UDR (UDR) 10-Q 27 Oct 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Oct. 25, 2021
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2021
Entity File Number	1-10524
Entity Registrant Name	UDR, Inc.
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	54-0857512
Entity Address, Address Line One	1745 Shea Center Drive, Suite 200
Entity Address, City or Town	Highlands Ranch
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80129
City Area Code	720
Local Phone Number	283-6120
Title of 12(b) Security	Common Stock, par value $0.01
Trading Symbol	UDR
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		309,186,379
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Central Index Key	0000074208
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Real estate owned:
Real estate held for investment	$ 13,902,872	$ 12,706,940
Less: accumulated depreciation	(4,983,109)	(4,590,577)
Real estate held for investment, net	8,919,763	8,116,363
Real estate under development (net of accumulated depreciation of $445 and $1,010, respectively)	331,200	246,867
Real estate held for disposition (net of accumulated depreciation of $34,387 and $13,779, respectively)	39,065	102,876
Total real estate owned, net of accumulated depreciation	9,290,028	8,466,106
Cash and cash equivalents	1,063	1,409
Restricted cash	28,170	22,762
Notes receivable, net	25,741	157,992
Investment in and advances to unconsolidated joint ventures, net	643,902	600,233
Operating lease right-of-use assets	198,339	200,913
Other assets	213,321	188,118
Total assets	10,400,564	9,637,533
Liabilities:
Secured debt, net	1,058,647	862,147
Unsecured debt, net	4,463,792	4,114,401
Operating lease liabilities	193,277	195,592
Real estate taxes payable	55,849	29,946
Accrued interest payable	25,674	44,760
Security deposits and prepaid rent	51,631	49,008
Distributions payable	120,830	115,795
Accounts payable, accrued expenses, and other liabilities	114,601	110,999
Total liabilities	6,084,301	5,522,648
Commitments and contingencies (Note 13)
Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	1,192,723	856,294
Equity:
Common stock, $0.01 par value; 450,000,000 shares authorized: 308,287,019 and 296,611,579 shares issued and outstanding at September 30, 2021 and December 31, 2020, respectively	3,083	2,966
Additional paid-in capital	6,390,547	5,881,383
Distributions in excess of net income	(3,335,108)	(2,685,770)
Accumulated other comprehensive income/(loss), net	(6,600)	(9,144)
Total stockholders' equity	3,096,687	3,234,200
Noncontrolling interests	26,853	24,391
Total equity	3,123,540	3,258,591
Total liabilities and equity	10,400,564	9,637,533
8.00% Series E Cumulative Convertible Preferred Stock
Equity:
Preferred stock, no par value; 50,000,000 shares authorized:	44,764	44,764
Series F
Equity:
Preferred stock, no par value; 50,000,000 shares authorized:	$ 1	$ 1

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Real estate owned:
Real estate under development accumulated depreciation	$ 445	$ 1,010
Real estate held for disposition accumulated depreciation	$ 34,387	$ 13,779
Equity:
Preferred stock, no par value	$ 0	$ 0
Preferred stock, shares authorized	50,000,000	50,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	450,000,000
Common stock, shares issued	308,287,019	296,611,579
Common stock, shares outstanding	308,287,019	296,611,579
8.00% Series E Cumulative Convertible Preferred Stock
Equity:
Preferred stock, dividend rate percentage	8.00%	8.00%
Preferred stock, shares issued	2,695,363	2,695,363
Preferred stock, shares outstanding	2,695,363	2,695,363
Series F
Equity:
Preferred stock, shares issued	14,331,810	14,440,519
Preferred stock, shares outstanding	14,331,810	14,440,519

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
REVENUES:
Rental income	$ 328,699	$ 308,845	$ 937,641	$ 934,920
Joint venture management and other fees	$ 1,071	$ 1,199	$ 4,918	$ 3,861
Type of revenue	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember
Total revenues	$ 329,770	$ 310,044	$ 942,559	$ 938,781
OPERATING EXPENSES:
Property operating and maintenance	57,708	53,385	160,424	151,585
Real estate taxes and insurance	51,511	44,328	148,043	134,485
Property management	9,861	8,879	28,129	26,879
Other operating expenses	4,237	5,543	13,045	16,609
Real estate depreciation and amortization	152,636	151,949	442,893	462,481
General and administrative	15,810	11,958	43,673	37,907
Casualty-related charges/(recoveries), net	1,568		4,682	1,353
Other depreciation and amortization	3,269	3,887	8,472	7,939
Total operating expenses	296,600	279,929	849,361	839,238
Gain/(loss) on sale of real estate owned			50,829	61,303
Operating income	33,170	30,115	144,027	160,846
Income/(loss) from unconsolidated entities	14,450	2,940	29,123	14,328
Interest expense	(36,289)	(62,268)	(149,849)	(140,182)
Interest income and other income/(expense), net	8,238	2,183	12,831	7,304
Income/(loss) before income taxes	19,569	(27,030)	36,132	42,296
Tax (provision)/benefit, net	(529)	(187)	(1,283)	(1,877)
Net income/(loss)	19,040	(27,217)	34,849	40,419
Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	(1,260)	1,990	(2,221)	(2,614)
Net (income)/loss attributable to noncontrolling interests	(49)	(31)	(73)	(71)
Net income/(loss) attributable to UDR, Inc.	17,731	(25,258)	32,555	37,734
Distributions to preferred stockholders - Series E (Convertible)	(1,058)	(1,051)	(3,171)	(3,179)
Net income/(loss) attributable to common stockholders	$ 16,673	$ (26,309)	$ 29,384	$ 34,555
Income/(loss) per weighted average common share - basic	$ 0.06	$ (0.09)	$ 0.10	$ 0.12
Income/(loss) per weighted average common share - diluted	$ 0.06	$ (0.09)	$ 0.10	$ 0.12
Weighted average number of common shares outstanding - basic	297,828	294,713	296,998	294,627
Weighted average number of common shares outstanding - diluted	301,164	295,003	298,045	294,938

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/(LOSS)
Net income/(loss)	$ 19,040	$ (27,217)	$ 34,849	$ 40,419
Other comprehensive income/(loss), including portion attributable to noncontrolling interests:
Unrealized holding gain/(loss)	1,389	(30)	1,422	(3,241)
(Gain)/loss reclassified into earnings from other comprehensive income/(loss)	441	1,585	1,314	3,234
Other comprehensive income/(loss), including portion attributable to noncontrolling interests	1,830	1,555	2,736	(7)
Comprehensive income/(loss)	20,870	(25,662)	37,585	40,412
Comprehensive (income)/loss attributable to noncontrolling interests	(1,437)	1,850	(2,486)	(2,724)
Comprehensive income/(loss) attributable to UDR, Inc.	$ 19,433	$ (23,812)	$ 35,099	$ 37,688

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Preferred Stock	Common Stock	Paid-in Capital	Distributions in Excess of Net Income [Member]Adjustment	Distributions in Excess of Net Income [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Noncontrolling Interest	Adjustment	Total
Consolidated Statements of Changes in Equity
Cumulative effect upon adoption of ASC 326	$ 46,201	$ 2,946	$ 5,781,975	$ (2,182)	$ (2,462,132)	$ (10,448)	$ 30,772	$ (2,182)	$ 3,389,314
Beginning Balance at Dec. 31, 2019	46,201	2,946	5,781,975	$ (2,182)	(2,462,132)	(10,448)	30,772	$ (2,182)	3,389,314
Consolidated Statements of Changes in Equity
Net income/(loss) attributable to UDR, Inc.					37,734				37,734
Net income/(loss) attributable to noncontrolling interests							24		24
Long Term Incentive Plan Unit grants/(vestings), net							(10,000)		(10,000)
Other comprehensive income/(loss)						(46)			(46)
Issuance/(forfeiture) of common and restricted shares, net		1	1,026						1,027
Conversion of Series E Cumulative Convertible Shares	(1,436)	1	1,435
Adjustment for conversion of noncontrolling interest of unitholders in the Operating Partnership and DownREIT Partnership		3	11,620						11,623
Common stock distributions declared					(318,442)				(318,442)
Repurchase of common shares		(6)	(19,789)						(19,795)
Preferred stock distributions declared-Series E					(3,179)				(3,179)
Adjustment to reflect redemption value of redeemable noncontrolling interests					247,374				247,374
Ending Balance at Sep. 30, 2020	44,765	2,945	5,776,267		(2,500,827)	(10,494)	20,796		3,333,452
Consolidated Statements of Changes in Equity
Cumulative effect upon adoption of ASC 326	44,765	2,951	5,794,428		(2,432,882)	(11,940)	17,623		3,414,945
Beginning Balance at Jun. 30, 2020	44,765	2,951	5,794,428		(2,432,882)	(11,940)	17,623		3,414,945
Consolidated Statements of Changes in Equity
Net income/(loss) attributable to UDR, Inc.					(25,258)				(25,258)
Net income/(loss) attributable to noncontrolling interests							15		15
Long Term Incentive Plan Unit grants/(vestings), net							3,158		3,158
Other comprehensive income/(loss)						1,446			1,446
Issuance/(forfeiture) of common and restricted shares, net			1,255						1,255
Adjustment for conversion of noncontrolling interest of unitholders in the Operating Partnership and DownREIT Partnership			373						373
Common stock distributions declared					(106,020)				(106,020)
Repurchase of common shares		(6)	(19,789)						(19,795)
Preferred stock distributions declared-Series E					(1,051)				(1,051)
Adjustment to reflect redemption value of redeemable noncontrolling interests					64,384				64,384
Ending Balance at Sep. 30, 2020	44,765	2,945	5,776,267		(2,500,827)	(10,494)	20,796		3,333,452
Consolidated Statements of Changes in Equity
Cumulative effect upon adoption of ASC 326	44,765	2,945	5,776,267		(2,500,827)	(10,494)	20,796		3,333,452
Cumulative effect upon adoption of ASC 326	44,765	2,966	5,881,383		(2,685,770)	(9,144)	24,391		3,258,591
Beginning Balance at Dec. 31, 2020	44,765	2,966	5,881,383		(2,685,770)	(9,144)	24,391		3,258,591
Consolidated Statements of Changes in Equity
Net income/(loss) attributable to UDR, Inc.					32,555				32,555
Net income/(loss) attributable to noncontrolling interests							57		57
Redemption of noncontrolling interests in consolidated real estate							(125)		(125)
Long Term Incentive Plan Unit grants/(vestings), net							2,530		2,530
Other comprehensive income/(loss)						2,544			2,544
Issuance/(forfeiture) of common and restricted shares, net		1	2,999						3,000
Issuance of common shares through public offering, net		114	499,223						499,337
Adjustment for conversion of noncontrolling interest of unitholders in the Operating Partnership and DownREIT Partnership		2	6,942						6,944
Common stock distributions declared					(327,015)				(327,015)
Preferred stock distributions declared-Series E					(3,171)				(3,171)
Adjustment to reflect redemption value of redeemable noncontrolling interests					(351,707)				(351,707)
Ending Balance at Sep. 30, 2021	44,765	3,083	6,390,547		(3,335,108)	(6,600)	26,853		3,123,540
Consolidated Statements of Changes in Equity
Cumulative effect upon adoption of ASC 326	44,765	2,968	5,887,838		(3,143,000)	(8,301)	20,903		2,805,173
Beginning Balance at Jun. 30, 2021	44,765	2,968	5,887,838		(3,143,000)	(8,301)	20,903		2,805,173
Consolidated Statements of Changes in Equity
Net income/(loss) attributable to UDR, Inc.					17,731				17,731
Net income/(loss) attributable to noncontrolling interests							41		41
Long Term Incentive Plan Unit grants/(vestings), net							5,909		5,909
Other comprehensive income/(loss)						1,701			1,701
Issuance/(forfeiture) of common and restricted shares, net			1,489						1,489
Issuance of common shares through public offering, net		114	499,616						499,730
Adjustment for conversion of noncontrolling interest of unitholders in the Operating Partnership and DownREIT Partnership		1	1,604						1,605
Common stock distributions declared					(111,755)				(111,755)
Preferred stock distributions declared-Series E					(1,058)				(1,058)
Adjustment to reflect redemption value of redeemable noncontrolling interests					(97,026)				(97,026)
Ending Balance at Sep. 30, 2021	44,765	3,083	6,390,547		(3,335,108)	(6,600)	26,853		3,123,540
Consolidated Statements of Changes in Equity
Cumulative effect upon adoption of ASC 326	$ 44,765	$ 3,083	$ 6,390,547		$ (3,335,108)	$ (6,600)	$ 26,853		$ 3,123,540

CONSOLIDATED STATEMENTS OF CH_2

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Common stock distributions declared per share	$ 0.3625	$ 0.36	$ 1.0875	$ 1.08
8.00% Series E Cumulative Convertible Preferred Stock
Preferred stock distributions declared	$ 0.3925	$ 0.3898	$ 1.1775	$ 1.1694

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating Activities
Net income/(loss)	$ 34,849	$ 40,419
Adjustments to reconcile net income/(loss) to net cash provided by/(used in) operating activities:
Depreciation and amortization	451,365	470,420
(Gain)/loss on sale of real estate owned	(50,829)	(61,303)
(Income)/loss from unconsolidated entities	(29,123)	(14,328)
Return on investment in unconsolidated joint ventures	19,402	1,832
Amortization of share-based compensation	17,473	15,086
Loss on extinguishment of debt, net	42,336	24,540
Other	15,102	4,771
Changes in operating assets and liabilities:
(Increase)/decrease in operating assets	(13,059)	(22,628)
Increase/(decrease) in operating liabilities	(4,347)	(2,217)
Net cash provided by/(used in) operating activities	483,169	456,592
Investing Activities
Acquisition of real estate assets	(904,434)	(157,101)
Proceeds from sales of real estate investments, net	154,857	133,934
Development of real estate assets	(119,254)	(88,261)
Capital expenditures and other major improvements - real estate assets	(112,001)	(105,257)
Capital expenditures - non-real estate assets	(10,087)	(11,345)
Investment in unconsolidated joint ventures	(67,665)	(66,893)
Distributions received from unconsolidated joint ventures	34,494	8,085
Purchase deposits on pending acquisitions	(10,000)	500
Repayment/(issuance) of notes receivable, net	112,815	(6,393)
Net cash provided by/(used in) investing activities	(921,275)	(292,731)
Financing Activities
Payments on secured debt	(818)	(358,098)
Proceeds from the issuance of secured debt		160,930
Payments on unsecured debt	(300,000)	(116,894)
Net proceeds from the issuance of unsecured debt	511,552	610,896
Net proceeds/(repayment) of commercial paper	125,000	(70,000)
Net proceeds/(repayment) of revolving bank debt	15,062	5,503
Proceeds from the issuance of common shares through public offering, net	499,337
Repurchase of common shares		(19,795)
Distributions paid to redeemable noncontrolling interests	(25,275)	(23,913)
Distributions paid to preferred stockholders	(3,160)	(3,150)
Distributions paid to common stockholders	(322,041)	(313,326)
Payment of prepayment and extinguishment costs	(40,769)	(35,495)
Other	(15,720)	(9,610)
Net cash provided by/(used in) financing activities	443,168	(172,952)
Net increase/(decrease) in cash, cash equivalents, and restricted cash	5,062	(9,091)
Cash, cash equivalents, and restricted cash, beginning of year	24,171	33,291
Cash, cash equivalents, and restricted cash, end of period	29,233	24,200
Supplemental Information:
Interest paid during the period, net of amounts capitalized	126,209	132,147
Operating cash flows from operating leases	9,377	9,377
Cash paid/(refunds received) for income taxes	3,909	864
Non-cash transactions:
Secured debt assumed upon acquisition of real estate assets	201,296
Acquisition of land parcel pursuant to a deed in lieu of foreclosure	25,000
Cancellation of secured note receivable pursuant to a deed in lieu of foreclosure	24,869
Transfer of investment in and advances to unconsolidated joint ventures to real estate owned		14,700
Acquisition of intellectual property in exchange for cancellation of secured note receivable		2,250
Recognition of allowance for credit losses		2,182
Vesting of LTIP Units	14,578	23,501
Development costs and capital expenditures incurred, but not yet paid	37,056	27,705
Conversion of Operating Partnership and DownREIT Partnership noncontrolling interests to common stock (168,953 shares in 2021 and 271,176 shares in 2020)	6,944	11,623
Dividends declared, but not yet paid	$ 120,830	$ 115,055

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS - SUPPLEMENTAL - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
The following reconciles cash, cash equivalents, and restricted cash to amounts as shown above:
Cash and cash equivalents	$ 1,063	$ 1,409	$ 927	$ 8,106
Restricted cash	28,170	22,762	23,273	25,185
Total cash, cash equivalents, and restricted cash as shown above	$ 29,233	$ 24,171	$ 24,200	$ 33,291

CONSOLIDATED STATEMENTS OF CA_3

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Non-cash transactions:
Conversion of OP Units into common shares	168,953	271,176

BASIS OF PRESENTATION

BASIS OF PRESENTATION	9 Months Ended
	Sep. 30, 2021
BASIS OF PRESENTATION
BASIS OF PRESENTATION	1. BASIS OF PRESENTATION Basis of Presentation UDR, Inc., collectively with our consolidated subsidiaries (“UDR,” the “Company,” “we,” “our,” or “us”), is a self-administered real estate investment trust, or REIT, that owns, operates, acquires, renovates, develops, redevelops, and manages apartment communities. The accompanying consolidated financial statements include the accounts of UDR and its subsidiaries, including United Dominion Realty, L.P. (the “Operating Partnership” or the “OP”) and UDR Lighthouse DownREIT L.P. (the “DownREIT Partnership”). As of September 30, 2021, there were 185.2 million units in the Operating Partnership (“OP Units”) outstanding, of which 176.2 million OP Units (including 0.1 million of general partnership units), or 95.1%, were owned by UDR and 9.0 million OP Units, or 4.9%, were owned by outside limited partners. As of September 30, 2021, there were 32.4 million units in the DownREIT Partnership (“DownREIT Units”) outstanding, of which 18.9 million, or 58.3%, were owned by UDR and its subsidiaries and 13.5 million, or 41.7%, were owned by outside limited partners. The consolidated financial statements of UDR include the noncontrolling interests of the unitholders in the Operating Partnership and DownREIT Partnership. The accompanying interim unaudited consolidated financial statements have been prepared according to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and note disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States have been condensed or omitted according to such rules and regulations, although management believes that the disclosures are adequate to make the information presented not misleading. In the opinion of management, all adjustments and eliminations necessary for the fair presentation of our financial position as of September 30, 2021, and results of operations for the three and nine months ended September 30, 2021 and 2020, have been included. Such adjustments are normal and recurring in nature. The interim results presented are not necessarily indicative of results that can be expected for a full year, particularly in light of the novel coronavirus disease (“COVID-19”) pandemic and measures intended to mitigate its spread. The accompanying interim unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and related notes for the year ended December 31, 2020 appearing in UDR’s Annual Report on Form 10-K, filed with the SEC on February 18, 2021. The accompanying interim unaudited consolidated financial statements are presented in accordance with U.S. generally accepted accounting principles (“GAAP”). GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent liabilities at the dates of the interim unaudited consolidated financial statements and the amounts of revenues and expenses during the reporting periods. Actual amounts realized or paid could differ from those estimates. All significant intercompany accounts and transactions have been eliminated in consolidation. The Company evaluated subsequent events through the date its financial statements were issued. No significant recognized or non-recognized subsequent events were noted other than those noted in Note 3, Real Estate Owned, Joint Ventures and Partnerships, , Secured and Unsecured Debt, Net, Income/(Loss) Per Share , Commitments and Contingencies

SIGNIFICANT ACCOUNTING POLICIES

SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2021
SIGNIFICANT ACCOUNTING POLICIES
SIGNIFICANT ACCOUNTING POLICIES	2. SIGNIFICANT ACCOUNTING POLICIES Recent Accounting Pronouncements In March 2020, the SEC adopted rules that amended the financial disclosure requirements for subsidiary issuers and guarantors of registered debt securities in Rule 3-10 of Regulation S-X. Subsequently, in November 2020, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2020-09, Debt (Topic 470): Amendments to SEC Paragraphs Pursuant to SEC Release No. 33-10762, which revised SEC paragraphs of the codification to reflect, as appropriate, the amended disclosure requirements mentioned above. Under the amended rules, parent companies can provide alternative disclosures in lieu of separate audited financial statements of subsidiary issuers and guarantors that meet certain criteria. We evaluated the criteria and determined that we are eligible for the exceptions, which allow us to provide alternative disclosures for the Operating Partnership, which guarantees certain outstanding debt securities issued by the Company. As a result of the amendments, the Operating Partnership, as subsidiary guarantor, is no longer subject to the filing requirements under Section 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and will no longer file separate periodic and current reports in reliance on Rule 12h-5 under the Exchange Act. The alternative disclosures related to the Operating Partnership are presented in Item 2 "Management's Discussion and Analysis of Financial Condition and Results of Operations” in this report. ​ I n August 2020, the FASB issued ASU 2020-06, Debt—Debt With Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in E ntity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity ​ In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848) ​ Principles of Consolidation The Company accounts for subsidiary partnerships, joint ventures and other similar entities in which it holds an ownership interest in accordance with the consolidation guidance. The Company first evaluates whether each entity is a variable interest entity (“VIE”). Under the VIE model, the Company consolidates an entity when it has control to direct the activities of the VIE and the obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. Under the voting model, the Company consolidates an entity when it controls the entity through ownership of a majority voting interest. Real Estate Sales Gain Recognition ​ For sale transactions resulting in a transfer of a controlling financial interest of a property, the Company generally derecognizes the related assets and liabilities from its Consolidated Balance Sheets and records the gain or loss in the period in which the transfer of control occurs. If control of the property has not transferred to the counterparty, the criteria for derecognition are not met and the Company will continue to recognize the related assets and liabilities on its Consolidated Balance Sheets. ​ Sale transactions to entities in which the Company sells a controlling financial interest in a property but retains a noncontrolling interest are accounted for as partial sales. Partial sales resulting in a change in control are accounted for at fair value and a full gain or loss is recognized. Therefore, the Company will record a gain or loss on the partial interest sold, and the initial measurement of our retained interest will be accounted for at fair value. ​ Sales of real estate to joint ventures or other noncontrolled investees are also accounted for at fair value and the Company will record a full gain or loss in the period the property is contributed. ​ To the extent that the Company acquires a controlling financial interest in a property that it previously accounted for as an equity method investment, the Company will not remeasure its previously held interest if the acquisition is treated as an asset acquisition. The Company will include the carrying amount of its previously held equity method interest along with the consideration paid and transaction costs incurred in determining the amounts to allocate to the related assets and liabilities acquired on its Consolidated Balance Sheets. When treated as an asset acquisition, the Company will not recognize a gain or loss on consolidation of a property. ​ Allowance for Credit Losses The Company accounts for allowance for credit losses under the current expected credit loss (“CECL”) impairment model for its financial assets, including trade and other receivables, held-to-maturity debt securities, loans and other financial instruments, and presents the net amount of the financial instrument expected to be collected. The CECL impairment model excludes operating lease receivables. The CECL impairment model requires an estimate of expected credit losses, measured over the contractual life of an instrument, that considers forecasts of future economic conditions in addition to information about past events and current conditions. Based on this model, we analyze the following criteria, as applicable in developing allowances for credit losses: historical loss information, the borrower’s ability to make scheduled payments, the remaining time to maturity, the value of underlying collateral, projected future performance of the borrower and macroeconomic trends. ​ The Company measures credit losses of financial assets on a collective (pool) basis when similar risk characteristics exist. If the Company determines that a financial asset does not share risk characteristics with its other financial assets, the Company evaluates the financial asset for expected credit losses on an individual basis. Allowance for credit losses are recorded as a direct reduction from an asset’s amortized cost basis. Credit losses and recoveries are recorded in Interest income and other income/(expense), net ​ The Company has made the optional election provided by the standard not to measure allowance for credit losses for accrued interest receivables as the Company writes off any uncollectible accrued interest receivables in a timely manner. The Company periodically evaluates the collectability of its accrued interest receivables. A write-off is recorded when the Company concludes that all or a portion of its accrued interest receivable balance is no longer collectible. ​ Notes Receivable Notes receivable relate to financing arrangements which are typically secured by real estate, real estate related projects or other assets. Certain of the loans we extend may include characteristics such as options to purchase the project within a specific time window following expected project completion. These characteristics can cause the loans to fall under the definition of a VIE, and thus trigger consolidation consideration. We consider the facts and circumstances pertinent to each loan, including the relative amount of financing we are contributing to the overall project cost, decision making rights or control we hold, and our rights to expected residual gains or our obligations to absorb expected residual losses from the project. If we are deemed to be the primary beneficiary of a VIE due to holding a controlling financial interest, the majority of decision making control, or by other means, consolidation of the VIE would be required. The Company has concluded that it is not the primary beneficiary of the borrowing entities. Additionally, we analyze each loan arrangement that involves real estate development to consider whether the loan qualifies for accounting as a loan or as an investment in a real estate development project. The Company has evaluated its real estate loans, where appropriate, for accounting treatment as loans versus real estate development projects, as required by ASC 310-10. For each loan, the Company has concluded that the characteristics and the facts and circumstances indicate that loan accounting treatment is appropriate. The following table summarizes our Notes receivable, net dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate at ​ Balance Outstanding ​ September 30, September 30, December 31, ​ ​ 2021 ​ 2021 ​ 2020 Note due February 2021 (a) ​ N/A ​ $ — ​ $ 4,000 Note due May 2022 (b) ​ N/A % ​ — ​ ​ 20,000 Note due May 2022 (c) ​ 14.00 % ​ 2,760 ​ ​ — Note due October 2022 (d) N/A % ​ — ​ ​ 115,000 Note due January 2023 (e) ​ 10.00 % ​ 23,110 ​ ​ 19,685 Notes Receivable ​ ​ ​ ​ 25,870 ​ ​ 158,685 Allowance for credit losses ​ ​ ​ ​ (129) ​ ​ (693) Total notes receivable, net ​ $ 25,741 ​ $ 157,992 (a) In May 2020, the Company entered into a promissory note with an unaffiliated third party with an aggregate commitment of $4.0 million, in connection with the sale of an operating community. In January 2021, the unaffiliated third party repaid the $4.0 million promissory note. (b) The Company previously had a secured note with an unaffiliated third party with an aggregate commitment of $20.0 million. The note was secured by a parcel of land and related land improvements located in Alameda, California. In September 2020, the developer defaulted on the loan. As a result of the default, in April 2021, the Company took title to the property pursuant to a deed in lieu of foreclosure. As such, t he Company increased its real estate assets owned by approximately $25.0 million, the fair market value of the property on the date of the title transfer, and recorded a $0.1 million gain on extinguishment of the secured note to Interest income and other income/(expense), net on the Consolidated Statements of Operations, which was based on the note’s principal balance and unpaid accrued interest of $4.9 million. (See Note 3, Real Estate Owned for further discussion.) (c) The Company has a secured note with an unaffiliated third party with an aggregate commitment of $2.8 million, all of which has been funded. The note is secured by a to-be-developed parcel of land in Kissimmee, Florida. Interest payments are due when the loan matures. The note matures in May 2022. (d) The Company previously had a secured note with an unaffiliated third party with an aggregate commitment of $115.0 million. Interest payments were due when the loan matured. The note was secured by a first priority deed of trust on a 259 apartment home operating community in Bellevue, Washington, which was completed in 2020 . In July 2021, the Company acquired the operating community. In connection with the acquisition of this community, the note and the unpaid accrued interest were paid in full. (See Note 3, Real Estate Owned (e) The Company has a secured note with an unaffiliated third party with an aggregate commitment of $25.4 million, of which $23.1 million has been funded, including $3.4 million funded during the nine months ended September 30, 2021. Interest payments are due monthly. The note matures at the earliest of the following: (a) the closing of any private or public capital raising in the amount of $5.0 million or greater; (b) an acquisition; (c) acceleration in the event of default; or (d) January 2023. In August 2021, the terms of this secured note were amended to increase the aggregate commitment from $22.0 million to $25.4 million. The Company recognized $0.7 million and $2.0 million of interest income from notes receivable described above during the three months ended September 30, 2021 and 2020, respectively, and $4.6 million and $7.0 million of interest income for the notes receivable described above during the nine months ended September 30, 2021 and 2020, respectively, none of which was related party interest. Interest income is included in Interest income and other income/(expense), net Comprehensive Income/(Loss) Comprehensive income/(loss), which is defined as the change in equity during each period from transactions and other events and circumstances from nonowner sources, including all changes in equity during a period except for those resulting from investments by or distributions to stockholders, is displayed in the accompanying Consolidated Statements of Comprehensive Income/(Loss). For the three and nine months ended September 30, 2021 and 2020, the Company’s other comprehensive income/(loss) consisted of the gain/(loss) on derivative instruments that are designated as and qualify as cash flow hedges, (gain)/loss on derivative instruments reclassified from other comprehensive income/(loss) into earnings, and the allocation of other comprehensive income/(loss) to noncontrolling interests. The (gain)/loss on derivative instruments reclassified from other comprehensive income/(loss) is included in Interest expense Derivatives and Hedging Activity, Income Taxes Due to the structure of the Company as a REIT and the nature of the operations for the operating properties, no provision for federal income taxes has been provided for at UDR. Historically, the Company has generally incurred only state and local excise and franchise taxes. UDR has elected for certain consolidated subsidiaries to be treated as taxable REIT subsidiaries (“TRS”). Income taxes for our TRS are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities from a change in tax rate is recognized in earnings in the period of the enactment date. The Company’s deferred tax assets/(liabilities) are generally the result of differing depreciable lives on capitalized assets, temporary differences between book and tax basis of assets and liabilities and timing of expense recognition for certain accrued liabilities. As of September 30, 2021 and December 31, 2020, UDR’s net deferred tax asset/(liability) was ($0.7) million and ($3.2) million, respectively, and are recorded in Accounts payable, accrued expenses and other liabilities GAAP defines a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. GAAP also provides guidance on derecognition, classification, interest and penalties, accounting for interim periods, disclosure and transition. The Company recognizes and evaluates its tax positions using a two-step process. First, UDR determines whether a tax position is more likely than not (greater than 50 percent probability) to be sustained upon examination, including resolution of any related appeals or litigation processes, based on the technical merits of the position. Second, the Company will determine the amount of benefit to recognize and record the amount that is more likely than not to be realized upon ultimate settlement. The Company invests in assets that qualify for federal investment tax credits (“ITC”) through our TRS. An ITC reduces federal income taxes payable when qualifying depreciable property is acquired. The ITC is determined as a percentage of cost of the assets. The Company accounts for ITCs under the deferral method, under which the tax benefit from the ITC is deferred and amortized as a tax benefit into Tax (provision)/benefit, net Accounts payable, accrued expenses and other liabilities UDR had no material unrecognized tax benefit, accrued interest or penalties at September 30, 2021. UDR and its subsidiaries are subject to federal income tax as well as income tax of various state and local jurisdictions. The tax years 2018 through 2020 remain open to examination by tax jurisdictions to which we are subject. When applicable, UDR recognizes interest and/or penalties related to uncertain tax positions in Tax (provision)/benefit, net ​ Forward Sales Agreements ​ The Company utilizes forward sales agreements for the future issuance of its common stock. When the Company enters into a forward sales agreement, the contract requires the Company to sell its shares to a counterparty at a predetermined price at a future date. The net sales price and proceeds attained by the Company will be determined on the dates of settlement, with adjustments during the term of the contract for the Company’s anticipated dividends as well as for a daily interest factor that varies with changes in the federal funds rate. The Company generally has the ability to determine the dates and method of settlement (i.e., gross physical settlement, net share settlement or cash settlement), subject to certain conditions and the right of the counterparty to accelerate settlement under certain circumstances. ​ The Company accounts for the shares of common stock reserved for issuance upon settlement as equity in accordance with ASC 815-40, Contracts in Entity's Own Equity ​ The guidance establishes a two-step process for evaluating whether an equity-linked financial instrument is considered indexed to the entity’s own stock, first, evaluating the instrument’s contingent exercise provisions and second, evaluating the instrument’s settlement provisions. When entering into forward sales agreements, we determined that (i) none of the agreement’s exercise contingencies are based on observable markets or indices besides those related to the market for our own stock price; and (ii) none of the settlement provisions preclude the agreements from being indexed to our own stock. ​ Before the issuance of shares of common stock, upon physical or net share settlement of the forward sales agreements, the Company expects that the shares issuable upon settlement of the forward sales agreements will be reflected in its diluted income/(loss) per share calculations using the treasury stock method. Under this method, the number of shares of common stock used in calculating diluted income/(loss) per share is deemed to be increased by the excess, if any, of the number of shares of common stock that would be issued upon full physical settlement of the forward sales agreements over the number of shares of common stock that could be purchased by the Company in the open market (based on the average market price during the period) using the proceeds receivable upon full physical settlement (based on the adjusted forward sale price at the end of the reporting period). When the Company physically or net share settles any forward sales agreement, the delivery of shares of common stock would result in an increase in the number of weighted average common shares outstanding and dilution to basic income/(loss) per share. (See Note 8, Income/(Loss) per Share ​ Impact of COVID-19 Pandemic ​ The Company continues to closely monitor the impact of the COVID-19 pandemic on all aspects of its business. The extent of the pandemic’s effect on our operational and financial performance will depend on future developments, including the duration and intensity of the pandemic, the timing and effectiveness of COVID-19 vaccines, the duration of government measures to mitigate the pandemic and the success of government rental assistance programs, all of which continue to be uncertain and difficult to predict. ​ Given the uncertainty, we cannot predict the effect on future periods, but the adverse impact that could occur on the Company’s future financial condition, results of operations and cash flows could be material ​ During the three and nine months ended September 30, 2021, the Company performed an analysis in accordance with the ASC 842, Leases, guidance to assess the collectibility of its operating lease receivables in light of the COVID-19 pandemic. This analysis included an assessment of collectibility of current and future rents and whether those lease payments were no longer probable of collection. In accordance with the leases guidance, if lease payments are no longer deemed to be probable over the life of the lease contract, we recognize revenue only when cash is received, and all existing contractual operating lease receivables and straight-line lease receivables are reserved. ​ As a result of its analysis, the Company reduced its reserve by approximately $3.0 million for multifamily tenant lease receivables and approximately $1.2 million for retail tenant lease receivables for its wholly-owned communities and communities held by joint ventures for the three months ended September 30, 2021. In aggregate, the reduction in reserve is reflected as a $4.1 million increase to Rental income and a $0.1 million increase to Income/(loss) from unconsolidated entities on the Consolidated Statements of Operations for the three months ended September 30, 2021. For the nine months ended September 30, 2021, the Company reserved approximately $1.8 million of incremental multifamily tenant lease receivables and approximately $0.3 million of incremental retail tenant lease receivables for its wholly-owned communities and communities held by joint ventures. In aggregate, the reserve is reflected as a $1.7 million reduction to Rental income and a $0.4 million reduction to Income/(loss) from unconsolidated entities on the Consolidated Statements of Operations for the nine months ended September 30, 2021. The impact to deferred leasing commissions was not material for the three and nine months ended September 30, 2021. ​ The Company did not recognize any other adjustments to the carrying amounts of assets or asset impairment charges due to the COVID-19 pandemic for the nine months ended September 30, 2021.

