) - Derivatives [member] - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about hedged items [line items]
Book value of hedged items	₩ 2,643,046	₩ 2,673,253
Changes in fair value to calculate the ineffective portion of hedges	151,817	(60,696)
Cash flow hedge reserves	19,779	(7,609)
USD
Disclosure of detailed information about hedged items [line items]
Book value of hedged items	1,924,576	1,822,477
Changes in fair value to calculate the ineffective portion of hedges	133,978	(45,855)
Cash flow hedge reserves	19,641	(5,214)
JPY
Disclosure of detailed information about hedged items [line items]
Book value of hedged items	484,960	850,776
Changes in fair value to calculate the ineffective portion of hedges	4,228	(14,841)
Cash flow hedge reserves	(2,569)	₩ (2,395)
SGD
Disclosure of detailed information about hedged items [line items]
Book value of hedged items	233,510
Changes in fair value to calculate the ineffective portion of hedges	13,611
Cash flow hedge reserves	₩ 2,707

Other Financial Assets and L_11

Other Financial Assets and Liabilities - Summary of Hedging instruments (Detail) - Derivatives [member] - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about hedging instruments [line items]
Contract amount	₩ 2,771,700	₩ 2,616,123
Assets	7,684	58,576
Liabilities	127,929	20,096
Changes in fair value to calculate the ineffective portion of hedges	(154,528)	64,876
USD
Disclosure of detailed information about hedging instruments [line items]
Foreign currency	1,768,912	1,574,068
Contract amount	2,037,568	1,788,831
Assets	2,111	30,175
Liabilities	100,623	10,692
Changes in fair value to calculate the ineffective portion of hedges	(136,852)	49,480
JPY
Disclosure of detailed information about hedging instruments [line items]
Foreign currency	46,000,000	80,000,000
Contract amount	488,924	827,292
Assets	5,573	28,401
Liabilities	13,839	9,404
Changes in fair value to calculate the ineffective portion of hedges	(4,065)	₩ 15,396
SGD
Disclosure of detailed information about hedging instruments [line items]
Foreign currency	284,000
Contract amount	245,208
Liabilities	13,467
Changes in fair value to calculate the ineffective portion of hedges	₩ (13,611)

Other Financial Assets and L_12

Other Financial Assets and Liabilities - Summary of Financial Liabilities at Fair Value Through Profit or Loss (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financial liabilities at fair value through profit or loss
Derivative liabilities held for trading	₩ 45	₩ 38
Conversion Rights and Redemption Rights	2,637
Total	₩ 2,682	₩ 38

Other Financial Assets and L_13

Other Financial Assets and Liabilities - Summary of Valuation Gain and Loss on Financial Liabilities at Fair Value Through Profit or Loss (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of financial liabilities [line items]
Derivative liabilities held for trading	₩ 45	₩ 38
Conversion Rights and Redemption Rights	2,637
Total	2,682	38
Valuation gain on financial liabilities [member]
Disclosure of financial liabilities [line items]
Derivative liabilities held for trading	10	78
Conversion Rights and Redemption Rights	162
Total	172	78
Valuation loss on financial liabilities [member]
Disclosure of financial liabilities [line items]
Derivative liabilities held for trading	53	2,014	₩ 2,707
Total	₩ 53	₩ 2,014	₩ 2,707

Inventories - Summary of Invent

Inventories - Summary of Inventories Net (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of inventories [line items]
Inventories	₩ 534,636	₩ 791,677
Merchandise [member]
Disclosure of inventories [line items]
Inventories	517,632	661,253
Others [member]
Disclosure of inventories [line items]
Inventories	17,004	130,424
Gross carrying amount [member]
Disclosure of inventories [line items]
Inventories	667,860	936,115
Gross carrying amount [member] | Merchandise [member]
Disclosure of inventories [line items]
Inventories	650,856	805,691
Gross carrying amount [member] | Others [member]
Disclosure of inventories [line items]
Inventories	17,004	130,424
Valuation allowance [member]
Disclosure of inventories [line items]
Inventories	(133,224)	(144,438)
Valuation allowance [member] | Merchandise [member]
Disclosure of inventories [line items]
Inventories	₩ (133,224)	₩ (144,438)

Inventories - Additional Inform

Inventories - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Classes of current inventories [abstract]
Inventories recognised as expense	₩ 3,938,842	₩ 3,905,630	₩ 3,926,199
Valuation loss and reversal of valuation loss	₩ 11,214	₩ 30,857	₩ 55,288

Other Assets and Liabilities -

Other Assets and Liabilities - Summary of Other Assets and Liabilities (Detail) - KRW (₩) ₩ in Millions		Dec. 31, 2020	Dec. 31, 2019
Other assets
Advance payments		₩ 168,302	₩ 179,475
Prepaid expenses		66,578	84,768
Contract Cost	[1]	1,804,948	1,849,243
Contract assets	[1]	586,438	557,041
Others		18,747	14,243
Less: Non-current		(768,661)	(685,488)
Current		1,876,352	1,999,282
Other liabilities
Advances received		328,491	333,342
Withholdings		105,415	99,844
Unearned revenue		29,593	65,228
Lease liabilities		1,143,640	1,211,352
Contract liabilities	[1]	384,133	365,610
Others		21,597	23,298
Less: Non-current		(909,570)	(1,030,117)
Current		₩ 1,103,299	₩ 1,068,557
[1]	The amounts include adjustments arising from adoption of IFRS 15 (Note 26).

Assets Held for Sale - Addition

Assets Held for Sale - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Assets Held For Sale [Line Items]
Proceeds from Assets held for Sale	₩ 83,241	₩ 28,834	₩ 9,842
Non-current assets held for sale [member]
Disclosure Of Assets Held For Sale [Line Items]
Impairment loss	0
Proceeds from Assets held for Sale	₩ 82,865

Assets Held for Sale - Summary

Assets Held for Sale - Summary of Assets Held for Sale (Detail) ₩ in Millions	Dec. 31, 2020KRW (₩)
Noncurrent assets or disposal groups classified as held for sale or as held for distribution to owners [line items]
Non-current assets held for sale	₩ 1,198
Land [member]
Noncurrent assets or disposal groups classified as held for sale or as held for distribution to owners [line items]
Non-current assets held for sale	172
Buildings And Other [Member]
Noncurrent assets or disposal groups classified as held for sale or as held for distribution to owners [line items]
Non-current assets held for sale	₩ 1,026

Property and Equipment - Summar

Property and Equipment - Summary of Changes in Property and Equipment (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	₩ 13,785,299	₩ 13,068,257
Changes in accounting policy		(210,028)
Acquisition and capital expenditure	3,151,849	3,693,428
Disposal and termination	(78,936)	(87,493)
Depreciation	(2,570,775)	(2,502,576)
Impairment	(79,775)	(43,260)
Transfer in (out)	(44,860)	(61,109)
Transfer to investment properties	(2,056)	(41,335)
Transfer assets held-for-sale		(90,451)
Changes in scope of consolidation	818
Others	44,555	59,866
Ending, net	14,206,119	13,785,299
Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	45,655,456	44,289,629
Ending, net	47,586,332	45,655,456
Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	(31,870,157)	(31,221,372)
Ending, net	(33,380,213)	(31,870,157)
Land [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	1,262,181	1,281,187
Acquisition and capital expenditure	25,156	338
Disposal and termination	(1,756)	(1,352)
Transfer in (out)	53,238	126,066
Transfer to investment properties	6,792	(33,254)
Transfer assets held-for-sale		(89,330)
Changes in scope of consolidation	56
Others	(11,040)	(21,474)
Ending, net	1,334,627	1,262,181
Land [member] | Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	1,262,313	1,281,319
Ending, net	1,334,759	1,262,313
Land [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	(132)	(132)
Ending, net	(132)	(132)
Buildings and structures [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	2,162,064	2,007,685
Changes in accounting policy		(149)
Acquisition and capital expenditure	7,249	4,523
Disposal and termination	(3,367)	(4,213)
Depreciation	(135,646)	(134,350)
Impairment	(36)	(32)
Transfer in (out)	283,937	270,980
Transfer to investment properties	(8,848)	(8,081)
Transfer assets held-for-sale		(1,121)
Changes in scope of consolidation	494
Others	2,175	26,822
Ending, net	2,308,022	2,162,064
Buildings and structures [member] | Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	4,125,229	3,873,074
Ending, net	4,402,691	4,125,229
Buildings and structures [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	(1,963,165)	(1,865,389)
Ending, net	(2,094,669)	(1,963,165)
Machinery and equipment1 [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	9,093,251	8,475,016
Changes in accounting policy		(12,947)
Acquisition and capital expenditure	112,085	205,359
Disposal and termination	(69,401)	(76,457)
Depreciation	(2,343,965)	(2,278,286)
Impairment	(35,271)	(41,450)
Transfer in (out)	2,489,138	2,742,671
Changes in scope of consolidation	225
Others	68,921	79,345
Ending, net	9,314,983	9,093,251
Machinery and equipment1 [member] | Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	37,654,635	36,327,007
Ending, net	39,182,265	37,654,635
Machinery and equipment1 [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	(28,561,384)	(27,851,991)
Ending, net	(29,867,282)	(28,561,384)
Others [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	267,535	478,381
Changes in accounting policy		(196,932)
Acquisition and capital expenditure	47,669	64,072
Disposal and termination	(3,385)	(4,109)
Depreciation	(91,164)	(89,940)
Impairment	(44,468)	(1,751)
Transfer in (out)	28,024	16,218
Transfer to investment properties		0
Changes in scope of consolidation	43
Others	1,398	1,596
Ending, net	205,652	267,535
Others [member] | Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	1,612,108	1,981,646
Ending, net	1,619,822	1,612,108
Others [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	(1,344,573)	(1,503,265)
Ending, net	(1,414,170)	(1,344,573)
Construction-in-progress [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	1,000,268	825,988
Acquisition and capital expenditure	2,959,690	3,419,136
Disposal and termination	(1,027)	(1,362)
Impairment	0	(27)
Transfer in (out)	(2,899,197)	(3,217,044)
Others	(16,899)	(26,423)
Ending, net	1,042,835	1,000,268
Construction-in-progress [member] | Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	1,001,171	826,583
Ending, net	1,046,795	1,001,171
Construction-in-progress [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	(903)	(595)
Ending, net	₩ (3,960)	₩ (903)

Property and Equipment - Summ_2

Property and Equipment - Summary of the Details of Property and Equipment Provided (Detail) ₩ in Millions	12 Months Ended
	Dec. 31, 2020KRW (₩)	Dec. 31, 2019KRW (₩)	Dec. 31, 2020SGD ($)	Dec. 31, 2020USD ($)
Disclosure of detailed information about property, plant and equipment [line items]
Related amount	₩ 7,316,298	₩ 7,298,867	$ 284,000,000	$ 519,598,989
Land and buildings [member]
Disclosure of detailed information about property, plant and equipment [line items]
Carrying amount	11,644	17,097
Secured amount	₩ 15,502	₩ 18,705
Related line item	Borrowings	Borrowings
Related amount	₩ 3,072	₩ 4,347
Secured party	Industrial Bank of Korea, Korea Development Bank	Industrial Bank of Korea, Korea Development Bank , K Bank, Inc.
Others [member]
Disclosure of detailed information about property, plant and equipment [line items]
Carrying amount	₩ 4,142	₩ 45,851
Secured amount	₩ 249	₩ 41,681
Related line item	Deposits	Borrowings
Related amount	₩ 249	₩ 3,473
Secured party	K Bank, Inc.	Shinhan Bank

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about property, plant and equipment [line items]
Borrowing cost capitalized	₩ 8,452	₩ 6,360
Interest rate of capitalized borrowing cost	2.36%	2.63%

Investment Properties - Summary

Investment Properties - Summary of Investment Properties (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about investment property [line items]
Beginning balance	₩ 1,387,430	₩ 1,091,084
Changes in accounting policy		46,666
Acquisition	53,062	254,066
Disposal and termination	(1,779)	(1,693)
Depreciation	(64,531)	(65,178)
Transfer from (to) property and equipment	2,056	41,335
Transfer and others	(7,785)	21,150
Ending balance	1,368,453	1,387,430
Gross carrying amount [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	1,880,584	1,518,917
Ending balance	1,927,776	1,880,584
Accumulated depreciation and amortisation [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	(493,154)	(427,833)
Ending balance	(559,323)	(493,154)
Land [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	553,596	348,848
Acquisition	11,723	148,511
Disposal and termination	(1,536)	(285)
Transfer from (to) property and equipment	(6,792)	33,254
Transfer and others	(18,656)	23,268
Ending balance	538,335	553,596
Land [member] | Gross carrying amount [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	555,164	350,417
Ending balance	539,903	555,164
Land [member] | Accumulated depreciation and amortisation [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	(1,568)	(1,569)
Ending balance	(1,568)	(1,568)
Buildings [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	831,932	742,115
Changes in accounting policy		46,666
Acquisition	7,096	103,774
Disposal and termination	(243)	(1,408)
Depreciation	(64,531)	(65,178)
Transfer from (to) property and equipment	8,848	8,081
Transfer and others	469	(2,118)
Ending balance	783,571	831,932
Buildings [member] | Gross carrying amount [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	1,323,518	1,168,379
Ending balance	1,341,326	1,323,518
Buildings [member] | Accumulated depreciation and amortisation [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	(491,586)	(426,264)
Ending balance	(557,755)	(491,586)
Investment property, construction-in-progress [Member]
Disclosure of detailed information about investment property [line items]
Beginning balance	1,902	121
Acquisition	34,243	1,781
Transfer and others	10,402
Ending balance	46,547	1,902
Investment property, construction-in-progress [Member] | Gross carrying amount [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	1,902	121
Ending balance	₩ 46,547	₩ 1,902

Investment Properties - Additio

Investment Properties - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about investment property [line items]
Fair value of investment properties	₩ 2,645,482	₩ 2,304,583
Rental income from investment properties	203,763	₩ 198,636
Future minimum lease fee	221,932
Less than 1 year [member]
Disclosure of detailed information about investment property [line items]
Future minimum lease fee	50,769
1-5 years [member]
Disclosure of detailed information about investment property [line items]
Future minimum lease fee	92,728
More than 5 years [member]
Disclosure of detailed information about investment property [line items]
Future minimum lease fee	₩ 78,435

Investment Properties - Summa_2

Investment Properties - Summary of Investment Properties Provided as Collateral (Detail) - Land and buildings [member] - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Deposits 1 [member]
Disclosure of detailed information about investment property [line items]
Carrying amount	₩ 790,414	₩ 854,874
Secured amount	₩ 62,968	₩ 62,896
Related account	Deposits	Deposits
Related amount	₩ 56,247	₩ 56,831
Borrowings [member]
Disclosure of detailed information about investment property [line items]
Carrying amount	2,861	1,915
Secured amount	₩ 3,434	₩ 3,044
Related account	Borrowings	Borrowings
Related amount	₩ 2,928	₩ 1,903

Intangible Assets - Summary of

Intangible Assets - Summary of Intangible Assets (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of detailed information about intangible assets [line items]
Beginning, net	₩ 2,834,037	₩ 3,407,124
Changes in accounting policy		(26,207)
Acquisition and capital expenditure	165,630	178,694
Disposal and termination	(13,820)	(15,679)
Amortization	(628,154)	(660,705)	₩ (629,526)
Impairment	(211,637)	(61,898)
Changes in scope of consolidation	4,342
Others	10,860	12,708
Ending, net	2,161,258	2,834,037	3,407,124
Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	7,996,482	8,064,270
Ending, net	7,898,325	7,996,482	8,064,270
Accumulated depreciation and amortisation [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	(5,162,445)	(4,657,146)
Ending, net	(5,737,067)	(5,162,445)	(4,657,146)
Goodwill [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	235,570	236,058
Impairment		(605)
Others	(5,485)	117
Ending, net	230,085	235,570	236,058
Goodwill [member] | Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	541,596	542,074
Ending, net	536,093	541,596	542,074
Goodwill [member] | Accumulated depreciation and amortisation [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	(306,026)	(306,016)
Ending, net	(306,008)	(306,026)	(306,016)
Development costs [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	272,634	335,110
Acquisition and capital expenditure	26,990	47,903
Disposal and termination	(1,849)	(3,019)
Amortization	(104,938)	(115,839)
Impairment		(1,333)
Changes in scope of consolidation	575
Others	87,587	9,812
Ending, net	280,999	272,634	335,110
Development costs [member] | Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	1,661,372	1,680,372
Ending, net	1,767,422	1,661,372	1,680,372
Development costs [member] | Accumulated depreciation and amortisation [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	(1,388,738)	(1,345,262)
Ending, net	(1,486,423)	(1,388,738)	(1,345,262)
Software [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	137,381	65,944
Acquisition and capital expenditure	37,077	30,965
Disposal and termination	(105)	(1,267)
Amortization	(54,191)	(68,222)
Impairment	(1,776)	(1,807)
Changes in scope of consolidation	77
Others	27,537	11,768
Ending, net	146,000	137,381	65,944
Software [member] | Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	978,139	947,312
Ending, net	1,053,980	978,139	947,312
Software [member] | Accumulated depreciation and amortisation [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	(840,758)	(781,368)
Ending, net	(907,980)	(840,758)	(781,368)
Frequency usage rights [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	1,753,941	2,156,500
Disposal and termination	0	(284)
Amortization	(399,348)	(399,382)
Impairment	(193,194)	(3,035)
Others	(736)	142
Ending, net	1,160,663	1,753,941	2,156,500
Frequency usage rights [member] | Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	3,622,327	3,641,231
Ending, net	3,373,095	3,622,327	3,641,231
Frequency usage rights [member] | Accumulated depreciation and amortisation [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	(1,868,386)	(1,484,731)
Ending, net	(2,212,432)	(1,868,386)	(1,484,731)
Others [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	434,511	513,512
Changes in accounting policy		(26,207)
Acquisition and capital expenditure	101,563	99,826
Disposal and termination	(11,866)	(11,109)
Amortization	(69,677)	(77,262)
Impairment	(16,667)	(55,118)
Changes in scope of consolidation	3,690
Others	(98,043)	(9,131)
Ending, net	343,511	434,511	513,512
Others [member] | Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	1,193,048	1,253,281
Ending, net	1,167,735	1,193,048	1,253,281
Others [member] | Accumulated depreciation and amortisation [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	(758,537)	(739,769)
Ending, net	₩ (824,224)	₩ (758,537)	₩ (739,769)

Intangible Assets - Summary o_2

Intangible Assets - Summary of Intangible Assets (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about intangible assets [abstract]
Indefinite useful life	₩ 221,099	₩ 203,240

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about intangible assets [line items]
Acquisition cost	₩ 201,461
Remaining useful life of Frequency usage rights	3 years
Carrying amount of the 28 gegahertz frequency usage [member]
Disclosure of detailed information about intangible assets [line items]
Impairment loss	₩ 190,929
KT Skylife Co Ltd [member] | Intangible assets with indefinite useful life [member]
Disclosure of detailed information about intangible assets [line items]
Impairment loss	₩ 0
Individual assets or cash-generating units [member]
Disclosure of detailed information about intangible assets [line items]
Impairment loss		₩ 38,519
Discount rate		7.30%

