INVESTMENTS IN OPERATING PARTNERSHIPS (Details 3) (USD $)	6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013
Revenues
Rental	$ 58,752,200		$ 65,812,209
Interest and other	1,559,748		1,877,511
Operating Partnerships Revenues	60,311,948		67,689,720
Expenses
Interest	10,397,667		12,535,596
Depreciation and amortization	16,816,124		19,567,361
Operating expenses	39,904,933		43,275,734
Operating Partnerships Total Expenses	67,118,724		75,378,691
NET LOSS	(6,806,776)		(7,688,971)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(6,738,709)	[1]	(7,612,081)	[1]
Net loss allocated to other Partners	(68,067)		(76,890)
Series Twenty [Member]
Revenues
Rental	914,710		1,138,528
Interest and other	29,883		28,521
Operating Partnerships Revenues	944,593		1,167,049
Expenses
Interest	181,868		209,562
Depreciation and amortization	264,205		285,766
Operating expenses	742,868		829,704
Operating Partnerships Total Expenses	1,188,941		1,325,032
NET LOSS	(244,348)		(157,983)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(241,905)	[2]	(156,403)	[2]
Net loss allocated to other Partners	(2,443)		(1,580)
Series Twenty One [Member]
Revenues
Rental	929,294		954,331
Interest and other	11,987		12,688
Operating Partnerships Revenues	941,281		967,019
Expenses
Interest	254,867		257,308
Depreciation and amortization	162,114		171,910
Operating expenses	570,648		544,717
Operating Partnerships Total Expenses	987,629		973,935
NET LOSS	(46,348)		(6,916)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(45,885)	[3]	(6,847)	[3]
Net loss allocated to other Partners	(463)		(69)
Series Twenty Two [Member]
Revenues
Rental	781,201		874,385
Interest and other	14,698		17,834
Operating Partnerships Revenues	795,899		892,219
Expenses
Interest	127,365		148,063
Depreciation and amortization	174,840		204,564
Operating expenses	560,182		659,198
Operating Partnerships Total Expenses	862,387		1,011,825
NET LOSS	(66,488)		(119,606)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(65,823)	[4]	(118,410)	[4]
Net loss allocated to other Partners	(665)		(1,196)
Series Twenty Three [Member]
Revenues
Rental	1,595,029		1,545,281
Interest and other	53,114		60,949
Operating Partnerships Revenues	1,648,143		1,606,230
Expenses
Interest	236,200		260,214
Depreciation and amortization	337,767		343,456
Operating expenses	1,191,095		1,195,494
Operating Partnerships Total Expenses	1,765,062		1,799,164
NET LOSS	(116,919)		(192,934)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(115,749)	[5]	(191,004)	[5]
Net loss allocated to other Partners	(1,170)		(1,930)
Series Twenty Four [Member]
Revenues
Rental	570,376		894,848
Interest and other	9,528		17,286
Operating Partnerships Revenues	579,904		912,134
Expenses
Interest	70,070		122,093
Depreciation and amortization	164,206		266,855
Operating expenses	436,960		626,443
Operating Partnerships Total Expenses	671,236		1,015,391
NET LOSS	(91,332)		(103,257)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(90,419)	[6]	(102,224)	[6]
Net loss allocated to other Partners	(913)		(1,033)
Series Twenty Five [Member]
Revenues
Rental	469,899		656,544
Interest and other	10,081		12,779
Operating Partnerships Revenues	479,980		669,323
Expenses
Interest	76,938		107,474
Depreciation and amortization	115,502		156,117
Operating expenses	328,358		496,347
Operating Partnerships Total Expenses	520,798		759,938
NET LOSS	(40,818)		(90,615)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(40,410)	[7]	(89,709)	[7]
Net loss allocated to other Partners	(408)		(906)
Series Twenty Six [Member]
Revenues
Rental	1,718,149		2,655,463
Interest and other	40,555		118,691
Operating Partnerships Revenues	1,758,704		2,774,154
Expenses
Interest	236,155		447,264
Depreciation and amortization	510,822		823,290
Operating expenses	1,339,035		1,936,497
Operating Partnerships Total Expenses	2,086,012		3,207,051
NET LOSS	(327,308)		(432,897)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(324,035)	[8]	(428,568)	[8]
Net loss allocated to other Partners	(3,273)		(4,329)
Series Twenty Seven [Member]
Revenues
Rental	2,171,611		2,627,431
Interest and other	40,710		38,857
Operating Partnerships Revenues	2,212,321		2,666,288
Expenses
Interest	463,601		554,456