REAL ESTATE OWNED

REAL ESTATE OWNED	9 Months Ended
	Sep. 30, 2021
REAL ESTATE OWNED
REAL ESTATE OWNED	3. REAL ESTATE OWNED Real estate assets owned by the Company consist of income producing operating properties, properties under development, land held for future development, and held for disposition properties. As of September 30, 2021, the Company owned and consolidated 158 communities in 13 states plus the District of Columbia totaling 52,071 apartment homes. The following table summarizes the carrying amounts for our real estate owned (at cost) as of September 30, 2021 and December 31, 2020 (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2021 ​ 2020 Land ​ $ 2,301,297 ​ $ 2,139,765 Depreciable property — held and used: ​ ​ Land improvements ​ 238,522 ​ 233,823 Building, improvements, and furniture, fixtures and equipment ​ 11,313,023 ​ 10,292,782 Real estate intangible assets ​ ​ 50,030 ​ ​ 40,570 Under development: ​ ​ Land and land improvements ​ 74,399 ​ 73,702 Building, improvements, and furniture, fixtures and equipment ​ 257,246 ​ 174,175 Real estate held for disposition: ​ ​ Land and land improvements ​ 17,091 ​ 15,184 Building, improvements, and furniture, fixtures and equipment ​ 56,361 ​ 101,471 Real estate owned ​ 14,307,969 ​ 13,071,472 Accumulated depreciation (a) ​ (5,017,941) ​ (4,605,366) Real estate owned, net ​ $ 9,290,028 ​ $ 8,466,106 (a) Accumulated depreciation is inclusive of $8.0 million and $5.8 million of accumulated amortization related to real estate intangible assets as of September 30, 2021 and December 31, 2020, respectively. ​ Acquisitions In January 2021, the Company acquired a 300 apartment home operating community located in Franklin, Massachusetts for approximately $77.4 million. In connection with the acquisition, the Company assumed an above-market mortgage note payable secured by the community with an outstanding balance of approximately $51.8 million. The Company increased its real estate assets owned by approximately $82.0 million, recorded $2.0 million of in-place lease intangibles, and recorded a $6.6 million debt premium in connection with the above-market debt assumed. In April 2021, the Company acquired a 636 apartment home operating community located in Farmers Branch, Texas for approximately $110.2 million. In connection with the acquisition, the Company assumed an above-market mortgage note payable secured by the community with an outstanding balance of approximately $42.0 million. The Company increased its real estate assets owned by approximately $111.5 million, recorded $3.0 million of in-place lease intangibles, and recorded a $4.3 million debt premium in connection with the above-market debt assumed. ​ The Company previously had a secured note with an unaffiliated third party with an aggregate commitment of $20.0 million. The note was secured by a parcel of land and related land improvements located in Alameda, California. In September 2020, the developer defaulted on the loan. As a result of the default, in April 2021, the Company took title to the property pursuant to a deed in lieu of foreclosure. The Company increased its real estate assets owned by approximately $25.0 million, the fair market value of the property on the date of the title transfer, and recorded a $0.1 million gain on extinguishment of the secured note to Interest income and other income/(expense), net on the Consolidated Statements of Operations. Significant Accounting Policies ​ In May 2021, the Company acquired a to-be-developed parcel of land located in Tampa, Florida for approximately $6.6 million. ​ In May 2021, the Company acquired a 945 apartment home operating community located in Frisco, Texas for approximately $166.9 million. In connection with the acquisition, the Company assumed an above-market mortgage note payable secured by the community with an outstanding balance of approximately $89.5 million. The Company increased its real estate assets owned by approximately $169.9 million, recorded $4.1 million of in-place lease intangibles, and recorded a $7.1 million debt premium in connection with the above-market debt assumed. ​ In June 2021, the Company acquired a 468 apartment home operating community located in Germantown, Maryland for approximately $121.9 million. The Company increased its real estate assets owned by approximately $119.3 million and recorded $2.6 million of in-place lease intangibles. ​ In July 2021, the Company acquired a 259 apartment home operating community located in Bellevue, Washington for approximately $171.9 million. The Company previously had a $115.0 million secured note receivable associated with this operating community. The Company increased its real estate assets owned by approximately $169.1 million and recorded $2.8 million of in-place lease intangibles. In connection with the acquisition of this community, the note and the unpaid accrued interest were paid in full. (See Note 2, Significant Accounting Policies ​ In August 2021, the Company acquired a 544 apartment home operating community located in Germantown, Maryland for approximately $127.2 million. The Company increased its real estate assets owned by approximately $124.4 million and recorded $2.8 million of in-place lease intangibles. ​ In September 2021, the Company acquired a 320 apartment home operating community located in King of Prussia, Pennsylvania for approximately $116.2 million. The Company increased its real estate assets owned by approximately $113.8 million and recorded $2.4 million of in-place lease intangibles. ​ In September 2021, the Company acquired a 192 apartment home operating community located in Towson, Maryland for approximately $57.6 million. The Company increased its real estate assets owned by approximately $54.0 million and recorded $2.4 million of real estate tax intangibles and $1.2 million of in-place lease intangibles. ​ In September 2021, the Company acquired a 339 apartment home operating community located in Philadelphia, Pennsylvania for approximately $147.0 million. The Company increased its real estate assets owned by approximately $137.1 million and recorded $7.1 million of real estate tax intangibles and $2.8 million of in-place lease intangibles. ​ In October 2021, the Company acquired its joint venture partner’s common equity interest in a 330 apartment home operating community located in Orlando, Florida, for a total purchase price of approximately $105.0 million. The Company paid for the community by issuing approximately 0.9 million OP Units (valued at $53.00 per unit) to the seller, which equaled $47.9 million. Joint Ventures and Partnerships As a result, in October 2021, the Company increased its ownership interest to 100% and consolidated the operating community no ​ In October 2021, the Company acquired a 663 apartment home operating community located in Orlando, Florida for approximately $177.5 million. ​ Dispositions ​ In February 2021, the Company sold an operating community located in Anaheim, California with a total of 386 apartment homes for gross proceeds of $156.0 million, resulting in a gain of approximately $50.8 million. ​ In October 2021, the Company sold an operating community located in Anaheim, California with a total of 265 apartment homes for a sales price of $126.0 million, resulting in a gain of approximately $85.3 million. ​ Other Activity Predevelopment, development, and redevelopment projects and related costs are capitalized and reported on the Consolidated Balance Sheets as Total real estate owned, net of accumulated depreciation We record impairment losses on long-lived assets used in operations when events and circumstances indicate that the assets might be impaired and the undiscounted cash flows estimated to be generated by the future operation and disposition of those assets are less than the net book value of those assets. Our cash flow estimates are based upon historical results adjusted to reflect our best estimate of future market and operating conditions and our estimated holding periods. The net book value of impaired assets is reduced to fair value. Our estimates of fair value represent our best estimate based upon Level 3 inputs such as industry trends and reference to market rates and transactions. The Company did not recognize any impairments in the value of its long-lived assets during the three and nine months ended September 30, 2021 and 2020. In connection with the acquisition of certain properties, the Company agreed to pay certain of the tax liabilities of certain contributors if the Company sells one or more of the properties contributed in a taxable transaction prior to the expiration of specified periods of time following the acquisition. The Company may, however, sell, without being required to pay any tax liabilities, any of such properties in a non-taxable transaction, including, but not limited to, a tax-deferred Section 1031 exchange. Further, the Company has agreed to maintain certain debt that may be guaranteed by certain contributors for specified periods of time following the acquisition. The Company, however, has the ability to refinance or repay guaranteed debt or to substitute new debt if the debt and the guaranty continue to satisfy certain conditions.

VARIABLE INTEREST ENTITIES

VARIABLE INTEREST ENTITIES	9 Months Ended
	Sep. 30, 2021
VARIABLE INTEREST ENTITIES
VARIABLE INTEREST ENTITIES	4. VARIABLE INTEREST ENTITIES The Company has determined that the Operating Partnership and DownREIT Partnership are VIEs as the limited partners lack substantive kick-out rights and substantive participating rights. The Company has concluded that it is the primary beneficiary of, and therefore consolidates, the Operating Partnership and DownREIT Partnership based on its role as the sole general partner of the Operating Partnership and DownREIT Partnership. The Company’s role as community manager and its equity interests give us the power to direct the activities that most significantly impact the economic performance and the obligation to absorb potentially significant losses or the right to receive potentially significant benefits of the Operating Partnership and DownREIT Partnership.

JOINT VENTURES AND PARTNERSHIPS

JOINT VENTURES AND PARTNERSHIPS	9 Months Ended
	Sep. 30, 2021
JOINT VENTURES AND PARTNERSHIPS
JOINT VENTURES AND PARTNERSHIPS	5. JOINT VENTURES AND PARTNERSHIPS UDR has entered into joint ventures and partnerships with unrelated third parties to own, operate, acquire, renovate, develop, redevelop, dispose of, and manage real estate assets that are either consolidated and included in Real estate owned Investment in and advances to unconsolidated joint ventures, net UDR’s joint ventures and partnerships are funded with a combination of debt and equity. Our losses are typically limited to our investment and except as noted below, the Company does not guarantee any debt, capital payout or other obligations associated with our joint ventures and partnerships. The Company recognizes earnings or losses from our investments in unconsolidated joint ventures and partnerships consisting of our proportionate share of the net earnings or losses of the joint ventures and partnerships. In addition, we may earn fees for providing management services for the communities held by the unconsolidated joint ventures and partnerships. The following table summarizes the Company’s investment in and advances to unconsolidated joint ventures and partnerships, net, which are accounted for under the equity method of accounting as of September 30, 2021 and December 31, 2020 (dollars in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of ​ Number of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating ​ Apartment ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income/(loss) from investments ​ ​ ​ ​ Communities ​ Homes ​ Investment at ​ UDR’s Ownership Interest ​ ​ Three Months Ended ​ Nine Months Ended ​ Location of September 30, September 30, September 30, December 31, ​ September 30, ​ December 31, ​ September 30, ​ September 30, Joint Ventures Properties 2021 2021 2021 2020 ​ 2021 ​ 2020 ​ 2021 2020 ​ 2021 2020 Operating: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ UDR/MetLife I ​ Los Angeles, CA ​ 1 ​ 150 ​ $ 24,497 ​ $ 26,426 ​ 50.0 % ​ 50.0 % ​ $ (608) ​ $ (751) ​ $ (1,922) ​ $ (1,863) UDR/MetLife II Various 7 1,250 ​ 183,116 ​ 151,353 ​ 50.0 % ​ 50.0 % ​ ​ (289) ​ ​ (441) ​ ​ (3,126) ​ ​ (522) Other UDR/MetLife Joint Ventures (a) Various 5 1,437 ​ 70,368 ​ 82,072 ​ 50.6 % ​ 50.6 % ​ ​ (2,859) ​ ​ (3,151) ​ ​ (9,611) ​ ​ (7,275) West Coast Development Joint Ventures (b) ​ Los Angeles, CA ​ — ​ — ​ ​ — ​ ​ 30,080 ​ 47.0 % ​ 47.0 % ​ ​ (128) ​ ​ (148) ​ ​ 2,358 ​ ​ (284) Investment in and advances to unconsolidated joint ventures, net, before preferred equity investments and real estate technology investments ​ $ 277,981 ​ $ 289,931 ​ ​ ​ ​ $ (3,884) ​ $ (4,491) ​ $ (12,301) ​ $ (9,944) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income/(loss) from investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Investment at ​ Three Months Ended ​ Nine Months Ended Developer Capital Program ​ ​ Years To ​ UDR September 30, December 31, September 30, ​ September 30, and Real Estate Technology Investments (c) Location Rate Maturity ​ Commitment (d) 2021 2020 2021 2020 2021 2020 Preferred equity investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 1532 Harrison ​ San Francisco, CA ​ 11.0 % 0.7 ​ $ 24,645 ​ $ 36,088 ​ $ 34,135 ​ ​ 1,003 ​ ​ 875 ​ $ 2,896 ​ $ 2,557 Junction ​ Santa Monica, CA ​ 12.0 % 0.8 ​ ​ 8,800 ​ ​ 12,792 ​ ​ 11,699 ​ ​ 379 ​ ​ 337 ​ ​ 1,093 ​ ​ 974 1200 Broadway (e) (f) ​ Nashville, TN ​ 12.25 % 1.0 ​ ​ 55,558 ​ ​ 60,594 ​ ​ 69,330 ​ ​ 1,837 ​ ​ 1,347 ​ ​ 4,936 ​ ​ 3,934 1300 Fairmount (f) ​ Philadelphia, PA ​ 8.5 % 1.9 ​ ​ 51,393 ​ ​ 63,413 ​ ​ 59,544 ​ ​ 1,338 ​ ​ 1,230 ​ ​ 3,869 ​ ​ 3,587 Essex (g) ​ Orlando, FL ​ 12.5 % 1.9 ​ ​ 12,886 ​ ​ 17,629 ​ ​ 16,770 ​ ​ 544 ​ ​ 501 ​ ​ 1,609 ​ ​ 1,448 Modera Lake Merritt (f) ​ Oakland, CA ​ 9.0 % 2.5 ​ ​ 27,250 ​ ​ 33,072 ​ ​ 30,928 ​ ​ 739 ​ ​ 675 ​ ​ 2,144 ​ ​ 1,901 Thousand Oaks (f) ​ Thousand Oaks, CA ​ 9.0 % 3.3 ​ ​ 20,059 ​ ​ 22,256 ​ ​ 17,919 ​ ​ 497 ​ ​ 240 ​ ​ 1,415 ​ ​ 417 Vernon Boulevard (f) ​ Queens, NY ​ 13.0 % 3.8 ​ ​ 40,000 ​ ​ 46,665 ​ ​ 42,360 ​ ​ 1,496 ​ ​ 990 ​ ​ 4,300 ​ ​ 990 Makers Rise (f) (h) ​ Herndon, VA ​ 9.0 % 4.2 ​ ​ 30,208 ​ ​ 14,799 ​ ​ — ​ ​ 251 ​ ​ — ​ ​ 519 ​ ​ — 121 at Watters (f) (i) ​ Allen, TX ​ 9.0 % 4.4 ​ ​ 19,846 ​ ​ 8,968 ​ ​ — ​ ​ 234 ​ ​ — ​ ​ 462 ​ ​ — Infield Phase I (j) ​ Kissimmee, FL ​ 14.0 % 2.6 ​ ​ 16,044 ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — Real estate technology investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ RETV I (k) ​ N/A ​ N/A ​ N/A ​ ​ 18,000 ​ ​ 38,628 ​ ​ 20,587 ​ ​ 9,869 ​ ​ (100) ​ ​ 17,975 ​ ​ 4,338 RETV II ​ N/A ​ N/A ​ N/A ​ $ 18,000 ​ ​ 5,438 ​ ​ 2,283 ​ ​ 147 ​ ​ (112) ​ ​ 209 ​ ​ — Total Preferred Equity Investments and Real Estate Technology Investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 360,342 ​ ​ 305,555 ​ ​ 18,334 ​ ​ 5,983 ​ ​ 41,427 ​ ​ 20,146 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sold joint ventures and other investments in prior year ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ — ​ ​ — ​ ​ — ​ ​ 1,448 ​ ​ (3) ​ ​ 4,126 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Joint Ventures and Developer Capital Program and Real Estate Technology Investments, net (a) ​ ​ ​ ​ $ 638,323 ​ $ 595,486 ​ $ 14,450 $ 2,940 ​ $ 29,123 $ 14,328 (a) As of September 30, 2021 and December 31, 2020, the Company’s negative investment in 13 th and Market Properties LLC of $5.6 million and $4.7 million, respectively, is included in Other UDR/MetLife Joint Ventures in the table above and recorded in Accounts payable, accrued expenses, and other liabilities on the Consolidated Balance Sheet. (b) In J anuary 2021, the joint venture sold its remaining community, a 293 home operating community located in Los Angeles, California, for a sales price of approximately $121.0 million. As a result, the Company recorded a gain on the sale of approximately $2.5 million . (c) The Developer Capital Program is the program through which the Company makes investments, including preferred equity investments, mezzanine loans or other structured investments that may receive a fixed yield on the investment and may include provisions pursuant to which the Company participates in the increase in value of the property upon monetization of the applicable property and/or holds fixed price purchase options. (d) Represents UDR’s maximum funding commitment only and therefore excludes other activity such as income from investments. (e) In April 2021, the investment balance was paid down by $12.5 million and the Company’s preferred return increased to 12.25%. The Company's preferred return will revert to 8.0% in February 2022 if no capital events occur prior to that date. (f) The Company’s preferred equity investment receives a variable percentage of the value created from the project upon a capital or liquidating event. (g) In October 2021, the Company acquired its joint venture partner’s common equity interest in a 330 apartment home operating community located in Orlando, Florida for a purchase price of approximately $47.9 million. As a result, in October 2021, the Company consolidated the operating community and it will no longer be accounted for as a preferred equity investment in an unconsolidated joint venture (see Note 3, Real Estate Owned ). (h) In January 2021, the Company entered into a joint venture agreement with an unaffiliated joint venture partner to develop and operate a 356 apartment home community in Herndon, Virginia. The Company’s preferred equity investment of $30.2 million earns a preferred return of 9.0% per annum and receives a variable percentage of the value created from the project upon a capital or liquidating event. The unaffiliated joint venture partner is the managing member of the joint venture and the developer of the community. The Company has concluded that it does not control the joint venture and accounts for it under the equity method of accounting . (i) In March 2021, the Company entered into a joint venture agreement with an unaffiliated joint venture partner to develop and operate a 469 apartment home community in Allen, Texas. The Company’s preferred equity investment of $19.8 million earns a preferred return of 9.0% per annum and receives a variable percentage of the value created from the project upon a capital or liquidating event. The unaffiliated joint venture partner is the managing member of the joint venture and the developer of the community. The Company has concluded that it does not control the joint venture and accounts for it under the equity method of accounting . (j) In May 2021, the Company entered into a joint venture agreement with an unaffiliated joint venture partner to develop and operate a 384 apartment home community in Kissimmee, Florida. The Company’s preferred equity investment of $16.0 million earns a preferred return of 14.0% per annum. The unaffiliated joint venture partner is the managing member of the joint venture and the developer of the community. The Company has concluded that it does not control the joint venture and accounts for it under the equity method of accounting. (k) The Company recognized $9.9 million and $18.0 million of investment income from RETV I for the three and nine months ended September 30, 2021, respectively, which primarily related to unrealized gains from real estate technology investments . ​ As of September 30, 2021 and December 31, 2020, the Company had deferred fees of $8.9 million and $8.4 million, respectively, which will be recognized through earnings over the weighted average life of the related properties, upon the disposition of the properties to a third party, or upon completion of certain development obligations. The Company recognized management fees of $1.1 million and $1.2 million for the three months ended September 30, 2021 and 2020, respectively, and $4.9 million and $ 3.9 million for the nine months ended September 30, 2021 and 2020, respectively, for management of the communities held by the joint ventures and partnerships. The management fees are included in Joint venture management and other fees on the Consolidated Statements of Operations. The Company may, in the future, make additional capital contributions to certain of our joint ventures and partnerships should additional capital contributions be necessary to fund acquisitions or operations. We consider various factors to determine if a decrease in the value of our Investment in and advances to unconsolidated joint ventures, net Combined summary balance sheets relating to the unconsolidated joint ventures’ and partnerships’ (not just our proportionate share) are presented below as of September 30, 2021 and December 31, 2020 ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 2020 Total real estate, net $ 2,172,424 $ 1,904,805 Real estate assets held for sale ​ 63,492 ​ 88,458 Cash and cash equivalents ​ 32,954 ​ 22,278 Other assets ​ ​ 281,456 ​ 150,894 Total assets $ 2,550,326 $ 2,166,435 ​ ​ ​ ​ ​ ​ ​ Third party debt, net ​ $ 1,275,903 ​ $ 1,188,710 Liabilities held for sale ​ 44,221 ​ 55,440 Accounts payable and accrued liabilities ​ ​ 59,854 ​ ​ 40,556 Total liabilities ​ 1,379,978 ​ 1,284,706 Total equity $ 1,170,348 $ 881,729 ​ Combined summary financial information relating to the unconsolidated joint ventures’ and partnerships’ operations (not just our proportionate share) is presented below for the three and nine months ended September 30, 2021 and 2020 ( dollars in thousands : ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ 2021 2020 2021 2020 Total revenues $ 33,635 $ 36,335 $ 97,777 $ 114,961 Property operating expenses ​ 18,128 ​ 16,697 ​ 51,983 ​ 46,462 Real estate depreciation and amortization ​ 17,486 ​ 16,929 ​ 50,082 ​ 50,085 Gain/(loss) on sale of property ​ ​ — ​ ​ — ​ ​ 34,757 ​ ​ — Operating income/(loss) ​ (1,979) ​ ​ 2,709 ​ 30,469 ​ ​ 18,414 Interest expense ​ (13,181) ​ (9,955) ​ (32,776) ​ (30,451) Net realized/unrealized gain/(loss) on held investments ​ ​ 62,013 ​ ​ (17) ​ ​ 108,851 ​ ​ 29,295 Other income/(loss) ​ ​ (156) ​ ​ 18 ​ ​ (1,826) ​ ​ 127 Net income/(loss) $ 46,697 $ (7,245) $ 104,718 $ 17,385 ​

LEASES

LEASES	9 Months Ended
	Sep. 30, 2021
LEASES
LEASES	6. LEASES Lessee - Ground Leases UDR owns six communities that are subject to ground leases, under which UDR is the lessee, expiring between 2043 and 2103, inclusive of extension options we are reasonably certain will be exercised. All of these leases are classified as operating leases through the lease term expiration based on our election of the practical expedient provided by the leasing standard. Rental expense for lease payments related to operating leases is recognized on a straight-line basis over the remaining lease term. We currently do not hold any finance leases. The Company also elected the short-term lease exception provided by the leasing standard and therefore only recognizes right-of-use assets and lease liabilities for leases with a term greater than one year. No leases qualified for the short-term lease exception during the three and nine months ended September 30, 2021 and 2020. As of September 30, 2021 and December 31, 2020, the Operating lease right-of-use assets Operating lease liabilities Operating lease right-of-use assets Operating lease liabilities from the right-of-use assets and lease liabilities and are recognized in earnings in the period in which the obligation for those payments is incurred. As the discount rate implicit in the leases was not readily determinable, we determined the discount rate for these leases utilizing the Company’s incremental borrowing rate at a portfolio level, adjusted for the remaining lease term, and the form of underlying collateral. The weighted average remaining lease term for these leases was 43.4 years and 43.9 years at September 30, 2021 and December 31, 2020, respectively, and the weighted average discount rate was 5.0% at both September 30, 2021 and December 31, 2020. Future minimum lease payments and total operating lease liabilities from our ground leases as of September 30, 2021 are as follows (dollars in thousands): ​ ​ ​ ​ ​ ​ Ground Leases 2021 ​ $ 3,110 2022 ​ ​ 12,442 2023 ​ ​ 12,442 2024 ​ ​ 12,442 2025 ​ ​ 12,442 Thereafter ​ ​ 442,778 Total future minimum lease payments (undiscounted) ​ ​ 495,656 Difference between future undiscounted cash flows and discounted cash flows ​ ​ (302,379) Total operating lease liabilities (discounted) ​ $ 193,277 ​ For purposes of recognizing our ground lease contracts, the Company uses the minimum lease payments, if stated in the agreement. For ground lease agreements where there is a rent reset provision based on a change in an index or a rate (i.e., changes in fair market rental rates or changes in the consumer price index) but that does not include a specified minimum lease payment, the Company uses the current rent over the remainder of the lease term. If there is a contingency upon which some or all of the variable lease payments that will be paid over the remainder of the lease term are based, which is resolved such that those payments now meet the definition of lease payments, the Company will remeasure the right-of-use asset and lease liability on the reset date. The components of operating lease expenses were as follows (dollars in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ ​ 2021 ​ 2020 ​ 2021 ​ 2020 Lease expense: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contractual lease expense ​ $ 3,231 ​ $ 3,217 ​ $ 9,691 ​ $ 9,603 Variable lease expense (a) ​ ​ 25 ​ ​ 33 ​ ​ 54 ​ ​ 120 Total operating lease expense (b)(c) ​ $ 3,256 ​ $ 3,250 ​ $ 9,745 ​ $ 9,723 (a) Variable lease expense includes adjustments such as changes in the consumer price index and payments based on a percentage of a community’s income. (b) Lease expense is reported within the line item Other operating expenses on the Consolidated Statements of Operations. (c) For the nine months ended September 30, 2021, Operating lease right-of-use assets and Operating lease liabilities amortized by $2.6 million and $2.3 million, respectively. For the nine months ended September 30, 2020, Operating lease right-of-use assets and Operating lease liabilities amortized by $2.5 million and $2.2 million, respectively. Due to the net impact of the amortization, the Company recorded $0.1 million and $0.1 million of total operating lease expense during the three months ended September 30, 2021 and 2020, respectively, and $0.3 million and $0.3 million of total operating lease expense during the nine months ended September 30, 2021 and 2020, respectively. ​ Lessor - Apartment Home, Retail and Commercial Space Leases ​ UDR’s communities and retail and commercial space are leased to tenants under operating leases. As of September 30, 2021, our apartment home leases generally have initial terms of 12 months or less and represent approximately 98.8% of our total lease revenue. As of September 30, 2021, our retail and commercial space leases generally have initial terms of between 5 and 15 years and represent approximately 1.2% of our total lease revenue. Our apartment home leases are generally renewable at the end of the lease term, subject to potential increases in rental rates, and our retail and commercial space leases generally have renewal options, subject to associated increases in rental rates due to market based or fixed price renewal options and certain other conditions. (See Note 14, Reportable Segments ​ Future minimum lease payments from our retail and commercial leases as of September 30, 2021 are as follows (dollars in thousands): ​ ​ ​ ​ ​ ​ Retail and Commercial Leases 2021 ​ $ 5,822 2022 ​ ​ 24,509 2023 ​ ​ 22,705 2024 ​ ​ 20,396 2025 ​ ​ 17,075 Thereafter ​ ​ 76,696 Total future minimum lease payments (a) ​ $ 167,203 (a) Certain of our leases with retail and commercial tenants provide for the payment by the lessee of additional variable rent based on a percentage of the tenant’s revenue. The amounts shown in the table above do not include these variable percentage rents. The Company recorded variable percentage rents of $0.2 million and less than $0.1 million for the three months ended September 30, 2021 and 2020, respectively, and $0.3 million and $0.1 million during the nine months ended September 30, 2021 and 2020, respectively.