Intangible Assets - Summary o_3

Intangible Assets - Summary of Goodwill Allocated to Each Cash-Generation Unit (Detail) ₩ in Millions	Dec. 31, 2020KRW (₩)
Disclosure of detailed information about intangible assets [line items]
Goodwill	₩ 230,085
Mobile services [member] | ICT [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill	65,057
BC Card Co., Ltd. [member] | Finance [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill	41,234
GENIE Music Corporation K T Music Corporation [member] | Others [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill	50,214
PlayD Co., Ltd. (N Search Marketing Co., Ltd.) [member] | Others [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill	42,745
KT Telecop Co., Ltd. [member] | Others [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill	15,418
KT MOS Bukbu Co Ltd and others [member] | Others [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill	₩ 15,417

Intangible Assets - Summary o_4

Intangible Assets - Summary of Goodwill Allocated to Each Cash-Generation Unit (Parenthetical) (Detail) - KRW (₩)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about intangible assets [line items]
Terminal growth rate		0.00%
Expected revenue growth rate		(1.25%)
Mobile services [member] | ICT [member]
Disclosure of detailed information about intangible assets [line items]
Terminal growth rate	0.00%
Discount rate	7.43%
Impairment loss on goodwill	₩ 0	₩ 0
Description of calculation of recoverable amount	The Group performed its impairment assessment for long-lived assets attributed to the Information and Communication Technology (“ICT”) reporting segment, which includes the Cash-Generating Units of Mobile, Fixed line, and Corporate Services (the “CGUs”). The Group compared the carrying value of each CGU to the estimated recoverable amount. The recoverable amounts of ICT reporting segment are calculated based on value-in use calculations. These calculations use discounted cash flow projections for the next five years based on financial budgets. A terminal growth rate of 0.0% was applied for the cash flows expected to be incurred after five years. This growth rate does not exceed the average growth rate of the industry which the cash-generating unit belongs in. The Group estimated its revenue growth rate 0.42% ~ 3.84% based on past performance and its expectation of future market changes. In addition, management estimated the cash flow based on past performance and its expectation of market growth, and the discount rate 6.21%. Accordingly, the Group did not recognize an impairment loss on ICT reporting segment for the years ended December 31, 2018, 2019 and 2020.
Mobile services [member] | Bottom of range [member] | ICT [member]
Disclosure of detailed information about intangible assets [line items]
Expected revenue growth rate	0.22%
Mobile services [member] | Top of range [member] | ICT [member]
Disclosure of detailed information about intangible assets [line items]
Expected revenue growth rate	4.93%
Marketing [member] | Mobile services [member]
Disclosure of detailed information about intangible assets [line items]
Terminal growth rate	0.00%
Expected revenue growth rate	0.22%
Discount rate	7.43%
Impairment loss on goodwill	₩ 0	0
Description of calculation of recoverable amount	The recoverable amounts of mobile business are calculated based on value-in use calculations. These calculations use discounted cash flow projections for the next five years based on financial budgets. A terminal growth rate of 0.0% was applied for the cash flows expected to be incurred after five years. This growth rate does not exceed the average growth rate of the industry which the cash-generating unit belongs in. The Group estimated its revenue growth rate 0.42% based on past performance and its expectation of future market changes. In addition, management estimated the cash flow based on past performance and its expectation of market growth, and the discount rates 6.21% used reflected specific risks relating to the relevant CGU. As a result of the impairment test, the Group concluded that the carrying amount of CGU does not exceed the recoverable amount. Accordingly, the Group did not recognize an impairment loss on goodwill on mobile business for the years ended December 31, 2018, 2019 and 2020.
Finance [member]
Disclosure of detailed information about intangible assets [line items]
Description of calculation of recoverable amount	The recoverable amounts of BC Card Co., Ltd. are calculated based on value-in use calculations. These calculations use discounted cash flow projections for the next five years based on financial budgets. A terminal growth rate of 0.0% was applied for the cash flows expected to be incurred after five years. This growth rate does not exceed the average growth rate of the industry which the cash-generating unit belongs in. The Group estimated its revenue growth rate 0.92% based on past performance and its expectation of future market changes. In addition, management estimated the cash flow based on past performance and its expectation of market growth, and the discount rates 7.75% used reflected specific risks relating to the relevant CGU. As a result of the impairment test, the Group concluded that the carrying amount of CGU does not exceed the recoverable amount. Accordingly, the Group did not recognize an impairment loss on goodwill on BC Card Co., Ltd. for the years ended December 31, 2018, 2019 and 2020.
Finance [member] | BC Card Co., Ltd. [member]
Disclosure of detailed information about intangible assets [line items]
Terminal growth rate	0.00%
Expected revenue growth rate	0.92%
Discount rate	7.75%
Impairment loss on goodwill	₩ 0	0
Others [member] | KT Telecop Co., Ltd. [member]
Disclosure of detailed information about intangible assets [line items]
Terminal growth rate	1.00%
Expected revenue growth rate	9.30%
Discount rate	9.78%
Impairment loss on goodwill	₩ 0	₩ 0
Description of calculation of recoverable amount	The recoverable amounts of KT Telecop Co., Ltd. are calculated based on value-in use calculations. These calculations use discounted cash flow projections for the next five years based on financial budgets. A terminal growth rate of 1.0% was applied for the cash flows expected to be incurred after five years. This growth rate does not exceed the average growth rate of the industry which the cash-generating unit belongs in. The Group estimated its revenue growth rate 9.30% based on past performance and its expectation of future market changes. In addition, management estimated the cash flow based on past performance and its expectation of market growth, and the discount rates 9.78% used reflected specific risks relating to the relevant CGUs. As a result of the impairment test, the Group concluded that the carrying amount of CGU does not exceed the recoverable amount. Accordingly, the Group did not recognize an impairment loss on goodwill on KT Telecop Co., Ltd. for the years ended December 31, 2018, 2019 and 2020.

Investments in Associates and_3

Investments in Associates and Joint Ventures - Summary of Details of Associates (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Korea Information & Technology Fund [member]
Disclosure of associates [line items]
Percentage of ownership	33.30%	33.30%
Location	Korea
Date of financial statements	December 31	December 31
KT-IBKC future investment fund [member]
Disclosure of associates [line items]
Percentage of ownership	50.00%	50.00%
Location	Korea
Date of financial statements	December 31	December 31
KT-CKP New Media Investment Fund [member]
Disclosure of associates [line items]
Percentage of ownership		49.70%
Location	Korea
Date of financial statements	December 31	December 31
K Bank Inc. [member]
Disclosure of associates [line items]
Percentage of ownership	34.00%	10.00%
Location	Korea
Date of financial statements	December 31	December 31
Hyundai Robotics Co., Ltd. [member]
Disclosure of associates [line items]
Percentage of ownership	10.00%
Location	Korea
Date of financial statements	December 31	December 31

Investments in Associates and_4

Investments in Associates and Joint Ventures - Summary of Changes in Investments in Associates and Joint Ventures (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Associates And Joint Ventures [Line Items]
Beginning	₩ 267,660	₩ 272,407
Acquisition (Disposal)	273,277	13,021
Share of net profit from associates and joint ventures	18,320	(3,252)
Others	(1,376)	(14,516)
Ending	557,881	267,660
Korea Information & Technology Fund [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Beginning	163,975	148,255
Share of net profit from associates and joint ventures	12,205	17,956
Others	(6,025)	(2,236)
Ending	170,155	163,975
KT-SB Venture Investment Fund [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Beginning		4,470
Acquisition (Disposal)		(4,470)
KT-CKP New Media Investment Fund [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Beginning	134	281
Acquisition (Disposal)	(134)	(174)
Share of net profit from associates and joint ventures		27
Ending		134
Hyundai Robotics Co., Ltd. [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Acquisition (Disposal)	50,000
Share of net profit from associates and joint ventures	(64)
Others	1,000
Ending	50,936
Others [Member]
Disclosure Of Associates And Joint Ventures [Line Items]
Beginning	44,293	56,785
Acquisition (Disposal)	28,400	(7,867)
Share of net profit from associates and joint ventures	34,298	7,241
Others	5,337	(11,866)
Ending	112,328	44,293
KT-IBKC future investment fund [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Beginning	14,100	9,961
Acquisition (Disposal)		3,750
Share of net profit from associates and joint ventures	2,090	389
Ending	16,190	14,100
K Bank Inc. [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Beginning	45,158	52,655
Acquisition (Disposal)	195,011	21,782
Share of net profit from associates and joint ventures	(30,209)	(28,865)
Others	(1,688)	(414)
Ending	₩ 208,272	₩ 45,158

Investments in Associates and_5

Investments in Associates and Joint Ventures - Summary of Changes in Investments in Associates and Joint Ventures (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Associates And Joint Ventures [Line Items]
Share gain from associates and joint ventures	₩ 18,041	₩ (3,304)	₩ (5,467)
KT Investment Co., Ltd. [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Share gain from associates and joint ventures	₩ 279	₩ 52	₩ 445

Investments in Associates and_6

Investments in Associates and Joint Ventures - Summary of Financial Information of Associates and Joint Ventures (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Associates And Joint Ventures [Line Items]
Current assets	₩ 11,154,180	₩ 11,975,659
Non-current assets	22,508,365	22,656,555
Current liabilities	9,192,472	10,148,054
Non-current liabilities	8,918,640	9,343,476
Operating revenue	24,440,647	24,899,189	₩ 23,436,050
Profit (loss) for the year	746,256	695,868	719,412
Other comprehensive income(loss)	23,255	172,338	(54,628)
Total comprehensive income(loss)	769,511	868,206	₩ 664,784
Korea Information & Technology Fund [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Current assets	107,652	113,233
Non-current assets	402,812	378,691
Operating revenue	54,473	70,577
Profit (loss) for the year	36,615	53,867
Other comprehensive income(loss)	9,647	6,132
Total comprehensive income(loss)	46,262	59,999
Dividends received from associates	9,241	4,280
KT-IBKC future investment fund [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Current assets	32,379	28,200
Operating revenue	6,551	1,694
Profit (loss) for the year	4,179	779
Total comprehensive income(loss)	4,179	779
KT-CKP New Media Investment Fund [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Current assets		3
Non-current assets		267
Operating revenue		56
Profit (loss) for the year		55
Total comprehensive income(loss)		55
K Bank Inc. [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Current assets	4,255,620	2,480,065
Non-current assets	74,193	78,566
Current liabilities	3,752,838	2,350,375
Non-current liabilities	88,155	3,784
Operating revenue	80,301	92,720
Profit (loss) for the year	(105,374)	(100,773)
Other comprehensive income(loss)	(1,126)	(23)
Total comprehensive income(loss)	(106,500)	₩ (100,796)
Hyundai Robotics Co., Ltd. [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Current assets	315,886
Non-current assets	125,619
Current liabilities	80,615
Non-current liabilities	59,324
Operating revenue	195,311
Profit (loss) for the year	(642)
Other comprehensive income(loss)	11,573
Total comprehensive income(loss)	₩ 10,931

Investments in Associates and_7

Investments in Associates and Joint Ventures - Summary of Reconciliation of Carrying Amount of Interests in the Associates and Joint Ventures (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Associates And Joint Ventures [Line Items]
Book amount	₩ 557,881	₩ 267,660
K Bank Inc. [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Net assets	₩ 488,819	₩ 204,472
Percentage of ownership	34.00%	10.00%
Share in net assets	₩ 166,198	₩ 45,158
Intercompany transaction and others	42,074
Book amount	208,272	45,158
Korea Information & Technology Fund [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Net assets	₩ 510,464	₩ 491,924
Percentage of ownership	33.30%	33.30%
Share in net assets	₩ 170,155	₩ 163,975
Book amount	170,155	163,975
KT-IBKC future investment fund [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Net assets	₩ 32,379	₩ 28,200
Percentage of ownership	50.00%	50.00%
Share in net assets	₩ 16,190	₩ 14,100
Book amount	16,190	14,100
KT-CKP New Media Investment Fund [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Net assets		₩ 270
Percentage of ownership		49.70%
Share in net assets		₩ 134
Book amount		₩ 134
Hyundai Robotics Co., Ltd. [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Net assets	₩ 301,566
Percentage of ownership	10.00%
Share in net assets	₩ 30,157
Intercompany transaction and others	20,779
Book amount	₩ 50,936

Investments in Associates and_8

Investments in Associates and Joint Ventures - Summary of Reconciliation of Carrying Amount of Interests in the Associates and Joint Ventures (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
K Bank Inc. [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Percentage of non-voting convertible stock are excluded	12.10%	12.10%

Investments in Associates and_9

Investments in Associates and Joint Ventures - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of associates [abstract]
Loss from associates and joint ventures not recognized	₩ 992	₩ 6,124
Accumulated comprehensive loss of associates and joint ventures not recognized	₩ 8,228	₩ 12,599

Trade and Other Payables - Summ

Trade and Other Payables - Summary of Trade and Other Payables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Current liabilities
Trade payables	₩ 1,239,717	₩ 1,304,795
Other payables	4,970,382	6,292,683
Total	6,210,099	7,597,478
Non-current liabilities
Trade payables	1,528	1,733
Other payables	806,012	1,080,487
Total	₩ 807,540	₩ 1,082,220

Trade and Other Payables - Su_2

Trade and Other Payables - Summary of Other Payables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Trade and other payables [abstract]
Non-trade payables	₩ 3,841,227	₩ 5,275,224
Accrued expenses	933,978	987,624
Operating deposits	803,904	910,045
Others	197,285	200,277
Less: non-current	(806,012)	(1,080,487)
Current	₩ 4,970,382	₩ 6,292,683

Trade and Other Payables - Su_3

Trade and Other Payables - Summary of Other Payables (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Trade and other payables [abstract]
Settlement payables related to credit card transaction	₩ 1,007,171	₩ 1,824,068

