Section 6659, added Pub. L. 97–34, title VII, § 722(a)(1), Aug. 13, 1981, 95 Stat. 341; amended Pub. L. 97–448, title I, § 107(a)(1), (2), Jan. 12, 1983, 96 Stat. 2391; Pub. L. 98–369, div. A, title I, § 155(c)(1), title VII, § 721(x)(4), July 18, 1984, 98 Stat. 693, 971, related to additions to tax in case of valuation overstatements for purposes of the income tax.

A prior section 6659 was renumbered section 6662 of this title.

Section 6659A, added Pub. L. 99–514, title XI, § 1138(a), Oct. 22, 1986, 100 Stat. 2486, related to additions to tax in case of overstatements of pension liabilities.

Section 6660, added Pub. L. 98–369, div. A, title I, § 155(c)(2)(A), July 18, 1984, 98 Stat. 694; amended Pub. L. 99–514, title XVIII, §§ 1811(d), 1899A(57), Oct. 22, 1986, 100 Stat. 2833, 2961, related to additions to tax in case of valuation understatements for purposes of estate or gift taxes.

A prior section 6660 was renumbered section 6662 of this title.

Section 6661, added Pub. L. 97–248, title III, § 323(a), Sept. 3, 1982, 96 Stat. 613; amended Pub. L. 97–354, § 5(a)(42), Oct. 19, 1982, 96 Stat. 1697; Pub. L. 98–369, div. A, title VII, § 714(h)(3), July 18, 1984, 98 Stat. 962; Pub. L. 99–509, title VIII, § 8002(a), (c), Oct. 21, 1986, 100 Stat. 1951; Pub. L. 99–514, title XV, § 1504(a), Oct. 22, 1986, 100 Stat. 2743, related to substantial understatements of liability.

Repeal applicable to returns the due date for which (determined without regard to extensions) is after Dec. 31, 1989, see section 7721(d) of Pub. L. 101–239, set out as an Effective Date of 1989 Amendment note under section 461 of this title.