SECURED AND UNSECURED DEBT, NET

SECURED AND UNSECURED DEBT, NET	9 Months Ended
	Sep. 30, 2021
SECURED AND UNSECURED DEBT, NET
SECURED AND UNSECURED DEBT, NET	7. SECURED AND UNSECURED DEBT, NET The following is a summary of our secured and unsecured debt at September 30, 2021 and December 31, 2020 ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Principal Outstanding ​ As of September 30, 2021 ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ Weighted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Average ​ Average ​ Number of ​ ​ September 30, ​ December 31, ​ Interest ​ Years to ​ Communities ​ 2021 2020 Rate Maturity Encumbered Secured Debt: ​ ​ ​ ​ ​ ​ ​ Fixed Rate Debt ​ ​ Mortgage notes payable (a) ​ $ 1,007,041 ​ $ 824,550 3.42 % 6.7 14 Deferred financing costs and other non-cash adjustments (b) ​ 24,668 ​ 10,665 Total fixed rate secured debt, net ​ 1,031,709 ​ 835,215 3.42 % 6.7 14 Variable Rate Debt ​ ​ Tax-exempt secured notes payable (c) ​ 27,000 ​ 27,000 0.69 % 10.5 1 Deferred financing costs ​ (62) ​ (68) Total variable rate secured debt, net ​ 26,938 ​ 26,932 0.69 % 10.5 1 Total Secured Debt, net ​ 1,058,647 ​ 862,147 3.35 % 6.8 15 Unsecured Debt: ​ ​ Variable Rate Debt ​ ​ Borrowings outstanding under unsecured credit facility due January 2026 (d) (o) ​ — ​ — — % 4.3 Borrowings outstanding under unsecured commercial paper program due October 2021 (e) (o) ​ ​ 315,000 ​ ​ 190,000 ​ 0.22 % 0.1 ​ ​ Borrowings outstanding under unsecured working capital credit facility due January 2024 (f) ​ 43,086 ​ 28,024 0.86 % 2.3 Term Loan due January 2027 (d) (o) ​ 35,000 ​ 35,000 0.99 % 5.3 Fixed Rate Debt ​ ​ Term Loan due January 2027 (d) (o) ​ ​ 315,000 ​ 315,000 1.02 % 5.3 ​ ​ 8.50% Debentures due September 2024 ​ 15,644 ​ 15,644 8.50 % 3.0 4.00% Medium-Term Notes due October 2025 (net of discounts of $0 and $327, respectively) (g) (o) ​ — ​ 299,673 — % — 2.95% Medium-Term Notes due September 2026 (h) (o) ​ 300,000 ​ 300,000 2.89 % 4.9 3.50% Medium-Term Notes due July 2027 (net of discounts of $406 and $458, respectively) (i) (o) ​ ​ 299,594 ​ ​ 299,542 ​ 4.03 % 5.8 ​ ​ 3.50% Medium-Term Notes due January 2028 (net of discounts of $746 and $835, respectively) (o) ​ ​ 299,254 ​ ​ 299,165 ​ 3.50 % 6.3 ​ ​ 4.40% Medium-Term Notes due January 2029 (net of discounts of $4 and $5, respectively) (j) (o) ​ ​ 299,996 ​ ​ 299,995 ​ 4.27 % 7.3 ​ ​ 3.20% Medium-Term Notes due January 2030 (net of premiums of $11,382 and $12,412, respectively) (k) (o) ​ ​ 611,382 ​ ​ 612,412 ​ 3.32 % 8.3 ​ ​ 3.00% Medium-Term Notes due August 2031 (net of premiums/discounts of $11,797 and $1,027, respectively) (l) (o) ​ ​ 611,797 ​ ​ 398,973 ​ 3.01 % 9.9 ​ ​ 2.10% Medium-Term Notes due August 2032 (net of discounts of $382 and $408, respectively) (o) ​ ​ 399,618 ​ ​ 399,592 ​ 2.10 % 10.8 ​ ​ 1.90% Medium-Term Notes due March 2033 (net of discounts of $1,381 and $1,471, respectively) (o) ​ ​ 348,619 ​ ​ 348,529 ​ 1.90 % 11.5 ​ ​ 2.10% Medium-Term Notes due June 2033 (net of discounts of $1,165 and $0, respectively) (m) (o) ​ ​ 298,835 ​ ​ — ​ 2.10 % 11.7 ​ ​ 3.10% Medium-Term Notes due November 2034 (net of discounts of $1,155 and $1,221, respectively) (n) (o) ​ ​ 298,845 ​ ​ 298,779 ​ 3.13 % 13.1 ​ ​ Other ​ 8 ​ 10 Deferred financing costs ​ (27,886) ​ (25,937) Total Unsecured Debt, net ​ 4,463,792 ​ 4,114,401 2.65 % 8.0 Total Debt, net ​ $ 5,522,439 ​ $ 4,976,548 2.75 % 7.8 ​ For purposes of classification of the above table, variable rate debt with a derivative financial instrument designated as a cash flow hedge is deemed as fixed rate debt due to the Company having effectively established a fixed interest rate for the underlying debt instrument. Our secured debt instruments generally feature either monthly interest and principal or monthly interest-only payments with balloon payments due at maturity. As of September 30, 2021, secured debt encumbered $1.7 billion or 12.0% of UDR’s total real estate owned based upon gross book value ($12.6 billion or 88.0% of UDR’s real estate owned based on gross book value is unencumbered). (a) During the nine months ended September 30, 2021, the Company assumed three fixed rate mortgage notes payable with an aggregate outstanding balance of $183.3 million and a fair value of $201.3 million in connection with the acquisition of three operating properties, which carry a weighted average interest rate of 3.93% . Real Estate Owned . ​ The Company will from time to time acquire properties subject to fixed rate debt instruments. In those situations, the Company records the debt at its estimated fair value and amortizes any difference between the fair value and par value to interest expense over the life of the underlying debt instrument. (b) Interest expense ​ (c) (d) six-month extension options, subject to certain conditions. The Term Loan has a scheduled maturity date of January 31, 2027. The Credit Agreement amended and restated the Company’s prior credit agreement, which provided for: (i) a $1.1 billion revolving credit facility scheduled to mature in January 2023 and (ii) a $350.0 million term loan scheduled to mature in September 2023. The prior credit agreement allowed the total commitments under the revolving credit facility and total borrowings under the term loan to be increased to an aggregate maximum amount of up to $2.0 billion, subject to certain conditions. ​ Based on the Company’s current credit rating, the Revolving Credit Facility has an interest rate equal to LIBOR plus a margin of 77.5 basis points and a facility fee of 15 basis points, and the Term Loan has an interest rate equal to LIBOR plus a margin of 85 basis points. Depending on the Company’s credit rating, the margin under the Revolving Credit Facility ranges from 70 to 140 basis points, the facility fee ranges from 10 to 30 basis points, and the margin under the Term Loan ranges from 75 to 160 basis points. In November 2020, the Company entered into three interest rate swaps, which became effective in January 2021, to hedge against interest rate risk on the Term Loan until July 2022. The all-in weighted average interest rate, inclusive of the impact of the interest rate swaps, was 1.02% . ​ The Credit Agreement contains customary representations and warranties and financial and other affirmative and negative covenants. The Credit Agreement also includes customary events of default, in certain cases subject to customary periods to cure. The occurrence of an event of default, following the applicable cure period, would permit the lenders to, among other things, declare the unpaid principal, accrued and unpaid interest and all other amounts payable under the Credit Agreement to be immediately due and payable. The following is a summary of short-term bank borrowings under the Revolving Credit Facility at September 30, 2021 and December 31, 2020 (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2021 2020 ​ Total revolving credit facility ​ $ 1,300,000 ​ $ 1,100,000 ​ Borrowings outstanding at end of period (1) ​ — ​ — ​ Weighted average daily borrowings during the period ended ​ 17,473 ​ 42,186 ​ Maximum daily borrowings during the period ended ​ 305,000 ​ 375,000 ​ Weighted average interest rate during the period ended ​ 0.9 % 1.4 % Interest rate at end of the period ​ — % — % (1) Excludes $2.6 million and $2.8 million of letters of credit at September 30, 2021 and December 31, 2020, respectively . (e) In July 2021, the maximum aggregate amount was increased from $500.0 million to $700.0 million. The following is a summary of short-term bank borrowings under the unsecured commercial paper program at September 30, 2021 and December 31, 2020 (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2021 ​ 2020 Total unsecured commercial paper program $ 700,000 ​ $ 500,000 ​ Borrowings outstanding at end of period ​ 315,000 ​ 190,000 ​ Weighted average daily borrowings during the period ended ​ 391,852 ​ 227,090 ​ Maximum daily borrowings during the period ended ​ 700,000 ​ 500,000 ​ Weighted average interest rate during the period ended ​ 0.2 % 0.9 % Interest rate at end of the period ​ 0.2 % 0.3 % ​ In October 2021, the entire $315.0 million of outstanding unsecured commercial paper as of September 30, 2021 was repaid at maturity with additional proceeds of unsecured commercial paper with maturity dates in October and November 2021. (f) The following is a summary of short-term bank borrowings under the Working Capital Credit Facility at September 30, 2021 and December 31, 2020 (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2021 ​ 2020 Total working capital credit facility ​ $ 75,000 ​ $ 75,000 ​ Borrowings outstanding at end of period ​ 43,086 ​ 28,024 ​ Weighted average daily borrowings during the period ended ​ 10,645 ​ 20,132 ​ Maximum daily borrowings during the period ended ​ 44,607 ​ 54,974 ​ Weighted average interest rate during the period ended ​ 0.9 % 1.4 % Interest rate at end of the period ​ 0.9 % 1.0 % ​ (g) (h) (i) (j) (k) The all-in weighted average interest rate, inclusive of the impact of the forward starting swaps and treasury locks, was 3.32% . (l) The Company entered into treasury lock agreements to hedge against interest rate risk on $250.0 million of the $600.0 million aggregate principal amount. The all-in weighted average interest rate, inclusive of the impact of the treasury locks, was 3.01%. ​ (m) . (n) . (o) The aggregate maturities, including amortizing principal payments on secured and unsecured debt, of total debt for the next ten calendar years subsequent to September 30, 2021 are as follows (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fixed Total Variable Total Total Total Year ​ Secured Debt ​ Secured Debt ​ Secured Debt ​ Unsecured Debt ​ Debt 2021 ​ $ 279 ​ $ — ​ $ 279 ​ $ 315,000 (a) $ 315,279 2022 ​ ​ 1,140 ​ ​ — ​ ​ 1,140 ​ ​ — ​ ​ 1,140 2023 ​ 1,242 ​ — ​ 1,242 ​ — ​ 1,242 2024 ​ 96,747 ​ — ​ 96,747 ​ 58,730 ​ 155,477 2025 ​ 174,793 ​ — ​ 174,793 ​ — ​ 174,793 2026 ​ 52,744 ​ — ​ 52,744 ​ 300,000 ​ 352,744 2027 ​ 2,860 ​ — ​ 2,860 ​ 650,000 ​ 652,860 2028 ​ 162,310 ​ — ​ 162,310 ​ 300,000 ​ 462,310 2029 ​ 191,986 ​ — ​ 191,986 ​ 300,000 ​ 491,986 2030 ​ 162,010 ​ — ​ 162,010 ​ 600,000 ​ 762,010 Thereafter ​ 160,930 ​ 27,000 ​ 187,930 ​ 1,950,000 ​ 2,137,930 Subtotal ​ 1,007,041 ​ 27,000 ​ 1,034,041 ​ 4,473,730 ​ 5,507,771 Non-cash (b) ​ 24,668 ​ (62) ​ 24,606 ​ (9,938) ​ 14,668 Total ​ $ 1,031,709 ​ $ 26,938 ​ $ 1,058,647 ​ $ 4,463,792 ​ $ 5,522,439 (a) All unsecured debt due in the remainder of 2021 is related to the Company’s commercial paper program. (b) Includes the unamortized balance of fair market value adjustments, premiums/discounts and deferred financing costs . The Company amortized $1.2 million and $1.1 million, respectively, during the three months ended September 30, 2021 and 2020, and $3.6 million and $3.2 million, respectively, during the nine months ended September 30, 2021 and 2020, of deferred financing costs into Interest expense. We were in compliance with the covenants of our debt instruments at September 30, 2021.

INCOME_(LOSS) PER SHARE

INCOME/(LOSS) PER SHARE	9 Months Ended
	Sep. 30, 2021
INCOME/(LOSS) PER SHARE
INCOME/(LOSS) PER SHARE	8. INCOME/(LOSS) PER SHARE The following table sets forth the computation of basic and diluted income/(loss) per share for the periods presented (dollars and shares in thousands, except per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ ​ September 30, ​ September 30, ​ ​ 2021 2020 2021 2020 ​ Numerator for income/(loss) per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income/(loss) ​ $ 19,040 ​ $ (27,217) ​ $ 34,849 ​ $ 40,419 ​ Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership ​ (1,260) ​ 1,990 ​ (2,221) ​ (2,614) ​ Net (income)/loss attributable to noncontrolling interests ​ (49) ​ (31) ​ (73) ​ (71) ​ Net income/(loss) attributable to UDR, Inc. ​ 17,731 ​ (25,258) ​ 32,555 ​ 37,734 ​ Distributions to preferred stockholders — Series E (Convertible) ​ (1,058) ​ (1,051) ​ (3,171) ​ (3,179) ​ Income/(loss) attributable to common stockholders - basic and diluted ​ $ 16,673 ​ $ (26,309) ​ $ 29,384 ​ $ 34,555 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator for income/(loss) per share: ​ ​ ​ ​ ​ Weighted average common shares outstanding ​ 298,075 ​ 294,972 ​ 297,252 ​ 294,891 ​ Non-vested restricted stock awards ​ (247) ​ (259) ​ (254) ​ (264) ​ Denominator for basic income/(loss) per share ​ 297,828 ​ 294,713 ​ 296,998 ​ 294,627 ​ Incremental shares issuable from assumed conversion of unvested LTIP Units, unvested restricted stock and shares issuable upon settlement of forward sales agreements ​ 3,336 ​ 290 ​ 1,047 ​ 311 ​ Denominator for diluted income/(loss) per share ​ 301,164 ​ 295,003 ​ 298,045 ​ 294,938 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income/(loss) per weighted average common share: ​ ​ ​ ​ ​ Basic ​ $ 0.06 ​ $ (0.09) ​ $ 0.10 ​ $ 0.12 ​ Diluted ​ $ 0.06 ​ $ (0.09) ​ $ 0.10 ​ $ 0.12 ​ ​ Basic income/(loss) per common share is computed based upon the weighted average number of common shares outstanding. Diluted income/(loss) per common share is computed based upon the weighted average number of common shares outstanding plus the common shares issuable from the assumed conversion of the OP Units and DownREIT Units, convertible preferred stock, stock options, unvested long-term incentive plan units (“LTIP Units”), unvested restricted stock and continuous equity program forward sales agreements. Only those instruments having a dilutive impact on our basic income/(loss) per share are included in diluted income/(loss) per share during the periods. For the three and nine months ended September 30, 2021 and 2020, the effect of the conversion of the OP Units, DownREIT Units and the Company’s Series E preferred stock was not dilutive and therefore not included in the above calculation. In July 2021, the Company entered into an ATM sales agreement under which the Company may offer and sell up to 20.0 million shares of its common stock, from time to time, to or through its sales agents and may enter into separate forward sales agreements to or through its forward purchasers. Upon entering into the ATM sales agreement, the Company simultaneously terminated the sales agreement for its prior at-the-market equity offering program, which was entered into in July 2017. During the nine months ended September 30, 2021, the Company did not sell any shares of common stock through its ATM program, other than the forward sales described below. As of September 30, 2021, we had 20.0 million shares of common stock available for future issuance under the ATM program, including an aggregate of 5.0 million shares subject to the forward sales agreements described below. In connection with any forward sales agreement under the Company’s ATM program, the relevant forward purchasers will borrow from third parties and, through the relevant sales agent, acting in its role as forward seller, sell a number of shares of the Company’s common stock equal to the number of shares underlying the agreement. The Company does not initially receive any proceeds from any sale of borrowed shares by the forward seller. ​ During the three months ended September 30, 2021, the Company entered into forward sales agreements under its ATM program for a total of 5.0 million shares of common stock at a weighted average initial forward price per share of $53.86. As of September 30, 2021, the Company had entered into forward sales agreements under its current or prior ATM programs for a total of 9.9 million shares of common stock at a weighted average initial forward price per share of $50.31, of which 5.5 million shares had not been settled. The actual forward price per share to be received by the Company upon settlement will be determined on the applicable settlement date based on adjustments made to the initial forward price to reflect the then-current federal funds rate and the amount of dividends paid to holders of UDR common stock over the term of the forward sales agreement. As of September 30, 2021, 4.4 million shares under the forward sales agreements under the ATM programs had been settled at a weighted average forward price per share of $45.68, which is inclusive of adjustments made to reflect the then-current federal funds rate, the amount of dividends paid to holders of UDR common stock and commissions paid to sales agents of approximately $2.1 million, for net proceeds of $201.5 million. The final dates by which the remaining shares sold under the forward sales agreements under the ATM programs must be settled range between June 9, 2022 and September 14, 2022. ​ In March 2021, the Company entered into forward sale agreements to sell 7.0 million shares of its common stock at an initial forward price per share of $43.51. The actual forward price per share to be received by the Company upon settlement was determined on the applicable settlement date based on adjustments made to the initial forward price to reflect the then-current federal funds rate and the amount of dividends paid to holders of UDR common stock over the term of the forward sales agreement. In September 2021, the Company settled all 7.0 million shares at a forward price per share of $42.65, which is inclusive of adjustments made to reflect the then-current federal funds rate, the amount of dividends paid to holders of UDR common stock and commissions paid to sales agents of approximately $6.0 million, for net proceeds of $298.5 million. ​ During the three and nine months ended September 30, 2021, the Company settled 11.4 million shares in aggregate under forward sales agreements under the ATM programs and previously announced forward sales agreements for net proceeds of $500.0 million. Aggregate net proceeds from such forward sales, after deducting related expenses, were $499.3 million. ​ In June 2021, the Company entered into forward sale agreements to sell 6.1 million shares of its common stock at an initial forward price per share of $49.22. The actual forward price per share to be received by the Company upon settlement will be determined on the applicable settlement date based on adjustments made to the initial forward price to reflect the then-current federal funds rate and the amount of dividends paid to holders of UDR common stock over the term of the forward sales agreement. As of September 30, 2021, no shares under the forward sale agreements have been settled. The final date by which shares sold under the forward sale agreements must be settled is June 20, 2022. ​ As of October 25, 2021, we had 20.0 million shares of common stock available for future issuance under the ATM program, including an aggregate of 6.0 million shares subject to the forward sales agreements. The Company generally has the ability to determine the dates and method of settlement (i.e., gross physical settlement, net share settlement or cash settlement), subject to certain conditions and the right of the counterparty to accelerate settlement under certain circumstances. The Company currently expects to fully physically settle each forward sales agreement with the relevant forward purchaser on one or more dates specified by the Company on or prior to the maturity date of that particular forward sales agreement, in which case the Company expects to receive aggregate net cash proceeds at settlement equal to the number of shares underlying the particular forward sales agreement multiplied by the relevant forward sale price. However, subject to certain exceptions, the Company may also elect, in its discretion, to cash settle or net share settle a particular forward sales agreement, in which case the Company may not receive any proceeds (in the case of cash settlement) or will not receive any proceeds (in the case of net share settlement), and the Company may owe cash (in the case of cash settlement) or shares of UDR common stock (in the case of net share settlement) to the relevant forward purchaser. ​ The following table sets forth the additional shares of common stock outstanding, by equity instrument, if converted to common stock for each of the three and nine months ended September 30, 2021 and 2020 (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ ​ September 30, ​ September 30, ​ ​ ​ 2021 ​ 2020 ​ 2021 ​ 2020 ​ OP/DownREIT Units 22,529 22,321 22,493 22,312 Convertible preferred stock 2,918 2,918 2,918 2,960 Unvested LTIP Units and unvested restricted stock 3,336 290 1,047 311 ​

NONCONTROLLING INTERESTS

NONCONTROLLING INTERESTS	9 Months Ended
	Sep. 30, 2021
NONCONTROLLING INTERESTS
NONCONTROLLING INTERESTS	9. NONCONTROLLING INTERESTS Redeemable Noncontrolling Interests in the Operating Partnership and DownREIT Partnership Interests in the Operating Partnership and the DownREIT Partnership held by limited partners are represented by OP Units and DownREIT Units, respectively. The income is allocated to holders of OP Units/DownREIT Units based upon net income attributable to common stockholders and the weighted average number of OP Units/DownREIT Units outstanding to total common shares plus OP Units/DownREIT Units outstanding during the period. Capital contributions, distributions, and profits and losses are allocated to noncontrolling interests in accordance with the terms of the partnership agreements of the Operating Partnership and the DownREIT Partnership. Limited partners of the Operating Partnership and the DownREIT Partnership have the right to require such partnership to redeem all or a portion of the OP Units/DownREIT Units held by the limited partner at a redemption price equal to and in the form of the Cash Amount (as defined in the partnership agreement of the Operating Partnership or the DownREIT Partnership, as applicable), provided that such OP Units/DownREIT Units have been outstanding for at least one year, subject to certain exceptions. UDR, as the general partner of the Operating Partnership and the DownREIT Partnership may, in its sole discretion, purchase the OP Units/DownREIT Units by paying to the limited partner either the Cash Amount or the REIT Share Amount (generally one share of common stock of the Company for each OP Unit/DownREIT Unit), as defined in the partnership agreement of the Operating Partnership or the DownREIT Partnership, as applicable. Accordingly, the Company records the OP Units/DownREIT Units outside of permanent equity and reports the OP Units/DownREIT Units at their redemption value using the Company’s stock price at each balance sheet date. The following table sets forth redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership for the following period ( dollars in thousands ​ ​ ​ ​ ​ Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership, December 31, 2020 $ 856,294 ​ Mark-to-market adjustment to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership ​ 351,707 ​ Conversion of OP Units/DownREIT Units to Common Stock ​ (6,944) ​ Net income/(loss) attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership ​ 2,221 ​ Distributions to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership ​ (25,325) ​ Vesting of Long-Term Incentive Plan Units ​ ​ 14,578 ​ Allocation of other comprehensive income/(loss) ​ 192 ​ Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership, September 30, 2021 ​ $ 1,192,723 ​ ​ Noncontrolling Interests Noncontrolling interests represent interests of unrelated partners and unvested LTIP Units in certain consolidated affiliates, and are presented as part of equity on the Consolidated Balance Sheets since these interests are not redeemable. Net (income)/loss attributable to noncontrolling interests The Company grants LTIP Units to certain employees and non-employee directors. The LTIP Units represent an ownership interest in the Operating Partnership and have vesting terms of between one Noncontrolling interests related to long-term incentive plan units represent the unvested LTIP Units of these employees and non-employee directors in the Operating Partnership. The net income/(loss) allocated to the unvested LTIP Units are included in Net (income)/loss attributable to noncontrolling interests

FAIR VALUE OF DERIVATIVES AND F

FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 2021
FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS
FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS	10. FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS Fair value is based on the price that would be received to sell an asset or the exit price that would be paid to transfer a liability in an orderly transaction between market participants at the measurement date. A three-level valuation hierarchy prioritizes observable and unobservable inputs used to measure fair value. The fair value hierarchy consists of three broad levels, which are described below: ● Level 1 — Quoted prices in active markets for identical assets or liabilities that the entity has the ability to access. ● Level 2 — Observable inputs other than prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated with observable market data. ● Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets and liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs. The estimated fair values of the Company’s financial instruments either recorded or disclosed on a recurring basis as of September 30, 2021 and December 31, 2020, are summarized as follows (dollars in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value at September 30, 2021, Using ​ ​ Total ​ ​ ​ Quoted ​ ​ ​ ​ ​ ​ Carrying ​ ​ ​ Prices in ​ ​ ​ ​ ​ ​ Amount in ​ ​ ​ Active ​ ​ ​ ​ ​ ​ ​ Statement of ​ ​ ​ ​ Markets ​ Significant ​ ​ ​ ​ ​ Financial ​ Fair Value ​ for Identical ​ Other ​ Significant ​ ​ Position at ​ Estimate at ​ Assets or ​ Observable ​ Unobservable ​ ​ September 30, ​ September 30, ​ Liabilities ​ Inputs ​ Inputs ​ ​ 2021 (a) ​ 2021 ​ (Level 1) ​ (Level 2) ​ (Level 3) Description: ​ ​ ​ ​ ​ ​ Notes receivable, net (b) ​ $ 25,741 ​ $ 26,166 ​ $ — ​ $ — ​ $ 26,166 Equity securities (c) ​ ​ 4,345 ​ ​ 4,345 ​ ​ — ​ ​ — ​ ​ 4,345 Derivatives - Interest rate contracts (d) ​ 1,285 ​ 1,285 ​ — ​ 1,285 ​ — Total assets ​ $ 31,371 ​ $ 31,796 ​ $ — ​ $ 1,285 ​ $ 30,511 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives - Interest rate contracts (d) ​ $ 148 ​ $ 148 ​ $ — ​ $ 148 ​ $ — Secured debt instruments - fixed rate: (e) ​ ​ ​ ​ ​ ​ Mortgage notes payable ​ ​ 1,035,158 ​ ​ 1,049,786 ​ ​ — ​ ​ — ​ ​ 1,049,786 Secured debt instruments - variable rate: (e) ​ ​ ​ ​ ​ ​ Tax-exempt secured notes payable ​ 27,000 ​ 27,000 ​ — ​ — ​ 27,000 Unsecured debt instruments: (e) ​ ​ ​ ​ ​ ​ Working capital credit facility ​ ​ 43,086 ​ ​ 43,086 ​ ​ — ​ ​ — ​ ​ 43,086 Commercial paper program ​ ​ 315,000 ​ ​ 315,000 ​ ​ — ​ ​ — ​ ​ 315,000 Unsecured notes ​ ​ 4,133,592 ​ ​ 4,265,616 ​ ​ — ​ ​ — ​ ​ 4,265,616 Total liabilities ​ $ 5,553,984 ​ $ 5,700,636 ​ $ — ​ $ 148 ​ $ 5,700,488 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership (f) ​ $ 1,192,723 ​ $ 1,192,723 ​ $ — ​ $ 1,192,723 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value at December 31, 2020, Using ​ ​ Total ​ ​ ​ Quoted ​ ​ ​ ​ ​ ​ Carrying ​ ​ ​ Prices in ​ ​ ​ ​ ​ ​ Amount in ​ ​ ​ Active ​ ​ ​ ​ ​ ​ Statement of ​ ​ ​ Markets ​ Significant ​ ​ ​ ​ Financial ​ Fair Value ​ for Identical ​ Other ​ Significant ​ ​ Position at ​ Estimate at ​ Assets or ​ Observable ​ Unobservable ​ ​ December 31, ​ December 31, ​ Liabilities ​ Inputs ​ Inputs ​ 2020 (a) ​ 2020 ​ (Level 1) ​ (Level 2) ​ (Level 3) Description: ​ ​ ​ ​ ​ ​ Notes receivable, net (b) ​ $ 157,992 ​ $ 170,411 ​ $ — ​ $ — ​ $ 170,411 Derivatives - Interest rate contracts (d) ​ 2 ​ 2 ​ — ​ 2 ​ — Total assets ​ $ 157,994 ​ $ 170,413 ​ $ — ​ $ 2 ​ $ 170,411 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives - Interest rate contracts (d) ​ $ 167 ​ $ 167 ​ $ — ​ $ 167 ​ $ — Secured debt instruments - fixed rate: (e) ​ ​ ​ ​ ​ ​ Mortgage notes payable ​ ​ 837,473 ​ ​ 854,084 ​ ​ — ​ ​ — ​ ​ 854,084 Secured debt instruments - variable rate: (e) ​ ​ ​ ​ ​ ​ Tax-exempt secured notes payable ​ 27,000 ​ 27,000 ​ — ​ — ​ 27,000 Unsecured debt instruments: (e) ​ ​ ​ ​ ​ ​ ​ Working capital credit facility ​ ​ 28,024 ​ ​ 28,024 ​ ​ — ​ ​ — ​ ​ 28,024 Commercial paper program ​ ​ 190,000 ​ ​ 190,000 ​ ​ — ​ ​ — ​ ​ 190,000 Unsecured notes ​ ​ 3,922,314 ​ ​ 4,283,045 ​ ​ — ​ ​ — ​ ​ 4,283,045 Total liabilities ​ $ 5,004,978 ​ $ 5,382,320 ​ $ — ​ $ 167 ​ $ 5,382,153 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership (f) ​ $ 856,294 ​ $ 856,294 ​ $ — ​ $ 856,294 ​ $ — (a) Balances include fair market value adjustments and exclude deferred financing costs. (b) See Note 2, Significant Accounting Policies . (c) The Company holds an investment in a publicly traded real estate technology company that is subject to a lock-up restriction on selling or transferring the investment for a period of time. The investment is valued at the market price at the end of the period less an illiquidity discount of 15.0%. The Company classifies the investment as Level 3 in the fair value hierarchy based upon the lock-up restriction. (d) See Note 11, Derivatives and Hedging Activity . (e) See Note 7, Secured and Unsecured Debt, Net . (f) See Note 9, Noncontrolling Interests. There were no transfers into or out of any of the levels of the fair value hierarchy during the nine months ended September 30, 2021. Financial Instruments Carried at Fair Value The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash receipts (or payments) and the discounted expected variable cash payments (or receipts). The variable cash payments (or receipts) are based on an expectation of future interest rates (forward curves) derived from observable market interest rate curves. The fair values of interest rate swaps and caps are determined using the market standard methodology of discounting the future expected cash receipts that would occur if variable interest rates rise above the strike rate of the caps. The variable interest rates used in the calculation of projected receipts on the cap are based on an expectation of future interest rates derived from observable market interest rate curves and volatilities. The Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts, and guarantees. Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by itself and its counterparties. However, as of September 30, 2021 and December 31, 2020, the Company has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives. As a result, the Company has determined that its derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. In conjunction with the FASB’s fair value measurement guidance, the Company made an accounting policy election to measure the credit risk of its derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio. Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership have a redemption feature and are marked to their redemption value. The redemption value is based on the fair value of the Company’s common stock at the redemption date, and therefore, is calculated based on the fair value of the Company’s common stock at the balance sheet date. Since the valuation is based on observable inputs such as quoted prices for similar instruments in active markets, redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership are classified as Level 2. Financial Instruments Not Carried at Fair Value At September 30, 2021 and December 31, 2020, the fair values of cash and cash equivalents, restricted cash, accounts receivable, prepaids, real estate taxes payable, accrued interest payable, security deposits and prepaid rent, distributions payable and accounts payable approximated their carrying values because of the short term nature of these instruments. The estimated fair values of other financial instruments, which includes notes receivable and debt instruments, are classified in Level 3 of the fair value hierarchy due to the significant unobservable inputs that are utilized in their respective valuations.