Borrowings - Summary of Borrowi

Borrowings - Summary of Borrowings (Detail) ¥ in Thousands, ₩ in Millions	12 Months Ended
	Dec. 31, 2020KRW (₩)	Dec. 31, 2020SGD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2020JPY (¥)	Dec. 31, 2019KRW (₩)	Dec. 31, 2019USD ($)	Dec. 31, 2019JPY (¥)
Disclosure of detailed information about borrowings [line items]
Maturity	Jun. 5, 2025
Annual interest rates	0.00%	0.00%	0.00%	0.00%
Less: Current portion	₩ (1,418,114)				₩ (1,185,725)
Borrowings	7,316,298	$ 284,000,000	$ 519,598,989		7,298,867
Gross carrying amount [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	₩ 7,338,522
Gross carrying amount [member] | Sept. 07, 2034 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Sept. 7, 2034
Annual interest rates	6.50%	6.50%	6.50%	6.50%
Annual interest rates description	LIBOR(3M)+0.900
Annual interest rates adjustment rate	0.90%	0.90%	0.90%	0.90%
Gross carrying amount [member] | July 18, 2026 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	July 18, 2026
Annual interest rates	2.50%	2.50%	2.50%	2.50%
Gross carrying amount [member] | Aug 07, 2022 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Aug. 7, 2022
Annual interest rates	2.63%	2.63%	2.63%	2.63%
Gross carrying amount [member] | Aug. 20, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Aug. 20, 2023
Gross carrying amount [member] | Aug. 20, 2020 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Aug. 20, 2020
Gross carrying amount [member] | Nov 01, 2024 [memebr]
Disclosure of detailed information about borrowings [line items]
Maturity	Nov. 1, 2024
Annual interest rates description	LIBOR(3M)+0.980
Annual interest rates adjustment rate	0.98%	0.98%	0.98%	0.98%
Gross carrying amount [member] | June 19, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	June 19, 2023
Annual interest rates description	SOR(6M)+0.500
Annual interest rates adjustment rate	0.50%	0.50%	0.50%	0.50%
Gross carrying amount [member] | Sept. 1, 2025 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Sept. 1, 2025
Annual interest rates	1.00%	1.00%	1.00%	1.00%
Gross carrying amount [member] | July 06, 2020 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	July 6, 2020
Gross carrying amount [member] | July 06, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	July 6, 2021
Annual interest rates	0.38%	0.38%	0.38%	0.38%
Gross carrying amount [member] | Nov 13, 2020 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Nov. 13, 2020
Gross carrying amount [member] | July 19, 2022 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	July 19, 2022
Annual interest rates	0.22%	0.22%	0.22%	0.22%
Gross carrying amount [member] | July 19, 2024 [memeber]
Disclosure of detailed information about borrowings [line items]
Maturity	July 19, 2024
Annual interest rates	0.33%	0.33%	0.33%	0.33%
Gross carrying amount [member] | Apr. 26, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Apr. 26, 2021
Annual interest rates	4.71%	4.71%	4.71%	4.71%
Gross carrying amount [member] | Aug. 26, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Aug. 26, 2021
Annual interest rates	4.09%	4.09%	4.09%	4.09%
Gross carrying amount [member] | Oct. 28, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Oct. 28, 2021
Annual interest rates	4.31%	4.31%	4.31%	4.31%
Gross carrying amount [member] | Dec. 22, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Dec. 22, 2021
Annual interest rates	4.09%	4.09%	4.09%	4.09%
Gross carrying amount [member] | Dec. 22, 2031 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Dec. 22, 2031
Annual interest rates	4.27%	4.27%	4.27%	4.27%
Gross carrying amount [member] | Apr. 10, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Apr. 10, 2023
Annual interest rates	2.95%	2.95%	2.95%	2.95%
Gross carrying amount [member] | Apr. 10, 2033 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Apr. 10, 2033
Annual interest rates	3.17%	3.17%	3.17%	3.17%
Gross carrying amount [member] | Sept. 16, 2020 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Sept. 16, 2020
Gross carrying amount [member] | June 26, 2024 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	June 26, 2024
Annual interest rates	3.42%	3.42%	3.42%	3.42%
Gross carrying amount [member] | June 26, 2034 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	June 26, 2024
Annual interest rates	3.70%	3.70%	3.70%	3.70%
Gross carrying amount [member] | Sept. 02, 2024 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Sept. 2, 2024
Annual interest rates	3.31%	3.31%	3.31%	3.31%
Gross carrying amount [member] | Sept. 02, 2034 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Sept. 2, 2034
Annual interest rates	3.55%	3.55%	3.55%	3.55%
Gross carrying amount [member] | Jan. 29, 2020 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 29, 2020
Gross carrying amount [member] | Jan. 29, 2025 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 29, 2025
Annual interest rates	2.45%	2.45%	2.45%	2.45%
Gross carrying amount [member] | Jan. 29, 2035 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 29, 2035
Annual interest rates	2.71%	2.71%	2.71%	2.71%
Gross carrying amount [member] | Jan. 28, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 28, 2021
Annual interest rates	1.95%	1.95%	1.95%	1.95%
Gross carrying amount [member] | Jan. 28, 2026 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 28, 2026
Annual interest rates	2.20%	2.20%	2.20%	2.20%
Gross carrying amount [member] | Jan. 28, 2036 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 28, 2036
Annual interest rates	2.35%	2.35%	2.35%	2.35%
Gross carrying amount [member] | Jan. 29, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 29, 2021
Annual interest rates	2.55%	2.55%	2.55%	2.55%
Gross carrying amount [member] | Jan. 30, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 30, 2023
Annual interest rates	2.75%	2.75%	2.75%	2.75%
Gross carrying amount [member] | Jan. 30, 2028 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 30, 2028
Annual interest rates	2.95%	2.95%	2.95%	2.95%
Gross carrying amount [member] | Jan. 30, 2038 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 30, 2038
Annual interest rates	2.93%	2.93%	2.93%	2.93%
Gross carrying amount [member] | Jan, 14, 2022 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 14, 2022
Annual interest rates	2.05%	2.05%	2.05%	2.05%
Gross carrying amount [member] | Jan, 15, 2024 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 15, 2024
Annual interest rates	2.09%	2.09%	2.09%	2.09%
Gross carrying amount [member] | Jan, 15, 2029 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 15, 2029
Annual interest rates	2.16%	2.16%	2.16%	2.16%
Gross carrying amount [member] | Jan, 14, 2039 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 14, 2039
Annual interest rates	2.21%	2.21%	2.21%	2.21%
Gross carrying amount [member] | Oct, 11, 2022 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Oct. 11, 2022
Annual interest rates	1.55%	1.55%	1.55%	1.55%
Gross carrying amount [member] | Oct, 11, 2024 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Oct. 11, 2024
Annual interest rates	1.58%	1.58%	1.58%	1.58%
Gross carrying amount [member] | Oct, 11, 2029 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Oct. 11, 2029
Annual interest rates	1.62%	1.62%	1.62%	1.62%
Gross carrying amount [member] | Oct, 11, 2039 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Oct. 11, 2039
Annual interest rates	1.67%	1.67%	1.67%	1.67%
Gross carrying amount [member] | June 16, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	June 16, 2023
Annual interest rates	1.17%	1.17%	1.17%	1.17%
Gross carrying amount [member] | June 17, 2025 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	June 17, 2025
Annual interest rates	1.43%	1.43%	1.43%	1.43%
Gross carrying amount [member] | June 17, 2030 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	June 17, 2030
Annual interest rates	1.61%	1.61%	1.61%	1.61%
Gross carrying amount [member] | June 15, 2040 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	June 15, 2040
Annual interest rates	1.71%	1.71%	1.71%	1.71%
Gross carrying amount [member] | June 23, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Maturity	June 23, 2023
Annual interest rates	1.51%	1.51%	1.51%	1.51%
Debentures [member]
Disclosure of detailed information about borrowings [line items]
Less: Current portion	₩ (1,228,283)				(1,052,032)
Discount on bonds	(19,847)				(20,780)
Borrowings	5,714,340				5,972,554
Debentures [member] | Gross carrying amount [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	6,962,470				7,045,366
Debentures [member] | Gross carrying amount [member] | Sept. 07, 2034 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	108,800		$ 100,000,000		115,780	$ 100,000,000
Debentures [member] | Gross carrying amount [member] | July 18, 2026 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	435,200		400,000,000		463,120	400,000,000
Debentures [member] | Gross carrying amount [member] | Aug 07, 2022 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	435,200		400,000,000		463,120	400,000,000
Debentures [member] | Gross carrying amount [member] | Aug. 20, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	108,800		100,000,000		115,780	100,000,000
Debentures [member] | Gross carrying amount [member] | Aug. 20, 2020 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings					231,560	200,000,000
Debentures [member] | Gross carrying amount [member] | Nov 01, 2024 [memebr]
Disclosure of detailed information about borrowings [line items]
Borrowings	380,800		350,000,000		405,230	$ 350,000,000
Debentures [member] | Gross carrying amount [member] | June 19, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	233,510	$ 284,000,000
Debentures [member] | Gross carrying amount [member] | Sept. 1, 2025 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	435,200		$ 400,000,000
Debentures [member] | Gross carrying amount [member] | July 06, 2020 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings					42,539		¥ 4,000,000
Debentures [member] | Gross carrying amount [member] | July 06, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	168,682			¥ 16,000,000	170,155		16,000,000
Debentures [member] | Gross carrying amount [member] | Nov 13, 2020 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings					319,041		30,000,000
Debentures [member] | Gross carrying amount [member] | July 19, 2022 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	312,061			29,600,000	314,787		29,600,000
Debentures [member] | Gross carrying amount [member] | July 19, 2024 [memeber]
Disclosure of detailed information about borrowings [line items]
Borrowings	4,217			¥ 400,000	4,254		¥ 400,000
Debentures [member] | Gross carrying amount [member] | Apr. 26, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	380,000				380,000
Debentures [member] | Gross carrying amount [member] | Aug. 26, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	250,000				250,000
Debentures [member] | Gross carrying amount [member] | Oct. 28, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	100,000				100,000
Debentures [member] | Gross carrying amount [member] | Dec. 22, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	90,000				90,000
Debentures [member] | Gross carrying amount [member] | Dec. 22, 2031 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	160,000				160,000
Debentures [member] | Gross carrying amount [member] | Apr. 10, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	190,000				190,000
Debentures [member] | Gross carrying amount [member] | Apr. 10, 2033 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	100,000				100,000
Debentures [member] | Gross carrying amount [member] | Sept. 16, 2020 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings					300,000
Debentures [member] | Gross carrying amount [member] | June 26, 2024 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	110,000				110,000
Debentures [member] | Gross carrying amount [member] | June 26, 2034 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	100,000				100,000
Debentures [member] | Gross carrying amount [member] | Sept. 02, 2024 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	170,000				170,000
Debentures [member] | Gross carrying amount [member] | Sept. 02, 2034 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	100,000				100,000
Debentures [member] | Gross carrying amount [member] | Jan. 29, 2020 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings					160,000
Debentures [member] | Gross carrying amount [member] | Jan. 29, 2025 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	240,000				240,000
Debentures [member] | Gross carrying amount [member] | Jan. 29, 2035 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	50,000				50,000
Debentures [member] | Gross carrying amount [member] | Jan. 28, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	130,000				130,000
Debentures [member] | Gross carrying amount [member] | Jan. 28, 2026 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	100,000				100,000
Debentures [member] | Gross carrying amount [member] | Jan. 28, 2036 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	70,000				70,000
Debentures [member] | Gross carrying amount [member] | Jan. 29, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	110,000				110,000
Debentures [member] | Gross carrying amount [member] | Jan. 30, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	150,000				150,000
Debentures [member] | Gross carrying amount [member] | Jan. 30, 2028 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	170,000				170,000
Debentures [member] | Gross carrying amount [member] | Jan. 30, 2038 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	70,000				70,000
Debentures [member] | Gross carrying amount [member] | Jan, 14, 2022 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	220,000				220,000
Debentures [member] | Gross carrying amount [member] | Jan, 15, 2024 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	80,000				80,000
Debentures [member] | Gross carrying amount [member] | Jan, 15, 2029 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	110,000				110,000
Debentures [member] | Gross carrying amount [member] | Jan, 14, 2039 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	90,000				90,000
Debentures [member] | Gross carrying amount [member] | Oct, 11, 2022 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	340,000				340,000
Debentures [member] | Gross carrying amount [member] | Oct, 11, 2024 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	100,000				100,000
Debentures [member] | Gross carrying amount [member] | Oct, 11, 2029 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	50,000				50,000
Debentures [member] | Gross carrying amount [member] | Oct, 11, 2039 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	110,000				₩ 110,000
Debentures [member] | Gross carrying amount [member] | June 16, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	150,000
Debentures [member] | Gross carrying amount [member] | June 17, 2025 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	70,000
Debentures [member] | Gross carrying amount [member] | June 17, 2030 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	20,000
Debentures [member] | Gross carrying amount [member] | June 15, 2040 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	60,000
Debentures [member] | Gross carrying amount [member] | June 23, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	₩ 100,000

Borrowings - Summary of Borro_2

Borrowings - Summary of Borrowings (Parenthetical) (Detail) ₩ in Millions	Dec. 31, 2020KRW (₩)	Dec. 31, 2020SGD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019KRW (₩)
Disclosure of detailed information about borrowings [line items]
Borrowings	₩ 7,316,298	$ 284,000,000	$ 519,598,989	₩ 7,298,867
Libor rate	0.238%	0.238%	0.238%
SOR rate	0.185%	0.185%	0.185%
Medium Term Note Programme [member] | Fixed interest rate [member]
Disclosure of detailed information about borrowings [line items]
Borrowings			$ 100,000,000
Medium Term Note Programme [member] | Top of range [member] | Fixed interest rate [member]
Disclosure of detailed information about borrowings [line items]
Borrowings			$ 2,000,000,000

Borrowings - Summary of Korean

Borrowings - Summary of Korean Won and Foreign Currency Borrowings (Detail) ₩ in Millions	12 Months Ended
	Dec. 31, 2020KRW (₩)	Dec. 31, 2020SGD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019KRW (₩)
Disclosure of detailed information about borrowings [line items]
Maturity	Jun. 5, 2025
Annual interest rates	0.00%	0.00%	0.00%
Borrowings	₩ 7,316,298	$ 284,000,000	$ 519,598,989	₩ 7,298,867
The 1st CB(Private) Jun. 5, 2020 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	5,623
Redemption premium	2,267
Bond discount issuance	(4,644)
The 1st CB(Private) Jun. 5, 2020 [member] | The 1st CB(Private) Jun. 5, 2025 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	₩ 8,000

Borrowings - Summary of Korea_2

Borrowings - Summary of Korean Won and Foreign Currency Borrowings (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2020
Disclosure of detailed information about borrowings [line items]
Interest rate	0.00%
Maturity yield	5.00%
Storywiz Co Ltd [Member]
Disclosure of detailed information about borrowings [line items]
Appraisal period of common stock conversion to debt	(appraisal period: June 5, 2021~ May 4, 2025)

Borrowings - Summary of Short-t

Borrowings - Summary of Short-term Borrowing (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about borrowings [line items]
Annual interest rates	0.00%
Short-term borrowings	₩ 95,789	₩ 83,500
NongHyup Bank [member]
Disclosure of detailed information about borrowings [line items]
Short-term borrowings	40,189	15,000
Shinhan Bank [member]
Disclosure of detailed information about borrowings [line items]
Short-term borrowings	22,500	57,500
Korea Development Bank [member]
Disclosure of detailed information about borrowings [line items]
Short-term borrowings	10,000	10,000
SooHyup Bank [member]
Disclosure of detailed information about borrowings [line items]
Short-term borrowings		₩ 1,000
Woori Bank [Member]
Disclosure of detailed information about borrowings [line items]
Short-term borrowings	1,900
Industrial Bank Of Korea [member]
Disclosure of detailed information about borrowings [line items]
Short-term borrowings	200
Hana Bank [Member]
Disclosure of detailed information about borrowings [line items]
Short-term borrowings	₩ 11,000
Short-term borrowings [member] | NongHyup Bank [member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	1.74%
Short-term borrowings [member] | NongHyup Bank [member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	2.36%
Short-term borrowings [member] | Shinhan Bank [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	1.431%
Annual interest rates description	CD91+1.431%
Short-term borrowings [member] | Shinhan Bank [member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	2.46%
Short-term borrowings [member] | Shinhan Bank [member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	2.96%
Short-term borrowings [member] | Korea Development Bank [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	3.34%
Short-term borrowings [member] | Woori Bank [Member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	3.57%
Short-term borrowings [member] | Industrial Bank Of Korea [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	1.74%
Short-term borrowings [member] | Hana Bank [Member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	4.20%

Borrowings - Summary of Long-te

Borrowings - Summary of Long-term Borrowings (Detail) ₩ in Millions	12 Months Ended
	Dec. 31, 2020KRW (₩)	Dec. 31, 2020SGD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019KRW (₩)	Dec. 31, 2019USD ($)
Disclosure of detailed information about borrowings [line items]
Annual interest rates	0.00%	0.00%	0.00%
Borrowings	₩ 7,316,298	$ 284,000,000	$ 519,598,989	₩ 7,298,867
Total	5,898,184			6,113,142
Shinhan Bank [member] | Facility loans [member]
Disclosure of detailed information about borrowings [line items]
Borrowings			25,918,000	30,008	$ 25,918,000
Shinhan Bank [member] | Kookmin Bank and other [member]
Disclosure of detailed information about borrowings [line items]
Borrowings | $					87,940,000
NongHyup Bank [member] | Facility loans [member]
Disclosure of detailed information about borrowings [line items]
Borrowings				79
Other Financial Instruments [member] | Kookmin Bank and other [member]
Disclosure of detailed information about borrowings [line items]
Borrowings			$ 48,855,000	950
Long-term borrowings [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	272,263			190,780
Less: Current portion	(94,042)			(50,192)
Total	178,221			140,588
Long-term borrowings [member] | General loans [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	₩ 30,000			30,000
Long-term borrowings [member] | Export-Import Bank of Korea [member] | Inter-Korean Cooperation Fund [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	1.50%	1.50%	1.50%
Borrowings	₩ 2,961			3,454
Long-term borrowings [member] | Industrial Bank of Korea [member] | General loans [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	2.98%	2.98%	2.98%
Borrowings	₩ 6,000			6,000
Long-term borrowings [member] | Shinhan Bank [member] | General loans [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	1.94%	1.94%	1.94%
Borrowings	₩ 5,000			5,000
Long-term borrowings [member] | Shinhan Bank [member] | General Loans 1 [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates description	LIBOR(3M)+1.650
Annual interest rates adjustment rate	1.65%	1.65%	1.65%
Borrowings	₩ 9,694		$ 8,910,000	3,473	$ 3,000,000
Long-term borrowings [member] | Shinhan Bank [member] | General Loans 2 [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates description	LIBOR(3M)+2.130
Annual interest rates adjustment rate	2.13%	2.13%	2.13%
Borrowings	₩ 27,200		$ 25,000,000
Long-term borrowings [member] | Shinhan Bank [member] | Facility loans [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates description	LIBOR(3M)+1.340
Annual interest rates adjustment rate	1.34%	1.34%	1.34%
Borrowings	₩ 28,199
Long-term borrowings [member] | CA-CIB [member] | Long-term CP [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	1.26%	1.26%	1.26%
Borrowings	₩ 100,000
Long-term borrowings [member] | NongHyup Bank [member] | General loans [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	₩ 54
Long-term borrowings [member] | NongHyup Bank [member] | Facility loans [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	2.00%	2.00%	2.00%
Long-term borrowings [member] | Korea Development Bank [member] | General loans [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	3.02%	3.02%	3.02%
Borrowings	₩ 10,000			10,000
Long-term borrowings [member] | Korea Development Bank [member] | General Loans 1 [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	3.31%	3.31%	3.31%
Long-term borrowings [member] | Other Financial Instruments [member] | Redeemable convertible preferred stock [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	₩ 53,155			₩ 101,816
Long-term borrowings [member] | Other Financial Instruments [member] | Kookmin Bank and other [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates description	LIBOR(3M)+1.850
Annual interest rates adjustment rate	1.85%	1.85%	1.85%

Borrowings - Summary of Long-_2

Borrowings - Summary of Long-term Borrowings (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2020
Inter-Korean Cooperation Fund [member]
Disclosure of detailed information about borrowings [line items]
Long term debt repayment	The above Inter-Korean Cooperation Fund is repayable in installments over 13 years after a seven-year grace period.
Vessel facility loans [member] | Shinhan Bank [member]
Disclosure of detailed information about borrowings [line items]
LIBOR rate	0.238%
Vessel facility loans [member] | Kookmin Bank [member]
Disclosure of detailed information about borrowings [line items]
LIBOR rate	0.238%

Borrowings - Summary of Repayme

Borrowings - Summary of Repayment of Borrowings Including the Current Liabilities (Detail) ₩ in Millions	Dec. 31, 2020KRW (₩)	Dec. 31, 2020SGD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019KRW (₩)
Disclosure of detailed information about borrowings [line items]
Borrowings	₩ 7,316,298	$ 284,000,000	$ 519,598,989	₩ 7,298,867
Debentures [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	5,714,340			5,972,554
Long-term borrowings [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	272,263			190,780
Gross carrying amount [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	7,338,522
Gross carrying amount [member] | Debentures [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	6,962,470			₩ 7,045,366
Gross carrying amount [member] | Debentures [member] | In local currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	4,348,000
Gross carrying amount [member] | Debentures [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	2,622,470
Gross carrying amount [member] | Long-term borrowings [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	368,052
Gross carrying amount [member] | Long-term borrowings [member] | In local currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	249,804
Gross carrying amount [member] | Long-term borrowings [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	118,248
Gross carrying amount [member] | Jan 1, 2020 - Dec 31, 2020 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	1,418,513
Gross carrying amount [member] | Jan 1, 2020 - Dec 31, 2020 [member] | Debentures [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	1,228,682
Gross carrying amount [member] | Jan 1, 2020 - Dec 31, 2020 [member] | Debentures [member] | In local currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	1,060,000
Gross carrying amount [member] | Jan 1, 2020 - Dec 31, 2020 [member] | Debentures [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	168,682
Gross carrying amount [member] | Jan 1, 2020 - Dec 31, 2020 [member] | Long-term borrowings [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	189,831
Gross carrying amount [member] | Jan 1, 2020 - Dec 31, 2020 [member] | Long-term borrowings [member] | In local currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	147,307
Gross carrying amount [member] | Jan 1, 2020 - Dec 31, 2020 [member] | Long-term borrowings [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	42,524
Gross carrying amount [member] | Jan 1, 2021 - Dec 31, 2021 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	1,346,609
Gross carrying amount [member] | Jan 1, 2021 - Dec 31, 2021 [member] | Debentures [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	1,307,261
Gross carrying amount [member] | Jan 1, 2021 - Dec 31, 2021 [member] | Debentures [member] | In local currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	560,000
Gross carrying amount [member] | Jan 1, 2021 - Dec 31, 2021 [member] | Debentures [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	747,261
Gross carrying amount [member] | Jan 1, 2021 - Dec 31, 2021 [member] | Long-term borrowings [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	39,348
Gross carrying amount [member] | Jan 1, 2021 - Dec 31, 2021 [member] | Long-term borrowings [member] | In local currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	518
Gross carrying amount [member] | Jan 1, 2021 - Dec 31, 2021 [member] | Long-term borrowings [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	38,830
Gross carrying amount [member] | Jan 1, 2022 - Dec 31, 2022 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	1,069,704
Gross carrying amount [member] | Jan 1, 2022 - Dec 31, 2022 [member] | Debentures [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	932,310
Gross carrying amount [member] | Jan 1, 2022 - Dec 31, 2022 [member] | Debentures [member] | In local currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	590,000
Gross carrying amount [member] | Jan 1, 2022 - Dec 31, 2022 [member] | Debentures [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	342,310
Gross carrying amount [member] | Jan 1, 2022 - Dec 31, 2022 [member] | Long-term borrowings [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	137,394
Gross carrying amount [member] | Jan 1, 2022 - Dec 31, 2022 [member] | Long-term borrowings [member] | In local currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	100,500
Gross carrying amount [member] | Jan 1, 2022 - Dec 31, 2022 [member] | Long-term borrowings [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	36,894
Gross carrying amount [member] | Jan 1, 2023 - Dec 31, 2023 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	845,510
Gross carrying amount [member] | Jan 1, 2023 - Dec 31, 2023 [member] | Debentures [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	845,017
Gross carrying amount [member] | Jan 1, 2023 - Dec 31, 2023 [member] | Debentures [member] | In local currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	460,000
Gross carrying amount [member] | Jan 1, 2023 - Dec 31, 2023 [member] | Debentures [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	385,017
Gross carrying amount [member] | Jan 1, 2023 - Dec 31, 2023 [member] | Long-term borrowings [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	493
Gross carrying amount [member] | Jan 1, 2023 - Dec 31, 2023 [member] | Long-term borrowings [member] | In local currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	493
Gross carrying amount [member] | After 2024 [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	2,658,186
Gross carrying amount [member] | After 2024 [member] | Debentures [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	2,657,200
Gross carrying amount [member] | After 2024 [member] | Debentures [member] | In local currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	1,678,000
Gross carrying amount [member] | After 2024 [member] | Debentures [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	979,200
Gross carrying amount [member] | After 2024 [member] | Long-term borrowings [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	986
Gross carrying amount [member] | After 2024 [member] | Long-term borrowings [member] | In local currency [member]
Disclosure of detailed information about borrowings [line items]
Borrowings	₩ 986

