26 U.S.C. § 86: Social security and tier 1 railroad retirement benefits

one-half of the social security benefits received during the taxable year, or one-half of the excess described in subsection (b)(1). 85 percent of such excess, plus the lesser of the amount determined under paragraph (1) or an amount equal to one-half of the difference between the adjusted base amount and the base amount of the taxpayer, or 85 percent of the social security benefits received during the taxable year. the modified adjusted gross income of the taxpayer for the taxable year, plus one-half of the social security benefits received during the taxable year, exceeds the base amount. determined without regard to this section and sections 85(c), 135, 137, 221, 911, 931, and 933, and increased by the amount of interest received or accrued by the taxpayer during the taxable year which is exempt from tax. except as otherwise provided in this paragraph, $25,000, $32,000 in the case of a joint return, and is married as of the close of the taxable year (within the meaning of section 7703) but does not file a joint return for such year, and does not live apart from his spouse at all times during the taxable year. except as otherwise provided in this paragraph, $34,000, $44,000 in the case of a joint return, and zero in the case of a taxpayer described in paragraph (1)(C). a monthly benefit under title II of the Social Security Act, or a tier 1 railroad retirement benefit. For purposes of this section, the amount of social security benefits received during any taxable year shall be reduced by any repayment made by the taxpayer during the taxable year of a social security benefit previously received by the taxpayer (whether or not such benefit was received during the taxable year). If (but for this subparagraph) any portion of the repayments referred to in subparagraph (A) would have been allowable as a deduction for the taxable year under section 165, such portion shall be allowable as a deduction only to the extent it exceeds the social security benefits received by the taxpayer during the taxable year (and not repaid during such taxable year). For purposes of this section, if, by reason of section 224 of the Social Security Act (or by reason of section 3(a)(1) of the Railroad Retirement Act of 1974), any social security benefit is reduced by reason of the receipt of a benefit under a workmen’s compensation act, the term “social security benefit” includes that portion of such benefit received under the workmen’s compensation act which equals such reduction. the amount of the annuity under the Railroad Retirement Act of 1974 equal to the amount of the benefit to which the taxpayer would have been entitled under the Social Security Act if all of the service after December 31, 1936 , of the employee (on whose employment record the annuity is being paid) had been included in the term “employment” as defined in the Social Security Act, and a monthly annuity amount under section 3(f)(3) of the Railroad Retirement Act of 1974. For purposes of subsection (a), in any case where section 708 of the Social Security Act causes social security benefit checks to be delivered before the end of the calendar month for which they are issued, the benefits involved shall be deemed to have been received in the succeeding calendar month. any portion of a lump-sum payment of social security benefits received during the taxable year is attributable to prior taxable years, and the taxpayer makes an election under this subsection for the taxable year, For purposes of this subsection, a social security benefit is attributable to a taxable year if the generally applicable payment date for such benefit occurred during such taxable year. An election under this subsection shall be made at such time and in such manner as the Secretary shall by regulations prescribe. Such election, once made, may be revoked only with the consent of the Secretary. section 22(c)(3)(A) (relating to reduction for amounts received as pension or annuity), section 32(c)(2) (defining earned income), section 219(f)(1) (defining compensation), and section 911(b)(1) (defining foreign earned income), Except as provided in paragraph (2), the amendments made by this section [enacting this section and section 6050F of this title , amending sections 85, 128, 861, 871, 1441, and 6103 of this title and section 3413 of Title 12 , Banks and Banking, and enacting provisions set out as a note under section 401 of Title 42 , The Public Health and Welfare] shall apply to benefits received after December 31, 1983 , in taxable years ending after such date. The amendments made by this section shall not apply to any portion of a lump-sum payment of social security benefits (as defined in section 86(d) of the Internal Revenue Code of 1986 [formerly I.R.C. 1954]) received after December 31, 1983 , if the generally applicable payment date for such portion was before January 1, 1984 .”