DERIVATIVES AND HEDGING ACTIVIT

DERIVATIVES AND HEDGING ACTIVITY	9 Months Ended
	Sep. 30, 2021
DERIVATIVES AND HEDGING ACTIVITY
DERIVATIVES AND HEDGING ACTIVITY	11. DERIVATIVES AND HEDGING ACTIVITY Risk Management Objective of Using Derivatives The Company is exposed to certain risks arising from both its business operations and economic conditions. The Company principally manages its exposures to a wide variety of business and operational risks through management of its core business activities. The Company manages economic risks, including interest rate, liquidity, and credit risk, primarily by managing the amount, sources, and duration of its debt funding and through the use of derivative financial instruments. Specifically, the Company may enter into derivative financial instruments to manage exposures that arise from business activities that result in the receipt or payment of future known and uncertain cash amounts, the value of which are determined by interest rates. The Company’s derivative financial instruments are used to manage differences in the amount, timing, and duration of the Company’s known or expected cash receipts and its known or expected cash payments principally related to the Company’s investments and borrowings. Cash Flow Hedges of Interest Rate Risk The Company’s objectives in using interest rate derivatives are to add stability to interest expense and to manage its exposure to interest rate movements. To accomplish this objective, the Company primarily uses interest rate swaps and caps as part of its interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty in exchange for the Company making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. Interest rate caps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty if interest rates rise above the strike rate on the contract in exchange for an up-front premium. The changes in the fair value of derivatives designated and that qualify as cash flow hedges are recorded in Accumulated other comprehensive income/(loss), net into earnings in the period that the hedged forecasted transaction affects earnings. During the three and nine months ended September 30, 2021 and 2020, such derivatives were used to hedge the variable cash flows associated with existing variable-rate debt. Amounts reported in Accumulated other comprehensive income/(loss), net Interest expense As of September 30, 2021, the Company had the following outstanding interest rate derivatives that were designated as cash flow hedges of interest rate risk ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ Number of ​ Product ​ Instruments ​ Notional Interest rate swaps and caps (a) ​ 4 ​ $ 334,880 (a) In addition to the interest rate swaps summarized above, the Company entered into two additional interest rate swaps with a total notional value of $175.0 million that will become effective in July 2022 upon maturity of the $315.0 million notional value interest rate swaps included above. Derivatives not designated as hedges are not speculative and are used to manage the Company’s exposure to interest rate movements and other identified risks but do not meet the strict hedge accounting requirements of GAAP. Changes in the fair value of derivatives not designated in hedging relationships are recorded directly in earnings. As of September 30, 2021, no derivatives not designated as hedges were held by the Company. Tabular Disclosure of Fair Values of Derivative Instruments on the Consolidated Balance Sheet The table below presents the fair value of the Company’s derivative financial instruments as well as their classification on the Consolidated Balance Sheets as of September 30, 2021 and December 31, 2020 ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset Derivatives ​ Liability Derivatives ​ ​ (included in Other assets ) ​ (included in Other liabilities ) ​ ​ Fair Value at: ​ Fair Value at: ​ ​ September 30, ​ December 31, ​ September 30, ​ December 31, ​ ​ 2021 ​ 2020 ​ 2021 ​ 2020 Derivatives designated as hedging instruments: ​ ​ ​ ​ Interest rate products ​ $ 1,285 ​ $ 2 ​ $ 148 ​ $ 167 ​ Tabular Disclosure of the Effect of Derivative Instruments on the Consolidated Statements of Operations The tables below present the effect of the Company’s derivative financial instruments on the Consolidated Statements of Operations for the three and nine months ended September 30, 2021 and 2020 ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gain/(Loss) Recognized in ​ ​ ​ ​ Gain/(Loss) Reclassified ​ Interest expense ​ ​ Unrealized holding gain/(loss) ​ from Accumulated OCI into ​ (Amount Excluded from ​ ​ Recognized in OCI ​ Interest expense ​ Effectiveness Testing) Derivatives in Cash Flow Hedging Relationships 2021 2020 2021 2020 2021 2020 Three Months Ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate products ​ $ 1,389 ​ $ (30) ​ $ (441) ​ $ (1,585) ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate products ​ $ 1,422 ​ $ (3,241) ​ $ (1,314) ​ $ (3,234) ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ ​ 2021 ​ 2020 ​ 2021 ​ 2020 Total amount of Interest expense ​ $ 36,289 ​ $ 62,268 ​ $ 149,849 ​ $ 140,182 ​ Credit-risk-related Contingent Features The Company has agreements with its derivative counterparties that contain a provision where the Company could be declared in default on its derivative obligations if repayment of the underlying indebtedness is accelerated by the lender due to the Company’s default on the indebtedness. The Company has certain agreements with some of its derivative counterparties that contain a provision where, in the event of default by the Company or the counterparty, the right of setoff may be exercised. Any amount payable to one party by the other party may be reduced by its setoff against any amounts payable by the other party. Events that give rise to default by either party may include, but are not limited to, the failure to pay or deliver payment under the derivative agreement, the failure to comply with or perform under the derivative agreement, bankruptcy, a merger without assumption of the derivative agreement, or in a merger, a surviving entity’s creditworthiness is materially weaker than the original party to the derivative agreement. Tabular Disclosure of Offsetting Derivatives The Company has elected not to offset derivative positions on the consolidated financial statements. The tables below present the effect on its financial position had the Company made the election to offset its derivative positions as of September 30, 2021 and December 31, 2020 (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross Net Amounts of Gross Amounts Not Offset ​ ​ ​ ​ ​ ​ ​ ​ Amounts ​ Assets ​ in the Consolidated ​ ​ ​ ​ ​ Gross ​ Offset in the ​ Presented in the ​ Balance Sheet ​ ​ ​ ​ ​ Amounts of ​ Consolidated ​ Consolidated ​ ​ ​ ​ Cash ​ ​ ​ ​ ​ Recognized ​ Balance ​ Balance Sheets ​ Financial ​ Collateral ​ ​ ​ Offsetting of Derivative Assets ​ Assets ​ Sheets ​ (a) ​ Instruments Received Net Amount September 30, 2021 ​ $ 1,285 ​ $ — ​ $ 1,285 ​ $ (100) ​ $ — ​ $ 1,185 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ $ 2 ​ $ — ​ $ 2 ​ $ — ​ $ — ​ $ 2 (a) Amounts reconcile to the aggregate fair value of derivative assets in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Consolidated Balance Sheets” located in this footnote. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross Net Amounts of Gross Amounts Not Offset ​ ​ ​ ​ ​ ​ ​ ​ Amounts ​ Liabilities ​ in the Consolidated ​ ​ ​ ​ ​ Gross ​ Offset in the ​ Presented in the ​ Balance Sheet ​ ​ ​ ​ ​ Amounts of ​ Consolidated ​ Consolidated ​ ​ ​ ​ Cash ​ ​ ​ ​ ​ Recognized ​ Balance ​ Balance Sheets ​ Financial ​ Collateral ​ ​ ​ Offsetting of Derivative Liabilities Liabilities Sheets (a) Instruments Posted Net Amount September 30, 2021 ​ $ 148 ​ $ — ​ $ 148 ​ $ (100) ​ $ — ​ $ 48 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ $ 167 ​ $ — ​ $ 167 ​ $ — ​ $ — ​ $ 167 (a) Amounts reconcile to the aggregate fair value of derivative liabilities in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Consolidated Balance Sheets” located in this footnote.

STOCK BASED COMPENSATION

STOCK BASED COMPENSATION	9 Months Ended
	Sep. 30, 2021
STOCK BASED COMPENSATION
STOCK BASED COMPENSATION	12. STOCK BASED COMPENSATION The Company recognized stock based compensation expense, inclusive of awards granted to our non-employee directors, net of capitalization, of $6.2 million and $4.3 million during the three months ended September 30, 2021 and 2020, respectively, and $17.5 million and $15.1 million during the nine months ended September 30, 2021 and 2020, respectively, which are included in General and Administrative In May 2021, the stockholders of UDR approved the amendment and restatement of the UDR, Inc. 1999 Long-Term Incentive Plan, which, among other things, increased the number of shares reserved for issuance under such plan by 16,000,000 shares, from 19,000,000 shares to 35,000,000 shares.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2021
COMMITMENTS AND CONTINGENCIES
COMMITMENTS AND CONTINGENCIES	13. COMMITMENTS AND CONTINGENCIES Commitments Real Estate Commitments The following summarizes the Company’s real estate commitments at September 30, 2021 ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number ​ UDR's ​ UDR's Remaining ​ ​ ​ Properties ​ Investment (a) ​ Commitment ​ Wholly-owned — under development 5 ​ $ 331,645 ​ $ 169,855 Joint ventures: ​ ​ Preferred equity investments 3 ​ ​ 23,767 (b) ​ 43,377 (b) Real estate technology investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ RETV I ​ - ​ ​ 38,628 ​ ​ 5,220 ​ RETV II ​ - ​ ​ 5,438 ​ ​ 12,600 ​ Total ​ $ 399,478 ​ $ 231,052 (a) Represents UDR’s investment as of September 30, 2021. (b) Represents UDR’s investment in and remaining commitment for Makers Rise, 121 at Watters and Infield Phase I, which are under development as of September 30, 2021. Purchase Commitments In September 2021, the Company entered into a contract to acquire a 663 apartment home operating community located in Orlando, Florida, for a purchase price of approximately $177.5 million. The Company made a $10.0 million deposit on the purchase, which is generally non-refundable other than due to a failure of closing conditions pursuant to the terms of the purchase agreement. The acquisition closed in October 2021. Contingencies Litigation and Legal Matters The Company is subject to various legal proceedings and claims arising in the ordinary course of business. The Company cannot determine the ultimate liability with respect to such legal proceedings and claims at this time. The Company believes that such liability, to the extent not provided for through insurance or otherwise, will not have a material adverse effect on our financial condition, results of operations or cash flows.

REPORTABLE SEGMENTS

REPORTABLE SEGMENTS	9 Months Ended
	Sep. 30, 2021
REPORTABLE SEGMENTS
REPORTABLE SEGMENTS	14. REPORTABLE SEGMENTS GAAP guidance requires that segment disclosures present the measure(s) used by the Chief Operating Decision Maker to decide how to allocate resources and for purposes of assessing such segments’ performance. UDR’s Chief Operating Decision Maker is comprised of several members of its executive management team who use several generally accepted industry financial measures to assess the performance of the business for our reportable operating segments. UDR owns and operates multifamily apartment communities that generate rental and other property related income through the leasing of apartment homes to a diverse base of tenants. The primary financial measures for UDR’s apartment communities are rental income and net operating income (“NOI”). Rental income represents gross market rent less adjustments for concessions, vacancy loss and bad debt. NOI is defined as rental income less direct property rental expenses. Rental expenses include real estate taxes, insurance, personnel, utilities, repairs and maintenance, administrative and marketing. Excluded from NOI is property management expense, which is calculated as 3.0% of property revenue, and land rent. Property management expense covers costs directly related to consolidated property operations, inclusive of corporate management, regional supervision, accounting and other costs. UDR’s Chief Operating Decision Maker utilizes NOI as the key measure of segment profit or loss. UDR’s two reportable segments are Same-Store Communities Non-Mature Communities/Other ● Same-Store Communities represent those communities acquired, developed, and stabilized prior to July 1, 2020 (for quarter-to-date comparison) and January 1, 2020 (for year-to-date comparison) and held as of September 30, 2021. A comparison of operating results from the prior year is meaningful as these communities were owned and had stabilized occupancy and operating expenses as of the beginning of the prior period, there is no plan to conduct substantial redevelopment activities, and the community is not classified as held for disposition within the current year. A community is considered to have stabilized occupancy once it achieves 90% occupancy for at least three consecutive months. ● Non-Mature Communities/Other represent those communities that do not meet the criteria to be included in Same-Store Communities , including, but not limited to, recently acquired, developed and redeveloped communities, and the non-apartment components of mixed use properties. Management evaluates the performance of each of our apartment communities on a Same-Store Community Non-Mature Community/Other All revenues are from external customers and no single tenant or related group of tenants contributed 10% or more of UDR’s total revenues during the three and nine months ended September 30, 2021 and 2020. ​ The following is a description of the principal streams from which the Company generates its revenue: Lease Revenue ​ Lease revenue related to leases is recognized on an accrual basis when due from residents or tenants in accordance with ASC 842, Leases ​ Lease revenue also includes all pass-through revenue from retail and residential leases and common area maintenance reimbursements from retail leases. These services represent non-lease components in a contract as the Company transfers a service to the lessee other than the right to use the underlying asset. The Company has elected the practical expedient under the leasing standard to not separate lease and non-lease components from its resident and retail lease contracts as the timing and pattern of revenue recognition for the non-lease component and related lease component are the same and the combined single lease component would be classified as an operating lease. ​ Other Revenue ​ Other revenue is generated by services provided by the Company to its retail and residential tenants and other unrelated third parties. Revenue is measured based on consideration specified in contracts with customers. The Company recognizes when it satisfies a performance obligation by providing the services specified in a contract to the customer. ​ Joint venture management and other fees ​ The Joint venture management and other fees Joint venture management and other fees ​ The following table details rental income and NOI for UDR’s reportable segments for the three and nine months ended September 30, 2021 and 2020, and reconciles NOI to Net income/(loss) attributable to UDR, Inc. (dollars in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, (a) ​ September 30, (b) ​ 2021 2020 2021 2020 Reportable apartment home segment lease revenue ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Same-Store Communities (a) ​ ​ ​ ​ ​ West Region ​ $ 108,042 ​ $ 101,424 ​ $ 304,594 ​ $ 314,060 Mid-Atlantic Region ​ 61,984 ​ 60,754 ​ 183,291 ​ 184,524 Northeast Region ​ 52,079 ​ 48,819 ​ 155,996 ​ 159,459 Southeast Region ​ 38,400 ​ 35,724 ​ 106,668 ​ 101,768 Southwest Region ​ 24,734 ​ 23,230 ​ 71,710 ​ 70,424 Non-Mature Communities/Other ​ 33,388 ​ 27,246 ​ 87,624 ​ 76,167 Total segment and consolidated lease revenue ​ $ 318,627 ​ $ 297,197 ​ $ 909,883 ​ $ 906,402 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reportable apartment home segment other revenue ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Same-Store Communities (a) ​ ​ ​ ​ ​ West Region ​ $ 2,673 ​ $ 3,420 ​ $ 7,877 ​ $ 9,186 Mid-Atlantic Region ​ 2,330 ​ 2,060 ​ 6,006 ​ 5,298 Northeast Region ​ 1,481 ​ 1,600 ​ 3,573 ​ 4,033 Southeast Region ​ 1,654 ​ 1,498 ​ 4,861 ​ 4,214 Southwest Region ​ 1,045 ​ 1,050 ​ 2,976 ​ 2,615 Non-Mature Communities/Other ​ 889 ​ 2,020 ​ 2,465 ​ 3,172 Total segment and consolidated other revenue ​ $ 10,072 ​ $ 11,648 ​ $ 27,758 ​ $ 28,518 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total reportable apartment home segment rental income ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Same-Store Communities (a) ​ ​ ​ ​ ​ West Region ​ $ 110,715 ​ $ 104,844 ​ $ 312,471 ​ $ 323,246 Mid-Atlantic Region ​ 64,314 ​ 62,814 ​ 189,297 ​ 189,822 Northeast Region ​ 53,560 ​ 50,419 ​ 159,569 ​ 163,492 Southeast Region ​ 40,054 ​ 37,222 ​ 111,529 ​ 105,982 Southwest Region ​ 25,779 ​ 24,280 ​ 74,686 ​ 73,039 Non-Mature Communities/Other ​ 34,277 ​ 29,266 ​ 90,089 ​ 79,339 Total segment and consolidated rental income ​ $ 328,699 ​ $ 308,845 ​ $ 937,641 ​ $ 934,920 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reportable apartment home segment NOI ​ ​ ​ ​ Same-Store Communities (a) ​ ​ ​ ​ West Region ​ $ 81,562 ​ $ 76,435 ​ $ 228,743 ​ $ 241,071 Mid-Atlantic Region ​ 43,794 ​ 43,189 ​ 129,931 ​ 132,435 Northeast Region ​ 33,049 ​ 30,655 ​ 100,619 ​ 108,164 Southeast Region ​ 26,444 ​ 24,517 ​ 74,926 ​ 71,701 Southwest Region ​ 16,104 ​ 14,331 ​ 46,253 ​ 44,248 Non-Mature Communities/Other ​ 18,527 ​ 22,005 ​ 48,702 ​ 51,231 Total segment and consolidated NOI ​ 219,480 ​ 211,132 ​ 629,174 ​ 648,850 Reconciling items: ​ ​ ​ ​ Joint venture management and other fees ​ 1,071 ​ 1,199 ​ 4,918 ​ 3,861 Property management ​ (9,861) ​ (8,879) ​ (28,129) ​ (26,879) Other operating expenses ​ (4,237) ​ (5,543) ​ (13,045) ​ (16,609) Real estate depreciation and amortization ​ (152,636) ​ (151,949) ​ (442,893) ​ (462,481) General and administrative ​ (15,810) ​ (11,958) ​ (43,673) ​ (37,907) Casualty-related (charges)/recoveries, net ​ (1,568) ​ — ​ (4,682) ​ (1,353) Other depreciation and amortization ​ (3,269) ​ (3,887) ​ (8,472) ​ (7,939) Gain/(loss) on sale of real estate owned ​ ​ — ​ ​ — ​ ​ 50,829 ​ ​ 61,303 Income/(loss) from unconsolidated entities ​ 14,450 ​ 2,940 ​ 29,123 ​ 14,328 Interest expense ​ (36,289) ​ (62,268) ​ (149,849) ​ (140,182) Interest income and other income/(expense), net ​ 8,238 ​ 2,183 ​ 12,831 ​ 7,304 Tax (provision)/benefit, net ​ (529) ​ (187) ​ (1,283) ​ (1,877) Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership ​ (1,260) ​ 1,990 ​ (2,221) ​ (2,614) Net (income)/loss attributable to noncontrolling interests ​ (49) ​ (31) ​ (73) ​ (71) Net income/(loss) attributable to UDR, Inc. ​ $ 17,731 ​ $ (25,258) ​ $ 32,555 ​ $ 37,734 (a) Same-Store Community population consisted of 45,713 apartment homes. (b) Same-Store Community population consisted of 45,143 apartment homes. ​ The following table details the assets of UDR’s reportable segments as of September 30, 2021 and December 31, 2020 (dollars in thousands) ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2021 ​ 2020 Reportable apartment home segment assets: ​ ​ Same-Store Communities (a): ​ ​ West Region ​ $ 4,273,694 ​ $ 4,242,973 Mid-Atlantic Region ​ 2,718,104 ​ 2,698,049 Northeast Region ​ 2,914,571 ​ 2,900,017 Southeast Region ​ 1,076,169 ​ 1,059,771 Southwest Region ​ 898,780 ​ 897,505 Non-Mature Communities/Other ​ 2,426,651 ​ 1,273,157 Total segment assets ​ 14,307,969 ​ 13,071,472 Accumulated depreciation ​ (5,017,941) ​ (4,605,366) Total segment assets — net book value ​ 9,290,028 ​ 8,466,106 Reconciling items: ​ ​ Cash and cash equivalents ​ 1,063 ​ 1,409 Restricted cash ​ 28,170 ​ 22,762 Notes receivable, net ​ 25,741 ​ 157,992 Investment in and advances to unconsolidated joint ventures, net ​ 643,902 ​ 600,233 Operating lease right-of-use assets ​ ​ 198,339 ​ ​ 200,913 Other assets ​ 213,321 ​ 188,118 Total consolidated assets ​ $ 10,400,564 ​ $ 9,637,533 (a) Same-Store Community population consisted of 45,713 apartment homes. ​ Markets included in the above geographic segments are as follows: i. West Region — Orange County, San Francisco, Seattle, Los Angeles, Monterey Peninsula, Other Southern California and Portland ii. Mid-Atlantic Region — Metropolitan D.C., Baltimore and Richmond iii. Northeast Region — Boston, New York and Philadelphia iv. Southeast Region — Tampa, Orlando, Nashville and Other Florida v. Southwest Region — Dallas, Austin and Denver

SIGNIFICANT ACCOUNTING POLICI_2

SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2021
SIGNIFICANT ACCOUNTING POLICIES
Recent Accounting Pronouncements	Recent Accounting Pronouncements In March 2020, the SEC adopted rules that amended the financial disclosure requirements for subsidiary issuers and guarantors of registered debt securities in Rule 3-10 of Regulation S-X. Subsequently, in November 2020, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2020-09, Debt (Topic 470): Amendments to SEC Paragraphs Pursuant to SEC Release No. 33-10762, which revised SEC paragraphs of the codification to reflect, as appropriate, the amended disclosure requirements mentioned above. Under the amended rules, parent companies can provide alternative disclosures in lieu of separate audited financial statements of subsidiary issuers and guarantors that meet certain criteria. We evaluated the criteria and determined that we are eligible for the exceptions, which allow us to provide alternative disclosures for the Operating Partnership, which guarantees certain outstanding debt securities issued by the Company. As a result of the amendments, the Operating Partnership, as subsidiary guarantor, is no longer subject to the filing requirements under Section 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and will no longer file separate periodic and current reports in reliance on Rule 12h-5 under the Exchange Act. The alternative disclosures related to the Operating Partnership are presented in Item 2 "Management's Discussion and Analysis of Financial Condition and Results of Operations” in this report. ​ I n August 2020, the FASB issued ASU 2020-06, Debt—Debt With Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in E ntity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity ​ In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848)
Principles of Consolidation	Principles of Consolidation The Company accounts for subsidiary partnerships, joint ventures and other similar entities in which it holds an ownership interest in accordance with the consolidation guidance. The Company first evaluates whether each entity is a variable interest entity (“VIE”). Under the VIE model, the Company consolidates an entity when it has control to direct the activities of the VIE and the obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. Under the voting model, the Company consolidates an entity when it controls the entity through ownership of a majority voting interest.
Real Estate Sales Gain Recognition	Real Estate Sales Gain Recognition ​ For sale transactions resulting in a transfer of a controlling financial interest of a property, the Company generally derecognizes the related assets and liabilities from its Consolidated Balance Sheets and records the gain or loss in the period in which the transfer of control occurs. If control of the property has not transferred to the counterparty, the criteria for derecognition are not met and the Company will continue to recognize the related assets and liabilities on its Consolidated Balance Sheets. ​ Sale transactions to entities in which the Company sells a controlling financial interest in a property but retains a noncontrolling interest are accounted for as partial sales. Partial sales resulting in a change in control are accounted for at fair value and a full gain or loss is recognized. Therefore, the Company will record a gain or loss on the partial interest sold, and the initial measurement of our retained interest will be accounted for at fair value. ​ Sales of real estate to joint ventures or other noncontrolled investees are also accounted for at fair value and the Company will record a full gain or loss in the period the property is contributed. ​ To the extent that the Company acquires a controlling financial interest in a property that it previously accounted for as an equity method investment, the Company will not remeasure its previously held interest if the acquisition is treated as an asset acquisition. The Company will include the carrying amount of its previously held equity method interest along with the consideration paid and transaction costs incurred in determining the amounts to allocate to the related assets and liabilities acquired on its Consolidated Balance Sheets. When treated as an asset acquisition, the Company will not recognize a gain or loss on consolidation of a property.
Allowance for Credit Losses	Allowance for Credit Losses The Company accounts for allowance for credit losses under the current expected credit loss (“CECL”) impairment model for its financial assets, including trade and other receivables, held-to-maturity debt securities, loans and other financial instruments, and presents the net amount of the financial instrument expected to be collected. The CECL impairment model excludes operating lease receivables. The CECL impairment model requires an estimate of expected credit losses, measured over the contractual life of an instrument, that considers forecasts of future economic conditions in addition to information about past events and current conditions. Based on this model, we analyze the following criteria, as applicable in developing allowances for credit losses: historical loss information, the borrower’s ability to make scheduled payments, the remaining time to maturity, the value of underlying collateral, projected future performance of the borrower and macroeconomic trends. ​ The Company measures credit losses of financial assets on a collective (pool) basis when similar risk characteristics exist. If the Company determines that a financial asset does not share risk characteristics with its other financial assets, the Company evaluates the financial asset for expected credit losses on an individual basis. Allowance for credit losses are recorded as a direct reduction from an asset’s amortized cost basis. Credit losses and recoveries are recorded in Interest income and other income/(expense), net ​ The Company has made the optional election provided by the standard not to measure allowance for credit losses for accrued interest receivables as the Company writes off any uncollectible accrued interest receivables in a timely manner. The Company periodically evaluates the collectability of its accrued interest receivables. A write-off is recorded when the Company concludes that all or a portion of its accrued interest receivable balance is no longer collectible.
Notes Receivable	Notes Receivable Notes receivable relate to financing arrangements which are typically secured by real estate, real estate related projects or other assets. Certain of the loans we extend may include characteristics such as options to purchase the project within a specific time window following expected project completion. These characteristics can cause the loans to fall under the definition of a VIE, and thus trigger consolidation consideration. We consider the facts and circumstances pertinent to each loan, including the relative amount of financing we are contributing to the overall project cost, decision making rights or control we hold, and our rights to expected residual gains or our obligations to absorb expected residual losses from the project. If we are deemed to be the primary beneficiary of a VIE due to holding a controlling financial interest, the majority of decision making control, or by other means, consolidation of the VIE would be required. The Company has concluded that it is not the primary beneficiary of the borrowing entities. Additionally, we analyze each loan arrangement that involves real estate development to consider whether the loan qualifies for accounting as a loan or as an investment in a real estate development project. The Company has evaluated its real estate loans, where appropriate, for accounting treatment as loans versus real estate development projects, as required by ASC 310-10. For each loan, the Company has concluded that the characteristics and the facts and circumstances indicate that loan accounting treatment is appropriate. The following table summarizes our Notes receivable, net dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate at ​ Balance Outstanding ​ September 30, September 30, December 31, ​ ​ 2021 ​ 2021 ​ 2020 Note due February 2021 (a) ​ N/A ​ $ — ​ $ 4,000 Note due May 2022 (b) ​ N/A % ​ — ​ ​ 20,000 Note due May 2022 (c) ​ 14.00 % ​ 2,760 ​ ​ — Note due October 2022 (d) N/A % ​ — ​ ​ 115,000 Note due January 2023 (e) ​ 10.00 % ​ 23,110 ​ ​ 19,685 Notes Receivable ​ ​ ​ ​ 25,870 ​ ​ 158,685 Allowance for credit losses ​ ​ ​ ​ (129) ​ ​ (693) Total notes receivable, net ​ $ 25,741 ​ $ 157,992 (a) In May 2020, the Company entered into a promissory note with an unaffiliated third party with an aggregate commitment of $4.0 million, in connection with the sale of an operating community. In January 2021, the unaffiliated third party repaid the $4.0 million promissory note. (b) The Company previously had a secured note with an unaffiliated third party with an aggregate commitment of $20.0 million. The note was secured by a parcel of land and related land improvements located in Alameda, California. In September 2020, the developer defaulted on the loan. As a result of the default, in April 2021, the Company took title to the property pursuant to a deed in lieu of foreclosure. As such, t he Company increased its real estate assets owned by approximately $25.0 million, the fair market value of the property on the date of the title transfer, and recorded a $0.1 million gain on extinguishment of the secured note to Interest income and other income/(expense), net on the Consolidated Statements of Operations, which was based on the note’s principal balance and unpaid accrued interest of $4.9 million. (See Note 3, Real Estate Owned for further discussion.) (c) The Company has a secured note with an unaffiliated third party with an aggregate commitment of $2.8 million, all of which has been funded. The note is secured by a to-be-developed parcel of land in Kissimmee, Florida. Interest payments are due when the loan matures. The note matures in May 2022. (d) The Company previously had a secured note with an unaffiliated third party with an aggregate commitment of $115.0 million. Interest payments were due when the loan matured. The note was secured by a first priority deed of trust on a 259 apartment home operating community in Bellevue, Washington, which was completed in 2020 . In July 2021, the Company acquired the operating community. In connection with the acquisition of this community, the note and the unpaid accrued interest were paid in full. (See Note 3, Real Estate Owned (e) The Company has a secured note with an unaffiliated third party with an aggregate commitment of $25.4 million, of which $23.1 million has been funded, including $3.4 million funded during the nine months ended September 30, 2021. Interest payments are due monthly. The note matures at the earliest of the following: (a) the closing of any private or public capital raising in the amount of $5.0 million or greater; (b) an acquisition; (c) acceleration in the event of default; or (d) January 2023. In August 2021, the terms of this secured note were amended to increase the aggregate commitment from $22.0 million to $25.4 million. The Company recognized $0.7 million and $2.0 million of interest income from notes receivable described above during the three months ended September 30, 2021 and 2020, respectively, and $4.6 million and $7.0 million of interest income for the notes receivable described above during the nine months ended September 30, 2021 and 2020, respectively, none of which was related party interest. Interest income is included in Interest income and other income/(expense), net
Comprehensive Income/(Loss)	Comprehensive Income/(Loss) Comprehensive income/(loss), which is defined as the change in equity during each period from transactions and other events and circumstances from nonowner sources, including all changes in equity during a period except for those resulting from investments by or distributions to stockholders, is displayed in the accompanying Consolidated Statements of Comprehensive Income/(Loss). For the three and nine months ended September 30, 2021 and 2020, the Company’s other comprehensive income/(loss) consisted of the gain/(loss) on derivative instruments that are designated as and qualify as cash flow hedges, (gain)/loss on derivative instruments reclassified from other comprehensive income/(loss) into earnings, and the allocation of other comprehensive income/(loss) to noncontrolling interests. The (gain)/loss on derivative instruments reclassified from other comprehensive income/(loss) is included in Interest expense Derivatives and Hedging Activity,
Income Taxes	Income Taxes Due to the structure of the Company as a REIT and the nature of the operations for the operating properties, no provision for federal income taxes has been provided for at UDR. Historically, the Company has generally incurred only state and local excise and franchise taxes. UDR has elected for certain consolidated subsidiaries to be treated as taxable REIT subsidiaries (“TRS”). Income taxes for our TRS are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities from a change in tax rate is recognized in earnings in the period of the enactment date. The Company’s deferred tax assets/(liabilities) are generally the result of differing depreciable lives on capitalized assets, temporary differences between book and tax basis of assets and liabilities and timing of expense recognition for certain accrued liabilities. As of September 30, 2021 and December 31, 2020, UDR’s net deferred tax asset/(liability) was ($0.7) million and ($3.2) million, respectively, and are recorded in Accounts payable, accrued expenses and other liabilities GAAP defines a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. GAAP also provides guidance on derecognition, classification, interest and penalties, accounting for interim periods, disclosure and transition. The Company recognizes and evaluates its tax positions using a two-step process. First, UDR determines whether a tax position is more likely than not (greater than 50 percent probability) to be sustained upon examination, including resolution of any related appeals or litigation processes, based on the technical merits of the position. Second, the Company will determine the amount of benefit to recognize and record the amount that is more likely than not to be realized upon ultimate settlement. The Company invests in assets that qualify for federal investment tax credits (“ITC”) through our TRS. An ITC reduces federal income taxes payable when qualifying depreciable property is acquired. The ITC is determined as a percentage of cost of the assets. The Company accounts for ITCs under the deferral method, under which the tax benefit from the ITC is deferred and amortized as a tax benefit into Tax (provision)/benefit, net Accounts payable, accrued expenses and other liabilities UDR had no material unrecognized tax benefit, accrued interest or penalties at September 30, 2021. UDR and its subsidiaries are subject to federal income tax as well as income tax of various state and local jurisdictions. The tax years 2018 through 2020 remain open to examination by tax jurisdictions to which we are subject. When applicable, UDR recognizes interest and/or penalties related to uncertain tax positions in Tax (provision)/benefit, net
Forward Sales Agreements	Forward Sales Agreements ​ The Company utilizes forward sales agreements for the future issuance of its common stock. When the Company enters into a forward sales agreement, the contract requires the Company to sell its shares to a counterparty at a predetermined price at a future date. The net sales price and proceeds attained by the Company will be determined on the dates of settlement, with adjustments during the term of the contract for the Company’s anticipated dividends as well as for a daily interest factor that varies with changes in the federal funds rate. The Company generally has the ability to determine the dates and method of settlement (i.e., gross physical settlement, net share settlement or cash settlement), subject to certain conditions and the right of the counterparty to accelerate settlement under certain circumstances. ​ The Company accounts for the shares of common stock reserved for issuance upon settlement as equity in accordance with ASC 815-40, Contracts in Entity's Own Equity ​ The guidance establishes a two-step process for evaluating whether an equity-linked financial instrument is considered indexed to the entity’s own stock, first, evaluating the instrument’s contingent exercise provisions and second, evaluating the instrument’s settlement provisions. When entering into forward sales agreements, we determined that (i) none of the agreement’s exercise contingencies are based on observable markets or indices besides those related to the market for our own stock price; and (ii) none of the settlement provisions preclude the agreements from being indexed to our own stock. ​ Before the issuance of shares of common stock, upon physical or net share settlement of the forward sales agreements, the Company expects that the shares issuable upon settlement of the forward sales agreements will be reflected in its diluted income/(loss) per share calculations using the treasury stock method. Under this method, the number of shares of common stock used in calculating diluted income/(loss) per share is deemed to be increased by the excess, if any, of the number of shares of common stock that would be issued upon full physical settlement of the forward sales agreements over the number of shares of common stock that could be purchased by the Company in the open market (based on the average market price during the period) using the proceeds receivable upon full physical settlement (based on the adjusted forward sale price at the end of the reporting period). When the Company physically or net share settles any forward sales agreement, the delivery of shares of common stock would result in an increase in the number of weighted average common shares outstanding and dilution to basic income/(loss) per share. (See Note 8, Income/(Loss) per Share
Impact of COVID-19 Pandemic	Impact of COVID-19 Pandemic ​ The Company continues to closely monitor the impact of the COVID-19 pandemic on all aspects of its business. The extent of the pandemic’s effect on our operational and financial performance will depend on future developments, including the duration and intensity of the pandemic, the timing and effectiveness of COVID-19 vaccines, the duration of government measures to mitigate the pandemic and the success of government rental assistance programs, all of which continue to be uncertain and difficult to predict. ​ Given the uncertainty, we cannot predict the effect on future periods, but the adverse impact that could occur on the Company’s future financial condition, results of operations and cash flows could be material ​ During the three and nine months ended September 30, 2021, the Company performed an analysis in accordance with the ASC 842, Leases, guidance to assess the collectibility of its operating lease receivables in light of the COVID-19 pandemic. This analysis included an assessment of collectibility of current and future rents and whether those lease payments were no longer probable of collection. In accordance with the leases guidance, if lease payments are no longer deemed to be probable over the life of the lease contract, we recognize revenue only when cash is received, and all existing contractual operating lease receivables and straight-line lease receivables are reserved. ​ As a result of its analysis, the Company reduced its reserve by approximately $3.0 million for multifamily tenant lease receivables and approximately $1.2 million for retail tenant lease receivables for its wholly-owned communities and communities held by joint ventures for the three months ended September 30, 2021. In aggregate, the reduction in reserve is reflected as a $4.1 million increase to Rental income and a $0.1 million increase to Income/(loss) from unconsolidated entities on the Consolidated Statements of Operations for the three months ended September 30, 2021. For the nine months ended September 30, 2021, the Company reserved approximately $1.8 million of incremental multifamily tenant lease receivables and approximately $0.3 million of incremental retail tenant lease receivables for its wholly-owned communities and communities held by joint ventures. In aggregate, the reserve is reflected as a $1.7 million reduction to Rental income and a $0.4 million reduction to Income/(loss) from unconsolidated entities on the Consolidated Statements of Operations for the nine months ended September 30, 2021. The impact to deferred leasing commissions was not material for the three and nine months ended September 30, 2021. ​ The Company did not recognize any other adjustments to the carrying amounts of assets or asset impairment charges due to the COVID-19 pandemic for the nine months ended September 30, 2021.