Provisions - Summary of Changes

Provisions - Summary of Changes in Provisions (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of other provisions [line items]
Beginning balance	₩ 254,162	₩ 281,876
Increase (Transfer)	33,004	66,603
Usage	(9,204)	(56,885)
Reversal	(27,092)	(37,432)
Change in scope of consolidation	1,322
Ending balance	252,192	254,162
Current	165,990	175,612
Non-current	86,202	78,550
Litigation [member]
Disclosure of other provisions [line items]
Beginning balance	64,241	58,760
Increase (Transfer)	17,064	42,684
Usage	(3,948)	(35,640)
Reversal	(857)	(1,563)
Ending balance	76,500	64,241
Current	76,500	64,241
Restoration cost [member]
Disclosure of other provisions [line items]
Beginning balance	113,289	118,828
Increase (Transfer)	(1,933)	6,591
Usage	(2,990)	(5,394)
Reversal	(3,023)	(6,736)
Change in scope of consolidation	424
Ending balance	105,767	113,289
Current	22,343	37,906
Non-current	83,424	75,383
Others [member]
Disclosure of other provisions [line items]
Beginning balance	76,632	104,288
Increase (Transfer)	17,873	17,328
Usage	(2,266)	(15,851)
Reversal	(23,212)	(29,133)
Change in scope of consolidation	898
Ending balance	69,925	76,632
Current	67,147	73,465
Non-current	₩ 2,778	₩ 3,167

Net Defined Benefit Liabiliti_3

Net Defined Benefit Liabilities - Summary of Amount Recognized in the Statements of Financial Position (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of net defined benefit liability (asset) [abstract]
Present value of defined benefit obligations	₩ 2,556,712	₩ 2,427,351
Fair value of plan assets	(2,189,375)	(2,069,710)
Liabilities	378,087	365,663
Assets in the statement of financial position	₩ 10,750	₩ 8,022

Net Defined Benefit Liabiliti_4

Net Defined Benefit Liabilities - Summary of Changes in the Defined Benefit Obligations (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of net defined benefit liability (asset) [Line Items]
Current service cost	₩ (248,047)	₩ (243,598)	₩ (225,667)
Interest expense	6,494	12,017	10,458
Present value of defined benefit obligation [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	2,427,351	2,201,876
Current service cost	248,047	243,598
Interest expense	45,083	47,403
Benefit paid	(258,866)	(100,663)
Changes due to settlements of plan	1,075	910
Remeasurements:
Actuarial gains and losses arising from changes in demographic assumptions	5,191	39
Actuarial gains and losses arising from changes in financial assumptions	17,077	11,773
Actuarial gains and losses arising from experience adjustments	57,703	19,465
Changes in scope of consolidation	14,051	2,950
Ending balance	₩ 2,556,712	₩ 2,427,351	₩ 2,201,876

Net Defined Benefit Liabiliti_5

Net Defined Benefit Liabilities - Summary of Changes in the Fair Value of Plan Assets (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of net defined benefit liability (asset) [Line Items]
Interest income	₩ 6,494	₩ 12,017	₩ 10,458
Plan assets [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning	2,069,710	1,643,046
Interest income	38,590	35,386
Remeasurements:
Return on plan assets (excluding amounts included in interest income)	2,589	(2,537)
Benefits paid	(213,953)	(87,119)
Employer contributions	284,243	476,916
Changes in scope of consolidation	8,196	4,018
Ending	₩ 2,189,375	₩ 2,069,710	₩ 1,643,046

Net Defined Benefit Liabiliti_6

Net Defined Benefit Liabilities - Summary of Amounts Recognized the Operating Expenses in the Consolidated Statements of Operations (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Changes in net defined benefit liability (asset) [abstract]
Current service cost	₩ 248,047	₩ 243,598	₩ 225,667
Net Interest cost	6,494	12,017	10,458
Past service cost	1,075	910	9,801
Transfer out	(16,514)	(16,215)	(13,881)
Total expenses	₩ 239,102	₩ 240,310	₩ 232,045

Net Defined Benefit Liabiliti_7

Net Defined Benefit Liabilities - Summary of Principal Actuarial Assumptions (Detail)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of defined benefit plans [line items]
Discount rate	1.93%	1.97%	2.32%
Future salary increase	4.88%	4.92%	5.08%

Net Defined Benefit Liabiliti_8

Net Defined Benefit Liabilities - Summary of Sensitivity of the Defined Benefit Obligations (Detail) ₩ in Millions	Dec. 31, 2020KRW (₩)
Discount rate [member]
Disclosure of sensitivity analysis for actuarial assumptions [Line items]
Percentage changes in assumption	0.50%
Effect on defined benefit obligation, increase in assumption	₩ (86,288)
Effect on defined benefit obligation, decrease in assumption	₩ 93,254
Salary growth rate [member]
Disclosure of sensitivity analysis for actuarial assumptions [Line items]
Percentage changes in assumption	0.50%
Effect on defined benefit obligation, increase in assumption	₩ 85,344
Effect on defined benefit obligation, decrease in assumption	₩ (79,970)

Net Defined Benefit Liabiliti_9

Net Defined Benefit Liabilities - Additional Information (Detail) ₩ in Millions	12 Months Ended
	Dec. 31, 2020KRW (₩)
Disclosure of net defined benefit liability (asset) [Line Items]
Expected contributions to post-employment benefit plans	₩ 355,481
Weighted average duration of the defined benefit obligations	6 years 8 months 12 days

Net Defined Benefit Liabilit_10

Net Defined Benefit Liabilities - Summary of Expected Maturity Analysis of Undiscounted Pension Benefits (Detail) ₩ in Millions	Dec. 31, 2020KRW (₩)
Disclosure of net defined benefit liability (asset) [Line Items]
Pension benefits	₩ 3,583,273
Less than 1 year [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Pension benefits	232,550
Between 1-2 years [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Pension benefits	271,366
Between 2-5 years [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Pension benefits	794,840
More than 5 years [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Pension benefits	₩ 2,284,517

Defined Contribution Plan - Add

Defined Contribution Plan - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Classes of employee benefits expense [abstract]
Defined Contribution plan recognized expenses	₩ 61,912	₩ 57,170	₩ 48,210

Commitments and Contingencies -

Commitments and Contingencies - Summary of Major Commitments with Local Financial Institutions (Detail) - Dec. 31, 2020 $ in Thousands, ₩ in Millions	KRW (₩)	USD ($)
Disclosure of detailed information about borrowings [line items]
Limit	₩ 2,559,505	$ 281,054
Used amount	202,577	93,471
Bank overdraft [member] | Kookmin Bank and others [member]
Disclosure of detailed information about borrowings [line items]
Limit	1,502,000
Used amount	0
Inter-Korean Cooperation Fund [member] | Export-Import Bank of Korea [member]
Disclosure of detailed information about borrowings [line items]
Limit	37,700
Used amount	2,714
Insurance for Economic Cooperation project [Member] | Export-Import Bank of Korea [member]
Disclosure of detailed information about borrowings [line items]
Limit	3,240
Used amount	1,732
Collateralised loans on electronic receivable-trade [member] | Shinhan Bank and others [member]
Disclosure of detailed information about borrowings [line items]
Limit	522,849
Used amount	23,475
Plus electronic notes payable [member] | Industrial Bank of Korea [member]
Disclosure of detailed information about borrowings [line items]
Limit	50,000
Used amount	331
Loans for working capital [member] | Korea Development Bank and others [member]
Disclosure of detailed information about borrowings [line items]
Limit	243,593
Used amount	152,243
Facility loans [member] | Kookmin Bank and others [member]
Disclosure of detailed information about borrowings [line items]
Limit | $		212,000
Used amount | $		48,855
Facility loans [member] | Shinhan Bank and others [member]
Disclosure of detailed information about borrowings [line items]
Limit	100,123
Used amount	55
Derivatives transaction limit [member] | Korea Development Bank [member]
Disclosure of detailed information about borrowings [line items]
Limit	100,000
Used amount	₩ 22,027
Derivatives transaction limit [member] | Woori Bank and others [Member]
Disclosure of detailed information about borrowings [line items]
Limit | $		69,054
Used amount | $		$ 44,616

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Guarantees Received from Financial Institutions (Detail) - Dec. 31, 2020 $ in Thousands, ₩ in Millions	KRW (₩)	USD ($)
Disclosure of detailed information about borrowings [line items]
Guarantees limit	₩ 1,205,141	$ 72,045
Performance guarantee [member] | Seoul Guarantee Insurance and others [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit	208,386
Performance guarantee [member] | Korea Development Bank and others [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit | $		8,569
Performance guarantee [member] | Seoul guarantee insurance [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit	9,690
Guarantee for import letters of credit [member] | Industrial Bank of Korea and others [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit | $		5,000
Guarantee for payment in foreign currency [member] | KEB Hana Bank and others [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit | $		40,840
Comprehensive credit line [member] | KEB Hana Bank and others [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit	41,100	8,700
Bid guarantee [member] | KEB Hana Bank [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit | $		400
Bid guarantee [member] | Korea Software Financial Cooperative and others [Member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit	80,246
Performance guarantee/Warrant guarantee [member] | Korea Software Financial Cooperative and others [Member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit	393,019
Guarantee for advance payments/others [member] | Korea Software Financial Cooperative and others [Member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit	388,656
Guarantees for licensing [member] | Seoul guarantee insurance [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit	7,748
Warranty guarantee [member] | Seoul guarantee insurance [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit	1,305
Merchant business guarantee insurance [member] | Seoul guarantee insurance [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit	237
Guarantee for payment in won currency [Member] | Shinhan Bank and others [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit	70,962
Refund guarantee for advances received [Member] | Korea Development Bank [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit | $		$ 8,536
Guarantees for depositions [Member] | Seoul guarantee insurance [member]
Disclosure of detailed information about borrowings [line items]
Guarantees limit	₩ 3,792

Commitments and Contingencies_3

Commitments and Contingencies - Summary of Guarantees Provided by the Group for Third Parties (Detail) ₩ in Millions	12 Months Ended
	Dec. 31, 2020KRW (₩)	Dec. 31, 2020SGD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019KRW (₩)
Disclosure of detailed information about borrowings [line items]
Used amount	₩ 7,316,298	$ 284,000,000	$ 519,598,989	₩ 7,298,867
Maturity	Jun. 5, 2025
KT Engineering Co Ltd KT ENGCORE Co Ltd [Member] | Shinhan Bank [member] | Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	Gasan Solar Power Plant Inc.
Limit	₩ 4,700
Used amount	₩ 1,371
Maturity	Jan. 08, 2025
KT Engineering Co Ltd KT ENGCORE Co Ltd [Member] | Suhyup Bank [Member] | Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	SPP Inc.
Limit	₩ 3,250
Used amount	₩ 932
Maturity	Feb. 16, 2024
KT Engineering Co Ltd KT ENGCORE Co Ltd [Member] | Suhyup Bank One [Member] | Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	Korea Cell Inc.
Limit	₩ 3,250
Used amount	₩ 880
Maturity	Feb. 16, 2024
KT Engineering Co Ltd KT ENGCORE Co Ltd [Member] | Suhyup Bank Two [Member] | Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	San-Ya Agricultural Association Corporation
Limit	₩ 3,250
Used amount	₩ 888
Maturity	Feb. 16, 2024
KT Engineering Co Ltd KT ENGCORE Co Ltd [Member] | NH Investment Securities CoLtd [Member] | Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	Ciocanesti Korea Co., Ltd.
Limit	₩ 7,600
Used amount	₩ 7,600
Maturity	Jun. 8, 2017
KT Hitel Co., Ltd. [member] | Cash payers [member] | Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	Shinhan Bank
Limit	₩ 700
Nasmedia Co Ltd [member] | Korea Securities Finance Corp [Member] | Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	Stockholders Association Members
Limit	₩ 5,654
Used amount	₩ 2,735
Bottom of range [member] | KT Hitel Co., Ltd. [member] | Cash payers [member] | Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Apr. 17, 2020
Top of range [member] | KT Hitel Co., Ltd. [member] | Cash payers [member] | Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Apr. 16, 2021

Commitments and Contingencies_4

Commitments and Contingencies - Additional Information (Detail) ₩ in Millions	12 Months Ended
	Dec. 31, 2020KRW (₩)Lawsuits	Dec. 31, 2019KRW (₩)
Commitments and contingencies [abstract]
Severally liable for reimbursement	₩ 1,618
Number of lawsuits | Lawsuits	195
Litigation settlement claim amount	₩ 110,409	₩ 214,877
Litigation provision	₩ 76,500	62,241
New town development consortium percentage of ownership interest	2.50%
Contract amount not yet recognized as liabilities	₩ 596,983	₩ 851,798

Leases - Summary of balance she

Leases - Summary of balance sheet information about leases for lessee (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of balance sheet information about leases for lessee [Line Items]
Right-of-use assets	₩ 1,217,179	₩ 1,268,329
Investment property	1,368,453	1,387,430	₩ 1,091,084
Lease liabilities
Current		392,433
Non-Current		818,919
Lease liability recognized	1,143,640	1,211,352
Previously stated [member]
Disclosure of balance sheet information about leases for lessee [Line Items]
Right-of-use assets	585,034	788,497
Investment property	19,456
Lease liabilities
Current	281,961	355,833
Non-Current	798,416	373,307
Lease liability recognized	1,143,640
Property and building [member]
Disclosure of balance sheet information about leases for lessee [Line Items]
Right-of-use assets		1,020,619
Property and building [member] | Previously stated [member]
Disclosure of balance sheet information about leases for lessee [Line Items]
Right-of-use assets	1,073,207
Machinery and track facilities [member]
Disclosure of balance sheet information about leases for lessee [Line Items]
Right-of-use assets		140,296
Machinery and track facilities [member] | Previously stated [member]
Disclosure of balance sheet information about leases for lessee [Line Items]
Right-of-use assets	42,127
Other [member]
Disclosure of balance sheet information about leases for lessee [Line Items]
Right-of-use assets		₩ 107,414
Other [member] | Previously stated [member]
Disclosure of balance sheet information about leases for lessee [Line Items]
Right-of-use assets	₩ 101,845

Leases - Summary of statement o

Leases - Summary of statement of profit or loss information about leases for lessee (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of statement of profit or loss information about leases for lessee [Line Items]
Depreciation of Right-of-use assets	₩ 404,175	₩ 442,629
Depreciation of Investment Properties	19,113	21,809
Interest expense relating to lease liabilities	44,091	55,001
Expense relating to short-term leases	10,998	14,718
Expense relating to leases of low-value assets that are not short-term leases	25,894	26,575
Expense relating to variable lease payments not included in lease liabilities	8,096	5,993
Property and building [member]
Disclosure of statement of profit or loss information about leases for lessee [Line Items]
Depreciation of Right-of-use assets	290,168	300,773
Machinery and track facilities [member]
Disclosure of statement of profit or loss information about leases for lessee [Line Items]
Depreciation of Right-of-use assets	58,419	89,452
Other [member]
Disclosure of statement of profit or loss information about leases for lessee [Line Items]
Depreciation of Right-of-use assets	₩ 55,588	₩ 52,402

Leases - Additional Information

Leases - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Arrangement Involving Legal Form Of Lease [Abstract]
Cash outflow for leases	₩ 492,772	₩ 532,730
Increase decrease in right of use assets	₩ 404,293

Share Capital - Summary of Shar

Share Capital - Summary of Share Capital (Detail) - KRW (₩) ₩ / shares in Units, ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of classes of share capital [Line Items]
Ordinary Shares	₩ 1,564,499	₩ 1,564,499
Ordinary shares [member]
Disclosure of classes of share capital [Line Items]
Number of issued shares	261,111,808	261,111,808
Par value per share	₩ 5,000	₩ 5,000
Ordinary Shares	₩ 1,564,499	₩ 1,564,499

Share Capital - Summary of Sh_2

Share Capital - Summary of Share Capital (Parenthetical) (Detail) - shares	Dec. 31, 2020	Dec. 31, 2019
Disclosure of classes of share capital [abstract]
Treasury shares	51,787,959	51,787,959

Retained Earnings - Summary of

Retained Earnings - Summary of Retained Earnings (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Miscellaneous equity [abstract]
Legal reserve	₩ 782,249	₩ 782,249
Voluntary reserves	4,651,362	4,651,362
Unappropriated retained earnings	6,721,809	6,157,305
Total	₩ 12,155,420	₩ 11,590,916

Retained Earnings - Summary o_2

Retained Earnings - Summary of Retained Earnings (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Miscellaneous equity [abstract]
Minimum percentage of cash dividend declared appropriation to legal reserve	10.00%	10.00%
Percentage of legal reserve equal to capital stock issued	50.00%	50.00%

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income and Other Components of Equity - Summary of Accumulated Other Comprehensive Income (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Total accumulated other comprehensive income	₩ 86,051	₩ 194,934	₩ 50,158
Changes in investments in associates and joint ventures [member]
Total accumulated other comprehensive income	16,257	1,556	(871)
Loss on derivatives valuation [member]
Total accumulated other comprehensive income	19,809	(7,624)
Gain on valuation of financial assets at fair value through other comprehensive income [member]
Total accumulated other comprehensive income	61,438	211,573	96,704
Exchange differences on translation for foreign operations [member]
Total accumulated other comprehensive income	₩ (11,453)	₩ (10,571)	₩ (15,201)

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income and Other Components of Equity - Summary of Changes in Accumulated Other Comprehensive Income (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Beginning	₩ 194,934	₩ 50,158
Increase /decrease	(220,314)	189,460
Reclassified to gain or loss	111,431	(44,684)
Ending	86,051	194,934
Changes in investments in associates and joint ventures [member]
Beginning	1,556	(871)
Increase /decrease	14,701	2,427
Ending	16,257	1,556
Gain or Loss on derivatives valuation [member]
Beginning	(7,624)	(30,474)
Increase /decrease	(83,998)	67,534
Reclassified to gain or loss	111,431	(44,684)
Ending	19,809	(7,624)
Gain on valuation of financial assets at fair value through other comprehensive income [member]
Beginning	211,573	96,704
Increase /decrease	(150,135)	114,869
Ending	61,438	211,573
Exchange differences on translation for foreign operations [member]
Beginning	(10,571)	(15,201)
Increase /decrease	(882)	4,630
Ending	₩ (11,453)	₩ (10,571)

Accumulated Other Comprehensi_5

Accumulated Other Comprehensive Income and Other Components of Equity - Summary of Other Components of Equity (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Miscellaneous equity [abstract]
Treasury stock	₩ (882,224)	₩ (825,838)
Gain or loss on disposal of treasury stock	(17,579)	1,229
Share-based payments	5,901	7,769
Others	(340,882)	(353,243)
Total	₩ (1,234,784)	₩ (1,170,083)

Accumulated Other Comprehensi_6

Accumulated Other Comprehensive Income and Other Components of Equity - Summary of Other Components of Equity (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Miscellaneous equity [abstract]
Number Of treasury shares reissued	1,150,580
Number of treasury shares acquired	4,550,000
Treasury shares, Amount directly reflected in equity	₩ 7,288	₩ 603

Accumulated Other Comprehensi_7

Accumulated Other Comprehensive Income and Other Components of Equity - Summary of Treasury Stock (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Miscellaneous equity [abstract]
Number of shares (in shares)	19,269,678	15,870,258
Amounts (In millions of Korean won)	₩ 882,224	₩ 825,838

