Notwithstanding sections 10001 and 10003 of this title, in the case of a sale or exchange of land to an organization that qualifies under 26 U.S.C. § 501(c)(3) and also meets the "public support" test of 26 U.S.C. § 509(a)(2), if one of the stated purposes of the organization is to provide affordable housing and if the land will be held for this purpose for at least six years following the sale, then one-half of the tax otherwise imposed under this chapter shall be due. If the land is not held for affordable housing purposes for at least six years following the transfer, the tax which would have been due from the seller or transferor shall become due from such organization for that portion of the property not so held. In cases coming within this section, the Commissioner may require the seller or transferor to file a land gains tax return at the time of the sale or exchange, in order to establish the amount of tax which will become the tax liability of such organization in such case. (Added 1989, No. 222 (Adj. Sess.), § 41, eff. May 31, 1990.)