SIGNIFICANT ACCOUNTING POLICI_3

SIGNIFICANT ACCOUNTING POLICIES (Tables)	9 Months Ended
	Sep. 30, 2021
SIGNIFICANT ACCOUNTING POLICIES
Summary of notes receivable, net	The following table summarizes our Notes receivable, net dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate at ​ Balance Outstanding ​ September 30, September 30, December 31, ​ ​ 2021 ​ 2021 ​ 2020 Note due February 2021 (a) ​ N/A ​ $ — ​ $ 4,000 Note due May 2022 (b) ​ N/A % ​ — ​ ​ 20,000 Note due May 2022 (c) ​ 14.00 % ​ 2,760 ​ ​ — Note due October 2022 (d) N/A % ​ — ​ ​ 115,000 Note due January 2023 (e) ​ 10.00 % ​ 23,110 ​ ​ 19,685 Notes Receivable ​ ​ ​ ​ 25,870 ​ ​ 158,685 Allowance for credit losses ​ ​ ​ ​ (129) ​ ​ (693) Total notes receivable, net ​ $ 25,741 ​ $ 157,992 (a) In May 2020, the Company entered into a promissory note with an unaffiliated third party with an aggregate commitment of $4.0 million, in connection with the sale of an operating community. In January 2021, the unaffiliated third party repaid the $4.0 million promissory note. (b) The Company previously had a secured note with an unaffiliated third party with an aggregate commitment of $20.0 million. The note was secured by a parcel of land and related land improvements located in Alameda, California. In September 2020, the developer defaulted on the loan. As a result of the default, in April 2021, the Company took title to the property pursuant to a deed in lieu of foreclosure. As such, t he Company increased its real estate assets owned by approximately $25.0 million, the fair market value of the property on the date of the title transfer, and recorded a $0.1 million gain on extinguishment of the secured note to Interest income and other income/(expense), net on the Consolidated Statements of Operations, which was based on the note’s principal balance and unpaid accrued interest of $4.9 million. (See Note 3, Real Estate Owned for further discussion.) (c) The Company has a secured note with an unaffiliated third party with an aggregate commitment of $2.8 million, all of which has been funded. The note is secured by a to-be-developed parcel of land in Kissimmee, Florida. Interest payments are due when the loan matures. The note matures in May 2022. (d) The Company previously had a secured note with an unaffiliated third party with an aggregate commitment of $115.0 million. Interest payments were due when the loan matured. The note was secured by a first priority deed of trust on a 259 apartment home operating community in Bellevue, Washington, which was completed in 2020 . In July 2021, the Company acquired the operating community. In connection with the acquisition of this community, the note and the unpaid accrued interest were paid in full. (See Note 3, Real Estate Owned (e) The Company has a secured note with an unaffiliated third party with an aggregate commitment of $25.4 million, of which $23.1 million has been funded, including $3.4 million funded during the nine months ended September 30, 2021. Interest payments are due monthly. The note matures at the earliest of the following: (a) the closing of any private or public capital raising in the amount of $5.0 million or greater; (b) an acquisition; (c) acceleration in the event of default; or (d) January 2023. In August 2021, the terms of this secured note were amended to increase the aggregate commitment from $22.0 million to $25.4 million.

REAL ESTATE OWNED (Tables)

REAL ESTATE OWNED (Tables)	9 Months Ended
	Sep. 30, 2021
REAL ESTATE OWNED
Summary of carrying amounts for real estate owned (at cost)	​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2021 ​ 2020 Land ​ $ 2,301,297 ​ $ 2,139,765 Depreciable property — held and used: ​ ​ Land improvements ​ 238,522 ​ 233,823 Building, improvements, and furniture, fixtures and equipment ​ 11,313,023 ​ 10,292,782 Real estate intangible assets ​ ​ 50,030 ​ ​ 40,570 Under development: ​ ​ Land and land improvements ​ 74,399 ​ 73,702 Building, improvements, and furniture, fixtures and equipment ​ 257,246 ​ 174,175 Real estate held for disposition: ​ ​ Land and land improvements ​ 17,091 ​ 15,184 Building, improvements, and furniture, fixtures and equipment ​ 56,361 ​ 101,471 Real estate owned ​ 14,307,969 ​ 13,071,472 Accumulated depreciation (a) ​ (5,017,941) ​ (4,605,366) Real estate owned, net ​ $ 9,290,028 ​ $ 8,466,106 (a) Accumulated depreciation is inclusive of $8.0 million and $5.8 million of accumulated amortization related to real estate intangible assets as of September 30, 2021 and December 31, 2020, respectively. ​

JOINT VENTURES AND PARTNERSHI_2

JOINT VENTURES AND PARTNERSHIPS (Tables)	9 Months Ended
	Sep. 30, 2021
JOINT VENTURES AND PARTNERSHIPS
Schedule of unconsolidated joint ventures and partnerships	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of ​ Number of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating ​ Apartment ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income/(loss) from investments ​ ​ ​ ​ Communities ​ Homes ​ Investment at ​ UDR’s Ownership Interest ​ ​ Three Months Ended ​ Nine Months Ended ​ Location of September 30, September 30, September 30, December 31, ​ September 30, ​ December 31, ​ September 30, ​ September 30, Joint Ventures Properties 2021 2021 2021 2020 ​ 2021 ​ 2020 ​ 2021 2020 ​ 2021 2020 Operating: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ UDR/MetLife I ​ Los Angeles, CA ​ 1 ​ 150 ​ $ 24,497 ​ $ 26,426 ​ 50.0 % ​ 50.0 % ​ $ (608) ​ $ (751) ​ $ (1,922) ​ $ (1,863) UDR/MetLife II Various 7 1,250 ​ 183,116 ​ 151,353 ​ 50.0 % ​ 50.0 % ​ ​ (289) ​ ​ (441) ​ ​ (3,126) ​ ​ (522) Other UDR/MetLife Joint Ventures (a) Various 5 1,437 ​ 70,368 ​ 82,072 ​ 50.6 % ​ 50.6 % ​ ​ (2,859) ​ ​ (3,151) ​ ​ (9,611) ​ ​ (7,275) West Coast Development Joint Ventures (b) ​ Los Angeles, CA ​ — ​ — ​ ​ — ​ ​ 30,080 ​ 47.0 % ​ 47.0 % ​ ​ (128) ​ ​ (148) ​ ​ 2,358 ​ ​ (284) Investment in and advances to unconsolidated joint ventures, net, before preferred equity investments and real estate technology investments ​ $ 277,981 ​ $ 289,931 ​ ​ ​ ​ $ (3,884) ​ $ (4,491) ​ $ (12,301) ​ $ (9,944) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income/(loss) from investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Investment at ​ Three Months Ended ​ Nine Months Ended Developer Capital Program ​ ​ Years To ​ UDR September 30, December 31, September 30, ​ September 30, and Real Estate Technology Investments (c) Location Rate Maturity ​ Commitment (d) 2021 2020 2021 2020 2021 2020 Preferred equity investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 1532 Harrison ​ San Francisco, CA ​ 11.0 % 0.7 ​ $ 24,645 ​ $ 36,088 ​ $ 34,135 ​ ​ 1,003 ​ ​ 875 ​ $ 2,896 ​ $ 2,557 Junction ​ Santa Monica, CA ​ 12.0 % 0.8 ​ ​ 8,800 ​ ​ 12,792 ​ ​ 11,699 ​ ​ 379 ​ ​ 337 ​ ​ 1,093 ​ ​ 974 1200 Broadway (e) (f) ​ Nashville, TN ​ 12.25 % 1.0 ​ ​ 55,558 ​ ​ 60,594 ​ ​ 69,330 ​ ​ 1,837 ​ ​ 1,347 ​ ​ 4,936 ​ ​ 3,934 1300 Fairmount (f) ​ Philadelphia, PA ​ 8.5 % 1.9 ​ ​ 51,393 ​ ​ 63,413 ​ ​ 59,544 ​ ​ 1,338 ​ ​ 1,230 ​ ​ 3,869 ​ ​ 3,587 Essex (g) ​ Orlando, FL ​ 12.5 % 1.9 ​ ​ 12,886 ​ ​ 17,629 ​ ​ 16,770 ​ ​ 544 ​ ​ 501 ​ ​ 1,609 ​ ​ 1,448 Modera Lake Merritt (f) ​ Oakland, CA ​ 9.0 % 2.5 ​ ​ 27,250 ​ ​ 33,072 ​ ​ 30,928 ​ ​ 739 ​ ​ 675 ​ ​ 2,144 ​ ​ 1,901 Thousand Oaks (f) ​ Thousand Oaks, CA ​ 9.0 % 3.3 ​ ​ 20,059 ​ ​ 22,256 ​ ​ 17,919 ​ ​ 497 ​ ​ 240 ​ ​ 1,415 ​ ​ 417 Vernon Boulevard (f) ​ Queens, NY ​ 13.0 % 3.8 ​ ​ 40,000 ​ ​ 46,665 ​ ​ 42,360 ​ ​ 1,496 ​ ​ 990 ​ ​ 4,300 ​ ​ 990 Makers Rise (f) (h) ​ Herndon, VA ​ 9.0 % 4.2 ​ ​ 30,208 ​ ​ 14,799 ​ ​ — ​ ​ 251 ​ ​ — ​ ​ 519 ​ ​ — 121 at Watters (f) (i) ​ Allen, TX ​ 9.0 % 4.4 ​ ​ 19,846 ​ ​ 8,968 ​ ​ — ​ ​ 234 ​ ​ — ​ ​ 462 ​ ​ — Infield Phase I (j) ​ Kissimmee, FL ​ 14.0 % 2.6 ​ ​ 16,044 ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — Real estate technology investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ RETV I (k) ​ N/A ​ N/A ​ N/A ​ ​ 18,000 ​ ​ 38,628 ​ ​ 20,587 ​ ​ 9,869 ​ ​ (100) ​ ​ 17,975 ​ ​ 4,338 RETV II ​ N/A ​ N/A ​ N/A ​ $ 18,000 ​ ​ 5,438 ​ ​ 2,283 ​ ​ 147 ​ ​ (112) ​ ​ 209 ​ ​ — Total Preferred Equity Investments and Real Estate Technology Investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 360,342 ​ ​ 305,555 ​ ​ 18,334 ​ ​ 5,983 ​ ​ 41,427 ​ ​ 20,146 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sold joint ventures and other investments in prior year ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ — ​ ​ — ​ ​ — ​ ​ 1,448 ​ ​ (3) ​ ​ 4,126 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Joint Ventures and Developer Capital Program and Real Estate Technology Investments, net (a) ​ ​ ​ ​ $ 638,323 ​ $ 595,486 ​ $ 14,450 $ 2,940 ​ $ 29,123 $ 14,328 (a) As of September 30, 2021 and December 31, 2020, the Company’s negative investment in 13 th and Market Properties LLC of $5.6 million and $4.7 million, respectively, is included in Other UDR/MetLife Joint Ventures in the table above and recorded in Accounts payable, accrued expenses, and other liabilities on the Consolidated Balance Sheet. (b) In J anuary 2021, the joint venture sold its remaining community, a 293 home operating community located in Los Angeles, California, for a sales price of approximately $121.0 million. As a result, the Company recorded a gain on the sale of approximately $2.5 million . (c) The Developer Capital Program is the program through which the Company makes investments, including preferred equity investments, mezzanine loans or other structured investments that may receive a fixed yield on the investment and may include provisions pursuant to which the Company participates in the increase in value of the property upon monetization of the applicable property and/or holds fixed price purchase options. (d) Represents UDR’s maximum funding commitment only and therefore excludes other activity such as income from investments. (e) In April 2021, the investment balance was paid down by $12.5 million and the Company’s preferred return increased to 12.25%. The Company's preferred return will revert to 8.0% in February 2022 if no capital events occur prior to that date. (f) The Company’s preferred equity investment receives a variable percentage of the value created from the project upon a capital or liquidating event. (g) In October 2021, the Company acquired its joint venture partner’s common equity interest in a 330 apartment home operating community located in Orlando, Florida for a purchase price of approximately $47.9 million. As a result, in October 2021, the Company consolidated the operating community and it will no longer be accounted for as a preferred equity investment in an unconsolidated joint venture (see Note 3, Real Estate Owned ). (h) In January 2021, the Company entered into a joint venture agreement with an unaffiliated joint venture partner to develop and operate a 356 apartment home community in Herndon, Virginia. The Company’s preferred equity investment of $30.2 million earns a preferred return of 9.0% per annum and receives a variable percentage of the value created from the project upon a capital or liquidating event. The unaffiliated joint venture partner is the managing member of the joint venture and the developer of the community. The Company has concluded that it does not control the joint venture and accounts for it under the equity method of accounting . (i) In March 2021, the Company entered into a joint venture agreement with an unaffiliated joint venture partner to develop and operate a 469 apartment home community in Allen, Texas. The Company’s preferred equity investment of $19.8 million earns a preferred return of 9.0% per annum and receives a variable percentage of the value created from the project upon a capital or liquidating event. The unaffiliated joint venture partner is the managing member of the joint venture and the developer of the community. The Company has concluded that it does not control the joint venture and accounts for it under the equity method of accounting . (j) In May 2021, the Company entered into a joint venture agreement with an unaffiliated joint venture partner to develop and operate a 384 apartment home community in Kissimmee, Florida. The Company’s preferred equity investment of $16.0 million earns a preferred return of 14.0% per annum. The unaffiliated joint venture partner is the managing member of the joint venture and the developer of the community. The Company has concluded that it does not control the joint venture and accounts for it under the equity method of accounting. (k) The Company recognized $9.9 million and $18.0 million of investment income from RETV I for the three and nine months ended September 30, 2021, respectively, which primarily related to unrealized gains from real estate technology investments .
Combined summary of balance sheets relating to unconsolidated joint ventures and partnerships	Combined summary balance sheets relating to the unconsolidated joint ventures’ and partnerships’ (not just our proportionate share) are presented below as of September 30, 2021 and December 31, 2020 ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2021 2020 Total real estate, net $ 2,172,424 $ 1,904,805 Real estate assets held for sale ​ 63,492 ​ 88,458 Cash and cash equivalents ​ 32,954 ​ 22,278 Other assets ​ ​ 281,456 ​ 150,894 Total assets $ 2,550,326 $ 2,166,435 ​ ​ ​ ​ ​ ​ ​ Third party debt, net ​ $ 1,275,903 ​ $ 1,188,710 Liabilities held for sale ​ 44,221 ​ 55,440 Accounts payable and accrued liabilities ​ ​ 59,854 ​ ​ 40,556 Total liabilities ​ 1,379,978 ​ 1,284,706 Total equity $ 1,170,348 $ 881,729
Schedule of combined financial information relating to unconsolidated joint ventures and partnerships operations (not just proportionate share)	Combined summary financial information relating to the unconsolidated joint ventures’ and partnerships’ operations (not just our proportionate share) is presented below for the three and nine months ended September 30, 2021 and 2020 ( dollars in thousands : ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ 2021 2020 2021 2020 Total revenues $ 33,635 $ 36,335 $ 97,777 $ 114,961 Property operating expenses ​ 18,128 ​ 16,697 ​ 51,983 ​ 46,462 Real estate depreciation and amortization ​ 17,486 ​ 16,929 ​ 50,082 ​ 50,085 Gain/(loss) on sale of property ​ ​ — ​ ​ — ​ ​ 34,757 ​ ​ — Operating income/(loss) ​ (1,979) ​ ​ 2,709 ​ 30,469 ​ ​ 18,414 Interest expense ​ (13,181) ​ (9,955) ​ (32,776) ​ (30,451) Net realized/unrealized gain/(loss) on held investments ​ ​ 62,013 ​ ​ (17) ​ ​ 108,851 ​ ​ 29,295 Other income/(loss) ​ ​ (156) ​ ​ 18 ​ ​ (1,826) ​ ​ 127 Net income/(loss) $ 46,697 $ (7,245) $ 104,718 $ 17,385

LEASES (Tables)

LEASES (Tables)	9 Months Ended
	Sep. 30, 2021
LEASES
Lessee - Future minimum lease payments and total operating lease liabilities	Future minimum lease payments and total operating lease liabilities from our ground leases as of September 30, 2021 are as follows (dollars in thousands): ​ ​ ​ ​ ​ ​ Ground Leases 2021 ​ $ 3,110 2022 ​ ​ 12,442 2023 ​ ​ 12,442 2024 ​ ​ 12,442 2025 ​ ​ 12,442 Thereafter ​ ​ 442,778 Total future minimum lease payments (undiscounted) ​ ​ 495,656 Difference between future undiscounted cash flows and discounted cash flows ​ ​ (302,379) Total operating lease liabilities (discounted) ​ $ 193,277
Lessee - components of operating lease expenses	The components of operating lease expenses were as follows (dollars in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ ​ 2021 ​ 2020 ​ 2021 ​ 2020 Lease expense: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contractual lease expense ​ $ 3,231 ​ $ 3,217 ​ $ 9,691 ​ $ 9,603 Variable lease expense (a) ​ ​ 25 ​ ​ 33 ​ ​ 54 ​ ​ 120 Total operating lease expense (b)(c) ​ $ 3,256 ​ $ 3,250 ​ $ 9,745 ​ $ 9,723 (a) Variable lease expense includes adjustments such as changes in the consumer price index and payments based on a percentage of a community’s income. (b) Lease expense is reported within the line item Other operating expenses on the Consolidated Statements of Operations. (c) For the nine months ended September 30, 2021, Operating lease right-of-use assets and Operating lease liabilities amortized by $2.6 million and $2.3 million, respectively. For the nine months ended September 30, 2020, Operating lease right-of-use assets and Operating lease liabilities amortized by $2.5 million and $2.2 million, respectively. Due to the net impact of the amortization, the Company recorded $0.1 million and $0.1 million of total operating lease expense during the three months ended September 30, 2021 and 2020, respectively, and $0.3 million and $0.3 million of total operating lease expense during the nine months ended September 30, 2021 and 2020, respectively.
Lessor - Future minimum lease payments	Future minimum lease payments from our retail and commercial leases as of September 30, 2021 are as follows (dollars in thousands): ​ ​ ​ ​ ​ ​ Retail and Commercial Leases 2021 ​ $ 5,822 2022 ​ ​ 24,509 2023 ​ ​ 22,705 2024 ​ ​ 20,396 2025 ​ ​ 17,075 Thereafter ​ ​ 76,696 Total future minimum lease payments (a) ​ $ 167,203 (a)

SECURED AND UNSECURED DEBT, N_2

SECURED AND UNSECURED DEBT, NET (Tables)	9 Months Ended
	Sep. 30, 2021
Unsecured Debt
Schedule of debt instruments	The following is a summary of our secured and unsecured debt at September 30, 2021 and December 31, 2020 ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Principal Outstanding ​ As of September 30, 2021 ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ Weighted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Average ​ Average ​ Number of ​ ​ September 30, ​ December 31, ​ Interest ​ Years to ​ Communities ​ 2021 2020 Rate Maturity Encumbered Secured Debt: ​ ​ ​ ​ ​ ​ ​ Fixed Rate Debt ​ ​ Mortgage notes payable (a) ​ $ 1,007,041 ​ $ 824,550 3.42 % 6.7 14 Deferred financing costs and other non-cash adjustments (b) ​ 24,668 ​ 10,665 Total fixed rate secured debt, net ​ 1,031,709 ​ 835,215 3.42 % 6.7 14 Variable Rate Debt ​ ​ Tax-exempt secured notes payable (c) ​ 27,000 ​ 27,000 0.69 % 10.5 1 Deferred financing costs ​ (62) ​ (68) Total variable rate secured debt, net ​ 26,938 ​ 26,932 0.69 % 10.5 1 Total Secured Debt, net ​ 1,058,647 ​ 862,147 3.35 % 6.8 15 Unsecured Debt: ​ ​ Variable Rate Debt ​ ​ Borrowings outstanding under unsecured credit facility due January 2026 (d) (o) ​ — ​ — — % 4.3 Borrowings outstanding under unsecured commercial paper program due October 2021 (e) (o) ​ ​ 315,000 ​ ​ 190,000 ​ 0.22 % 0.1 ​ ​ Borrowings outstanding under unsecured working capital credit facility due January 2024 (f) ​ 43,086 ​ 28,024 0.86 % 2.3 Term Loan due January 2027 (d) (o) ​ 35,000 ​ 35,000 0.99 % 5.3 Fixed Rate Debt ​ ​ Term Loan due January 2027 (d) (o) ​ ​ 315,000 ​ 315,000 1.02 % 5.3 ​ ​ 8.50% Debentures due September 2024 ​ 15,644 ​ 15,644 8.50 % 3.0 4.00% Medium-Term Notes due October 2025 (net of discounts of $0 and $327, respectively) (g) (o) ​ — ​ 299,673 — % — 2.95% Medium-Term Notes due September 2026 (h) (o) ​ 300,000 ​ 300,000 2.89 % 4.9 3.50% Medium-Term Notes due July 2027 (net of discounts of $406 and $458, respectively) (i) (o) ​ ​ 299,594 ​ ​ 299,542 ​ 4.03 % 5.8 ​ ​ 3.50% Medium-Term Notes due January 2028 (net of discounts of $746 and $835, respectively) (o) ​ ​ 299,254 ​ ​ 299,165 ​ 3.50 % 6.3 ​ ​ 4.40% Medium-Term Notes due January 2029 (net of discounts of $4 and $5, respectively) (j) (o) ​ ​ 299,996 ​ ​ 299,995 ​ 4.27 % 7.3 ​ ​ 3.20% Medium-Term Notes due January 2030 (net of premiums of $11,382 and $12,412, respectively) (k) (o) ​ ​ 611,382 ​ ​ 612,412 ​ 3.32 % 8.3 ​ ​ 3.00% Medium-Term Notes due August 2031 (net of premiums/discounts of $11,797 and $1,027, respectively) (l) (o) ​ ​ 611,797 ​ ​ 398,973 ​ 3.01 % 9.9 ​ ​ 2.10% Medium-Term Notes due August 2032 (net of discounts of $382 and $408, respectively) (o) ​ ​ 399,618 ​ ​ 399,592 ​ 2.10 % 10.8 ​ ​ 1.90% Medium-Term Notes due March 2033 (net of discounts of $1,381 and $1,471, respectively) (o) ​ ​ 348,619 ​ ​ 348,529 ​ 1.90 % 11.5 ​ ​ 2.10% Medium-Term Notes due June 2033 (net of discounts of $1,165 and $0, respectively) (m) (o) ​ ​ 298,835 ​ ​ — ​ 2.10 % 11.7 ​ ​ 3.10% Medium-Term Notes due November 2034 (net of discounts of $1,155 and $1,221, respectively) (n) (o) ​ ​ 298,845 ​ ​ 298,779 ​ 3.13 % 13.1 ​ ​ Other ​ 8 ​ 10 Deferred financing costs ​ (27,886) ​ (25,937) Total Unsecured Debt, net ​ 4,463,792 ​ 4,114,401 2.65 % 8.0 Total Debt, net ​ $ 5,522,439 ​ $ 4,976,548 2.75 % 7.8
Schedule of aggregate maturities, including amortizing principal payments of secured and unsecured debt	The aggregate maturities, including amortizing principal payments on secured and unsecured debt, of total debt for the next ten calendar years subsequent to September 30, 2021 are as follows (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fixed Total Variable Total Total Total Year ​ Secured Debt ​ Secured Debt ​ Secured Debt ​ Unsecured Debt ​ Debt 2021 ​ $ 279 ​ $ — ​ $ 279 ​ $ 315,000 (a) $ 315,279 2022 ​ ​ 1,140 ​ ​ — ​ ​ 1,140 ​ ​ — ​ ​ 1,140 2023 ​ 1,242 ​ — ​ 1,242 ​ — ​ 1,242 2024 ​ 96,747 ​ — ​ 96,747 ​ 58,730 ​ 155,477 2025 ​ 174,793 ​ — ​ 174,793 ​ — ​ 174,793 2026 ​ 52,744 ​ — ​ 52,744 ​ 300,000 ​ 352,744 2027 ​ 2,860 ​ — ​ 2,860 ​ 650,000 ​ 652,860 2028 ​ 162,310 ​ — ​ 162,310 ​ 300,000 ​ 462,310 2029 ​ 191,986 ​ — ​ 191,986 ​ 300,000 ​ 491,986 2030 ​ 162,010 ​ — ​ 162,010 ​ 600,000 ​ 762,010 Thereafter ​ 160,930 ​ 27,000 ​ 187,930 ​ 1,950,000 ​ 2,137,930 Subtotal ​ 1,007,041 ​ 27,000 ​ 1,034,041 ​ 4,473,730 ​ 5,507,771 Non-cash (b) ​ 24,668 ​ (62) ​ 24,606 ​ (9,938) ​ 14,668 Total ​ $ 1,031,709 ​ $ 26,938 ​ $ 1,058,647 ​ $ 4,463,792 ​ $ 5,522,439 (a) All unsecured debt due in the remainder of 2021 is related to the Company’s commercial paper program. (b) Includes the unamortized balance of fair market value adjustments, premiums/discounts and deferred financing costs . The Company amortized $1.2 million and $1.1 million, respectively, during the three months ended September 30, 2021 and 2020, and $3.6 million and $3.2 million, respectively, during the nine months ended September 30, 2021 and 2020, of deferred financing costs into Interest expense.
Commercial Paper
Unsecured Debt
Schedule of short-term debt	The following is a summary of short-term bank borrowings under the unsecured commercial paper program at September 30, 2021 and December 31, 2020 (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2021 ​ 2020 Total unsecured commercial paper program $ 700,000 ​ $ 500,000 ​ Borrowings outstanding at end of period ​ 315,000 ​ 190,000 ​ Weighted average daily borrowings during the period ended ​ 391,852 ​ 227,090 ​ Maximum daily borrowings during the period ended ​ 700,000 ​ 500,000 ​ Weighted average interest rate during the period ended ​ 0.2 % 0.9 % Interest rate at end of the period ​ 0.2 % 0.3 %
Revolving Credit Facility
Unsecured Debt
Schedule of short-term debt	The following is a summary of short-term bank borrowings under the Revolving Credit Facility at September 30, 2021 and December 31, 2020 (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2021 2020 ​ Total revolving credit facility ​ $ 1,300,000 ​ $ 1,100,000 ​ Borrowings outstanding at end of period (1) ​ — ​ — ​ Weighted average daily borrowings during the period ended ​ 17,473 ​ 42,186 ​ Maximum daily borrowings during the period ended ​ 305,000 ​ 375,000 ​ Weighted average interest rate during the period ended ​ 0.9 % 1.4 % Interest rate at end of the period ​ — % — % (1) Excludes $2.6 million and $2.8 million of letters of credit at September 30, 2021 and December 31, 2020, respectively .
Working capital credit facility
Unsecured Debt
Schedule of short-term debt	The following is a summary of short-term bank borrowings under the Working Capital Credit Facility at September 30, 2021 and December 31, 2020 (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2021 ​ 2020 Total working capital credit facility ​ $ 75,000 ​ $ 75,000 ​ Borrowings outstanding at end of period ​ 43,086 ​ 28,024 ​ Weighted average daily borrowings during the period ended ​ 10,645 ​ 20,132 ​ Maximum daily borrowings during the period ended ​ 44,607 ​ 54,974 ​ Weighted average interest rate during the period ended ​ 0.9 % 1.4 % Interest rate at end of the period ​ 0.9 % 1.0 %