Share-based Payments - Summary

Share-based Payments - Summary of Details of Share-based Payments (Detail)	12 Months Ended
	Dec. 31, 2020KRW (₩)
Disclosure of terms and conditions of share-based payment arrangement [line items]
Grant date	14th grant June 16, 2020
Vesting conditions	Service condition: 1 year Non-market performance condition: achievement of performance
Fair value per option	₩ 22,700
Total compensation costs	₩ 5,187,000,000
Employee wage negotiation [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Grant date	Employee wage negotiation September 21, 2020
Vesting conditions	All employees Current employees as of September 21, 2020
Fair value per option	₩ 22,950
Total compensation costs	₩ 23,317,000,000

Share-based Payments - Summar_2

Share-based Payments - Summary of Changes in the Number of Stock Options and the Weighted-Average Exercise Price (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Beginning	372,023	353,325
Granted	1,418,961	372,023
Expired	241,548	256,543
Exercised	1,150,580	96,782
Ending	398,856	372,023
12th grant [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Beginning		353,325
Expired		256,543
Exercised		96,782
13th grant [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Beginning	372,023
Granted		372,023
Expired	241,548
Exercised	130,475
Ending		372,023
14Th grant [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Granted	398,856
Ending	398,856
Employee wage negotiation [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Granted	1,020,105
Exercised	1,020,105

Share-based Payments - Summar_3

Share-based Payments - Summary of Changes in the Number of Stock Options and the Weighted-Average Exercise Price (Parenthetical) (Detail) - ₩ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of terms and conditions of share-based payment arrangement [abstract]
Weighted average exercise price of share options exercised	₩ 25,486	₩ 27,482

Revenue from Contracts with C_3

Revenue from Contracts with Customers and Relevant Contract Assets and Liabilities - Detail Explanation of Revenue in the Consolidated Statement of operations (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of disaggregation of revenue from contracts with customers [abstract]
Revenue from contracts with customers	₩ 23,895,631	₩ 24,441,122	₩ 23,012,257
Revenue from other sources	545,016	458,067	423,793
Operating revenue	₩ 24,440,647	₩ 24,899,189	₩ 23,436,050

Revenue from Contracts with C_4

Revenue from Contracts with Customers and Relevant Contract Assets and Liabilities - Detail explanation of Operating revenue (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of disaggregation of revenue from contracts with customers [abstract]
Mobile services	₩ 6,805,218	₩ 6,795,124	₩ 6,827,685
Fixed-line services:	4,827,015	4,866,698	4,869,253
Fixed-line and VoIP telephone services	1,463,553	1,578,546	1,708,319
Broadband Internet access services	2,256,188	2,177,447	2,112,763
Data communication services	1,107,274	1,110,705	1,048,171
Media and content	2,637,691	2,516,256	2,261,808
Financial services	3,493,920	3,641,655	3,444,917
Sale of goods	3,593,127	4,194,168	3,288,911
Others	3,083,676	2,885,288	2,743,476
Operating revenue	₩ 24,440,647	₩ 24,899,189	₩ 23,436,050

Revenue from Contracts with C_5

Revenue from Contracts with Customers and Relevant Contract Assets and Liabilities - Detail Analysis of Contract with Customer Assets and Liabilities (Detail) - KRW (₩) ₩ in Millions		Dec. 31, 2020	Dec. 31, 2019
Disclosure of revenue from contracts with customers [line items]
Contract assets	[1]	₩ 586,438	₩ 557,041
Contract liabilities	[1]	384,133	365,610
Deferred revenue		29,593	65,228
Revenue from contracts with customers [member]
Disclosure of revenue from contracts with customers [line items]
Contract assets		672,672	655,329
Contract liabilities		413,707	413,442
Deferred revenue		₩ 89,694	₩ 92,557
[1]	The amounts include adjustments arising from adoption of IFRS 15 (Note 26).

Revenue from Contracts with C_6

Revenue from Contracts with Customers and Relevant Contract Assets and Liabilities - Detail Analysis of Contract with Customer Assets and Liabilities (Parenthetical) (Detail) - KRW (₩) ₩ in Millions		Dec. 31, 2020	Dec. 31, 2019
Disclosure of revenue from contracts with customers [line items]
Contract assets	[1]	₩ 586,438	₩ 557,041
Contract liabilities	[1]	384,133	365,610
long term construction contract [Member]
Disclosure of revenue from contracts with customers [line items]
Contract assets		86,234	98,288
Contract liabilities		₩ 29,574	₩ 47,832
[1]	The amounts include adjustments arising from adoption of IFRS 15 (Note 26).

Revenue from Contracts with C_7

Revenue from Contracts with Customers and Relevant Contract Assets and Liabilities - Detail Analysis of Contract Costs Recognized as Assets (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Incremental cost of contract establishment [Member]
Statement [Line Items]
Incremental cost of contract establishment	₩ 1,726,191	₩ 1,764,009
Cost of Contract performance [Member]
Statement [Line Items]
Incremental cost of contract establishment	₩ 78,757	₩ 85,234

Revenue from Contracts with C_8

Revenue from Contracts with Customers and Relevant Contract Assets and Liabilities - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of disaggregation of revenue from contracts with customers [abstract]
Operating expenses	₩ 1,831,638	₩ 1,681,039

Revenue from Contracts with C_9

Revenue from Contracts with Customers and Relevant Contract Assets and Liabilities - Detail of Revenue Arising from Carried-Forward Contract Liabilities (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of disaggregation of revenue from contracts with customers [abstract]
Allocation of the transaction price	₩ 251,975	₩ 266,478	₩ 183,905
Deferred revenue of joining/installment fee	42,685	44,032	39,975
Others			1,536
Total	₩ 294,660	₩ 310,510	₩ 225,416

Operating Expenses - Summary of

Operating Expenses - Summary of Operating Expenses (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Profit (loss) [abstract]
Salaries and wages	₩ 4,123,680	₩ 3,974,233	₩ 3,845,842
Depreciation	2,605,128	2,530,252	2,674,205
Depreciation of right-of-use assets	404,175	442,629
Amortization of intangible assets	624,982	656,611	607,527
Commissions	965,461	1,115,477	1,080,168
Interconnection charges	500,081	534,025	579,613
International interconnection fee	172,529	240,254	226,627
Purchase of inventories	3,681,801	4,453,820	4,414,094
Changes of inventories	257,041	282,957	(432,607)
Sales commission	2,337,127	2,315,731	1,942,841
Service cost	2,102,875	1,610,261	1,540,869
Utilities	360,797	332,816	323,411
Taxes and dues	283,197	277,742	285,131
Rent	136,355	193,357	460,377
Insurance premium	71,018	82,404	73,654
Installation fee	132,117	155,178	143,669
Advertising expenses	132,466	150,166	157,675
Research and development expenses	156,940	165,028	176,758
Card service cost	2,941,669	3,066,766	3,112,618
Others	1,428,875	1,292,512	1,122,718
Total	₩ 23,418,314	₩ 23,872,219	₩ 22,335,190

Operating Expenses - Summary _2

Operating Expenses - Summary of Details of Employee Benefits (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Profit (loss) [abstract]
Short-term employee benefits	₩ 3,770,786	₩ 3,663,337	₩ 3,505,214
Post-employment benefits (Defined benefit plan)	239,102	240,310	232,045
Post-employment benefits (Defined contribution plan)	61,912	57,170	48,210
Share-based payment	28,604	6,398	8,439
Others	23,276	7,018	51,934
Total	₩ 4,123,680	₩ 3,974,233	₩ 3,845,842

Financial Income and Costs - Su

Financial Income and Costs - Summary of Details of Financial Income (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Profit (loss) [abstract]
Interest income	₩ 270,571	₩ 282,704	₩ 244,796
Gain on foreign currency transactions	17,493	24,596	17,175
Gain on foreign currency translation	164,351	17,979	3,691
Gain on settlement of derivatives	9,397	9,016	27,950
Gain on valuation of derivatives	172	77,353	66,305
Others	36,630	12,747	14,326
Total	₩ 498,614	₩ 424,395	₩ 374,243

Financial Income and Costs - _2

Financial Income and Costs - Summary of Details of Financial Expense (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Finance Income [line items]
Interest expenses	₩ 263,579	₩ 278,427	₩ 296,874
Loss on foreign currency transactions	27,805	30,267	49,156
Loss on foreign currency translation	26,340	93,977	72,642
Loss on settlement of derivatives	1,406	20
Loss on valuation of derivatives	163,763	15,867	2,045
Others	16,338	2,277	1,124
Total	507,383	432,133	435,659
Loans and receivables [member]
Disclosure Of Finance Income [line items]
Loss on disposal of trade receivables	₩ 8,152	₩ 11,298	₩ 13,818

Deferred Income Tax and Incom_3

Deferred Income Tax and Income Tax Expense - Summary of Analysis of Deferred Tax Assets and Deferred Tax Liabilities (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred income tax assets	₩ 433,698	₩ 424,856
Deferred income tax liabilities	(429,331)	(425,468)
Gross carrying amount [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred income tax assets	2,036,193	2,033,725
Deferred income tax liabilities	(2,031,826)	(2,034,337)
Gross carrying amount [member] | Less than 1 year [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred income tax assets	404,434	419,889
Deferred income tax liabilities	(637,317)	(538,578)
Gross carrying amount [member] | Over 12 months [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred income tax assets	1,631,759	1,613,836
Deferred income tax liabilities	₩ (1,394,509)	₩ (1,495,759)

Deferred Income Tax and Incom_4

Deferred Income Tax and Income Tax Expense - Summary of Gross Movements on the Deferred Income Tax Account (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets and liabilities [abstract]
Beginning	₩ (612)	₩ 260,584
Changes to the statement of operations	(72,124)	(199,527)	₩ 15,016
Changes to other comprehensive loss (income)	77,103	(61,669)	36,115
Ending	₩ 4,367	₩ (612)	₩ 260,584

Deferred Income Tax and Incom_5

Deferred Income Tax and Income Tax Expense - Summary of Movement in Deferred Income Tax Assets and Liabilities (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	₩ (612)	₩ 260,584
Consolidated statements of operations	(72,124)	(199,527)	₩ 15,016
Other comprehensive income	77,103	(61,669)
Ending	4,367	(612)	260,584
Deferred tax liabilities derivative assets [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(10,898)
Consolidated statements of operations	10,055	(10,250)
Other comprehensive income		(648)
Ending	(843)	(10,898)
Deferred tax liabilities investment in subsidiaries associates and joint ventures [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(108,191)	(93,604)
Consolidated statements of operations	(64,553)	(14,622)
Other comprehensive income	(8,820)	35
Ending	(181,564)	(108,191)	(93,604)
Deferred tax liabilities depreciation [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(11,606)	(424)
Consolidated statements of operations	7,431	(11,182)
Ending	(4,175)	(11,606)	(424)
Deferred tax liabilities advanced depreciation provision [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(313,121)	(313,184)
Consolidated statements of operations	1,203	63
Ending	(311,918)	(313,121)	(313,184)
Deferred tax liabilities deposits for severance benefits [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(496,853)	(398,982)
Consolidated statements of operations	(26,419)	(99,126)
Other comprehensive income	2,015	1,255
Ending	(521,257)	(496,853)	(398,982)
Deferred tax liabilities accrued income [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(1,541)	(1,558)
Consolidated statements of operations	(212)	17
Ending	(1,753)	(1,541)	(1,558)
Deferred tax liabilities reserve for technology and human resource development [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(204)	(204)
Ending	(204)	(204)	(204)
Other deferred tax liabilities [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(523,150)	(284,255)
Consolidated statements of operations	53,797	(238,725)
Other comprehensive income	0	(170)
Ending	(469,353)	(523,150)	(284,255)
Deferred tax derivative assets [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning		8,341
Consolidated statements of operations		(850)
Other comprehensive income		(7,491)
Ending			8,341
Deferred tax assets provision for impairment or trade receivables [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	84,071	99,887
Consolidated statements of operations	4,994	(15,816)
Ending	89,065	84,071	99,887
Deferred tax assets inventory valuation [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	23	121
Consolidated statements of operations	(259)	(98)
Ending	(236)	23	121
Deferred tax assets contribution for construction [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	16,154	16,800
Consolidated statements of operations	246	(646)
Ending	16,400	16,154	16,800
Deferred Tax Assets Provisions [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	32,824	36,178
Consolidated statements of operations	1,198	(3,354)
Ending	34,022	32,824	36,178
Deferred tax assets property, plant and equipment [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	228,655	230,278
Consolidated statements of operations	(1,695)	(1,623)
Ending	226,960	228,655	230,278
Deferred Tax assets assets retirement obligation [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	29,016	24,532
Consolidated statements of operations	(883)	4,484
Ending	28,133	29,016	24,532
Deferred tax assets withholding of facilities expenses [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	6,183	6,609
Consolidated statements of operations	(436)	(426)
Ending	5,747	6,183	6,609
Deferred tax assets deduction of installment receivables [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	48	42
Consolidated statements of operations	(20)	6
Ending	28	48	42
Deferred tax assets gain or loss foreign currency translation [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	20,677	10,672
Consolidated statements of operations	(20,539)	10,005
Ending	138	20,677	10,672
Deferred tax assets deferred revenue [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	35,800	39,641
Consolidated statements of operations	7,230	(3,841)
Ending	43,030	35,800	39,641
Deferred tax assets real-estate sales [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	13,685	21,728
Consolidated statements of operations	(13,685)	(8,043)
Ending		13,685	21,728
Other deferred tax assets [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	708,437	537,209
Consolidated statements of operations	(123,798)	174,177
Other comprehensive income	948	(2,949)
Ending	585,587	708,437	537,209
Deferred tax assets [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	1,905,480	1,673,777
Consolidated statements of operations	(20,492)	235,361
Other comprehensive income	6,274	(3,658)
Ending	1,891,262	1,905,480	1,673,777
Deferred tax assets defined benefit liabilities [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	569,471	513,842
Consolidated statements of operations	13,707	48,847
Other comprehensive income	15,186	6,782
Ending	598,364	569,471	513,842
Deferred tax assets tax credit carry forwards [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	128,245	102,898
Consolidated statements of operations	16,686	25,347
Ending	144,931	128,245	102,898
Deferred tax liabilities contract assets [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(53,750)	(11,505)
Consolidated statements of operations	(112,794)	(42,245)
Ending	(166,544)	(53,750)	(11,505)
Deferred tax liabilities financial assets at fair value through profit or loss [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(323)	(661)
Consolidated statements of operations	(304)	338
Ending	(627)	(323)	(661)
Deferred tax liabilities Financial assets at fair value through other comprehensive income [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(103,837)	(41,798)
Consolidated statements of operations	(4,420)	(3,556)
Other comprehensive income	77,634	(58,483)
Ending	(30,623)	(103,837)	(41,798)
Deferred tax assets unsettled expenses [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	160,436	127,897
Consolidated statements of operations	(24,358)	32,539
Ending	136,078	160,436	127,897
Temporary differences [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(128,857)	157,686
Consolidated statements of operations	(88,810)	(224,874)
Other comprehensive income	77,103	(61,669)
Ending	(140,564)	(128,857)	157,686
Deferred tax liabilities [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(2,034,337)	(1,516,091)
Consolidated statements of operations	(68,318)	(460,235)
Other comprehensive income	70,829	(58,011)
Ending	(2,031,826)	(2,034,337)	(1,516,091)
Deferred Tax Liabilities Contract Cost [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(410,863)	(369,916)
Consolidated statements of operations	67,898	(40,947)
Ending	(342,965)	₩ (410,863)	₩ (369,916)
Deferred Tax Assets Derivative instrument [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Consolidated statements of operations	40,342
Other comprehensive income	(9,860)
Ending	30,482
Deferred Tax Assets Contract Assets [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Consolidated statements of operations	97,464
Ending	₩ 97,464

Deferred Income Tax and Incom_6

Deferred Income Tax and Income Tax Expense - Summary of Tax Impacts Recognized Directly To Equity (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets and liabilities [abstract]
Gain on valuation of financial assets at fair value through other comprehensive income, Before recognition	₩ 54,969	₩ 225,635	₩ 59,384
Gain (loss) on valuation of hedge instruments (loss)liabilities, Before recognition	37,247	31,003	(36,756)
Remeasurements of net defined benefit liabilities, Before recognition	(77,382)	(33,814)	(116,324)
Share of Gain (loss) of associates and joint ventures, and others, Before recognition	25,538	4,493	(1,036)
Exchange differences on translation for foreign operations, Before recognition	(3,614)	6,692	3,989
Total, Before recognition	36,758	234,009	(90,743)
Gain on valuation of financial assets at fair value through other comprehensive income, Tax effect	(12,972)	(58,483)	(15,573)
Gain (loss) on valuation of hedge instruments (loss)liabilities, Tax effect	(9,860)	(8,139)	9,745
Remeasurements of net defined benefit liabilities, Tax effect	17,201	8,037	42,813
Share of Gain (loss) of associates and joint ventures, and others, Tax effect	(8,820)	(1,327)	179
Exchange differences on translation for foreign operations, Tax effect	948	(1,759)	(1,049)
Total, Tax effect	77,103	(61,669)	36,115
Gain on valuation of financial assets at fair value through other comprehensive income, After recognition	41,997	167,152	43,811
Gain (loss) on valuation of hedge instruments (loss)liabilities, After recognition	27,387	22,864	(27,011)
Remeasurements of net defined benefit liabilities, After recognition	(60,181)	(25,777)	(73,511)
Share of Gain (loss) of associates and joint ventures, and others, After recognition	16,718	3,166	(857)
Exchange differences on translation for foreign operations, After recognition	(2,666)	4,933	2,940
Total other comprehensive income (loss)	₩ 23,255	₩ 172,338	₩ (54,628)

Deferred Income Tax and Incom_7

Deferred Income Tax and Income Tax Expense - Summary of Details of Income Tax Expense (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets and liabilities [abstract]
Current income tax expense	₩ 213,225	₩ 120,533	₩ 329,581
Impact of change in deferred taxes	72,124	199,527	(15,016)
Income tax expense	₩ 285,349	₩ 320,060	₩ 314,565

Deferred Income Tax and Incom_8

Deferred Income Tax and Income Tax Expense - Summary of Tax on the Group's Profit Before Tax (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets and liabilities [abstract]
Profit before income tax expense	₩ 1,031,605	₩ 1,015,928	₩ 1,033,977
Statutory income tax expense	273,329	269,018	273,982
Tax effect
Income not taxable for taxation purposes	(24,657)	(1,265)	(85,322)
Non-deductible expenses	31,741	19,543	18,126
Tax credit	(47,056)	(39,190)	(20,319)
Additional payment of income taxes	429	3,832	11,439
Tax effect and adjustment on consolidation
Goodwill impairment		159	137
Eliminated dividend income form subsidiaries	20,682	21,917	31,966
Changes of out-side tax effect	38,552	13,539	618
Tax effect of investment in kind			82,820
Intangible Asset impairment and amortization	3,790	14,052
Reversal expenses of contract cost assets	(6,643)	11,213
Others	(4,818)	7,242	1,118
Income tax expense	₩ 285,349	₩ 320,060	₩ 314,565

