Section 20.2001-2 - Valuation of adjusted taxable gifts for purposes of determining the deceased spousal unused exclusion amount of last deceased spouse(a)General rule. Notwithstanding § 20.2001-1(b) , §§ 20.2010-2(d) and 20.2010-3(d) provide additional rules regarding the authority of the Internal Revenue Service to examine any gift or other tax return(s), even if the time within which a tax may be assessed under section 6501 has expired, for the purpose of determining the deceased spousal unused exclusion amount available under section 2010(c) of the Internal Revenue Code.(b)Effective/applicability date. Paragraph (a) of this section applies to the estates of decedents dying on or after June 12, 2015. See 26 CFR 20.2001-2 T(a), as contained in 26 CFR part 20, revised as of April 1, 2015, for the rules applicable to estates of decedents dying on or after January 1, 2011, and before June 12, 2015.T.D. 9725, 80 FR 34284 , June 16, 2015