INCOME_(LOSS) PER SHARE (Tables

INCOME/(LOSS) PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2021
INCOME/(LOSS) PER SHARE
Computation of basic and diluted income/(loss) per share	The following table sets forth the computation of basic and diluted income/(loss) per share for the periods presented (dollars and shares in thousands, except per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ ​ September 30, ​ September 30, ​ ​ 2021 2020 2021 2020 ​ Numerator for income/(loss) per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income/(loss) ​ $ 19,040 ​ $ (27,217) ​ $ 34,849 ​ $ 40,419 ​ Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership ​ (1,260) ​ 1,990 ​ (2,221) ​ (2,614) ​ Net (income)/loss attributable to noncontrolling interests ​ (49) ​ (31) ​ (73) ​ (71) ​ Net income/(loss) attributable to UDR, Inc. ​ 17,731 ​ (25,258) ​ 32,555 ​ 37,734 ​ Distributions to preferred stockholders — Series E (Convertible) ​ (1,058) ​ (1,051) ​ (3,171) ​ (3,179) ​ Income/(loss) attributable to common stockholders - basic and diluted ​ $ 16,673 ​ $ (26,309) ​ $ 29,384 ​ $ 34,555 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator for income/(loss) per share: ​ ​ ​ ​ ​ Weighted average common shares outstanding ​ 298,075 ​ 294,972 ​ 297,252 ​ 294,891 ​ Non-vested restricted stock awards ​ (247) ​ (259) ​ (254) ​ (264) ​ Denominator for basic income/(loss) per share ​ 297,828 ​ 294,713 ​ 296,998 ​ 294,627 ​ Incremental shares issuable from assumed conversion of unvested LTIP Units, unvested restricted stock and shares issuable upon settlement of forward sales agreements ​ 3,336 ​ 290 ​ 1,047 ​ 311 ​ Denominator for diluted income/(loss) per share ​ 301,164 ​ 295,003 ​ 298,045 ​ 294,938 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income/(loss) per weighted average common share: ​ ​ ​ ​ ​ Basic ​ $ 0.06 ​ $ (0.09) ​ $ 0.10 ​ $ 0.12 ​ Diluted ​ $ 0.06 ​ $ (0.09) ​ $ 0.10 ​ $ 0.12 ​
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table sets forth the additional shares of common stock outstanding, by equity instrument, if converted to common stock for each of the three and nine months ended September 30, 2021 and 2020 (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ ​ September 30, ​ September 30, ​ ​ ​ 2021 ​ 2020 ​ 2021 ​ 2020 ​ OP/DownREIT Units 22,529 22,321 22,493 22,312 Convertible preferred stock 2,918 2,918 2,918 2,960 Unvested LTIP Units and unvested restricted stock 3,336 290 1,047 311

NONCONTROLLING INTERESTS (Table

NONCONTROLLING INTERESTS (Tables)	9 Months Ended
	Sep. 30, 2021
NONCONTROLLING INTERESTS
Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	The following table sets forth redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership for the following period ( dollars in thousands ​ ​ ​ ​ ​ Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership, December 31, 2020 $ 856,294 ​ Mark-to-market adjustment to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership ​ 351,707 ​ Conversion of OP Units/DownREIT Units to Common Stock ​ (6,944) ​ Net income/(loss) attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership ​ 2,221 ​ Distributions to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership ​ (25,325) ​ Vesting of Long-Term Incentive Plan Units ​ ​ 14,578 ​ Allocation of other comprehensive income/(loss) ​ 192 ​ Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership, September 30, 2021 ​ $ 1,192,723 ​

FAIR VALUE OF DERIVATIVES AND_2

FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2021
FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS
Schedule of estimated fair values	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value at September 30, 2021, Using ​ ​ Total ​ ​ ​ Quoted ​ ​ ​ ​ ​ ​ Carrying ​ ​ ​ Prices in ​ ​ ​ ​ ​ ​ Amount in ​ ​ ​ Active ​ ​ ​ ​ ​ ​ ​ Statement of ​ ​ ​ ​ Markets ​ Significant ​ ​ ​ ​ ​ Financial ​ Fair Value ​ for Identical ​ Other ​ Significant ​ ​ Position at ​ Estimate at ​ Assets or ​ Observable ​ Unobservable ​ ​ September 30, ​ September 30, ​ Liabilities ​ Inputs ​ Inputs ​ ​ 2021 (a) ​ 2021 ​ (Level 1) ​ (Level 2) ​ (Level 3) Description: ​ ​ ​ ​ ​ ​ Notes receivable, net (b) ​ $ 25,741 ​ $ 26,166 ​ $ — ​ $ — ​ $ 26,166 Equity securities (c) ​ ​ 4,345 ​ ​ 4,345 ​ ​ — ​ ​ — ​ ​ 4,345 Derivatives - Interest rate contracts (d) ​ 1,285 ​ 1,285 ​ — ​ 1,285 ​ — Total assets ​ $ 31,371 ​ $ 31,796 ​ $ — ​ $ 1,285 ​ $ 30,511 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives - Interest rate contracts (d) ​ $ 148 ​ $ 148 ​ $ — ​ $ 148 ​ $ — Secured debt instruments - fixed rate: (e) ​ ​ ​ ​ ​ ​ Mortgage notes payable ​ ​ 1,035,158 ​ ​ 1,049,786 ​ ​ — ​ ​ — ​ ​ 1,049,786 Secured debt instruments - variable rate: (e) ​ ​ ​ ​ ​ ​ Tax-exempt secured notes payable ​ 27,000 ​ 27,000 ​ — ​ — ​ 27,000 Unsecured debt instruments: (e) ​ ​ ​ ​ ​ ​ Working capital credit facility ​ ​ 43,086 ​ ​ 43,086 ​ ​ — ​ ​ — ​ ​ 43,086 Commercial paper program ​ ​ 315,000 ​ ​ 315,000 ​ ​ — ​ ​ — ​ ​ 315,000 Unsecured notes ​ ​ 4,133,592 ​ ​ 4,265,616 ​ ​ — ​ ​ — ​ ​ 4,265,616 Total liabilities ​ $ 5,553,984 ​ $ 5,700,636 ​ $ — ​ $ 148 ​ $ 5,700,488 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership (f) ​ $ 1,192,723 ​ $ 1,192,723 ​ $ — ​ $ 1,192,723 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value at December 31, 2020, Using ​ ​ Total ​ ​ ​ Quoted ​ ​ ​ ​ ​ ​ Carrying ​ ​ ​ Prices in ​ ​ ​ ​ ​ ​ Amount in ​ ​ ​ Active ​ ​ ​ ​ ​ ​ Statement of ​ ​ ​ Markets ​ Significant ​ ​ ​ ​ Financial ​ Fair Value ​ for Identical ​ Other ​ Significant ​ ​ Position at ​ Estimate at ​ Assets or ​ Observable ​ Unobservable ​ ​ December 31, ​ December 31, ​ Liabilities ​ Inputs ​ Inputs ​ 2020 (a) ​ 2020 ​ (Level 1) ​ (Level 2) ​ (Level 3) Description: ​ ​ ​ ​ ​ ​ Notes receivable, net (b) ​ $ 157,992 ​ $ 170,411 ​ $ — ​ $ — ​ $ 170,411 Derivatives - Interest rate contracts (d) ​ 2 ​ 2 ​ — ​ 2 ​ — Total assets ​ $ 157,994 ​ $ 170,413 ​ $ — ​ $ 2 ​ $ 170,411 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives - Interest rate contracts (d) ​ $ 167 ​ $ 167 ​ $ — ​ $ 167 ​ $ — Secured debt instruments - fixed rate: (e) ​ ​ ​ ​ ​ ​ Mortgage notes payable ​ ​ 837,473 ​ ​ 854,084 ​ ​ — ​ ​ — ​ ​ 854,084 Secured debt instruments - variable rate: (e) ​ ​ ​ ​ ​ ​ Tax-exempt secured notes payable ​ 27,000 ​ 27,000 ​ — ​ — ​ 27,000 Unsecured debt instruments: (e) ​ ​ ​ ​ ​ ​ ​ Working capital credit facility ​ ​ 28,024 ​ ​ 28,024 ​ ​ — ​ ​ — ​ ​ 28,024 Commercial paper program ​ ​ 190,000 ​ ​ 190,000 ​ ​ — ​ ​ — ​ ​ 190,000 Unsecured notes ​ ​ 3,922,314 ​ ​ 4,283,045 ​ ​ — ​ ​ — ​ ​ 4,283,045 Total liabilities ​ $ 5,004,978 ​ $ 5,382,320 ​ $ — ​ $ 167 ​ $ 5,382,153 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership (f) ​ $ 856,294 ​ $ 856,294 ​ $ — ​ $ 856,294 ​ $ — (a) Balances include fair market value adjustments and exclude deferred financing costs. (b) See Note 2, Significant Accounting Policies . (c) The Company holds an investment in a publicly traded real estate technology company that is subject to a lock-up restriction on selling or transferring the investment for a period of time. The investment is valued at the market price at the end of the period less an illiquidity discount of 15.0%. The Company classifies the investment as Level 3 in the fair value hierarchy based upon the lock-up restriction. (d) See Note 11, Derivatives and Hedging Activity . (e) See Note 7, Secured and Unsecured Debt, Net . (f) See Note 9, Noncontrolling Interests.

DERIVATIVES AND HEDGING ACTIV_2

DERIVATIVES AND HEDGING ACTIVITY (Tables)	9 Months Ended
	Sep. 30, 2021
DERIVATIVES AND HEDGING ACTIVITY
Schedule of outstanding interest rate derivatives	As of September 30, 2021, the Company had the following outstanding interest rate derivatives that were designated as cash flow hedges of interest rate risk ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ Number of ​ Product ​ Instruments ​ Notional Interest rate swaps and caps (a) ​ 4 ​ $ 334,880
Fair value of Company's derivative financial instruments and their classification on Consolidated Balance Sheets	The table below presents the fair value of the Company’s derivative financial instruments as well as their classification on the Consolidated Balance Sheets as of September 30, 2021 and December 31, 2020 ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset Derivatives ​ Liability Derivatives ​ ​ (included in Other assets ) ​ (included in Other liabilities ) ​ ​ Fair Value at: ​ Fair Value at: ​ ​ September 30, ​ December 31, ​ September 30, ​ December 31, ​ ​ 2021 ​ 2020 ​ 2021 ​ 2020 Derivatives designated as hedging instruments: ​ ​ ​ ​ Interest rate products ​ $ 1,285 ​ $ 2 ​ $ 148 ​ $ 167
Effect of Company's derivative financial instruments on Consolidated Statements of Operations	The tables below present the effect of the Company’s derivative financial instruments on the Consolidated Statements of Operations for the three and nine months ended September 30, 2021 and 2020 ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gain/(Loss) Recognized in ​ ​ ​ ​ Gain/(Loss) Reclassified ​ Interest expense ​ ​ Unrealized holding gain/(loss) ​ from Accumulated OCI into ​ (Amount Excluded from ​ ​ Recognized in OCI ​ Interest expense ​ Effectiveness Testing) Derivatives in Cash Flow Hedging Relationships 2021 2020 2021 2020 2021 2020 Three Months Ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate products ​ $ 1,389 ​ $ (30) ​ $ (441) ​ $ (1,585) ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate products ​ $ 1,422 ​ $ (3,241) ​ $ (1,314) ​ $ (3,234) ​ $ — ​ $ —
Effect of Company's derivatives not designated as hedging instruments on the Consolidated Statements of Operations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ ​ 2021 ​ 2020 ​ 2021 ​ 2020 Total amount of Interest expense ​ $ 36,289 ​ $ 62,268 ​ $ 149,849 ​ $ 140,182 ​
Offsetting of Derivative Assets	The Company has elected not to offset derivative positions on the consolidated financial statements. The tables below present the effect on its financial position had the Company made the election to offset its derivative positions as of September 30, 2021 and December 31, 2020 (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross Net Amounts of Gross Amounts Not Offset ​ ​ ​ ​ ​ ​ ​ ​ Amounts ​ Assets ​ in the Consolidated ​ ​ ​ ​ ​ Gross ​ Offset in the ​ Presented in the ​ Balance Sheet ​ ​ ​ ​ ​ Amounts of ​ Consolidated ​ Consolidated ​ ​ ​ ​ Cash ​ ​ ​ ​ ​ Recognized ​ Balance ​ Balance Sheets ​ Financial ​ Collateral ​ ​ ​ Offsetting of Derivative Assets ​ Assets ​ Sheets ​ (a) ​ Instruments Received Net Amount September 30, 2021 ​ $ 1,285 ​ $ — ​ $ 1,285 ​ $ (100) ​ $ — ​ $ 1,185 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ $ 2 ​ $ — ​ $ 2 ​ $ — ​ $ — ​ $ 2 (a) Amounts reconcile to the aggregate fair value of derivative assets in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Consolidated Balance Sheets” located in this footnote.
Offsetting of Derivative Liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross Net Amounts of Gross Amounts Not Offset ​ ​ ​ ​ ​ ​ ​ ​ Amounts ​ Liabilities ​ in the Consolidated ​ ​ ​ ​ ​ Gross ​ Offset in the ​ Presented in the ​ Balance Sheet ​ ​ ​ ​ ​ Amounts of ​ Consolidated ​ Consolidated ​ ​ ​ ​ Cash ​ ​ ​ ​ ​ Recognized ​ Balance ​ Balance Sheets ​ Financial ​ Collateral ​ ​ ​ Offsetting of Derivative Liabilities Liabilities Sheets (a) Instruments Posted Net Amount September 30, 2021 ​ $ 148 ​ $ — ​ $ 148 ​ $ (100) ​ $ — ​ $ 48 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ $ 167 ​ $ — ​ $ 167 ​ $ — ​ $ — ​ $ 167 (a) Amounts reconcile to the aggregate fair value of derivative liabilities in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Consolidated Balance Sheets” located in this footnote.

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	9 Months Ended
	Sep. 30, 2021
COMMITMENTS AND CONTINGENCIES
Summary of real estate commitments	The following summarizes the Company’s real estate commitments at September 30, 2021 ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number ​ UDR's ​ UDR's Remaining ​ ​ ​ Properties ​ Investment (a) ​ Commitment ​ Wholly-owned — under development 5 ​ $ 331,645 ​ $ 169,855 Joint ventures: ​ ​ Preferred equity investments 3 ​ ​ 23,767 (b) ​ 43,377 (b) Real estate technology investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ RETV I ​ - ​ ​ 38,628 ​ ​ 5,220 ​ RETV II ​ - ​ ​ 5,438 ​ ​ 12,600 ​ Total ​ $ 399,478 ​ $ 231,052 (a) Represents UDR’s investment as of September 30, 2021. (b) Represents UDR’s investment in and remaining commitment for Makers Rise, 121 at Watters and Infield Phase I, which are under development as of September 30, 2021.

REPORTABLE SEGMENTS (Tables)

REPORTABLE SEGMENTS (Tables)	9 Months Ended
	Sep. 30, 2021
REPORTABLE SEGMENTS
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to Net income/(loss)	​ The following table details rental income and NOI for UDR’s reportable segments for the three and nine months ended September 30, 2021 and 2020, and reconciles NOI to Net income/(loss) attributable to UDR, Inc. (dollars in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, (a) ​ September 30, (b) ​ 2021 2020 2021 2020 Reportable apartment home segment lease revenue ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Same-Store Communities (a) ​ ​ ​ ​ ​ West Region ​ $ 108,042 ​ $ 101,424 ​ $ 304,594 ​ $ 314,060 Mid-Atlantic Region ​ 61,984 ​ 60,754 ​ 183,291 ​ 184,524 Northeast Region ​ 52,079 ​ 48,819 ​ 155,996 ​ 159,459 Southeast Region ​ 38,400 ​ 35,724 ​ 106,668 ​ 101,768 Southwest Region ​ 24,734 ​ 23,230 ​ 71,710 ​ 70,424 Non-Mature Communities/Other ​ 33,388 ​ 27,246 ​ 87,624 ​ 76,167 Total segment and consolidated lease revenue ​ $ 318,627 ​ $ 297,197 ​ $ 909,883 ​ $ 906,402 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reportable apartment home segment other revenue ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Same-Store Communities (a) ​ ​ ​ ​ ​ West Region ​ $ 2,673 ​ $ 3,420 ​ $ 7,877 ​ $ 9,186 Mid-Atlantic Region ​ 2,330 ​ 2,060 ​ 6,006 ​ 5,298 Northeast Region ​ 1,481 ​ 1,600 ​ 3,573 ​ 4,033 Southeast Region ​ 1,654 ​ 1,498 ​ 4,861 ​ 4,214 Southwest Region ​ 1,045 ​ 1,050 ​ 2,976 ​ 2,615 Non-Mature Communities/Other ​ 889 ​ 2,020 ​ 2,465 ​ 3,172 Total segment and consolidated other revenue ​ $ 10,072 ​ $ 11,648 ​ $ 27,758 ​ $ 28,518 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total reportable apartment home segment rental income ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Same-Store Communities (a) ​ ​ ​ ​ ​ West Region ​ $ 110,715 ​ $ 104,844 ​ $ 312,471 ​ $ 323,246 Mid-Atlantic Region ​ 64,314 ​ 62,814 ​ 189,297 ​ 189,822 Northeast Region ​ 53,560 ​ 50,419 ​ 159,569 ​ 163,492 Southeast Region ​ 40,054 ​ 37,222 ​ 111,529 ​ 105,982 Southwest Region ​ 25,779 ​ 24,280 ​ 74,686 ​ 73,039 Non-Mature Communities/Other ​ 34,277 ​ 29,266 ​ 90,089 ​ 79,339 Total segment and consolidated rental income ​ $ 328,699 ​ $ 308,845 ​ $ 937,641 ​ $ 934,920 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reportable apartment home segment NOI ​ ​ ​ ​ Same-Store Communities (a) ​ ​ ​ ​ West Region ​ $ 81,562 ​ $ 76,435 ​ $ 228,743 ​ $ 241,071 Mid-Atlantic Region ​ 43,794 ​ 43,189 ​ 129,931 ​ 132,435 Northeast Region ​ 33,049 ​ 30,655 ​ 100,619 ​ 108,164 Southeast Region ​ 26,444 ​ 24,517 ​ 74,926 ​ 71,701 Southwest Region ​ 16,104 ​ 14,331 ​ 46,253 ​ 44,248 Non-Mature Communities/Other ​ 18,527 ​ 22,005 ​ 48,702 ​ 51,231 Total segment and consolidated NOI ​ 219,480 ​ 211,132 ​ 629,174 ​ 648,850 Reconciling items: ​ ​ ​ ​ Joint venture management and other fees ​ 1,071 ​ 1,199 ​ 4,918 ​ 3,861 Property management ​ (9,861) ​ (8,879) ​ (28,129) ​ (26,879) Other operating expenses ​ (4,237) ​ (5,543) ​ (13,045) ​ (16,609) Real estate depreciation and amortization ​ (152,636) ​ (151,949) ​ (442,893) ​ (462,481) General and administrative ​ (15,810) ​ (11,958) ​ (43,673) ​ (37,907) Casualty-related (charges)/recoveries, net ​ (1,568) ​ — ​ (4,682) ​ (1,353) Other depreciation and amortization ​ (3,269) ​ (3,887) ​ (8,472) ​ (7,939) Gain/(loss) on sale of real estate owned ​ ​ — ​ ​ — ​ ​ 50,829 ​ ​ 61,303 Income/(loss) from unconsolidated entities ​ 14,450 ​ 2,940 ​ 29,123 ​ 14,328 Interest expense ​ (36,289) ​ (62,268) ​ (149,849) ​ (140,182) Interest income and other income/(expense), net ​ 8,238 ​ 2,183 ​ 12,831 ​ 7,304 Tax (provision)/benefit, net ​ (529) ​ (187) ​ (1,283) ​ (1,877) Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership ​ (1,260) ​ 1,990 ​ (2,221) ​ (2,614) Net (income)/loss attributable to noncontrolling interests ​ (49) ​ (31) ​ (73) ​ (71) Net income/(loss) attributable to UDR, Inc. ​ $ 17,731 ​ $ (25,258) ​ $ 32,555 ​ $ 37,734 (a) Same-Store Community population consisted of 45,713 apartment homes. (b) Same-Store Community population consisted of 45,143 apartment homes. ​
Details of assets of UDR's reportable segments	The following table details the assets of UDR’s reportable segments as of September 30, 2021 and December 31, 2020 (dollars in thousands) ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2021 ​ 2020 Reportable apartment home segment assets: ​ ​ Same-Store Communities (a): ​ ​ West Region ​ $ 4,273,694 ​ $ 4,242,973 Mid-Atlantic Region ​ 2,718,104 ​ 2,698,049 Northeast Region ​ 2,914,571 ​ 2,900,017 Southeast Region ​ 1,076,169 ​ 1,059,771 Southwest Region ​ 898,780 ​ 897,505 Non-Mature Communities/Other ​ 2,426,651 ​ 1,273,157 Total segment assets ​ 14,307,969 ​ 13,071,472 Accumulated depreciation ​ (5,017,941) ​ (4,605,366) Total segment assets — net book value ​ 9,290,028 ​ 8,466,106 Reconciling items: ​ ​ Cash and cash equivalents ​ 1,063 ​ 1,409 Restricted cash ​ 28,170 ​ 22,762 Notes receivable, net ​ 25,741 ​ 157,992 Investment in and advances to unconsolidated joint ventures, net ​ 643,902 ​ 600,233 Operating lease right-of-use assets ​ ​ 198,339 ​ ​ 200,913 Other assets ​ 213,321 ​ 188,118 Total consolidated assets ​ $ 10,400,564 ​ $ 9,637,533 (a) Same-Store Community population consisted of 45,713 apartment homes. ​

BASIS OF PRESENTATION (Details)

BASIS OF PRESENTATION (Details) shares in Millions	Sep. 30, 2021communityhomeshares
Consolidation And Basis Of Presentation
Number of Real Estate Properties | community	158
Number Of Apartment Homes Owned And Consolidated By Company | home	52,071
Operating Partnership outstanding units	185.2
United Dominion Reality L.P. [Member]
Consolidation And Basis Of Presentation
Operating Partnership units outstanding related to limited partner	176.2
General Partnership units outstanding	0.1
General Partners' ownership (as a percent)	95.10%
UDR Lighthouse DownREIT L.P.
Consolidation And Basis Of Presentation
Operating Partnership outstanding units	32.4
Non-affiliated Partners
Consolidation And Basis Of Presentation
Operating Partnership units outstanding related to limited partner	9
Percentage of units outstanding in Partnership	4.90%
Non-affiliated Partners | UDR Lighthouse DownREIT L.P.
Consolidation And Basis Of Presentation
Operating Partnership outstanding units	13.5
Percentage of units outstanding in Partnership	41.70%
UDR, Inc.
Consolidation And Basis Of Presentation
General Partners' ownership (as a percent)	58.30%
Operating Partnership outstanding units	18.9

SIGNIFICANT ACCOUNTING POLICI_4

SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Significant Accounting Policies
Total real estate, net	$ 9,290,028		$ 9,290,028		$ 8,466,106
Gain on extinguishment of debt			(42,336)	$ (24,540)
Unpaid accrued interest	25,674		25,674		44,760
Note receivable interest income	700	$ 2,000	4,600	7,000
Interest income, related party	0	0	0	0
Allocation of other comprehensive income/(loss)			192
Current income tax expense (benefit)			0
Net deferred tax assets/(liabilities)	(700)		(700)		$ (3,200)
Unrecognized tax benefit, accrued interest or penalties due to examination	0		0
Credit losses	600	600
Adjustment to rental income	4,100		1,700
Adjustment to income (loss)	100		400
Noncontrolling Interest
Significant Accounting Policies
Allocation of other comprehensive income/(loss)		$ 100	200	100
Maximum
Significant Accounting Policies
Credit losses			(100)	$ (100)
Maximum | Noncontrolling Interest
Significant Accounting Policies
Allocation of other comprehensive income/(loss)	100
Multifamily tenant lease
Significant Accounting Policies
Increase (decrease) in reserves	(3,000)		1,800
Retail tenant lease
Significant Accounting Policies
Increase (decrease) in reserves	$ (1,200)		$ 300

SIGNIFICANT ACCOUNTING POLICI_5

SIGNIFICANT ACCOUNTING POLICIES - Notes Receivable (Details) $ in Thousands	1 Months Ended		9 Months Ended
	Jul. 31, 2021USD ($)	Apr. 30, 2021USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Aug. 31, 2021USD ($)	Jan. 31, 2021USD ($)	Dec. 31, 2020USD ($)	May 31, 2020USD ($)	Nov. 30, 2019USD ($)home
Accounting policies
Notes receivable			$ 25,870				$ 158,685
Allowance for credit losses			(129)				(693)
Notes receivable, net			25,741				157,992
Total real estate, net			9,290,028				8,466,106
Gain on extinguishment of debt			(42,336)	$ (24,540)
Unpaid accrued interest			25,674				44,760
Bellevue, WA 259 Home Community
Accounting policies
Number of apartment homes | home									259
Aggregate Commitment on Note Receivable	$ 115,000
Payment to acquire real estate	171,900
Note due February 2021
Accounting policies
Notes receivable						$ 4,000	4,000	$ 4,000
Note due May 2022, One
Accounting policies
Notes receivable		$ 20,000	20,000				20,000
Total real estate, net		25,000
Gain on extinguishment of debt		100
Unpaid accrued interest		$ 4,900
Note due May 2022, Two
Accounting policies
Notes receivable			$ 2,760
Note Receivable Interest Rate			14.00%
Aggregate Commitment on Note Receivable			$ 2,800
Note due October 2022
Accounting policies
Notes receivable							115,000
Note due October 2022 | Bellevue, WA 259 Home Community
Accounting policies
Aggregate Commitment on Note Receivable									$ 115,000
Note due January 2023
Accounting policies
Notes receivable			$ 23,110				$ 19,685
Note Receivable Interest Rate			10.00%
Aggregate Commitment on Note Receivable	$ 22,000		$ 25,400		$ 25,400
Note maturity public capital threshold			5,000
Additional amount loaned			$ 3,400