Deferred Income Tax and Incom_9

Deferred Income Tax and Income Tax Expense - Summary of expected period of expiry for unused tax losses not recognized in deferred tax assets (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused tax losses for which no deferred tax asset recognised	₩ 127,793	₩ 142,075
2021
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused tax losses for which no deferred tax asset recognised	2,140	18,582
2022
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused tax losses for which no deferred tax asset recognised	80,649	2,140
2023
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused tax losses for which no deferred tax asset recognised	5,848	80,649
2024
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused tax losses for which no deferred tax asset recognised	4,867	5,848
2025
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused tax losses for which no deferred tax asset recognised	2,847	4,867
2026
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused tax losses for which no deferred tax asset recognised	9,709	9,390
2027
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused tax losses for which no deferred tax asset recognised	8,389	7,888
2028
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused tax losses for which no deferred tax asset recognised	8,426	10,064
2029
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused tax losses for which no deferred tax asset recognised	2,579	2,030
2030
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused tax losses for which no deferred tax asset recognised	₩ 2,339	₩ 617

Deferred Income Tax and Inco_10

Deferred Income Tax and Income Tax Expense - Summary of deferred tax assets and liabilities that are not recognized (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Deductible Temporary Differences For Which No Deferred Tax Asset and Liabiities Is Recognised	₩ 679,419	₩ 674,102
Taxable Temporary Differences For Which No Deferred Tax Asset and Liabilities Is Recognised	142,416	152,036
Investment in subsidiaries, associates, and joint ventures
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Deductible Temporary Differences For Which No Deferred Tax Asset and Liabiities Is Recognised	583,890	610,351
Taxable Temporary Differences For Which No Deferred Tax Asset and Liabilities Is Recognised	132,848	141,664
Unused tax loss
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Deductible Temporary Differences For Which No Deferred Tax Asset and Liabiities Is Recognised	28,115	31,257
Unused Tax credit
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Deductible Temporary Differences For Which No Deferred Tax Asset and Liabiities Is Recognised	2,654
Others
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Deductible Temporary Differences For Which No Deferred Tax Asset and Liabiities Is Recognised	64,760	32,494
Others
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Taxable Temporary Differences For Which No Deferred Tax Asset and Liabilities Is Recognised	₩ 9,568	₩ 10,372

Earnings per Share - Summary of

Earnings per Share - Summary of Basic and Diluted Earnings per Share from Operations (Detail) - KRW (₩) ₩ / shares in Units, ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Basic earnings per share [abstract]
Profit (loss) attributable to ordinary shares	₩ 700,889	₩ 645,703	₩ 645,571
Weighted average number of ordinary shares outstanding	245,207,307	245,171,283	245,049,466
Basic earnings per share (In Korean won)	₩ 2,858	₩ 2,634	₩ 2,634
Profit attributable to ordinary shares (In millions of Korean won)	₩ 700,889	₩ 645,703	₩ 645,571
Adjustment to net income attributable to ordinary shares (In millions of Korean won)		(157)
Diluted profit attributable to ordinary shares (In millions of Korean won)	₩ 700,889	₩ 645,546	₩ 645,571
Number of dilutive potential ordinary shares outstanding	69,598	70,267	1,163
Weighted average number of ordinary shares outstanding	245,276,905	245,241,550	245,050,629
Diluted earnings per share (In Korean won)	₩ 2,858	₩ 2,632	₩ 2,634

Dividend - Additional Informati

Dividend - Additional Information (Detail) - KRW (₩) ₩ / shares in Units, ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of Dividends [abstract]
Dividends paid	₩ 269,766	₩ 269,659	₩ 245,097
Dividends paid per share	₩ 1,100	₩ 1,100	₩ 1,000
Dividends declared	₩ 326,487
Dividends declared per share	₩ 1,350

Cash Generated from Operation_2

Cash Generated from Operations - Summary of Cash Flows from Operating Activities (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from (used in) operating activities [abstract]
Profit for the year	₩ 746,256	₩ 695,868	₩ 719,412
Adjustments to reconcile net income
Income tax expense	285,349	320,060	314,565
Interest income	(291,425)	(303,722)	(265,817)
Interest expense	265,035	278,975	296,894
Dividends income	(4,442)	(3,408)	(2,910)
Depreciation	2,635,307	2,567,754	2,735,413
Amortization of intangible assets	628,154	660,705	629,526
Depreciation of right-of-use assets	404,175	442,629
Provision for severance benefits	255,615	256,525	245,926
Impairment losses on trade receivables	139,957	60,193	113,064
Share of net profit or loss of associates and joint ventures	(18,041)	3,252	5,912
Loss(gain) on disposal of associates and joint ventures	111	30	(3,737)
Loss(gain) on disposal of right-of-use assets	2,047	1,556
Impairment losses on assets held for sale		7,586
Loss on disposal of property and equipment and investment in properties	55,590	49,284	68,688
Loss(gain) on disposal of intangible assets	246	(1,248)	(4,256)
Loss on impairment of intangible assets	211,636	61,899	12,997
Loss(gain) on foreign currency translation	(138,011)	75,998	68,952
Loss(gain) on valuation and settlement of derivatives, net	155,600	(70,482)	(92,210)
Loss(gain) on disposal of financial assets at fair value through profit or loss	329	(5,115)	(1,712)
Gain on valuation of financial assets at fair value through profit or loss	(59,044)	(4,335)	(10,768)
Loss(gain) on disposal of financial assets at amortized cost	(138)	43	(44)
Others	127,949	143,500	(55,969)
Changes in operating assets and liabilities
Decrease(increase) in trade receivables	66,462	(433,292)	(81,217)
Decrease(increase) in other receivables	685,209	(79,130)	356,643
Decrease(increase) in other current assets	9,089	984	(123,258)
Decrease(increase) in other non-current assets	(86,039)	(178,180)	19,556
Decrease(increase) in inventories	288,507	240,488	(480,543)
Increase(decrease) in trade payables	(135,760)	44,354	(167,841)
Decrease in other payables	(1,232,646)	(102,375)	(448,301)
Increase in other current liabilities	127,076	43,384	291,548
Increase(decrease) in other non-current liabilities	(56,319)	(199,547)	144,072
Decrease(Increase) in provisions	2,264	(12,164)	85,946
Decrease(Increase) in deferred revenue	(1,948)	641	48,201
Increase in plan assets	(136,336)	(375,499)	(53,301)
Payment of severance benefits	(186,520)	(119,716)	(153,209)
Cash generated from operations (1+2+3)	₩ 4,745,293	₩ 4,058,065	₩ 4,212,222

Cash Generated from Operation_3

Cash Generated from Operations - Summary of Significant Transactions not Affecting Cash Flows (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from (used in) operating activities [abstract]
Reclassification of the current portion of borrowings	₩ 1,229,359	₩ 1,030,056	₩ 1,149,599
Reclassification of construction-in-progress to property and equipment	3,011,519	2,698,146	1,988,014
Reclassification of accounts payable from property and equipment	22,052	685,859	122,185
Reclassification of accounts payable from intangible assets	(345,675)	(356,911)	584,595
Reclassification of payable from defined benefit liability	72,346	(19,053)	(31,838)
Reclassification of payable from plan assets	₩ 66,046	₩ (14,298)	₩ (9,497)

Changes in Liabilities Arisin_3

Changes in Liabilities Arising from Financing Activities - Summary of Changes in Liabilities Arising from Financial Activities (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning	₩ 8,471,738	₩ 6,847,376
Cash flows	(259,601)	112,632
Changes in Accounting Policy		771,410
Newly acquired	507,472	774,906
Exchange difference	(12,607)	6,435
Fair value change	(27,085)	(31,456)
Change in Consolidation Scope	3,564
Other changes	(100,576)	(9,565)
Ending	8,582,905	8,471,738
Borrowings [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning	7,298,867	6,648,294
Cash flows	167,867	574,175
Newly acquired	17,523
Exchange difference	(157,985)	64,398
Other changes	(9,974)	12,000
Ending	7,316,298	7,298,867
Financial lease liabilities [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning	1,211,351	163,858
Cash flows	(447,784)	(485,444)
Changes in Accounting Policy		771,410
Newly acquired	473,477	774,906
Exchange difference	(3)
Fair value change	40
Change in Consolidation Scope	3,564
Other changes	(97,005)	(13,379)
Ending	1,143,640	1,211,351
Lease liabilities [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Cash flows	(13,674)
Newly acquired	13,674
Derivative assets [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning	(58,576)	(29,843)
Cash flows	34,933	33,635
Exchange difference	2,870	(53,729)
Fair value change	(3,456)	(11,398)
Other changes	16,623	2,759
Ending	(7,606)	(58,576)
Derivative liabilities [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning	20,096	65,067
Cash flows	(943)	(9,734)
Newly acquired	2,798
Exchange difference	142,511	(4,234)
Fair value change	(23,669)	(20,058)
Other changes	(10,220)	(10,945)
Ending	₩ 130,573	₩ 20,096

Segment Information - Summary o

Segment Information - Summary of Segment Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of operating segments [Line Items]
Operating revenues	₩ 24,440,647	₩ 24,899,189	₩ 23,436,050
Operating income (loss)	1,022,333	1,026,970	1,100,860
Depreciation and Amortization	3,634,284	3,629,492	3,281,732
Operating segments [member]
Disclosure of operating segments [Line Items]
Operating revenues	28,612,919	28,863,426	27,346,281
Operating income (loss)	1,175,172	1,080,040	1,201,682
Depreciation and Amortization	3,718,122	3,709,297	3,274,768
Operating segments [member] | ICT [member]
Disclosure of operating segments [Line Items]
Operating revenues	18,275,765	18,527,631	17,724,320
Operating income (loss)	809,741	634,046	933,191
Depreciation and Amortization	3,233,878	3,229,159	2,917,163
Operating segments [member] | Finance [member]
Disclosure of operating segments [Line Items]
Operating revenues	3,686,430	3,795,185	3,771,681
Operating income (loss)	85,008	158,235	148,440
Depreciation and Amortization	53,098	27,852	22,580
Operating segments [member] | Satellite TV [member]
Disclosure of operating segments [Line Items]
Operating revenues	706,631	694,637	690,821
Operating income (loss)	71,345	69,357	66,735
Depreciation and Amortization	84,931	94,992	98,310
Operating segments [member] | Others [member]
Disclosure of operating segments [Line Items]
Operating revenues	5,944,093	5,845,973	5,159,459
Operating income (loss)	209,078	218,402	53,316
Depreciation and Amortization	346,215	357,294	236,715
Elimination [member]
Disclosure of operating segments [Line Items]
Operating revenues	(4,172,272)	(3,964,237)	(3,910,231)
Operating income (loss)	(152,839)	(53,070)	(100,822)
Depreciation and Amortization	₩ (83,838)	₩ (79,805)	₩ 6,964

Segment Information - Summary_2

Segment Information - Summary of Segment Information (Parenthetical) (Detail) ₩ in Millions	Dec. 31, 2020KRW (₩)
ICT [member]
Disclosure of operating segments [line items]
Property and equipment and intangible assets	₩ 13,583,173

Segment Information - Summary_3

Segment Information - Summary of Operating Revenues and Non Current Assets by Geographical Regions (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of geographical areas [Line Items]
Operating revenues	₩ 24,440,647	₩ 24,899,189	₩ 23,436,050
Non-current assets	18,953,009	19,275,095
Domestic [member]
Disclosure of geographical areas [Line Items]
Operating revenues	24,368,729	24,832,068	23,376,218
Non-current assets	18,934,766	19,198,416
Overseas [member]
Disclosure of geographical areas [Line Items]
Operating revenues	71,918	67,121	₩ 59,832
Non-current assets	₩ 18,243	₩ 76,679

Related Party Transactions - Su

Related Party Transactions - Summary of Related Parties Outstanding Balances of Receivables and Payables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of transactions between related parties [line items]
Dividend Income			₩ 11,146
Payables	₩ 20,857	₩ 57,907
K-Realty CR-REITs No.1 [member]
Disclosure of transactions between related parties [line items]
Dividend Income			8,932
Others [member]
Disclosure of transactions between related parties [line items]
Dividend Income			₩ 2,148
Trade receivables [member]
Disclosure of transactions between related parties [line items]
Dividend Income	1,304	1,625
Trade receivables [member] | K-Realty CR-REITs No.1 [member]
Disclosure of transactions between related parties [line items]
Dividend Income	457	608
Trade receivables [member] | K Bank Inc. [member]
Disclosure of transactions between related parties [line items]
Dividend Income	775	583
Trade receivables [member] | Others [member]
Disclosure of transactions between related parties [line items]
Dividend Income	72	434
Loans and receivables [member]
Disclosure of transactions between related parties [line items]
Dividend Income	50,311	37,941
Loans and receivables [member] | K-Realty CR-REITs No.1 [member]
Disclosure of transactions between related parties [line items]
Dividend Income	16,200	23,100
Loans and receivables [member] | K Bank Inc. [member]
Disclosure of transactions between related parties [line items]
Dividend Income	32,964	13,664
Loans and receivables [member] | Others [member]
Disclosure of transactions between related parties [line items]
Dividend Income	1,147	1,177
Other payables [member]
Disclosure of transactions between related parties [line items]
Payables	1,749	1,268
Other payables [member] | K-Realty CR-REITs No.1 [member]
Disclosure of transactions between related parties [line items]
Payables	20,857	57,907
Other payables [member] | K Bank Inc. [member]
Disclosure of transactions between related parties [line items]
Payables	891	557
Other payables [member] | Others [member]
Disclosure of transactions between related parties [line items]
Payables	₩ 858	₩ 711

Related Party Transactions - _2

Related Party Transactions - Summary of Significant Transactions with Related Parties (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of transactions between related parties [line items]
Sales	₩ 18,765	₩ 23,416	₩ 24,312
Purchases	18,499	19,055	128,252
Dividend Income			11,146
K-Realty CR-REITs No.1 [member]
Disclosure of transactions between related parties [line items]
Sales	2,298	1,302	2,088
Purchases			31,984
Dividend Income			8,932
MOS GS Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Sales			493
Purchases			12,023
Dividend Income			8
MOS Daegu Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Sales			229
Purchases			8,775
Dividend Income			8
MOS Chungcheong Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Sales			540
Purchases			9,159
Dividend Income			8
MOS Gangnam Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Sales			333
Purchases			11,549
Dividend Income			10
MOS GB Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Sales			1,378
Purchases			16,519
Dividend Income			12
MOS BS Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Sales			324
Purchases			11,193
Dividend Income			10
MOS Honam Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Sales			331
Purchases			10,499
Dividend Income			10
Others [member]
Disclosure of transactions between related parties [line items]
Sales	809		2,888
Purchases	10,272		9,547
Dividend Income			2,148
K Bank Inc. [member]
Disclosure of transactions between related parties [line items]
Sales	15,658	17,815	15,705
Purchases	₩ 8,227	8,524	7,004
NgeneBio [member]
Disclosure of transactions between related parties [line items]
Sales		1,498	₩ 3
Purchases		10,531
K-Realty CR-REITs No.10 [member]
Disclosure of transactions between related parties [line items]
Sales		₩ 2,801

Related Party Transactions - _3

Related Party Transactions - Summary of Key Management Compensation (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of transactions between related parties [abstract]
Salaries and other short-term benefits	₩ 2,086	₩ 2,955	₩ 2,762
Post-employment benefits	390	321	751
Stock-based compensation	5,613	891	878
Total	₩ 8,089	₩ 4,167	₩ 4,391

Related Party Transactions - _4

Related Party Transactions - Summary of Transactions Prior Liquidation (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement [Line Items]
Dividend Income			₩ 11,146
Payables	₩ 20,857	₩ 57,907
K-Realty CR-REITs No.1 [member]
Statement [Line Items]
Dividend Income			8,932
Others [member]
Statement [Line Items]
Dividend Income			₩ 2,148
Acquisition of right of use assets [member]
Statement [Line Items]
Dividend Income		776
Acquisition of right of use assets [member] | K-Realty CR-REITs No.1 [member]
Statement [Line Items]
Dividend Income		776
Finance costs [member] | K-Realty CR-REITs No.1 [member]
Statement [Line Items]
Payables		2,225
Interest Expense [member]
Statement [Line Items]
Payables	917	2,225
Interest Expense [member] | K-Realty CR-REITs No.1 [member]
Statement [Line Items]
Payables	917
Dividend Income [member]
Statement [Line Items]
Payables	17,345	15,354
Dividend Income [member] | K-Realty CR-REITs No.1 [member]
Statement [Line Items]
Payables	8,061	10,928
Dividend Income [member] | Others [member]
Statement [Line Items]
Payables	43	146
Dividend Income [member] | Korea Information & Technology Investment Fund (KIF Investment Fund) [member]
Statement [Line Items]
Payables	9,241	₩ 4,280
Interest income [member]
Statement [Line Items]
Dividend Income	14
Interest income [member] | K Bank Inc. [member]
Statement [Line Items]
Dividend Income	₩ 14

Related Party Transactions - _5

Related Party Transactions - Summary of Fund Transactions with Related Parties (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of transactions between related parties [line items]
Equity contributions in cash	₩ 255,302	₩ 25,603	₩ 24,713
Repayment	20,304	30,385
PT. Mitra Transaksi Indonesia [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			1,567
KT-IBKC future investment fund [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash		3,750	(1,050)
Korea Electronic Vehicle Charging Service [Member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			168
Gyeonggi-KT Yoojin Superman Fund [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash	1,000	1,000	1,000
K-REALTY CR REIT [member]
Disclosure of transactions between related parties [line items]
Repayment		30,385
K Bank Inc. [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash	195,011	21,782	26,725
MOS GS Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			(147)
MOS Daegu Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			(147)
MOS Chungcheong Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			(153)
MOS Gangnam Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			(180)
MOS GB Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			(203)
MOS BS Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			(183)
MOS Honam Co., Ltd. [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			(206)
PHI Healthcare Inc [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			1,000
KT-CKP New Media Investment Fund [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash	(109)	(174)	(1,229)
KT-DSC creative economy youth start-up investment fund [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash		(1,800)	(1,800)
GE Premier 1st Corporate Restructuring Real Estate Investment Trust Company [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			(3,423)
JB Emerging Market Specialty Investment Private Equity Trust No one[member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			3,960
Boston Global Film Contents Fund Lp [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash			₩ (986)
KT Philippines co. Ltd. {member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash		99
Virtua Realm Sendirian Berhad [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash		550
KT-Smart Factory Investment Fund [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash	2,800	2,800
KT-SB Venture Investment Fund [member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash		₩ (2,404)
Studio Discovery Co Ltd [Member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash	3,000
KT Young Entrepreneurs DNA Investment Fund [Member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash	3,600
Hyundai Robotics Co Ltd [Member]
Disclosure of transactions between related parties [line items]
Equity contributions in cash	50,000
K-Realty CR-REITs No.1 [member]
Disclosure of transactions between related parties [line items]
Repayment	₩ 20,304

