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TITLE 26-INTERNAL REVENUE CODE Termination Dates of 1975 Amendments note set out below. 1969-Par. (8). Pub. L. 91-172 added par. (8). 1964-Par. (8). Pub. L. 88-272 deleted par. (8) which referred to section 1503 for additional tax for corpora- tions filing consolidated returns. EFFECTIVE AND TERMINATION DATES OF 1975 AMENDMENT Amendment by Pub. L. 94-12 applicable to taxsble years ending after Dec. 31, 1974, but to cease to apply for taxable years ending after Dec. 31, 1975, see sec- tion 305(b)(1) of Pub. L. 94-12, set out as an Effective and Termination Dates of 1975 Amendments note under section 11 of this title. EFFECTIVE DATE OF 1969 AMENDMENT Par. (8) of this section applicable to taxable years ending after Dec. 31, 1969, see section 301(c) of Pub. L. 91-172, set out as an Effective Date note under section 56 of this title. EFFECTIVE DATE OF 1964 AMENDMENT Amendment by Pub. L. 88-272 applicable to taxable years beginning after Dec. 31, 1963, see section 234(c) of Pub. L. 88-272, set out as an Effect've Date of 1964 Amendment note under section 1503 of this title. PART III-CHANGES IN RATES DURING A TAXABLE YEAR Sec. 21. Effect of changes. § 21. Effect of changes (a) General rule If any rate of tax imposed by this chapter changes, and if the taxable year includes the ef- fective date of the change (unless that date is the first day of the taxable year), then- (1) tentative taxes shall be computed by ap- plying the rate for the period before the ef- fective date of the change, and the rate for the period on and after such date, to the tax- able income for the entire taxable year; and (2) the tax for such taxable year shall be the sum of that proportion of each tentative tax which the number of days in each period bears to the number of days in the entire tax- able year. (b) Repeal of tax For purposes of subsection (a)- (1) if a tax is repealed, the repeal shall be considered a change of rate; and (2) the rate for the period after the repeal shall be zero. (c) Effective date of change For purposes of subsections (a) and (b)-- (1) if the rate changes for taxable years "beginning after" or "ending after" a certain date, the following day shall be considered the effective date of the change; and (2) if a rate changes for taxable years "be- ginning on or after" a certain date, that date shall be considered the effective date of the change. (d) Changes made by Tax Reform Act of 1969 in case of individuals In applying subsection (a) to a taxable year of an individual which is not a calendar year, each change made by the Tax Reform Act of 1969 in part I or in the application of part IV or V of subehapter B for purposes of the determination of taxable income shall be treated as a change in a rate of tax. (e) Changes made by Revenue Act of 1971 In applying subsection (a) to a taxable year of an individual which is not a calendar year, each change made by the Revenue Act of 1971 in se- tion 141 (relating to the standard deduction) and section 151 (relating to personal exemp- tions) shall be treated as a change in a rate of tax. (f) Change in surtax exemption In applying subsection (a) to a taxable year of a taxpayer which is not a calendar year, the change made by section 303(b) of the Tax Re- duction Act of 1975 in the surtax exemption and any change under section 11(d) in the surtax exemption shall be treated as a change in a rate of tax. (Aug. 16, 1954, ch. 736, 68A Stat. 12; Feb. 26, 1964, Pub. L. 88-272, title I, § 132, 78 Stat. 30; Dec. 30, 1969, Pub. L. 91-172, title VIII, § 803(e), 83 Stat. 685; Dec. 10, 1971, Pub. L. 92-178, title II, § 205, 85 Stat. 511; Mar. 29, 1975, Pub. L. 94- 12, title III, § 305(b)(2), 89 Stat. 45; Dec. 23, 1975, Pub. L. 94-164, § 4(d)(2), 89 Stat. 975; Oct. 4, 1976, Pub. L. 94-455, title IX, § 901(c)(2), 90 Stat. 1607.) REFERENCES IN TEXT The Tax Reform Act of 1969, referred to in subsec. (d), is Pub. L. 91-172, Dec. 30, 1969, 83 Stat. 487. For complete classification of this Act to the Code, see Short Title of 1969 Amendment note set out under section 1 of this title and Tables volume. The Revenue Act of 1971, referred to in subsec. (e), is Pub. L. 92-178, Dec. 10, 1971, 85 Stat. 497. For com- plete classification of this Act to the Code, see Short Title of 1971 Amendment note set out under section 1 of this title and Tables volume. The Tax Reduction Act of 1975, referred to in subsec. (f), is Pub. L. 94-12, Mar. 29, 1975, 89 Stat. 26. Section 303(b) of the Tax Reduction Act of 1975 is classified to section 11 of this title. For complete clas- sification of this Act to the Code, see Short Title of 1975 Amendment note set out under section 1 of this title and Tables volume. AMENDMENTS 1976-Subsec. (f). ub. L. 94-455 substituted "in the surtax exemption and any change under section 11(d) in the surtax exemption" for "and the change made by section 3(c) of the Revenue Adjustment Act of 1975 in section 11(d) (relating to corporate surtax exemp- tion)". 1975-Subsec. (f). Pub. L. 94-164 added reference to change made by section 3(c) of the Revenue Adjust- ment Act of 1975. Pub. L. 94-12 added subsec. (f). 1971-Subsec. (e). Pub. L. 92-178 added subsec. (e). 1969-Subsec, (d). Pub. L. 91-172 substituted provi- sions covering changes made by the Tax Reform Act of 1969 in case of individuals for provisions covering changes made by Revenue Act of 1964. 1964-Subsec. (d). Pub. L. 88-272 amended subsec- tion generally by substituting provisions relating to changes made by the Revenue Act of 1964, for provi- sions relating to taxable years beginning before Jan. 1, 1954, and ending after Dec. 31, 1953. EFFECTIVE DATE OF 1976 AMENDMENT Amendment by Pub. L. 94-455 applicable with re- spect to taxable years ending after Dec. 31, 1975, see section 901(d) of Pub. L. 94-455, set out as an Effective Date of 1976 Amendment note under section 11 of this title. Page 38