REAL ESTATE OWNED - Summarizes

REAL ESTATE OWNED - Summarizes the carrying amounts for our real estate owned (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Real estate owned
Land	$ 2,301,297	$ 2,139,765
Depreciable property - held and used:
Land improvements	238,522	233,823
Building, improvements, and furniture, fixtures and equipment	11,313,023	10,292,782
Real estate intangible assets	50,030	40,570
Under development:
Real estate under development	331,200	246,867
Real estate owned	14,307,969	13,071,472
Accumulated depreciation	(5,017,941)	(4,605,366)
Total real estate owned, net of accumulated depreciation	9,290,028	8,466,106
Accumulated amortization	8,000	5,800
Land and land improvements
Under development:
Real estate under development	74,399	73,702
Real estate held for disposition	17,091	15,184
Building, improvements and furniture, fixtures and equipment
Under development:
Real estate under development	257,246	174,175
Real estate held for disposition	$ 56,361	$ 101,471

REAL ESTATE OWNED - Additional

REAL ESTATE OWNED - Additional Information (Details) $ / shares in Units, $ in Thousands, shares in Millions	1 Months Ended									3 Months Ended		9 Months Ended
	Oct. 31, 2021USD ($)home$ / sharesshares	Sep. 30, 2021USD ($)communityhomestate	Aug. 31, 2021USD ($)home	Jul. 31, 2021USD ($)home	Jun. 30, 2021USD ($)home	May 31, 2021USD ($)home	Apr. 30, 2021USD ($)home	Feb. 28, 2021USD ($)home	Jan. 31, 2021USD ($)home	Sep. 30, 2021USD ($)communitystatehome	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)communitystatehome	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)	May 31, 2020USD ($)	Nov. 30, 2019home
Real Estate Owned Disclosure
Number of real estate properties | community		158								158		158
Number of states in which there are owned and consolidated communities | state		13								13		13
Financing Receivable, before Allowance for Credit Loss		$ 25,870								$ 25,870		$ 25,870		$ 158,685
Number of apartment homes owned and consolidated | home		52,071								52,071		52,071
Investment in unconsolidated entities		$ 638,323								$ 638,323		$ 638,323		595,486
Gain/(loss) on sale of property												50,829	$ 61,303
Total real estate, net		9,290,028								9,290,028		9,290,028		8,466,106
Debt premium		28,100								28,100		28,100		12,900
Gain on extinguishment of debt												(42,336)	(24,540)
In-place intangibles		50,030								50,030		50,030		40,570
Long-term Debt		$ 5,507,771								5,507,771		5,507,771
Development costs excluding direct costs and capitalized interest										2,400	$ 1,600	9,200	10,300
Interest capitalized during period										$ 2,400	$ 1,800	$ 6,800	$ 4,900
Weighted average interest rate (as a percent)		2.75%								2.75%		2.75%
386 Home Operating Community In Anaheim
Real Estate Owned Disclosure
Number of apartment homes sold | home								386
Proceeds from sale of real estate								$ 156,000
Gain/(loss) on sale of property								$ 50,800
Operating Community 265 Homes in Anaheim [Member]
Real Estate Owned Disclosure
Number of apartment homes sold | home	265
Proceeds from sale of real estate	$ 126,000
Gain/(loss) on sale of property	$ 85,300
Note due February 2021
Real Estate Owned Disclosure
Financing Receivable, before Allowance for Credit Loss									$ 4,000					4,000	$ 4,000
Note due May 2022, One
Real Estate Owned Disclosure
Financing Receivable, before Allowance for Credit Loss		$ 20,000					$ 20,000			$ 20,000		$ 20,000		$ 20,000
Total real estate, net							25,000
Gain on extinguishment of debt							$ 100
300 Home Operating Community in Franklin
Real Estate Owned Disclosure
Number of apartment homes acquired | home									300
Debt premium									$ 6,600
Real estate acquired									82,000
In-place intangibles									2,000
Payment to acquire real estate									77,400
Long-term Debt									$ 51,800
636 Home Operating Community in Farmers Branch, Texas
Real Estate Owned Disclosure
Number of apartment homes acquired | home							636
Debt premium							$ 4,300
Real estate acquired							111,500
In-place intangibles							3,000
Payment to acquire real estate							110,200
Long-term Debt							$ 42,000
945 Home Operating Community in Frisco, Texas
Real Estate Owned Disclosure
Number of apartment homes acquired | home						945
Debt premium						$ 7,100
Real estate acquired						169,900
In-place intangibles						4,100
Payment to acquire real estate						166,900
Long-term Debt						89,500
Bellevue, WA 259 Home Community
Real Estate Owned Disclosure
Number of apartment homes acquired | home				259
Amount of a promissory note				$ 115,000
Number of apartment homes | home																259
Real estate acquired				169,100
In-place intangibles				2,800
Payment to acquire real estate				$ 171,900
468 Home Operating Community in Germantown, Maryland
Real Estate Owned Disclosure
Number of apartment homes acquired | home					468
Real estate acquired					$ 119,300
In-place intangibles					2,600
Payment to acquire real estate					$ 121,900
Operating Community 544 Apartment Home Germantown Maryland [Member]
Real Estate Owned Disclosure
Number of apartment homes acquired | home			544
Real estate acquired			$ 124,400
In-place intangibles			2,800
Payment to acquire real estate			$ 127,200
330 Home Operating Community in Orlando, FL
Real Estate Owned Disclosure
Number of apartment homes acquired | home	330
Investment in unconsolidated entities		$ 16,400								$ 16,400		$ 16,400
Ownership (as a percent)	100.00%
Repayment of construction loan	$ 39,600
Gain or loss on consolidation	0
Payment to acquire real estate	$ 105,000
Number of community issued (in shares) | shares	0.9
Number of valued (per unit) | $ / shares	$ 53
Number of valued	$ 47,900
663 Home Operating Community in Orlando, FL
Real Estate Owned Disclosure
Number of apartment homes acquired | home	663
Number of apartment homes | home		663								663		663
Payment to acquire real estate	$ 177,500
Operating community in Philadelphia, PA
Real Estate Owned Disclosure
Number of apartment homes acquired | home		339
Real estate acquired		$ 137,100								$ 137,100		$ 137,100
In-place intangibles		2,800								2,800		2,800
Payment to acquire real estate		147,000
Real estate intangibles		$ 7,100								7,100		7,100
To Be Developed Parcel Of Land In Tampa, Florida
Real Estate Owned Disclosure
Payment to acquire real estate						$ 6,600
Operating Community In Towson Maryland
Real Estate Owned Disclosure
Number of apartment homes acquired | home		192
Real estate acquired		$ 54,000								54,000		54,000
In-place intangibles		1,200								1,200		1,200
Payment to acquire real estate		57,600
Real estate intangibles		$ 2,400								2,400		2,400
Operating Community In King Of Prussia Pennsylvania
Real Estate Owned Disclosure
Number of apartment homes acquired | home		320
Real estate acquired		$ 113,800								113,800		113,800
In-place intangibles		2,400								$ 2,400		$ 2,400
Payment to acquire real estate		$ 116,200

JOINT VENTURES AND PARTNERSHI_3

JOINT VENTURES AND PARTNERSHIPS - Summary (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)communityhomeproperty	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)communityhomeproperty	Sep. 30, 2020USD ($)	Oct. 31, 2021home	May 31, 2021USD ($)home	Apr. 28, 2021	Mar. 31, 2021USD ($)home	Jan. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Unconsolidated entities
Number of real estate properties | community	158		158
Investment in unconsolidated entities	$ 638,323		$ 638,323							$ 595,486
Sold joint ventures and other investments in prior year		$ 1,448	(3)	$ 4,126
Income/(loss) from investments	14,450	2,940	29,123	14,328
Preferred Equity Investment 1200 Broadway Nashville TN
Unconsolidated entities
Rate							12.25%
Preferred Equity Investment Essex Orlando, FL
Unconsolidated entities
Number of apartment homes | home					330
Preferred Equity Investment Herndon, Virginia
Unconsolidated entities
Investment in unconsolidated entities									$ 30,200
Rate									9.00%
Preferred Equity Investment Allen, Texas
Unconsolidated entities
Number of apartment homes | home								469
Investment in unconsolidated entities								$ 19,800
Rate								9.00%
Preferred Equity Investment Kissimmee, Florida
Unconsolidated entities
Number of apartment homes | home						384
Investment in unconsolidated entities						$ 16,000
Rate						14.00%
Operating Community
Unconsolidated entities
Investment in unconsolidated entities	277,981		277,981							289,931
Income/(loss) from investments	$ (3,884)	(4,491)	$ (12,301)	(9,944)
Operating Community | Unconsolidated Joint Venture UDR Met Life I Partnership [Member]
Unconsolidated entities
Number of real estate properties | property	1		1
Number of apartment homes | home	150		150
Investment in unconsolidated entities	$ 24,497		$ 24,497							$ 26,426
UDR's Ownership Interest	50.00%		50.00%							50.00%
Income/(loss) from investments	$ (608)	(751)	$ (1,922)	(1,863)
Operating Community | Unconsolidated Joint Venture UDR MetLife II Partnership [Member]
Unconsolidated entities
Number of real estate properties | property	7		7
Number of apartment homes | home	1,250		1,250
Investment in unconsolidated entities	$ 183,116		$ 183,116							$ 151,353
UDR's Ownership Interest	50.00%		50.00%							50.00%
Income/(loss) from investments	$ (289)	(441)	$ (3,126)	(522)
Operating Community | Unconsolidated Joint Venture Other MetLife
Unconsolidated entities
Number of real estate properties | property	5		5
Number of apartment homes | home	1,437		1,437
Investment in unconsolidated entities	$ 70,368		$ 70,368							$ 82,072
UDR's Ownership Interest	50.60%		50.60%							50.60%
Income/(loss) from investments	$ (2,859)	(3,151)	$ (9,611)	(7,275)
Operating Community | Unconsolidated Joint Venture West Coast Development JV
Unconsolidated entities
Investment in unconsolidated entities										$ 30,080
UDR's Ownership Interest	47.00%		47.00%							47.00%
Income/(loss) from investments	$ (128)	(148)	$ 2,358	(284)
Development Community | Preferred Equity Investment 1532 Harrison San Francisco, CA
Unconsolidated entities
Investment in unconsolidated entities	36,088		36,088							$ 34,135
UDR Commitment	$ 24,645		$ 24,645
Rate	11.00%		11.00%
Years to Maturity			8 months 12 days
Income/(loss) from investments	$ 1,003	875	$ 2,896	2,557
Development Community | Preferred Equity Investment 1641 Lincoln Santa Monica CA
Unconsolidated entities
Investment in unconsolidated entities	12,792		12,792							11,699
UDR Commitment	$ 8,800		$ 8,800
Rate	12.00%		12.00%
Years to Maturity			9 months 18 days
Income/(loss) from investments	$ 379	337	$ 1,093	974
Development Community | Preferred Equity Investment 1200 Broadway Nashville TN
Unconsolidated entities
Investment in unconsolidated entities	60,594		60,594							69,330
UDR Commitment	$ 55,558		$ 55,558
Rate	12.25%		12.25%
Years to Maturity			1 year
Income/(loss) from investments	$ 1,837	1,347	$ 4,936	3,934
Development Community | Preferred Equity Investment 1300 Fairmount Philadelphia, PA
Unconsolidated entities
Investment in unconsolidated entities	63,413		63,413							59,544
UDR Commitment	$ 51,393		$ 51,393
Rate	8.50%		8.50%
Years to Maturity			1 year 10 months 24 days
Income/(loss) from investments	$ 1,338	1,230	$ 3,869	3,587
Development Community | Preferred Equity Investment Essex Orlando, FL
Unconsolidated entities
Investment in unconsolidated entities	17,629		17,629							16,770
UDR Commitment	$ 12,886		$ 12,886
Rate	12.50%		12.50%
Years to Maturity			1 year 10 months 24 days
Income/(loss) from investments	$ 544	501	$ 1,609	1,448
Development Community | Preferred Equity Investment Modera Lake Merritt, Oakland
Unconsolidated entities
Investment in unconsolidated entities	33,072		33,072							30,928
UDR Commitment	$ 27,250		$ 27,250
Rate	9.00%		9.00%
Years to Maturity			2 years 6 months
Income/(loss) from investments	$ 739	675	$ 2,144	1,901
Development Community | Preferred Equity Investment Thousand Oaks, CA
Unconsolidated entities
Investment in unconsolidated entities	22,256		22,256							17,919
UDR Commitment	$ 20,059		$ 20,059
Rate	9.00%		9.00%
Years to Maturity			3 years 3 months 18 days
Income/(loss) from investments	$ 497	240	$ 1,415	417
Development Community | Preferred Equity Investment Queens, New York
Unconsolidated entities
Investment in unconsolidated entities	46,665		46,665							42,360
UDR Commitment	$ 40,000		$ 40,000
Rate	13.00%		13.00%
Years to Maturity			3 years 9 months 18 days
Income/(loss) from investments	$ 1,496	990	$ 4,300	990
Development Community | Preferred Equity Investment Herndon, Virginia
Unconsolidated entities
Investment in unconsolidated entities	14,799		14,799
UDR Commitment	$ 30,208		$ 30,208
Rate	9.00%		9.00%
Years to Maturity			4 years 2 months 12 days
Income/(loss) from investments	$ 251		$ 519
Development Community | Preferred Equity Investment Allen, Texas
Unconsolidated entities
Investment in unconsolidated entities	8,968		8,968
UDR Commitment	$ 19,846		$ 19,846
Rate	9.00%		9.00%
Years to Maturity			4 years 4 months 24 days
Income/(loss) from investments	$ 234		$ 462
Development Community | Preferred Equity Investment Infield Phase I
Unconsolidated entities
UDR Commitment	$ 16,044		$ 16,044
Rate	14.00%		14.00%
Years to Maturity			2 years 7 months 6 days
Development Community | Real estate technology investments RETV I
Unconsolidated entities
Investment in unconsolidated entities	$ 38,628		$ 38,628							20,587
UDR Commitment	18,000		18,000
Income/(loss) from investments	9,869	(100)	17,975	4,338
Development Community | Real estate technology investments RETV II
Unconsolidated entities
Investment in unconsolidated entities	5,438		5,438							2,283
UDR Commitment	18,000		18,000
Income/(loss) from investments	147	(112)	209
Development Community | Preferred Equity Investments and Real Estate Technology Investments
Unconsolidated entities
Investment in unconsolidated entities	360,342		360,342							$ 305,555
Income/(loss) from investments	$ 18,334	$ 5,983	$ 41,427	$ 20,146

JOINT VENTURES AND PARTNERSHI_4

JOINT VENTURES AND PARTNERSHIPS - Commitments (Details) $ in Thousands	1 Months Ended			3 Months Ended		9 Months Ended
	Oct. 31, 2021USD ($)home	Apr. 28, 2021USD ($)	Jan. 31, 2021USD ($)communityhome	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Feb. 28, 2022	Mar. 31, 2021USD ($)home	Dec. 31, 2020USD ($)
Joint Ventures
Investment in unconsolidated entities				$ 638,323		$ 638,323				$ 595,486
Balance payments made		$ 12,500
Gain/(loss) on sale of real estate owned						50,829	$ 61,303
Deferred fees from the sale of properties				8,900		8,900				8,400
Joint venture management and other fees				$ 1,071	$ 1,199	$ 4,918	$ 3,861
Type of revenue				udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember
Preferred Equity Investment Herndon, Virginia
Joint Ventures
Investment in unconsolidated entities			$ 30,200
Preferred return (as a percent)			9.00%
Joint venture, number of homes in communities | home			356
Preferred Equity Investment Allen, Texas
Joint Ventures
Investment in unconsolidated entities									$ 19,800
Number of apartment homes | home									469
Preferred return (as a percent)									9.00%
Preferred Equity Investment Los Angeles, California
Joint Ventures
Number of apartment homes | community			293
Proceeds from sale of real estate			$ 121,000
Gain/(loss) on sale of real estate owned			$ 2,500
Preferred Equity Investment 1200 Broadway Nashville TN
Joint Ventures
Preferred return (as a percent)		12.25%
Preferred Equity Investment 1200 Broadway Nashville TN | Forecast
Joint Ventures
Preferred return (as a percent)								8.00%
Preferred Equity Investment Essex Orlando, FL
Joint Ventures
Number of apartment homes | home	330
Payment to acquire real estate	$ 47,900
Accounts Payable, Accrued Expenses and Other Liabilities | 13th and Market Properties LLC
Joint Ventures
Investment in unconsolidated entities				$ (5,600)		$ (5,600)				$ (4,700)

JOINT VENTURES AND PARTNERSHI_5

JOINT VENTURES AND PARTNERSHIPS - Unconsolidated joint ventures and partnerships (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Combined summary of balance sheets relating to unconsolidated joint ventures
Total real estate, net	$ 9,290,028		$ 9,290,028			$ 8,466,106
Cash and cash equivalents	1,063	$ 927	1,063	$ 927		1,409		$ 8,106
Other Assets	213,321		213,321			188,118
Total assets	10,400,564		10,400,564			9,637,533
Accounts payable, accrued expenses, and other liabilities	114,601		114,601			110,999
Total liabilities	6,084,301		6,084,301			5,522,648
Total equity	3,123,540	3,333,452	3,123,540	3,333,452	$ 2,805,173	3,258,591	$ 3,414,945	$ 3,389,314
Financial information relating to unconsolidated joint ventures operations
Total revenues	329,770	310,044	942,559	938,781
Property operating expenses	57,708	53,385	160,424	151,585
Real estate depreciation and amortization	152,636	151,949	442,893	462,481
Gain/(loss) on sale of property			50,829	61,303
Operating income	33,170	30,115	144,027	160,846
Interest expense	(36,289)	(62,268)	(149,849)	(140,182)
Other income/(loss)	8,238	2,183	12,831	7,304
Net income/(loss)	19,040	(27,217)	34,849	40,419
Unconsolidated Joint Ventures
Combined summary of balance sheets relating to unconsolidated joint ventures
Total real estate, net	2,172,424		2,172,424			1,904,805
Real Estate Held-for-sale	63,492		63,492			88,458
Cash and cash equivalents	32,954		32,954			22,278
Other Assets	281,456		281,456			150,894
Total assets	2,550,326		2,550,326			2,166,435
Third party debt, net	1,275,903		1,275,903			1,188,710
Liabilities held for sale	44,221		44,221			55,440
Accounts payable, accrued expenses, and other liabilities	59,854		59,854			40,556
Total liabilities	1,379,978		1,379,978			1,284,706
Total equity	1,170,348		1,170,348			$ 881,729
Financial information relating to unconsolidated joint ventures operations
Total revenues	33,635	36,335	97,777	114,961
Property operating expenses	18,128	16,697	51,983	46,462
Real estate depreciation and amortization	17,486	16,929	50,082	50,085
Gain/(loss) on sale of property			34,757
Operating income	(1,979)	2,709	30,469	18,414
Interest expense	(13,181)	(9,955)	(32,776)	(30,451)
Net realized/unrealized gain/(loss) on held investments	62,013	(17)	108,851	29,295
Other income/(loss)	(156)	18	(1,826)	127
Net income/(loss)	$ 46,697	$ (7,245)	$ 104,718	$ 17,385

LEASES - Lessee Future Minimum

LEASES - Lessee Future Minimum Payments (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)community	Dec. 31, 2020USD ($)
Lease expense:
Number of communities subject to ground leases | community	6
Operating leases existence of option to extend	true
Operating lease right-of-use assets	$ 198,339	$ 200,913
Weighted average remaining lease term	43 years 4 months 24 days	43 years 10 months 24 days
Weighted average discount rate	5.00%	5.00%
Future minimum lease payments
Total operating lease liabilities (discounted)	$ 193,277	$ 195,592
Land
Future minimum lease payments
2021	3,110
2022	12,442
2023	12,442
2024	12,442
2025	12,442
Thereafter	442,778
Total future minimum lease payments (undiscounted)	495,656
Difference between future undiscounted cash flows and discounted cash flows	(302,379)
Total operating lease liabilities (discounted)	$ 193,277

LEASES - Lessee Expenses (Detai

LEASES - Lessee Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Lease expense:
Contractual lease expense	$ 100	$ 100	$ 300	$ 300
Variable lease expense		100	300	100
Operating lease right-of-use asset amortization			2,600	2,500
Operating lease liabilities amortization			2,300	2,200
Maximum
Lease expense:
Variable lease expense	200
Land
Lease expense:
Contractual lease expense	3,231	3,217	9,691	9,603
Variable lease expense	25	33	54	120
Land | Other operating expense
Lease expense:
Total operating lease expense	$ 3,256	$ 3,250	$ 9,745	$ 9,723

LEASES - Lessor (Details)

LEASES - Lessor (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Future minimum lease payments
Variable lease expense		$ 100	$ 300	$ 100
Maximum
Future minimum lease payments
Variable lease expense	$ 200
Land
Future minimum lease payments
Variable lease expense	$ 25	$ 33	$ 54	$ 120
Apartment Homes
Lessor leases
Percentage of lease revenue			98.80%
Option to extend			true
Apartment Homes | Maximum
Lessor leases
Lease terms	12 months		12 months
Retail and Commercial Spaces
Lessor leases
Percentage of lease revenue			1.20%
Option to extend			true
Future minimum lease payments
2021	$ 5,822		$ 5,822
2022	24,509		24,509
2023	22,705		22,705
2024	20,396		20,396
2025	17,075		17,075
Thereafter	76,696		76,696
Total future minimum payments	$ 167,203		$ 167,203
Retail and Commercial Spaces | Minimum
Lessor leases
Lease terms	5 years		5 years
Retail and Commercial Spaces | Maximum
Lessor leases
Lease terms	15 years		15 years

SECURED AND UNSECURED DEBT, N_3

SECURED AND UNSECURED DEBT, NET - Summary (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)community	Aug. 31, 2021USD ($)	Feb. 28, 2021	Dec. 31, 2020USD ($)	Jul. 31, 2020USD ($)
Secured debt instruments
Total Debt, net	$ 5,522,439			$ 4,976,548
Long-term Debt	5,507,771
Unamortized net premium	$ 28,100			12,900
Weighted average interest rate (as a percent)	2.75%
Weighted Average
Secured debt instruments
Years to maturity	7 years 9 months 18 days
3.00% Medium-Term Notes due August 2031
Secured debt instruments
Long-term Debt	$ 600,000	$ 400,000
Stated interest rate	3.00%
Secured Debt
Secured debt instruments
Total Debt, net	$ 1,058,647			862,147
Long-term Debt	$ 1,034,041
Weighted average interest rate (as a percent)	3.35%
Number of Communities Encumbered | community	15
Secured Debt | Weighted Average
Secured debt instruments
Years to maturity	6 years 9 months 18 days
Unsecured Debt
Secured debt instruments
Total Debt, net	$ 4,463,792			4,114,401
Long-term Debt	$ 4,473,730
Weighted average interest rate (as a percent)	2.65%
Deferred finance costs, net	$ (27,886)			(25,937)
Unsecured Debt | Weighted Average
Secured debt instruments
Years to maturity	8 years
Fixed Rate Debt
Secured debt instruments
Long-term Debt	$ 183,300
Weighted average interest rate (as a percent)	3.93%
Fixed Rate Debt | Secured Debt
Secured debt instruments
Total Debt, net	$ 1,031,709
Long-term Debt	1,007,041
Fixed Rate Debt | Secured Debt | Mortgages Notes Payable
Secured debt instruments
Total Debt, net	1,007,041			824,550
Deferred financing costs and other non-cash adjustments	(24,668)			(10,665)
Long-term Debt	$ 1,031,709			835,215
Weighted average interest rate (as a percent)	3.42%
Number of Communities Encumbered | community	14
Fixed Rate Debt | Secured Debt | Mortgages Notes Payable | Weighted Average
Secured debt instruments
Years to maturity	6 years 8 months 12 days
Fixed Rate Debt | Unsecured Debt
Secured debt instruments
Unamortized discount	$ 4			5
Fixed Rate Debt | Unsecured Debt | Term Loan due January 2027
Secured debt instruments
Long-term Debt	$ 315,000			315,000
Weighted average interest rate (as a percent)	1.02%
Fixed Rate Debt | Unsecured Debt | Term Loan due January 2027 | Weighted Average
Secured debt instruments
Years to maturity	5 years 3 months 18 days
Fixed Rate Debt | Unsecured Debt | 8.50% Debentures, Due September 2024
Secured debt instruments
Long-term Debt	$ 15,644			$ 15,644
Stated interest rate	8.50%			8.50%
Weighted average interest rate (as a percent)	8.50%
Fixed Rate Debt | Unsecured Debt | 8.50% Debentures, Due September 2024 | Weighted Average
Secured debt instruments
Years to maturity	3 years
Fixed Rate Debt | Unsecured Debt | 4.00% Medium-Term Note due October 2025
Secured debt instruments
Total Debt, net				$ 299,673
Stated interest rate	4.00%		4.00%	4.00%
Unamortized discount	$ 0			$ 327
Fixed Rate Debt | Unsecured Debt | 2.95% Medium-Term Note due September 2026
Secured debt instruments
Long-term Debt	$ 300,000			$ 300,000
Stated interest rate	2.95%			2.95%
Weighted average interest rate (as a percent)	2.89%
Fixed Rate Debt | Unsecured Debt | 2.95% Medium-Term Note due September 2026 | Weighted Average
Secured debt instruments
Years to maturity	4 years 10 months 24 days
Fixed Rate Debt | Unsecured Debt | 3.50 Medium-Term Note due July 2027
Secured debt instruments
Total Debt, net	$ 299,594			$ 299,542
Stated interest rate	3.50%			3.50%
Unamortized discount	$ 406			$ 458
Weighted average interest rate (as a percent)	4.03%
Fixed Rate Debt | Unsecured Debt | 3.50 Medium-Term Note due July 2027 | Weighted Average
Secured debt instruments
Years to maturity	5 years 9 months 18 days
Fixed Rate Debt | Unsecured Debt | 3.50% Medium-Term Notes Due January 2028
Secured debt instruments
Total Debt, net	$ 299,254			$ 299,165
Stated interest rate	3.50%			3.50%
Unamortized discount	$ 746			$ 835
Weighted average interest rate (as a percent)	3.50%
Fixed Rate Debt | Unsecured Debt | 3.50% Medium-Term Notes Due January 2028 | Weighted Average
Secured debt instruments
Years to maturity	6 years 3 months 18 days
Fixed Rate Debt | Unsecured Debt | 4.40% Medium-Term Notes due January 2029
Secured debt instruments
Total Debt, net	$ 299,996			$ 299,995
Principal outstanding					$ 300,000
Stated interest rate	4.40%			4.40%
Weighted average interest rate (as a percent)	4.27%
Fixed Rate Debt | Unsecured Debt | 4.40% Medium-Term Notes due January 2029 | Weighted Average
Secured debt instruments
Years to maturity	7 years 3 months 18 days
Fixed Rate Debt | Unsecured Debt | 3.20% Medium-Term Notes due January 2030
Secured debt instruments
Total Debt, net	$ 611,382			$ 612,412
Stated interest rate	3.20%			3.20%
Unamortized discount	$ 11,382			$ 12,412
Weighted average interest rate (as a percent)	3.32%
Fixed Rate Debt | Unsecured Debt | 3.20% Medium-Term Notes due January 2030 | Weighted Average
Secured debt instruments
Years to maturity	8 years 3 months 18 days
Fixed Rate Debt | Unsecured Debt | 3.00% Medium-Term Notes due August 2031
Secured debt instruments
Total Debt, net	$ 611,797			$ 398,973
Stated interest rate	3.00%			3.00%
Unamortized discount				$ 1,027
Unamortized net premium	$ 11,797
Weighted average interest rate (as a percent)	3.01%
Fixed Rate Debt | Unsecured Debt | 3.00% Medium-Term Notes due August 2031 | Weighted Average
Secured debt instruments
Years to maturity	9 years 10 months 24 days
Fixed Rate Debt | Unsecured Debt | 2.10% Medium Term Note Due August 2032
Secured debt instruments
Total Debt, net	$ 399,618			399,592
Stated interest rate	2.10%
Unamortized discount	$ 382			408
Weighted average interest rate (as a percent)	2.10%
Fixed Rate Debt | Unsecured Debt | 2.10% Medium Term Note Due August 2032 | Weighted Average
Secured debt instruments
Years to maturity	10 years 9 months 18 days
Fixed Rate Debt | Unsecured Debt | 1.90% Medium-Term Notes due March 2033
Secured debt instruments
Total Debt, net	$ 348,619			$ 348,529
Stated interest rate	1.90%			1.90%
Unamortized discount	$ 1,381			$ 1,471
Weighted average interest rate (as a percent)	1.90%
Fixed Rate Debt | Unsecured Debt | 1.90% Medium-Term Notes due March 2033 | Weighted Average
Secured debt instruments
Years to maturity	11 years 6 months
Fixed Rate Debt | Unsecured Debt | 2.10% Medium-Term Note due June 2033
Secured debt instruments
Total Debt, net	$ 298,835
Stated interest rate	2.10%		2.10%	2.10%
Unamortized discount	$ 1,165			$ 0
Weighted average interest rate (as a percent)	2.10%
Fixed Rate Debt | Unsecured Debt | 2.10% Medium-Term Note due June 2033 | Weighted Average
Secured debt instruments
Years to maturity	11 years 8 months 12 days
Fixed Rate Debt | Unsecured Debt | 3.10% Medium-Term Notes due November 2034
Secured debt instruments
Total Debt, net	$ 298,845			$ 298,779
Stated interest rate	3.10%			3.10%
Unamortized discount	$ 1,155			$ 1,221
Weighted average interest rate (as a percent)	3.13%
Fixed Rate Debt | Unsecured Debt | 3.10% Medium-Term Notes due November 2034 | Weighted Average
Secured debt instruments
Years to maturity	13 years 1 month 6 days
Fixed Rate Debt | Unsecured Debt | Other [Member]
Secured debt instruments
Total Debt, net	$ 8			10
Variable Rate Debt | Secured Debt
Secured debt instruments
Total Debt, net	26,938
Long-term Debt	27,000
Variable Rate Debt | Secured Debt | Tax-exempt notes payable
Secured debt instruments
Total Debt, net	26,938			26,932
Long-term Debt	$ 27,000			27,000
Weighted average interest rate (as a percent)	0.69%
Number of Communities Encumbered | community	1
Deferred finance costs, net	$ (62)			(68)
Variable Rate Debt | Secured Debt | Tax-exempt notes payable | Weighted Average
Secured debt instruments
Years to maturity	10 years 6 months
Variable Rate Debt | Unsecured Debt | Commercial Paper
Secured debt instruments
Borrowings outstanding	$ 315,000			190,000
Weighted average interest rate (as a percent)	0.22%
Borrowings outstanding at end of period	$ 315,000			190,000
Variable Rate Debt | Unsecured Debt | Commercial Paper | Weighted Average
Secured debt instruments
Years to maturity	1 month 6 days
Variable Rate Debt | Unsecured Debt | Unsecured Revolving Credit Facility Due January 2026 | Weighted Average
Secured debt instruments
Years to maturity	4 years 3 months 18 days
Variable Rate Debt | Unsecured Debt | Working capital credit facility
Secured debt instruments
Borrowings outstanding	$ 43,086			28,024
Weighted average interest rate (as a percent)	0.86%
Variable Rate Debt | Unsecured Debt | Working capital credit facility | Weighted Average
Secured debt instruments
Years to maturity	2 years 3 months 18 days
Variable Rate Debt | Unsecured Debt | Term Loan due January 2027
Secured debt instruments
Long-term Debt	$ 35,000			$ 35,000
Weighted average interest rate (as a percent)	0.99%
Variable Rate Debt | Unsecured Debt | Term Loan due January 2027 | Weighted Average
Secured debt instruments
Years to maturity	5 years 3 months 18 days