Financial Risk Management - Sum

Financial Risk Management - Summary of Exposures to Risks, Effects on Profit before Income Tax and Shareholders' Equity (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
10% strengthening in foreign exchange rate [member]
Disclosure of detailed information about financial instruments [line items]
Fluctuation of foreign exchange rate	10.00%	10.00%	10.00%
Income before tax	₩ 25,220	₩ 45,149	₩ 7,212
Shareholders' equity	₩ 36,961	₩ 52,092	₩ 10,196
10% weakening in foreign exchange rate [member]
Disclosure of detailed information about financial instruments [line items]
Fluctuation of foreign exchange rate	10.00%	10.00%	10.00%
Income before tax	₩ (25,220)	₩ (45,149)	₩ (12,413)
Shareholders' equity	₩ (36,961)	₩ (52,092)	₩ (9,625)
Ten percentage increase in market equity price [member]
Disclosure of detailed information about financial instruments [line items]
Fluctuation of price	10.00%	10.00%	10.00%
Income before tax	₩ 2,811	₩ 24	₩ 12
Shareholders' equity	₩ 3,472	₩ 613	₩ 898
10% decrease in market equity price [member]
Disclosure of detailed information about financial instruments [line items]
Fluctuation of price	10.00%	10.00%	10.00%
Income before tax	₩ (2,811)	₩ (24)	₩ (12)
Shareholders' equity	₩ (3,472)	₩ (613)	₩ (898)
100 basis point increase in market interest rate [Member]
Disclosure of detailed information about financial instruments [line items]
Fluctuation of interest rate	1.00%	1.00%	1.00%
Income before tax	₩ 973	₩ 425	₩ 1,059
Shareholders' equity	₩ 18,584	₩ 14,764	₩ 9,689
100 basis point decrease in market interest rate [Member]
Disclosure of detailed information about financial instruments [line items]
Fluctuation of interest rate	1.00%	1.00%	1.00%
Income before tax	₩ (973)	₩ (482)	₩ (1,958)
Shareholders' equity	₩ (19,377)	₩ (19,280)	₩ (10,237)

Financial Risk Management - S_2

Financial Risk Management - Summary of Details of Financial Assets and Liabilities in Foreign Currencies (Detail) € in Thousands, ₫ in Thousands, ฿ in Thousands, ৳ in Thousands, دج in Thousands, ¥ in Thousands, ¥ in Thousands, £ in Thousands, zł in Thousands, Tsh in Thousands, P in Thousands, K in Thousands, FRw in Thousands, $ in Thousands, $ in Thousands, $ in Thousands, in Thousands, in Thousands, in Thousands, ₩ in Millions

Dec. 31, 2020KRW (₩)

Dec. 31, 2020TZS (Tsh)

Dec. 31, 2020XAF ( )

Dec. 31, 2020SGD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2020XDR ( )

Dec. 31, 2020JPY (¥)

Dec. 31, 2020EUR (€)

Dec. 31, 2020PLN (zł)

Dec. 31, 2020VND (₫)

Dec. 31, 2020CNY (¥)

Dec. 31, 2020RWF (FRw)

Dec. 31, 2020THB (฿)

Dec. 31, 2020BWP (P)

Dec. 31, 2020HKD ($)

Dec. 31, 2019KRW (₩)

Dec. 31, 2019TZS (Tsh)

Dec. 31, 2019XAF ( )

Dec. 31, 2019USD ($)

Dec. 31, 2019XDR ( )

Dec. 31, 2019JPY (¥)

Dec. 31, 2019EUR (€)

Dec. 31, 2019BDT (৳)

Dec. 31, 2019VND (₫)

Dec. 31, 2019CNY (¥)

Dec. 31, 2019RWF (FRw)

Dec. 31, 2019MMK (K)

Dec. 31, 2019BWP (P)

Dec. 31, 2019HKD ($)

Dec. 31, 2019GBP (£)

Dec. 31, 2018TZS (Tsh)

Dec. 31, 2018XAF ( )

Dec. 31, 2018USD ($)

Dec. 31, 2018XDR ( )

Dec. 31, 2018JPY (¥)

Dec. 31, 2018EUR (€)

Dec. 31, 2018BDT (৳)

Dec. 31, 2018PLN (zł)

Dec. 31, 2018VND (₫)

Dec. 31, 2018DZD (دج)

Dec. 31, 2018CNY (¥)

Dec. 31, 2018UZS ( )

Dec. 31, 2018RWF (FRw)

Dec. 31, 2018MMK (K)

Dec. 31, 2018BWP (P)

Dec. 31, 2018GBP (£)

Disclosure of detailed information about financial instruments [line items]

Financial assets

₩ 10,476,853

₩ 11,000,665

Financial liabilities

₩ 14,597,106

₩ 16,128,644

Currency risk [Member]

Disclosure of detailed information about financial instruments [line items]

Financial assets

Tsh 1,019

16,229

$ 6

$ 400,046

255

¥ 209,376

€ 316

zł 26

₫ 242,370

¥ 458

FRw 646

฿ 535

P 212

Tsh 6,919

97,411

$ 645,941

255

¥ 24,930

€ 1

৳ 18,897

₫ 271,563

¥ 457

FRw 706

K 84

P 911

666

$ 528,539

267

¥ 66,078

€ 2

৳ 39,494

zł 26

₫ 467,272

دج 618

¥ 1,954

121,053

FRw 857

K 84

P 897

Financial liabilities

$ 284,000

$ 1,937,935

728

¥ 46,000,009

€ 162

¥ 491

$ 198

$ 1,830,764

729

¥ 80,000,000

€ 6

¥ 161

$ 268

£ 56

Tsh 2,876

$ 1,893,849

730

¥ 50,000,000

€ 6

¥ 171

£ 256

Financial Risk Management - S_3

Financial Risk Management - Summary of Maximum Exposure to Credit Risk (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about financial instruments [line items]
Maximum exposure to credit risk	₩ 10,731,034	₩ 10,873,266
Cash and cash equivalents (except for cash on hand) [member]
Disclosure of detailed information about financial instruments [line items]
Maximum exposure to credit risk	2,625,581	2,226,608
Financial assets at amortized costs [member]
Disclosure of detailed information about financial instruments [line items]
Maximum exposure to credit risk	5,034,621	5,784,228
Financial assets at fair value through other comprehensive income [member]
Disclosure of detailed information about financial instruments [line items]
Maximum exposure to credit risk	1,118,619	1,256,266
Contract assets [member]
Disclosure of detailed information about financial instruments [line items]
Maximum exposure to credit risk	586,438	557,041
Derivatives financial assets for hedging [member]
Disclosure of detailed information about financial instruments [line items]
Maximum exposure to credit risk	7,684	58,576
Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Maximum exposure to credit risk	680,453	541,657
Other financial assets at fair value through other comprehensive income [member]
Disclosure of detailed information about financial instruments [line items]
Maximum exposure to credit risk	6,570	7,086
Other financial assets at amortized costs [member]
Disclosure of detailed information about financial instruments [line items]
Maximum exposure to credit risk	₩ 671,068	₩ 441,804

Financial Risk Management - S_4

Financial Risk Management - Summary of Contractual Undiscounted Cash Flows (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Trade and other payables	₩ 7,576,809	₩ 9,324,730
Borrowings(including debentures)	8,205,838	8,216,212
Lease liabilities	1,143,640	1,211,352
Other non-derivative financial liabilities	131,816	196,475
Financial guarantee contracts	22,422	19,422
Total	17,122,317	19,064,221
Less than 1 year [member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Trade and other payables	6,587,796	8,149,445
Borrowings(including debentures)	1,573,944	1,304,936
Lease liabilities	336,024	397,609
Other non-derivative financial liabilities	574	1,749
Financial guarantee contracts	22,422	19,422
Total	8,520,760	9,873,161
1-5 years [member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Trade and other payables	730,758	805,241
Borrowings(including debentures)	4,373,534	4,417,639
Lease liabilities	658,501	688,518
Other non-derivative financial liabilities	131,242	175,764
Financial guarantee contracts
Total	5,894,035	6,087,162
More than 5 years [member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Trade and other payables	258,255	370,044
Borrowings(including debentures)	2,258,360	2,493,637
Lease liabilities	190,907	221,255
Other non-derivative financial liabilities		18,962
Financial guarantee contracts
Total	₩ 2,707,522	₩ 3,103,898

Financial Risk Management - S_5

Financial Risk Management - Summary of Cash Outflow and Inflow of Derivatives Settled Gross or Net are Undiscounted Contractual Cash Flow (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Outflow	₩ 2,925,965	₩ 2,760,957	₩ 2,439,559
Inflow	2,804,618	2,857,949	2,496,356
Less than 1 year [member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Outflow	248,300	650,497	455,343
Inflow	249,301	684,720	484,505
1-5 years [member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Outflow	2,179,046	1,602,513	1,466,915
Inflow	2,074,747	1,648,746	1,492,718
More than 5 years [member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Outflow	498,619	507,947	517,301
Inflow	₩ 480,570	₩ 524,483	₩ 519,133

Financial Risk Management - S_6

Financial Risk Management - Summary of Debt-to-equity Ratios (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure of detailed information about financial instruments [abstract]
Total liabilities	₩ 18,111,112	₩ 19,491,530
Total equity	₩ 15,551,433	₩ 15,140,684	₩ 14,658,490	₩ 13,183,354
Debt-to-equity ratio	116.00%	129.00%

Financial Risk Management - S_7

Financial Risk Management - Summary of Gearing Ratios (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure of detailed information about financial instruments [abstract]
Total borrowings	₩ 7,316,298	₩ 7,298,867
Less: cash and cash equivalents	(2,634,624)	(2,305,894)	₩ (2,703,422)	₩ (1,928,182)
Net debt	4,681,674	4,992,973
Total equity	15,551,433	15,140,684	₩ 14,658,490	₩ 13,183,354
Total capital	₩ 20,233,107	₩ 20,133,657
Gearing ratio	23.00%	25.00%

Financial Risk Management - S_8

Financial Risk Management - Summary of Group's Recognized Financial Assets Subject to Enforceable Master Netting Arrangements or Similar Agreements (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of offsetting of financial assets [line items]
Gross assets		₩ 85,058
Gross liabilities offset		(14)
Net amounts presented in the statement of financial position		85,044
Amounts not offset, Financial instruments		(82,130)
Amounts not offset, Cash collateral		0
Net amount		2,914
Trade receivables [member]
Disclosure of offsetting of financial assets [line items]
Gross assets	₩ 71,497	66,487
Gross liabilities offset	(1)	(1)
Net amounts presented in the statement of financial position	71,496	66,486
Amounts not offset, Financial instruments	(67,421)	(63,604)
Amounts not offset, Cash collateral	0	0
Net amount	₩ 4,075	2,882
Other Financial Assets1 [member]
Disclosure of offsetting of financial assets [line items]
Gross assets		18,571
Gross liabilities offset		(13)
Net amounts presented in the statement of financial position		18,558
Amounts not offset, Financial instruments		(18,526)
Amounts not offset, Cash collateral		0
Net amount		₩ 32

Financial Risk Management - S_9

Financial Risk Management - Summary of Group's Recognized Financial Liabilities Subject to Enforceable Master Netting Arrangements or Similar Agreements (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of offsetting of financial liabilities [Line Items]
Gross liabilities	₩ 69,362	₩ 84,178
Gross assets offset	(1)	(14)
Net amounts presented in the statement of financial position	69,361	84,164
Amounts not offset, Financial instruments	(67,421)	(82,130)
Amounts not offset, Cash collateral	0	0
Net amount	1,940	2,034
Trade payables [member]
Disclosure of offsetting of financial liabilities [Line Items]
Gross liabilities	69,361	65,669
Gross assets offset		(13)
Net amounts presented in the statement of financial position	69,361	65,656
Amounts not offset, Financial instruments	(67,421)	(63,628)
Amounts not offset, Cash collateral	0	0
Net amount	1,940	2,028
Other [member]
Disclosure of offsetting of financial liabilities [Line Items]
Gross liabilities	1	18,509
Gross assets offset	(1)	(1)
Net amounts presented in the statement of financial position		18,508
Amounts not offset, Financial instruments		(18,502)
Amounts not offset, Cash collateral	₩ 0	0
Net amount		₩ 6

Fair Value - Summary of Carryin

Fair Value - Summary of Carrying Amount and Fair Value of Financial Instruments by Category (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about financial instruments [line items]
Financial assets	₩ 10,476,853	₩ 11,000,665
Financial liabilities	14,597,106	16,128,644
Trade and other payables [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	7,017,639	8,679,698
Borrowings [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	7,316,298	7,298,867
Financial Liabilities At Amortized Costs [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	132,558	129,945
Financial liabilities designated as at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	2,682	38
Derivative financial liabilities for hedging [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	127,929	20,096
Cash and cash equivalents [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	2,634,624	2,305,894
Financial assets at amortized costs [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	4,976,423	5,748,459
Financial assets at fair value through other comprehensive income [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	1,118,619	1,256,266
Other financial assets at amortized costs [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	671,068	441,804
Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	809,919	632,324
Other financial assets at fair value through other comprehensive income [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	258,516	557,342
Derivatives financial assets for hedging [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	7,684	58,576
Fair value [member] | Trade and other payables [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	1	1
Fair value [member] | Borrowings [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	1	1
Fair value [member] | Financial Liabilities At Amortized Costs [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	1	1
Fair value [member] | Financial liabilities designated as at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	2,682	38
Fair value [member] | Derivative financial liabilities for hedging [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	127,929	20,096
Fair value [member] | Cash and cash equivalents [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	1	1
Fair value [member] | Financial assets at amortized costs [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	1	1
Fair value [member] | Financial assets at fair value through other comprehensive income [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	1,118,619	1,256,266
Fair value [member] | Other financial assets at amortized costs [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	1	1
Fair value [member] | Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	809,919	632,324
Fair value [member] | Other financial assets at fair value through other comprehensive income [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	258,516	557,342
Fair value [member] | Derivatives financial assets for hedging [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	₩ 7,684	₩ 58,576

Fair Value - Summary of Fair Va

Fair Value - Summary of Fair Value Non of Financial Instruments (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about financial instruments [line items]
Non financial assets	₩ 4,840,220	₩ 4,809,091
Non financial liabilities	130,611	20,134
Level 1 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	52,055	6,970
Non financial liabilities	0
Level 2 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	1,659,385	1,942,555
Non financial liabilities	123,780	20,134
Level 3 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	3,128,780	2,859,566
Non financial liabilities	6,831	0
Financial assets at fair value through other comprehensive income [member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	1,118,619	1,256,266
Financial assets at fair value through other comprehensive income [member] | Level 1 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets		0
Financial assets at fair value through other comprehensive income [member] | Level 2 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	1,118,619	1,256,266
Financial assets at fair value through other comprehensive income [member] | Level 3 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets		0
Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	809,919	632,324
Financial assets at fair value through profit or loss [member] | Level 1 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	46,449	232
Non financial liabilities	0
Financial assets at fair value through profit or loss [member] | Level 2 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	330,961	136,951
Financial assets at fair value through profit or loss [member] | Level 3 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	432,509	495,141
Non financial liabilities		0
Other financial assets at fair value through other comprehensive income [member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	258,516	557,342
Other financial assets at fair value through other comprehensive income [member] | Level 1 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	5,606	6,738
Other financial assets at fair value through other comprehensive income [member] | Level 2 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	202,121	508,550
Other financial assets at fair value through other comprehensive income [member] | Level 3 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	50,789	42,054
Derivative financial assets for hedging [member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	7,684	58,576
Derivative financial assets for hedging [member] | Level 2 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	7,684	40,788
Derivative financial assets for hedging [member] | Level 3 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets		17,788
Investment Properties [member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	2,645,482	2,304,583
Investment Properties [member] | Level 1 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets		0
Investment Properties [member] | Level 2 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets		0
Investment Properties [member] | Level 3 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets	2,645,482	2,304,583
Other financial liabilities at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Non financial liabilities	2,682	38
Other financial liabilities at fair value through profit or loss [member] | Level 2 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial liabilities	45	38
Other financial liabilities at fair value through profit or loss [member] | Level 3 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial liabilities	2,637
Derivative financial liabilities for hedging [member]
Disclosure of detailed information about financial instruments [line items]
Non financial liabilities	127,929	20,096
Derivative financial liabilities for hedging [member] | Level 1 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial assets		0
Non financial liabilities	0
Derivative financial liabilities for hedging [member] | Level 2 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial liabilities	123,735	20,096
Derivative financial liabilities for hedging [member] | Level 3 [Member]
Disclosure of detailed information about financial instruments [line items]
Non financial liabilities	₩ 4,194	₩ 0

Fair Value - Summary of Changes

Fair Value - Summary of Changes in Level 3 of Fair Value Hierarchy for Recurring Fair Value Measurements (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about financial instruments [line items]
Beginning balance	₩ 11,000,665
Ending balance	10,476,853	₩ 11,000,665
Beginning balance	16,128,644
Ending balance	14,597,106	16,128,644
Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Beginning balance	632,324
Ending balance	809,919	632,324
Level 3 [Member] | Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Disposal		(9,734)
Recurring fair value measurement [Member] | Level 3 [Member] | Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Beginning balance	495,141
Purchases	374,259
Reclassification	208
Disposal	(451,663)	(485,419)
Amount recognized in profit or loss	14,564
Ending balance	432,509	495,141
Recurring fair value measurement [Member] | Level 3 [Member] | Derivative financial liabilities [member]
Disclosure of detailed information about financial instruments [line items]
Beginning balance	17,788	(10,183)
Amount recognized in profit or loss		14,462
Amount recognized in other comprehensive income		13,509
Ending balance		17,788
Beginning balance	(17,788)
Amount recognized in profit or loss	29,345
Amount recognized in other comprehensive income	(7,363)
Ending balance	4,194	(17,788)
Recurring fair value measurement [Member] | Level 3 [Member] | Financial liabilities designated as at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Beginning balance		7,758
Amount recognized in profit or loss	(161)	1,976
Recurring fair value measurement [Member] | Level 3 [Member] | Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [line items]
Beginning balance	495,141	163,600
Purchases		584,671
Reclassification		225,873
Amount recognized in profit or loss		6,416
Ending balance		495,141
Purchases	2,798
Ending balance	2,637
Recurring fair value measurement [Member] | Level 3 [Member] | Financial assets at fair value through other comprehensive income [member]
Disclosure of detailed information about financial instruments [line items]
Beginning balance	42,054	311,536
Purchases	13,142	6,081
Reclassification		(444,782)
Disposal	(571)	(941)
Amount recognized in profit or loss	(428)
Amount recognized in other comprehensive income	(3,408)	170,160
Ending balance	₩ 50,789	₩ 42,054

Fair Value - Summary of Valuati

Fair Value - Summary of Valuation Techniques and Inputs (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets
Financial assets at fair value through other comprehensive income	₩ 258,516	₩ 557,342
Other financial assets
Financial assets at fair value through profit or loss	809,919	632,324
Derivative financial assets for hedging	7,684	58,576
Investment properties	1,368,453	1,387,430	₩ 1,091,084
Other financial liabilities
Financial liabilities at fair value through profit or loss	2,682	38
Derivative financial liabilities for hedging	127,929	20,096
Level 2 [Member]
Other financial assets
Derivative financial assets for hedging	₩ 7,684	₩ 58,576
Other financial liabilities
Valuation techniques	DCF Model
Valuation techniques		DCF Model
Level 2 [Member] | Financial assets at fair value through profit or loss [member]
Other financial liabilities
Valuation techniques		DCF Model
Level 2 [Member] | Financial assets at fair value through other comprehensive income [member]
Other financial liabilities
Valuation techniques	DCF Model	DCF Model
Level 2 [Member] | Financial assets at fair value through other comprehensive income [member] | Trades and other receivables [member]
Assets
Financial assets at fair value through other comprehensive income	₩ 1,118,619	₩ 1,256,266
Level 2, 3 [Member]
Other financial liabilities
Derivative financial liabilities for hedging	₩ 127,929	20,096
Valuation techniques	Hull-White model, DCF Model
Level 2, 3 [Member] | Financial assets at fair value through profit or loss [member]
Other financial assets
Financial assets at fair value through profit or loss	₩ 763,470	₩ 632,092
Other financial liabilities
Valuation techniques	DCF Model, Adjusted net asset model	DCF Model, Adjusted net asset model
Valuation techniques	DCF Model, Binomial Option Pricing
Level 2, 3 [Member] | Financial assets at fair value through other comprehensive income [member]
Assets
Financial assets at fair value through other comprehensive income	₩ 252,910	₩ 550,604
Other financial liabilities
Valuation techniques	DCF Model, Comparable Company Analysis	DCF Model, Comparable Company Analysis
Level 3 [Member]
Other financial assets
Investment properties	₩ 2,645,482	₩ 2,304,583
Other financial liabilities
Valuation techniques	DCF Model	DCF Model
Level 3 [Member] | Financial assets at fair value through profit or loss [member]
Other financial liabilities
Financial liabilities at fair value through profit or loss	₩ 2,682	₩ 38