Depreciation and amortization	477,495		619,496
Operating expenses	1,366,802		1,524,731
Operating Partnerships Total Expenses	2,307,898		2,698,683
NET LOSS	(95,577)		(32,395)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(94,621)	[9]	(32,071)	[9]
Net loss allocated to other Partners	(956)		(324)
Series Twenty Eight [Member]
Revenues
Rental	2,148,878		3,487,727
Interest and other	47,058		58,744
Operating Partnerships Revenues	2,195,936		3,546,471
Expenses
Interest	262,345		564,470
Depreciation and amortization	675,167		968,103
Operating expenses	1,508,029		2,321,846
Operating Partnerships Total Expenses	2,445,541		3,854,419
NET LOSS	(249,605)		(307,948)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(247,109)	[10]	(304,869)	[10]
Net loss allocated to other Partners	(2,496)		(3,079)
Series Twenty Nine [Member]
Revenues
Rental	3,028,110		3,788,792
Interest and other	85,697		92,261
Operating Partnerships Revenues	3,113,807		3,881,053
Expenses
Interest	507,296		676,134
Depreciation and amortization	1,041,329		1,226,934
Operating expenses	2,088,837		2,536,914
Operating Partnerships Total Expenses	3,637,462		4,439,982
NET LOSS	(523,655)		(558,929)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(518,418)	[11]	(553,340)	[11]
Net loss allocated to other Partners	(5,237)		(5,589)
Series Thirty [Member]
Revenues
Rental	2,353,170		2,297,936
Interest and other	38,623		53,713
Operating Partnerships Revenues	2,391,793		2,351,649
Expenses
Interest	294,615		302,594
Depreciation and amortization	514,679		523,236
Operating expenses	1,905,714		1,828,341
Operating Partnerships Total Expenses	2,715,008		2,654,171
NET LOSS	(323,215)		(302,522)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(319,983)	[12]	(299,497)	[12]
Net loss allocated to other Partners	(3,232)		(3,025)
Series Thirty One [Member]
Revenues
Rental	4,839,778		4,992,390
Interest and other	162,996		147,098
Operating Partnerships Revenues	5,002,774		5,139,488
Expenses
Interest	619,446		744,517
Depreciation and amortization	1,439,908		1,445,388
Operating expenses	3,410,087		3,305,387
Operating Partnerships Total Expenses	5,469,441		5,495,292
NET LOSS	(466,667)		(355,804)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(462,000)	[13]	(352,246)	[13]
Net loss allocated to other Partners	(4,667)		(3,558)
Series Thirty Two [Member]
Revenues
Rental	2,732,738		2,995,370
Interest and other	87,404		100,388
Operating Partnerships Revenues	2,820,142		3,095,758
Expenses
Interest	508,328		580,376
Depreciation and amortization	1,028,652		1,078,792
Operating expenses	1,849,277		2,017,429
Operating Partnerships Total Expenses	3,386,257		3,676,597
NET LOSS	(566,115)		(580,839)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(560,454)	[14]	(575,031)	[14]
Net loss allocated to other Partners	(5,661)		(5,808)
Series Thirty Three [Member]
Revenues
Rental	1,397,127		1,392,022
Interest and other	49,573		57,491
Operating Partnerships Revenues	1,446,700		1,449,513
Expenses
Interest	284,465		299,811
Depreciation and amortization	458,107		436,954
Operating expenses	904,149		888,694
Operating Partnerships Total Expenses	1,646,721		1,625,459
NET LOSS	(200,021)		(175,946)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(198,021)	[15]	(174,187)	[15]
Net loss allocated to other Partners	(2,000)		(1,759)
Series Thirty Four [Member]
Revenues
Rental	2,773,001		2,879,271
Interest and other	74,762		85,044
Operating Partnerships Revenues	2,847,763		2,964,315
Expenses
Interest	384,420		434,095
Depreciation and amortization	930,323		953,559
Operating expenses	1,859,035		1,818,714
Operating Partnerships Total Expenses	3,173,778		3,206,368
NET LOSS	(326,015)		(242,053)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(322,755)	[16]	(239,632)	[16]
Net loss allocated to other Partners	(3,260)		(2,421)
Series Thirty Five [Member]
Revenues
Rental	2,272,296		2,205,596
Interest and other	84,087		75,812
Operating Partnerships Revenues	2,356,383		2,281,408
Expenses
Interest	393,620		403,134
Depreciation and amortization	715,206		739,918
Operating expenses	1,405,360		1,366,054
Operating Partnerships Total Expenses	2,514,186		2,509,106
NET LOSS	(157,803)		(227,698)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(156,225)	[17]	(225,421)	[17]