SECURED AND UNSECURED DEBT, N_4

SECURED AND UNSECURED DEBT, NET - Credit Facilities (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)loan	Dec. 31, 2020USD ($)	Aug. 31, 2021USD ($)instrument	Jun. 30, 2021USD ($)	Nov. 30, 2020instrument
Unsecured Debt
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Basis points added to to variable rate	85.00%
Revolving Credit Facility
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Total revolving credit facility	$ 1,300,000
Potential maximum available	$ 2,500,000			$ 2,000
Number of Extensions of loan | loan	2
Extension period of option on loan	6 months
Revolving credit facility due 2023 | Letter of Credit
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Borrowings outstanding at end of year	$ 2,600	$ 2,800
Revolving credit facility due 2023 | Unsecured Debt
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Commitment fee	0.15%
Basis points added to to variable rate	0.775%
Revolving credit facility due 2023 | Unsecured Debt | Minimum
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Commitment fee	0.10%
Basis points added to to variable rate	0.70%
Revolving credit facility due 2023 | Unsecured Debt | Maximum
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Commitment fee	0.30%
Basis points added to to variable rate	1.40%
Revolving credit facility due 2023 | Revolving Credit Facility
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Total revolving credit facility	$ 1,300,000	1,100,000		1,100
Weighted average daily borrowings during the year ended	17,473	42,186
Maximum daily borrowings during the year ended	$ 305,000	$ 375,000
Weighted average interest rate during the year ended	0.90%	1.40%
Term Loan due September 2023 | Unsecured Debt
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Number of interest rate swaps | instrument					3
All-in weighted average interest rate					1.02%
Term Loan due September 2023 | Unsecured Debt | Minimum
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Basis points added to to variable rate	0.75%
Term Loan due September 2023 | Unsecured Debt | Maximum
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Basis points added to to variable rate	1.60%
Term Loan due September 2023 | Revolving Credit Facility
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Total revolving credit facility				$ 350,000
Working capital credit facility | Variable Rate Debt | Unsecured Debt
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Total revolving credit facility	$ 75,000	$ 75,000
Borrowings outstanding at end of year	43,086	28,024
Weighted average daily borrowings during the year ended	10,645	20,132
Maximum daily borrowings during the year ended	$ 44,607	$ 54,974
Weighted average interest rate during the year ended	0.90%	1.40%
Interest rate at end of the period	0.90%	1.00%
Basis points added to to variable rate	0.775%
Working capital credit facility | Variable Rate Debt | Unsecured Debt | Minimum
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Basis points added to to variable rate	0.70%
Working capital credit facility | Variable Rate Debt | Unsecured Debt | Maximum
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Basis points added to to variable rate	1.40%
Term Loan Facility Due January 2027
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Total revolving credit facility	$ 350,000
Term Loan Facility Due July 2025 | Unsecured Debt
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Notional			$ 175,000
Number of interest rate swaps | instrument			2
All-in weighted average interest rate			1.48%

SECURED AND UNSECURED DEBT, N_5

SECURED AND UNSECURED DEBT, NET - Short Term Debt (Details) - Variable Rate Debt - Unsecured Debt - Commercial Paper - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Jul. 31, 2021	Jun. 30, 2021
Unsecured Debt
Total unsecured commercial paper program	$ 700,000	$ 500,000	$ 700,000	$ 500,000
Borrowings outstanding at end of period	315,000	190,000
Weighted average daily borrowings during the period ended	391,852	227,090
Maximum daily borrowings during the period ended	$ 700,000	$ 500,000
Weighted average interest rate during the period ended	0.20%	0.90%
Interest rate at end of the period	0.20%	0.30%

SECURED AND UNSECURED DEBT, N_6

SECURED AND UNSECURED DEBT, NET - Unsecured Maturities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Aggregate maturities of unsecured debt
2021	$ 315,279		$ 315,279
2022	1,140		1,140
2023	1,242		1,242
2024	155,477		155,477
2025	174,793		174,793
2026	352,744		352,744
2027	652,860		652,860
2028	462,310		462,310
2029	491,986		491,986
2030	762,010		762,010
Thereafter	2,137,930		2,137,930
Subtotal	5,507,771		5,507,771
Non-cash	14,668		14,668
Total	5,522,439		5,522,439		$ 4,976,548
Interest expense
Aggregate maturities of unsecured debt
Amortization of financing costs	1,200	$ 1,100	3,600	$ 3,200
Fixed Rate Debt
Aggregate maturities of unsecured debt
Subtotal	183,300		183,300
Secured Debt
Aggregate maturities of unsecured debt
2021	279		279
2022	1,140		1,140
2023	1,242		1,242
2024	96,747		96,747
2025	174,793		174,793
2026	52,744		52,744
2027	2,860		2,860
2028	162,310		162,310
2029	191,986		191,986
2030	162,010		162,010
Thereafter	187,930		187,930
Subtotal	1,034,041		1,034,041
Non-cash	24,606		24,606
Total	1,058,647		1,058,647		862,147
Secured Debt | Fixed Rate Debt
Aggregate maturities of unsecured debt
2021	279		279
2022	1,140		1,140
2023	1,242		1,242
2024	96,747		96,747
2025	174,793		174,793
2026	52,744		52,744
2027	2,860		2,860
2028	162,310		162,310
2029	191,986		191,986
2030	162,010		162,010
Thereafter	160,930		160,930
Subtotal	1,007,041		1,007,041
Non-cash	24,668		24,668
Total	1,031,709		1,031,709
Secured Debt | Variable Rate Debt
Aggregate maturities of unsecured debt
Thereafter	27,000		27,000
Subtotal	27,000		27,000
Non-cash	(62)		(62)
Total	26,938		26,938
Unsecured Debt
Aggregate maturities of unsecured debt
2021	315,000		315,000
2022	0		0
2023	0		0
2024	58,730		58,730
2025	0		0
2026	300,000		300,000
2027	650,000		650,000
2028	300,000		300,000
2029	300,000		300,000
2030	600,000		600,000
Thereafter	1,950,000		1,950,000
Subtotal	4,473,730		4,473,730
Non-cash	(9,938)		(9,938)
Total	$ 4,463,792		$ 4,463,792		$ 4,114,401

SECURED AND UNSECURED DEBT, N_7

SECURED AND UNSECURED DEBT, NET - Narrative (Details) $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)	Feb. 28, 2021USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)loanproperty	Sep. 30, 2020USD ($)	Aug. 31, 2021USD ($)	Jan. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Jul. 31, 2020USD ($)	Feb. 29, 2020
Secured Debt
Secured debt amount which encumbers real estate owned based upon book value	$ 1,700,000		$ 1,700,000		$ 1,700,000
Percentage of secured debt which encumbers real estate owned based upon book value	12.00%		12.00%		12.00%
Secured debt amount of real estate owned which is unencumbered	$ 12,600,000		$ 12,600,000		$ 12,600,000
Percentage of secured debt of real estate owned which is unencumbered	88.00%		88.00%		88.00%
Long-term Debt	$ 5,507,771		$ 5,507,771		$ 5,507,771
Extinguishment of debt costs					40,769	$ 35,495
Unamortized net premium	28,100		28,100		28,100				$ 12,900
300 Home Operating Community in Franklin
Secured Debt
Long-term Debt								$ 51,800
Unamortized net premium								$ 6,600
3.00% Medium-Term Notes due August 2031
Secured Debt
Long-term Debt	$ 600,000		$ 600,000		$ 600,000		$ 400,000
Stated interest rate	3.00%		3.00%		3.00%
Long-term Debt, Weighted Average Interest Rate	2.259%
Percentage of principal amount at issuance	106.388		106.388		106.388
Interest rate risk	$ 250,000		$ 250,000		$ 250,000
All-in weighted average interest rate	3.01%		3.01%		3.01%
Debt	$ 200,000		$ 200,000		$ 200,000
Unsecured Debt
Secured Debt
Long-term Debt	4,473,730		4,473,730		$ 4,473,730
Basis points added to to variable rate					85.00%
Secured Debt
Secured Debt
Long-term Debt	1,034,041		1,034,041		$ 1,034,041
Fixed Rate Debt
Secured Debt
Number of mortgage loans payable assumed | loan					3
Long-term Debt	183,300		183,300		$ 183,300
Long term debt fair value	$ 201,300		$ 201,300		$ 201,300
Number of operating properties acquired | property					3
Fixed Rate Debt | Mortgages Notes Payable | Minimum
Secured Debt
Notes payable maximum interest rates range	2.62%		2.62%		2.62%
Fixed Rate Debt | Mortgages Notes Payable | Maximum
Secured Debt
Notes payable maximum interest rates range	4.39%		4.39%		4.39%
Fixed Rate Debt | Unsecured Debt | 4.00% Medium-Term Note due October 2025
Secured Debt
Repayments of outstanding borrowing		$ 300,000
Stated interest rate	4.00%	4.00%	4.00%		4.00%				4.00%
Fixed Rate Debt | Unsecured Debt | 4.00% Medium-Term Note due October 2025 | Interest expense
Secured Debt
Extinguishment of debt costs		$ 42,000
Fixed Rate Debt | Unsecured Debt | 2.95% Medium-Term Note due September 2026
Secured Debt
Long-term Debt	$ 300,000		$ 300,000		$ 300,000				$ 300,000
Stated interest rate	2.95%		2.95%		2.95%				2.95%
Portion of medium term note subject to interest rate swaps	$ 100,000		$ 100,000		$ 100,000
All-in weighted average interest rate	2.89%		2.89%		2.89%
Fixed Rate Debt | Unsecured Debt | 3.50 Medium-Term Note due July 2027
Secured Debt
Stated interest rate	3.50%		3.50%		3.50%				3.50%
Portion of medium term note subject to interest rate swaps	$ 200,000		$ 200,000		$ 200,000
All-in weighted average interest rate	4.03%		4.03%		4.03%
Fixed Rate Debt | Unsecured Debt | 4.40% Medium-Term Notes due January 2029
Secured Debt
Principal outstanding										$ 300,000
Stated interest rate	4.40%		4.40%		4.40%				4.40%
Portion of medium term note subject to interest rate swaps	$ 150,000		$ 150,000		$ 150,000
All-in weighted average interest rate	4.27%		4.27%		4.27%
Fixed Rate Debt | Unsecured Debt | 3.20% Medium-Term Notes due January 2030
Secured Debt
Stated interest rate	3.20%		3.20%		3.20%				3.20%
All-in weighted average interest rate											3.32%
Fixed Rate Debt | Unsecured Debt | 3.00% Medium-Term Notes due August 2031
Secured Debt
Stated interest rate	3.00%		3.00%		3.00%				3.00%
Unamortized net premium	$ 11,797		$ 11,797		$ 11,797
Fixed Rate Debt | Unsecured Debt | 2.10% Medium Term Note Due August 2032
Secured Debt
Stated interest rate	2.10%		2.10%		2.10%
Fixed Rate Debt | Unsecured Debt | 2.10% Medium-Term Note due June 2033
Secured Debt
Stated interest rate	2.10%	2.10%	2.10%		2.10%				2.10%
Medium-term notes		$ 300,000
Percentage of principal amount at issuance		99.592
Fixed Rate Debt | Unsecured Debt | 3.10% senior unsecured notes due 2034
Secured Debt
All-in weighted average interest rate	3.13%		3.13%		3.13%
Fixed Rate Debt | Unsecured Debt | 1.90% Medium-Term Notes due March 2033
Secured Debt
Stated interest rate	1.90%		1.90%		1.90%				1.90%
Fixed Rate Debt | Secured Debt
Secured Debt
Long-term Debt	$ 1,007,041		$ 1,007,041		$ 1,007,041
Fixed Rate Debt | Secured Debt | Mortgages Notes Payable
Secured Debt
Long-term Debt	1,031,709		1,031,709		1,031,709				$ 835,215
Fixed Rate Debt | Debt Assumed As Part of Acquisition | Mortgages Notes Payable
Secured Debt
Amortization of debt discount (Premium)			1,100	$ 14,000	2,800	$ 19,100
Variable Rate Debt | Secured Debt
Secured Debt
Long-term Debt	27,000		27,000		27,000
Variable Rate Debt | Tax-exempt notes payable | Mortgages Notes Payable
Secured Debt
Principal outstanding	$ 27,000		$ 27,000		$ 27,000
Variable Rate Debt | Tax-exempt secured notes payable | Mortgages Notes Payable
Secured Debt
Notes payable maximum interest rates range	0.69%		0.69%		0.69%

INCOME_(LOSS) PER SHARE (Detail

INCOME/(LOSS) PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	Oct. 25, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jul. 31, 2021
Antidilutive securities
Net income/(loss)					$ 19,040	$ (27,217)	$ 34,849	$ 40,419
Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership					(1,260)	1,990	(2,221)	(2,614)
Net (income)/loss attributable to noncontrolling interests					(49)	(31)	(73)	(71)
Net income/(loss) attributable to UDR, Inc.					17,731	(25,258)	32,555	37,734
Distributions to preferred stockholders - Series E (Convertible)					(1,058)	(1,051)	(3,171)	(3,179)
Net income/(loss) attributable to common stockholders					$ 16,673	$ (26,309)	$ 29,384	$ 34,555
Denominator for income/(loss) per share:
Weighted average common shares outstanding					298,075,000	294,972,000	297,252,000	294,891,000
Non-vested restricted stock awards					(247,000)	(259,000)	(254,000)	(264,000)
Denominator for basic income/(loss) per share					297,828,000	294,713,000	296,998,000	294,627,000
Incremental shares issuable from assumed conversion of unvested LTIP Units, unvested restricted stock and shares issuable upon settlement of forward sales agreements					3,336,000	290,000	1,047,000	311,000
Denominator for diluted income/(loss) per share					301,164,000	295,003,000	298,045,000	294,938,000
Income/(loss) per weighted average common share - basic					$ 0.06	$ (0.09)	$ 0.10	$ 0.12
Income/(loss) per weighted average common share - diluted					$ 0.06	$ (0.09)	$ 0.10	$ 0.12
Number of shares authorized		450,000,000			450,000,000		450,000,000
Aggregate net proceeds							$ 499,337
Aggregate net proceeds from sales, after deducting related costs					$ 499,730		$ 499,337
Total consideration								$ 19,795
OP Units [Member]
Antidilutive securities
Antidilutive securities					22,529,000	22,321,000	22,493,000	22,312,000
Convertible Preferred Stock
Antidilutive securities
Antidilutive securities					2,918,000	2,918,000	2,918,000	2,960,000
Unvested LTIP Units and unvested restricted stock
Antidilutive securities
Antidilutive securities					3,336,000	290,000	1,047,000	311,000
ATM
Denominator for income/(loss) per share:
Number of shares authorized	20,000,000								20,000,000
Aggregate number of shares					5,000,000		9,900,000
Number of shares sold					11,400,000		11,400,000
Net proceeds					$ 500,000		$ 500,000
Aggregate net proceeds					$ 499,300		$ 499,300
Weighted average price per share					$ 53.86		$ 50.31
Shares of common stock available for future issuance		20,000,000			20,000,000		20,000,000
Shares non-settled							5,500,000
Forward Sales Agreement
Denominator for income/(loss) per share:
Aggregate number of shares	6,000,000	7,000,000					5,000,000
Number of shares sold							4,400,000
Commissions paid to sales agents		$ 6,000					$ 2,100
Net proceeds		$ 298,500					$ 201,500
Weighted average price per share							$ 45.68
Forward price		$ 42.65	$ 49.22	$ 43.51
Shares of common stock available for future issuance			6,100,000	7,000,000
Shares settled							0

NONCONTROLLING INTERESTS (Detai

NONCONTROLLING INTERESTS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Redeemable noncontrolling interests in the Operating Partnership
Minimum holding period prior to redemption (in years)			1 year
Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership, beginning of year			$ 856,294
Mark-to-market adjustment to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	$ 97,026	$ (64,384)	351,707	$ (247,374)
Conversion of OP Units/DownREIT Units to Common Stock			(6,944)
Net income/(loss) attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	1,260	(1,990)	2,221	2,614
Distributions to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership			(25,325)
Vesting of Long-Term Incentive Plan Units			14,578
Allocation of other comprehensive income/(loss)			192
Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership, end of year	1,192,723		1,192,723
Net income/(loss) attributable to noncontrolling interests	41	15	57	24
Maximum
Redeemable noncontrolling interests in the Operating Partnership
Net income/(loss) attributable to noncontrolling interests	$ (100)	$ (100)	$ (100)	$ (100)
LTIP Units | Minimum
Redeemable noncontrolling interests in the Operating Partnership
Vesting period			1 year
LTIP Units | Maximum
Redeemable noncontrolling interests in the Operating Partnership
Vesting period			3 years

FAIR VALUE OF DERIVATIVES AND_3

FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Fair Value
Notes receivable, net	$ 25,741	$ 157,992
Debt instruments - fair value
Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	1,192,723	856,294
Transfers between levels of fair value hierarchy	$ 0
Equity Securities
Debt instruments - fair value
Percentage Of illiquidity discount	15.00%
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring
Fair Value
Notes receivable, net	$ 25,741	157,992
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	31,371	157,994
Debt instruments - fair value
Total liabilities	5,553,984	5,004,978
Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	1,192,723	856,294
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	148	167
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset Designated as Hedging Instrument, Fair Value	1,285	2
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Equity Securities | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Equity securities	4,345
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring
Fair Value
Notes receivable, net	26,166	170,411
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	31,796	170,413
Debt instruments - fair value
Total liabilities	5,700,636	5,382,320
Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	1,192,723	856,294
Estimate of Fair Value, Fair Value Disclosure [Member] | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	148	167
Estimate of Fair Value, Fair Value Disclosure [Member] | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset Designated as Hedging Instrument, Fair Value	1,285	2
Estimate of Fair Value, Fair Value Disclosure [Member] | Equity Securities | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Equity securities	4,345
Estimate of Fair Value, Fair Value Disclosure [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	1,285	2
Debt instruments - fair value
Total liabilities	148	167
Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	1,192,723	856,294
Estimate of Fair Value, Fair Value Disclosure [Member] | Level 2 [Member] | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	148	167
Estimate of Fair Value, Fair Value Disclosure [Member] | Level 2 [Member] | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset Designated as Hedging Instrument, Fair Value	1,285	2
Estimate of Fair Value, Fair Value Disclosure [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring
Fair Value
Notes receivable, net	26,166	170,411
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	30,511	170,411
Debt instruments - fair value
Total liabilities	5,700,488	5,382,153
Estimate of Fair Value, Fair Value Disclosure [Member] | Level 3 [Member] | Equity Securities | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Equity securities	4,345
Unsecured Debt | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	4,133,592	3,922,314
Unsecured Debt | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	4,265,616	4,283,045
Unsecured Debt | Estimate of Fair Value, Fair Value Disclosure [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	4,265,616	4,283,045
Unsecured Debt | Working capital credit facility | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	43,086	28,024
Unsecured Debt | Working capital credit facility | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	43,086	28,024
Unsecured Debt | Working capital credit facility | Estimate of Fair Value, Fair Value Disclosure [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	43,086	28,024
Unsecured Debt | Commercial Paper | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	315,000	190,000
Unsecured Debt | Commercial Paper | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	315,000	190,000
Unsecured Debt | Commercial Paper | Estimate of Fair Value, Fair Value Disclosure [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	315,000	190,000
Fixed Rate Debt | Secured Debt | Mortgages Notes Payable | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	1,035,158	837,473
Fixed Rate Debt | Secured Debt | Mortgages Notes Payable | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	1,049,786	854,084
Fixed Rate Debt | Secured Debt | Mortgages Notes Payable | Estimate of Fair Value, Fair Value Disclosure [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	1,049,786	854,084
Variable Rate Debt | Secured Debt | Tax-exempt secured notes payable | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	27,000	27,000
Variable Rate Debt | Secured Debt | Tax-exempt secured notes payable | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	27,000	27,000
Variable Rate Debt | Secured Debt | Tax-exempt secured notes payable | Estimate of Fair Value, Fair Value Disclosure [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring
Debt instruments - fair value
Fair value	$ 27,000	$ 27,000

DERIVATIVES AND HEDGING ACTIV_3

DERIVATIVES AND HEDGING ACTIVITY - Interest Rate Derivatives (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)instrument
Derivatives
Estimated additional accumulated other comprehensive Income/(Loss) transferred to interest expense	$ 1,800
Designated as Hedging Instrument | Interest rate swap and caps
Derivatives
Number of Interest Rate Derivatives Held | instrument	4
Notional	$ 334,880
Designated as Hedging Instrument | Interest rate swaps [Member] | Derivative Instrument That Becomes Effective In July 2022
Derivatives
Notional	$ 175,000
Number of additional interest rate derivative instruments entered | instrument	2
Notional value of contracts maturing	$ 315,000
Not Designated as Hedging Instrument
Derivatives
Notional	$ 0

DERIVATIVES AND HEDGING ACTIV_4

DERIVATIVES AND HEDGING ACTIVITY - Undesignated Interest Rate Derivatives (Details) - Interest rate contracts - Designated as Hedging Instrument - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Other assets
Fair value of Company's derivative financial instruments and their classification on Consolidated Balance Sheet
Derivative Asset Designated as Hedging Instrument, Fair Value	$ 1,285	$ 2
Other liabilities
Fair value of Company's derivative financial instruments and their classification on Consolidated Balance Sheet
Gross Amounts of Recognized Liabilities	$ 148	$ 167

DERIVATIVES AND HEDGING ACTIV_5

DERIVATIVES AND HEDGING ACTIVITY - Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Effect of derivative instruments on the Consolidated Statements of Operations
Unrealized holding gain/(loss)	$ 1,389	$ (30)	$ 1,422	$ (3,241)
Interest rate contracts | Interest expense | Cash Flow Hedging
Effect of derivative instruments on the Consolidated Statements of Operations
Unrealized holding gain/(loss)	1,389	(30)	1,422	(3,241)
Gain/(Loss) reclassified from Accumulated OCI in Interest Expense	$ (441)	$ (1,585)	$ (1,314)	$ (3,234)

DERIVATIVES AND HEDGING ACTIV_6

DERIVATIVES AND HEDGING ACTIVITY - Effectiveness (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivatives and hedging activity
Total amount of Interest expense presented on the Consolidated Statements of Operations	$ 36,289	$ 62,268	$ 149,849	$ 140,182

DERIVATIVES AND HEDGING ACTIV_7

DERIVATIVES AND HEDGING ACTIVITY - Offsetting Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Offsetting derivative assets
Net Amounts of Assets Presented in the Consolidated Balance Sheets (a)	$ 1,285	$ 2
Gross Amounts Not Offset in the Consolidated Balance Sheets, Financial Instruments	(100)
Net Amount	1,185	2
Offsetting derivative liabilities
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets (a)	148	167
Gross Amounts Not Offset in the Consolidated Balance Sheets, Financial Instruments	(100)
Net Amount	$ 48	$ 167

STOCK BASED COMPENSATION (Detai

STOCK BASED COMPENSATION (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020
Long Term Incentive Plan
Stock based compensation
Shares reserved for issuance under plan						35,000,000	19,000,000
Increase in shares reserved for issuance	16,000,000
General and administrative expense
Stock based compensation
Stock based compensation expense		$ 6.2	$ 4.3	$ 17.5	$ 15.1

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES (Details) $ in Thousands	Sep. 30, 2021USD ($)homecommunity
Real estate properties
Number of communities owned (in communities) | community	158
Costs Incurred to Date	$ 399,478
UDR's Remaining Commitment	231,052
Real estate technology investments RETV I
Real estate properties
Costs Incurred to Date	38,628
UDR's Remaining Commitment	5,220
Real estate technology investments RETV II
Real estate properties
Costs Incurred to Date	5,438
UDR's Remaining Commitment	$ 12,600
Wholly owned - under development [Member]
Real estate properties
Number of communities owned (in communities) | community	5
Costs Incurred to Date	$ 331,645
UDR's Remaining Commitment	$ 169,855
Preferred Equity Investments
Real estate properties
Number of communities owned (in communities) | community	3
Costs Incurred to Date	$ 23,767
UDR's Remaining Commitment	$ 43,377
Operating Community 663 Apartment Home Orlando Florida
Real estate properties
Number of apartment homes | home	663
Contractual purchase price commitment	$ 177,500
Deposit on purchase	$ 10,000

REPORTABLE SEGMENTS (Details)

REPORTABLE SEGMENTS (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)home	Sep. 30, 2020USD ($)home	Sep. 30, 2021USD ($)segmenthome	Sep. 30, 2020USD ($)home	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Segments
Same store communities | home	45,713	45,713	45,143	45,143
Reportable Segments
Number of reportable segments | segment			2
Condition for Community considered to have stabilized occupancy			90%
Time to maintain percent occupancy to be considered a community			3 months
Practical expedient, single lease component			true
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Rental income	$ 328,699	$ 308,845	$ 937,641	$ 934,920
Reconciling items:
Joint venture management and other fees	$ 1,071	$ 1,199	$ 4,918	$ 3,861
Type of revenue	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember
Property management	$ (9,861)	$ (8,879)	$ (28,129)	$ (26,879)
Other operating expenses	(4,237)	(5,543)	(13,045)	(16,609)
Real estate depreciation and amortization	(152,636)	(151,949)	(442,893)	(462,481)
General and administrative	(15,810)	(11,958)	(43,673)	(37,907)
Casualty-related (charges)/recoveries, net	(1,568)		(4,682)	(1,353)
Other depreciation and amortization	(3,269)	(3,887)	(8,472)	(7,939)
Gain/(loss) on sale of real estate owned			50,829	61,303
Income/(loss) from unconsolidated entities	14,450	2,940	29,123	14,328
Interest expense	(36,289)	(62,268)	(149,849)	(140,182)
Interest income and other income/(expense), net	8,238	2,183	12,831	7,304
Tax (provision)/benefit, net	(529)	(187)	(1,283)	(1,877)
Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	(1,260)	1,990	(2,221)	(2,614)
Net (income)/loss attributable to noncontrolling interests	(49)	(31)	(73)	(71)
Net income/(loss) attributable to UDR, Inc.	17,731	(25,258)	32,555	37,734
Reportable apartment home segment assets:
Total segment assets	14,307,969		14,307,969		$ 13,071,472
Accumulated depreciation	(5,017,941)		(5,017,941)		(4,605,366)
Total real estate owned, net of accumulated depreciation	9,290,028		9,290,028		8,466,106
Reconciling items:
Cash and cash equivalents	1,063	927	1,063	927	1,409	$ 8,106
Restricted cash	28,170	23,273	28,170	23,273	22,762	$ 25,185
Notes receivable, net	25,741		25,741		157,992
Investment in and advances to unconsolidated joint ventures, net	643,902		643,902		600,233
Operating lease right-of-use assets	198,339		198,339		200,913
Other assets	213,321		213,321		188,118
Total consolidated assets	10,400,564		10,400,564		9,637,533
Same Store Communities Western Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue	108,042	101,424	304,594	314,060
Other revenue	2,673	3,420	7,877	9,186
Rental income	110,715	104,844	312,471	323,246
Reportable apartment home segment NOI	81,562	76,435	228,743	241,071
Reportable apartment home segment assets:
Total segment assets	4,273,694		4,273,694		4,242,973
Same Store Communities Mid-Atlantic Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue	61,984	60,754	183,291	184,524
Other revenue	2,330	2,060	6,006	5,298
Rental income	64,314	62,814	189,297	189,822
Reportable apartment home segment NOI	43,794	43,189	129,931	132,435
Reportable apartment home segment assets:
Total segment assets	2,718,104		2,718,104		2,698,049
Same Store Communities Northeast Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue	52,079	48,819	155,996	159,459
Other revenue	1,481	1,600	3,573	4,033
Rental income	53,560	50,419	159,569	163,492
Reportable apartment home segment NOI	33,049	30,655	100,619	108,164
Reportable apartment home segment assets:
Total segment assets	2,914,571		2,914,571		2,900,017
Same Store Communities Southeastern Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue	38,400	35,724	106,668	101,768
Other revenue	1,654	1,498	4,861	4,214
Rental income	40,054	37,222	111,529	105,982
Reportable apartment home segment NOI	26,444	24,517	74,926	71,701
Reportable apartment home segment assets:
Total segment assets	1,076,169		1,076,169		1,059,771
Same Store Communities Southwestern Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue	24,734	23,230	71,710	70,424
Other revenue	1,045	1,050	2,976	2,615
Rental income	25,779	24,280	74,686	73,039
Reportable apartment home segment NOI	16,104	14,331	46,253	44,248
Reportable apartment home segment assets:
Total segment assets	898,780		898,780		897,505
Non-Mature communities/Other [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue	33,388	27,246	87,624	76,167
Other revenue	889	2,020	2,465	3,172
Rental income	34,277	29,266	90,089	79,339
Reportable apartment home segment NOI	18,527	22,005	48,702	51,231
Reportable apartment home segment assets:
Total segment assets	2,426,651		2,426,651		$ 1,273,157
Total Communities
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue	318,627	297,197	909,883	906,402
Other revenue	10,072	11,648	27,758	28,518
Rental income	328,699	308,845	937,641	934,920
Reportable apartment home segment NOI	$ 219,480	$ 211,132	$ 629,174	$ 648,850
Taxable REIT Subsidiaries
Reportable Segments
Management fee (as a percent)			3.00%