Fair Value - Summary of Details

Fair Value - Summary of Details and Changes of Total Deferred Difference (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about financial instruments [line items]
Beginning balance	₩ 11,000,665
Recognized at fair value through profit or loss	(809,919)	₩ (632,324)
Ending balance	10,476,853	11,000,665
Beginning balance	16,128,644
Recognized at fair value through profit or loss	2,682	38
Ending balance	14,597,106	16,128,644
Derivatives held for trading [member]
Disclosure of detailed information about financial instruments [line items]
Beginning balance	0	(2,824)
New transactions	0	0
Recognized at fair value through profit or loss	0	2,824
Ending balance	0	0
Derivatives used for hedging [member]
Disclosure of detailed information about financial instruments [line items]
Beginning balance	3,682	5,107
New transactions	0	0
Recognized at fair value through profit or loss		(1,425)
Ending balance	₩ 2,257	₩ 3,682

Interests in Unconsolidated S_3

Interests in Unconsolidated Structured Entities - Summary of Unconsolidated Structured Entities and Nature of Risks (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of unconsolidated structured entities [line items]
Other financial assets	₩ 1,747,187	₩ 1,690,046
Joint ventures and associates	557,881	267,660
Real Estate Finance [member]
Disclosure of unconsolidated structured entities [line items]
Total assets of unconsolidated structured entities	2,004,869	1,595,895
Other financial assets	29,874	15,816
Joint ventures and associates	51,607	8,542
Total	81,481	24,358
Maximum loss exposure Investment assets	81,481	24,358
PEF &Investment Fund [member]
Disclosure of unconsolidated structured entities [line items]
Total assets of unconsolidated structured entities	4,380,534	4,060,992
Other financial assets	128,332	100,496
Joint ventures and associates	219,753	192,022
Total	348,085	292,518
Maximum loss exposure Investment assets	348,085	292,518
Cash deficiency support	29,130
Asset Securitization [member]
Disclosure of unconsolidated structured entities [line items]
Total assets of unconsolidated structured entities	2,152,412	2,562,931
Unconsolidated structured entities [member]
Disclosure of unconsolidated structured entities [line items]
Total assets of unconsolidated structured entities	8,537,815	8,219,818
Other financial assets	158,206	116,312
Joint ventures and associates	271,360	200,564
Total	429,566	316,876
Maximum loss exposure Investment assets	429,566	₩ 316,876
Cash deficiency support	₩ 29,130

Information About Non-control_3

Information About Non-controlling Interests - Summary of Changes in Accumulated Non-controlling Interests (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of subsidiaries [line items]
Accumulated non-controlling interests at the beginning of the year	₩ 1,520,160
Profit or loss allocated to non-controlling interests	45,367	₩ 50,165	₩ 73,841
Accumulated non-controlling interests at the end of the year	₩ 1,539,989	₩ 1,520,160
KT Skylife Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Non-controlling Interests rate(%)	49.70%	49.70%	49.70%
Accumulated non-controlling interests at the beginning of the year	₩ 375,906	₩ 374,150	₩ 328,302
Profit or loss allocated to non-controlling interests	22,171	10,029	23,405
Dividend paid to non-controlling interests	(8,279)	(8,279)	(8,279)
Others	(898)	6	30,722
Accumulated non-controlling interests at the end of the year	₩ 388,900	₩ 375,906	₩ 374,150
BC Card Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Non-controlling Interests rate(%)	30.50%	30.50%	30.50%
Accumulated non-controlling interests at the beginning of the year	₩ 417,475	₩ 345,547	₩ 339,067
Profit or loss allocated to non-controlling interests	9,899	37,795	28,418
Dividend paid to non-controlling interests	(22,787)	(18,900)	(35,924)
Others	7,239	53,033	13,986
Accumulated non-controlling interests at the end of the year	₩ 411,826	₩ 417,475	₩ 345,547
KT Powertel Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Non-controlling Interests rate(%)	55.20%	55.20%	55.20%
Accumulated non-controlling interests at the beginning of the year	₩ 54,276	₩ 52,865	₩ 53,053
Profit or loss allocated to non-controlling interests	2,151	1,751	(3,058)
Dividend paid to non-controlling interests	(478)
Others	(202)	(340)	2,870
Accumulated non-controlling interests at the end of the year	₩ 55,747	₩ 54,276	₩ 52,865
KT Hitel Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Non-controlling Interests rate(%)	32.90%	32.90%	32.90%
Accumulated non-controlling interests at the beginning of the year	₩ 54,709	₩ 52,336	₩ 53,146
Profit or loss allocated to non-controlling interests	(1,840)	1,720	454
Others	(2,563)	653	(1,264)
Accumulated non-controlling interests at the end of the year	₩ 50,306	₩ 54,709	₩ 52,336
KT Telecop Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Non-controlling Interests rate(%)	13.20%	13.20%	13.20%
Accumulated non-controlling interests at the beginning of the year	₩ 3,650	₩ 103,357	₩ 103,468
Profit or loss allocated to non-controlling interests	152	(588)	59
Others	(208)	(99,119)	(170)
Accumulated non-controlling interests at the end of the year	₩ 3,594	₩ 3,650	₩ 103,357

Information About Non-control_4

Information About Non-controlling Interests - Summary of Financial Information on Subsidiaries (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure of subsidiaries [line items]
Current assets	₩ 11,154,180	₩ 11,975,659
Non-current assets	22,508,365	22,656,555
Current liabilities	9,192,472	10,148,054
Non-current liabilities	8,918,640	9,343,476
Equity	15,551,433	15,140,684	₩ 14,658,490	₩ 13,183,354
Operating revenue	24,440,647	24,899,189	23,436,050
Profit or loss for the year	746,256	695,868	719,412
Total comprehensive income (loss)	769,511	868,206	664,784
Cash flows from operating activities	4,739,827	3,745,173	4,010,464
Cash flows from investing activities	(3,761,470)	(3,887,472)	(2,704,130)
Cash flows from financing activities	(647,585)	(249,748)	(531,675)
Net (decrease)/increase in cash and cash equivalents	328,730	(397,528)	775,240
Cash and cash equivalents at beginning of year	2,305,894	2,703,422	1,928,182
Exchange differences	(2,042)	(5,481)	581
Cash and cash equivalents at end of year	₩ 2,634,624	₩ 2,305,894	₩ 2,703,422
KT Skylife Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Non-controlling Interests rate (%)	49.70%	49.70%	49.70%
Current assets	₩ 480,450	₩ 459,077	₩ 301,739
Non-current assets	439,026	389,199	514,263
Current liabilities	153,236	123,506	112,411
Non-current liabilities	21,803	19,333	37,430
Equity	744,437	705,437	666,161
Operating revenue	706,631	704,996	694,059
Profit or loss for the year	58,190	56,008	52,010
Total comprehensive income (loss)	55,647	55,936	47,787
Cash flows from operating activities	160,934	152,549	183,474
Cash flows from investing activities	(105,293)	(101,594)	(139,846)
Cash flows from financing activities	(19,650)	(18,833)	(77,647)
Net (decrease)/increase in cash and cash equivalents	35,991	32,122	(34,019)
Cash and cash equivalents at beginning of year	63,850	31,728	65,747
Exchange differences	(7)	0
Cash and cash equivalents at end of year	₩ 99,834	₩ 63,850	₩ 31,728
BC Card Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Non-controlling Interests rate (%)	30.50%	30.50%	30.50%
Current assets	₩ 1,785,914	₩ 2,580,634	₩ 2,997,429
Non-current assets	1,298,484	1,332,348	724,950
Current liabilities	1,602,667	2,452,219	2,520,050
Non-current liabilities	176,083	142,013	110,486
Equity	1,305,648	1,318,750	1,091,843
Operating revenue	3,387,640	3,553,008	3,551,715
Profit or loss for the year	39,455	115,885	70,889
Total comprehensive income (loss)	61,796	289,122	116,604
Cash flows from operating activities	(119,163)	429,331	86,299
Cash flows from investing activities	58,042	(419,894)	128,538
Cash flows from financing activities	22,790	(5,744)	(117,561)
Net (decrease)/increase in cash and cash equivalents	(38,331)	3,693	97,276
Cash and cash equivalents at beginning of year	279,162	275,089	177,826
Exchange differences	(247)	380	(13)
Cash and cash equivalents at end of year	₩ 240,584	₩ 279,162	₩ 275,089
KT Powertel Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Non-controlling Interests rate (%)	55.20%	55.20%	55.20%
Current assets	₩ 90,056	₩ 86,465	₩ 84,785
Non-current assets	29,638	31,587	39,279
Current liabilities	17,045	17,757	27,187
Non-current liabilities	1,788	2,009	1,030
Equity	100,861	98,286	95,847
Operating revenue	65,897	62,846	65,620
Profit or loss for the year	3,809	3,085	(5,545)
Total comprehensive income (loss)	3,442	2,469	(5,792)
Cash flows from operating activities	6,011	780	11,603
Cash flows from investing activities	(3,353)	(9,525)	(2,580)
Cash flows from financing activities	(1,515)	(687)
Net (decrease)/increase in cash and cash equivalents	1,143	(9,432)	9,023
Cash and cash equivalents at beginning of year	6,217	15,649	6,626
Exchange differences	0	0
Cash and cash equivalents at end of year	₩ 7,360	₩ 6,217	₩ 15,649
KT Hitel Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Non-controlling Interests rate (%)	32.90%	32.90%	32.90%
Current assets	₩ 140,948	₩ 115,694	₩ 161,162
Non-current assets	148,001	164,124	111,546
Current liabilities	74,045	62,378	63,231
Non-current liabilities	18,554	12,391	2,812
Equity	196,350	205,049	206,665
Operating revenue	350,231	323,065	279,117
Profit or loss for the year	2,080	1,426	657
Total comprehensive income (loss)	(8,700)	(1,840)	738
Cash flows from operating activities	62,521	49,870	43,855
Cash flows from investing activities	(58,186)	(50,138)	(26,335)
Cash flows from financing activities	(1,856)	(1,860)
Net (decrease)/increase in cash and cash equivalents	2,479	(2,128)	17,520
Cash and cash equivalents at beginning of year	37,043	39,186	21,647
Exchange differences	(83)	(15)	19
Cash and cash equivalents at end of year	₩ 39,439	₩ 37,043	₩ 39,186
KT Telecop Co., Ltd. [member]
Disclosure of subsidiaries [line items]
Non-controlling Interests rate (%)	13.20%	13.20%	13.20%
Current assets	₩ 79,076	₩ 55,908	₩ 52,367
Non-current assets	239,380	223,969	220,125
Current liabilities	136,565	64,218	85,648
Non-current liabilities	57,172	89,622	54,666
Equity	124,719	126,037	132,178
Operating revenue	392,489	332,063	328,262
Profit or loss for the year	212	(4,875)	166
Total comprehensive income (loss)	(1,319)	(6,558)	(1,517)
Cash flows from operating activities	35,834	52,693	40,351
Cash flows from investing activities	(57,976)	(44,393)	(76,969)
Cash flows from financing activities	14,652	(5,227)	10,000
Net (decrease)/increase in cash and cash equivalents	(7,490)	3,073	(26,618)
Cash and cash equivalents at beginning of year	8,781	5,708	32,326
Exchange differences	0	0
Cash and cash equivalents at end of year	₩ 1,291	₩ 8,781	₩ 5,708

Information About Non-control_5

Information About Non-controlling Interests - Summary of Changes in Ownership Interest on the Equity Attributable to Owners (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of subsidiaries [abstract]
Carrying amount of non-controlling interests acquired	₩ 1,750	₩ (9,566)	₩ (194)
Consideration paid to non-controlling interests	9,878	484	11,312
Excess of consideration paid recognized in parent's equity	₩ 11,628	₩ (9,082)	₩ 11,118

Business Combination - Addition

Business Combination - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Apr. 30, 2020
Disclosure of detailed information about business combination [Line Items]
identifiable intangible assets generated	₩ 410
Goodwill generated	407
operating income of combined entity	250,380
net loss of combined entity	1,948
operating income	387,697
net loss	8,461
KT Engineering Co Ltd [Member]
Disclosure of detailed information about business combination [Line Items]
Number of shares acquired		1,400,000
Percentage of ownership interest		59.80%
KT Estate [Member]
Disclosure of detailed information about business combination [Line Items]
Number of shares acquired		940,000
Percentage of ownership interest		40.20%
Business combinations [member]
Disclosure of detailed information about business combination [Line Items]
identifiable intangible assets generated	3
Goodwill generated	₩ 407

Business Combination - Schedule

Business Combination - Schedule of Fair Value of Assets and Liabilities Recognized as a Result of Acquisition at Acquisition Date (Detail) ₩ in Millions	Dec. 31, 2020KRW (₩)
Disclosure of detailed information about business combination [Line Items]
Total transfer cost (a)	₩ 46,800
Recognized amount of assets acquired and liabilities assumed (b)	46,393
Cash and cash equivalents	57,845
Trade and other receivables	95,814
Other financial assets	3,110
Other assets	14,021
Inventories	1,521
Property and equipment	3,128
Intangible assets	410
Trade and other payables	(105,964)
Other liabilities	(4,815)
Current income tax liabilities	(3,664)
Other provisions	(13,745)
Retirement benefit liabilities	(1,268)
Goodwill	₩ 407

Changes in Accounting Policie_3

Changes in Accounting Policies - Determination of Lease Term Considering Economic Penalty - Summary of Impact on Consolidated Financial Statements Due to Application of accounting policy (Detail) - KRW (₩) ₩ / shares in Units, ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current assets
Prepaid expenses	₩ 66,578	₩ 84,768
Non-current assets
Right-of-use assets	1,217,179	1,268,329
Current liabilities
Lease liabilities		392,433
Non-current liabilities
Lease liabilities		818,919
Total liabilities	18,111,112	19,491,530
Retained earnings	12,155,420	11,590,916
Total equity	15,551,433	15,140,684	₩ 14,658,490	₩ 13,183,354
Operating revenue	24,440,647	24,899,189	23,436,050
Operating expenses	23,418,314	23,872,219	22,335,190
Finance income	498,614	424,395	374,243
Financial costs	507,383	432,133	435,659
Income tax expense	285,349	320,060	314,565
Profit for the year	₩ 746,256	₩ 695,868	₩ 719,412
Basic earnings per share	₩ 2,858	₩ 2,634	₩ 2,634
Diluted earnings per share	₩ 2,858	₩ 2,632	₩ 2,634
Adjustment on Accounting policy
Current assets
Prepaid expenses	₩ (2,119)	₩ (1,026)
Non-current assets
Right-of-use assets	632,145	479,832
Current liabilities
Lease liabilities	63,263	36,600
Non-current liabilities
Lease liabilities	566,532	445,612
Total liabilities	629,795	482,212
Retained earnings	232	(3,406)
Total equity	232	(3,406)
Operating revenue	5,796
Operating expenses	(7,063)	(6,796)
Financial costs	9,222	10,202
Profit for the year	₩ 3,637	₩ (3,406)
Basic earnings per share	₩ 15	₩ (14)
Diluted earnings per share	₩ 18	₩ (14)
Previously stated [member]
Current assets
Prepaid expenses	₩ 61,930	₩ 76,036
Non-current assets
Right-of-use assets	585,034	788,497
Current liabilities
Lease liabilities	281,961	355,833
Non-current liabilities
Lease liabilities	798,416	373,307
Total liabilities	513,845	729,140
Retained earnings	12,155,188	11,594,322
Total equity	12,155,188	11,594,322
Operating revenue	24,434,851	24,899,189
Operating expenses	23,425,377	23,879,015
Finance income	498,614	424,395
Financial costs	498,161	421,931
Income tax expense	285,349	320,060
Profit for the year	₩ 742,619	₩ 699,274
Basic earnings per share	₩ 2,843	₩ 2,648
Diluted earnings per share	₩ 2,840	₩ 2,646
Adjustment on Accounting policy
Current assets
Prepaid expenses	₩ 59,811	₩ 75,010
Non-current assets
Right-of-use assets	1,217,179	1,268,329
Current liabilities
Lease liabilities	345,224	392,433
Non-current liabilities
Lease liabilities	798,416	818,919
Total liabilities	1,143,640	1,211,352
Retained earnings	12,155,420	11,590,916
Total equity	12,155,420	11,590,916
Operating revenue	24,440,647	24,899,189
Operating expenses	23,418,314	23,872,219
Finance income	498,614	424,395
Financial costs	507,383	432,133
Income tax expense	285,349	320,060
Profit for the year	₩ 746,256	₩ 695,868
Basic earnings per share	₩ 2,858	₩ 2,634
Diluted earnings per share	₩ 2,858	₩ 2,632

Changes in Accounting Policie_4

Changes in Accounting Policies - Determination of Lease Term Considering Economic Penalty - Additional Information (Detail) ₩ in Millions	Jan. 01, 2019KRW (₩)
Increase (decrease) due to changes in accounting policy [member]
Disclosure of reclassifications or changes in presentation [line items]
Increase (decrease) through changes in accounting policy, right of use assets	₩ 128,035
Increase (decrease) through changes in accounting policy, lease liabilities	128,035
IFRS 16 [Member]
Disclosure of reclassifications or changes in presentation [line items]
Increase (decrease) through changes in accounting policy, right of use assets	899,783
Increase (decrease) through changes in accounting policy, lease liabilities	₩ 643,375

Events after Reporting Period -

Events after Reporting Period - Summary of Public Bonds Issued After Reporting Period (Detail) ₩ in Millions	12 Months Ended
	Dec. 31, 2020KRW (₩)
Disclosure of non-adjusting events after reporting period [line items]
Interest rate	0.00%
Redemption date	Jun. 5, 2025
Gross carrying amount [member] | The 194-1st Public bond, January Twenty six, twenty twenty four [member]
Disclosure of non-adjusting events after reporting period [line items]
Issue date	Jan. 27, 2021
Carrying amount	₩ 130,000
Interest rate	1.13%
Redemption date	Jan. 26, 2024
Gross carrying amount [member] | The 194-2nd Public bond, January twenty seven, twenty twenty six [member]
Disclosure of non-adjusting events after reporting period [line items]
Issue date	Jan. 27, 2021
Carrying amount	₩ 140,000
Interest rate	1.45%
Redemption date	Jan. 27, 2026
Gross carrying amount [member] | The194-3rd Public bond, January twenty seven, twenty thirty one [member]
Disclosure of non-adjusting events after reporting period [line items]
Issue date	Jan. 27, 2021
Carrying amount	₩ 50,000
Interest rate	1.85%
Redemption date	Jan. 27, 2031
Gross carrying amount [member] | The194-4th Public bond, January twenty five, twenty forty one [member]
Disclosure of non-adjusting events after reporting period [line items]
Issue date	Jan. 27, 2021
Carrying amount	₩ 80,000
Interest rate	1.98%
Redemption date	Jan. 25, 2041