Net loss allocated to other Partners	(1,578)		(2,277)
Series Thirty Six [Member]
Revenues
Rental	1,396,537		1,485,112
Interest and other	30,442		37,997
Operating Partnerships Revenues	1,426,979		1,523,109
Expenses
Interest	258,059		282,455
Depreciation and amortization	415,107		454,034
Operating expenses	954,812		1,008,482
Operating Partnerships Total Expenses	1,627,978		1,744,971
NET LOSS	(200,999)		(221,862)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(198,989)	[18]	(219,643)	[18]
Net loss allocated to other Partners	(2,010)		(2,219)
Series Thirty Seven [Member]
Revenues
Rental	2,224,541		2,271,853
Interest and other	52,728		55,711
Operating Partnerships Revenues	2,277,269		2,327,564
Expenses
Interest	319,153		330,728
Depreciation and amortization	765,457		789,608
Operating expenses	1,692,586		1,703,027
Operating Partnerships Total Expenses	2,777,196		2,823,363
NET LOSS	(499,927)		(495,799)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(494,928)	[19]	(490,841)	[19]
Net loss allocated to other Partners	(4,999)		(4,958)
Series Thirty Eight [Member]
Revenues
Rental	1,899,670		1,827,590
Interest and other	43,161		35,034
Operating Partnerships Revenues	1,942,831		1,862,624
Expenses
Interest	357,365		363,659
Depreciation and amortization	500,522		538,297
Operating expenses	1,251,174		1,176,460
Operating Partnerships Total Expenses	2,109,061		2,078,416
NET LOSS	(166,230)		(215,792)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(164,568)	[20]	(213,634)	[20]
Net loss allocated to other Partners	(1,662)		(2,158)
Series Thirty Nine [Member]
Revenues
Rental	1,394,283		1,364,590
Interest and other	50,964		42,844
Operating Partnerships Revenues	1,445,247		1,407,434
Expenses
Interest	250,509		251,989
Depreciation and amortization	395,553		459,407
Operating expenses	1,009,938		936,743
Operating Partnerships Total Expenses	1,656,000		1,648,139
NET LOSS	(210,753)		(240,705)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(208,645)	[21]	(238,298)	[21]
Net loss allocated to other Partners	(2,108)		(2,407)
Series Forty [Member]
Revenues
Rental	2,056,995		2,051,199
Interest and other	56,391		51,861
Operating Partnerships Revenues	2,113,386		2,103,060
Expenses
Interest	405,134		459,787
Depreciation and amortization	609,238		655,177
Operating expenses	1,403,259		1,476,476
Operating Partnerships Total Expenses	2,417,631		2,591,440
NET LOSS	(304,245)		(488,380)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(301,203)	[22]	(483,496)	[22]
Net loss allocated to other Partners	(3,042)		(4,884)
Series Forty One [Member]
Revenues
Rental	2,853,752		2,787,882
Interest and other	77,982		68,138
Operating Partnerships Revenues	2,931,734		2,856,020
Expenses
Interest	603,816		582,758
Depreciation and amortization	741,438		1,116,889
Operating expenses	1,798,460		1,573,041
Operating Partnerships Total Expenses	3,143,714		3,272,688
NET LOSS	(211,980)		(416,668)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(209,860)	[23]	(412,501)	[23]
Net loss allocated to other Partners	(2,120)		(4,167)
Series Forty Two [Member]
Revenues
Rental	3,170,198		3,151,540
Interest and other	119,907		95,947
Operating Partnerships Revenues	3,290,105		3,247,487
Expenses
Interest	603,697		650,495
Depreciation and amortization	809,899		888,503
Operating expenses	1,980,640		1,865,177
Operating Partnerships Total Expenses	3,394,236		3,404,175
NET LOSS	(104,131)		(156,688)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(103,090)	[24]	(155,121)	[24]
Net loss allocated to other Partners	(1,041)		(1,567)
Series Forty Three [Member]
Revenues
Rental	3,848,253		3,792,566
Interest and other	111,543		119,385
Operating Partnerships Revenues	3,959,796		3,911,951
Expenses
Interest	676,059		732,424
Depreciation and amortization	1,108,887		1,133,122
Operating expenses	2,420,231		2,298,643
Operating Partnerships Total Expenses	4,205,177		4,164,189
NET LOSS	(245,381)		(252,238)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(242,927)	[25]	(249,716)	[25]
Net loss allocated to other Partners	(2,454)		(2,522)
Series Forty Four [Member]
Revenues
Rental	2,946,601		3,972,351
Interest and other	76,719		145,750
Operating Partnerships Revenues	3,023,320		4,118,101
