The tax imposed by section 2501 for each calendar year shall be an amount equal to the excess of—

(A) a tentative tax, computed under paragraph (2), on the aggregate sum of the taxable gifts for such calendar year and for each of the preceding calendar periods, over

(B) a tentative tax, computed under paragraph (2), on the aggregate sum of the taxable gifts for each of the preceding calendar periods.

1987—Subsec. (a)(1). Pub. L. 100–203, § 10401(b)(2)(B)(i), substituted “under section 2001 (c)” for “in accordance with the rate schedule set forth in section 2001 (c)”.

Subsec. (a)(2). Pub. L. 100–203, § 10401(b)(2)(B)(ii), substituted “under such section” for “in accordance with such rate schedule”.

1981—Subsec. (a). Pub. L. 97–34 substituted in introductory text and par. (1) “calendar year” for “calendar quarter” and in pars. (1) and (2) “calendar periods” for “calendar years and calendar quarters”.

Subsec. (b). Pub. L. 97–34 substituted definition of “preceding calendar period” for “calendar quarter”, the latter including only the first calendar quarter of the calendar year 1971 and succeeding calendar quarters (covered in par. (2)), the former incorporating former subsec. (c)(1) definition of “preceding calendar years” as meaning calendar years 1932 and 1970 and all calendar years intervening between calendar year 1932 and calendar year 1970 and “calendar year 1932” as including only the portion of such year after June 6, 1932, and former subsec. (c)(2) definition of “preceding calendar quarters” as meaning the first calendar quarter of calendar year 1971 and all calendar quarters intervening between such calendar quarter and the calendar quarter for which the tax is being computed.

Subsecs. (c), (d). Pub. L. 97–34 redesignated subsec. (d) as (c). Former subsec. (c), defining “preceding calendar years” and “preceding calendar quarters”, was incorporated in subsec. (b).

1976—Subsec. (a). Pub. L. 94–455 inserted “tentative” after “(1) a” and “(2) a” and substituted in par. (1) “section 2001 (c)” for “this subsection” after “set forth in”.

1970—Subsec. (a). Pub. L. 91–614, § 102(a)(2)(A), substituted a computation of tax formula based on the current calendar quarter, preceding calendar quarters, and preceding calendar years for a formula based entirely on the current and preceding calendar years.

Subsec. (b). Pub. L. 91–614, § 102(a)(2)(B), substituted definition of “calendar quarter” for definition of “calendar year”.

Subsec. (c). Pub. L. 91–614, § 102(a)(2)(B), substituted definition of “preceding calendar years and quarters” for definition of “preceding calendar years”.

Pub. L. 107–16, title V, § 511(f)(3), June 7, 2001, 115 Stat. 71, provided that: “The amendments made by subsections (d) and (e) [amending this section and section 2511 of this title] shall apply to gifts made after December 31, 2009.”

Amendment by Pub. L. 107–16 inapplicable to estates of decedents dying, gifts made, or generation skipping transfers, after Dec. 31, 2010, and the Internal Revenue Code of 1986 to be applied and administered to such estates, gifts, and transfers as if such amendment had never been enacted, see section 901 of Pub. L. 107–16, set out as a note under section 1 of this title.

Amendment by Pub. L. 100–203 applicable in the case of decedents dying, and gifts made, after Dec. 31, 1987, see section 10401(c) of Pub. L. 100–203, set out as a note under section 2001 of this title.

Amendment by Pub. L. 97–34 applicable with respect to gifts made after Dec. 31, 1981, see section 442(e) of Pub. L. 97–34, set out as a note under section 2501 of this title.

Section 2001(d)(2) of Pub. L. 94–455 provided that: “The amendments made by subsections (b) and (c)(2) [enacting section 2505 of this title, amending this section and section 2504 of this title, and repealing section 2521 of this title] shall apply to gifts made after December 31, 1976.”

Amendment by Pub. L. 91–614 applicable with respect to gifts made after Dec. 31, 1970, see section 102(e) of Pub. L. 91–614, set out as a note under section 2501 of this title.