Expenses
Interest	812,995		1,165,325
Depreciation and amortization	762,487		1,178,857
Operating expenses	1,679,198		2,290,549
Operating Partnerships Total Expenses	3,254,680		4,634,731
NET LOSS	(231,360)		(516,630)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(229,046)	[26]	(511,464)	[26]
Net loss allocated to other Partners	(2,314)		(5,166)
Series Forty Five [Member]
Revenues
Rental	3,488,932		4,973,421
Interest and other	62,913		143,957
Operating Partnerships Revenues	3,551,845		5,117,378
Expenses
Interest	561,294		979,175
Depreciation and amortization	1,004,836		1,457,360
Operating expenses	2,418,055		3,182,712
Operating Partnerships Total Expenses	3,984,185		5,619,247
NET LOSS	(432,340)		(501,869)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(428,017)	[27]	(496,850)	[27]
Net loss allocated to other Partners	(4,323)		(5,019)
Series Forty Six [Member]
Revenues
Rental	2,777,071		2,748,190
Interest and other	36,242		102,731
Operating Partnerships Revenues	2,813,313		2,850,921
Expenses
Interest	647,987		625,236
Depreciation and amortization	692,378		651,769
Operating expenses	1,830,144		1,867,914
Operating Partnerships Total Expenses	3,170,509		3,144,919
NET LOSS	(357,196)		(293,998)
Net loss allocated to Boston Capital Tax Credit Fund IV L.P.	(353,624)	[28]	(291,058)	[28]
Net loss allocated to other Partners	$ (3,572)		$ (2,940)

[1] Amounts include $(6,205,874) and $(6,583,960) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[2] Amounts include $(241,905) and $(156,403) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[3] Amounts include $(45,885) and $(6,847) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[4] Amounts include $(65,823) and $(118,410) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[5] Amounts include $(115,749) and $(191,004) for 2014 and 2013, of net loss not recognized under the equity method of accounting.

[6] Amounts include $(90,419) and $(102,224) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[7] Amounts include $(40,410) and $(89,709) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[8] Amounts include $(324,035) and $(428,568) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[9] Amounts include $(94,621) and $(32,071) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[10] Amounts include $(247,109) and $(304,869) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[11] Amounts include $(518,418) and $(553,340) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[12] Amounts include $(319,983) and $(299,497) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[13] Amounts include $(462,000) and $(352,246) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[14] Amounts include $(560,454) and $(575,031) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[15] Amounts include $(198,021) and $(174,187) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[16] Amounts include $(322,755) and $(239,632) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[17] Amounts include $(156,225) and $(225,421) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[18] Amounts include $(198,989) and $(219,643) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[19] Amounts include $(494,928) and $(490,841) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[20] Amounts include $(164,568) and $(213,634) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[21] Amounts include $(208,645) and $(238,298) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[22] Amounts include $(301,203) and $(483,496) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[23] Amounts include $(209,860) and $(412,501) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[24] Amounts include $(103,090) and $(68,339) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[25] Amounts include $(234,564) and $(50,657) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[26] Amounts include $(229,046) and $(450,944) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[27] Amounts include $(212,095) and $(106,148) for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.

[28] Amounts include $(45,074) and $- for 2014 and 2013, respectively, of net loss not recognized under the equity method of accounting.