42 U.S.C. § 424a

(a) Conditions for reduction; computation If for any month prior to the month in which an individual attains retirement age (as defined in section 416( l )(1) of this title)— (1) such individual is entitled to benefits under section 423 of this title , and (2) such individual is entitled for such month to— (A) periodic benefits on account of his or her total or partial disability (whether or not permanent) under a workmen’s compensation law or plan of the United States or a State, or (B) periodic benefits on account of his or her total or partial disability (whether or not permanent) under any other law or plan of the United States, a State, a political subdivision (as that term is used in section 418(b)(2) of this title ), or an instrumentality of two or more States (as that term is used in section 418(g) of this title ), other than (i) benefits payable under title 38, (ii) benefits payable under a program of assistance which is based on need, (iii) benefits based on service all or substantially all of which was included under an agreement entered into by a State and the Commissioner of Social Security under section 418 of this title , and (iv) benefits under a law or plan of the United States based on service all or substantially all of which is employment as defined in section 410 of this title , the total of his benefits under section 423 of this title for such month and of any benefits under section 402 of this title for such month based on his wages and self-employment income shall be reduced (but not below zero) by the amount by which the sum of— (3) such total of benefits under sections 423 and 402 of this title for such month, and (4) such periodic benefits payable (and actually paid) for such month to such individual under such laws or plans, exceeds the higher of— (5) 80 per centum of his “average current earnings”, or (6) the total of such individual’s disability insurance benefits under section 423 of this title for such month and of any monthly insurance benefits under section 402 of this title for such month based on his wages and self-employment income, prior to reduction under this section. In no case shall the reduction in the total of such benefits under sections 423 and 402 of this title for a month (in a continuous period of months) reduce such total below the sum of— (7) the total of the benefits under sections 423 and 402 of this title, after reduction under this section, with respect to all persons entitled to benefits on the basis of such individual’s wages and self-employment income for such month which were determined for such individual and such persons for the first month for which reduction under this section was made (or which would have been so determined if all of them had been so entitled in such first month), and (8) any increase in such benefits with respect to such individual and such persons, before reduction under this section, which is made effective for months after the first month for which reduction under this section is made. For purposes of clause (5), an individual’s average current earnings means the largest of (A) the average monthly wage (determined under section 415(b) of this title as in effect prior to January 1979) used for purposes of computing his benefits under section 423 of this title , (B) one-sixtieth of the total of his wages and self-employment income (computed without regard to the limitations specified in sections 409(a)(1) and 411(b)(1) of this title) for the five consecutive calendar years after 1950 for which such wages and self-employment income were highest, or (C) one-twelfth of the total of his wages and self-employment income (computed without regard to the limitations specified in sections 409(a)(1) and 411(b)(1) of this title) for the calendar year in which he had the highest such wages and income during the period consisting of the calendar year in which he became disabled (as defined in section 423(d) of this title ) and the five years preceding that year. (b) Reduction where benefits payable on other than monthly basis If any periodic benefit for a total or partial disability under a law or plan described in subsection (a)(2) is payable on other than a monthly basis (excluding a benefit payable as a lump sum except to the extent that it is a commutation of, or a substitute for, periodic payments), the reduction under this section shall be made at such time or times and in such amounts as the Commissioner of Social Security finds will approximate as nearly as practicable the reduction prescribed by subsection (a). (c) Reductions and deductions under other provisions Reduction of benefits under this section shall be made after any reduction under subsection (a) of section 403 of this title , but before deductions under such section and under section 422(b) 1 1 See References in Text note below. of this title. (d) Exception The reduction of benefits required by this section shall not be made if the law or plan described in subsection (a)(2) under which a periodic benefit is payable provides for the reduction thereof when anyone is entitled to benefits under this subchapter on the basis of the wages and self-employment income of an individual entitled to benefits under section 423 of this title , and such law or plan so provided on February 18, 1981 . (e) Conditions for payment If it appears to the Commissioner of Social Security that an individual may be eligible for periodic benefits under a law or plan which would give rise to reduction under this section, the Commissioner may require, as a condition of certification for payment of any benefits under section 423 of this title to any individual for any month and of any benefits under section 402 of this title for such month based on such individual’s wages and self-employment income, that such individual certify (i) whether he has filed or intends to file any claim for such periodic benefits, and (ii) if he has so filed, whether there has been a decision on such claim. The Commissioner of Social Security may, in the absence of evidence to the contrary, rely upon such a certification by such individual that he has not filed and does not intend to file such a claim, or that he has so filed and no final decision thereon has been made, in certifying benefits for payment pursuant to section 405(i) of this title . (f) Redetermination of reduction (1) In the second calendar year after the year in which reduction under this section in the total of an individual’s benefits under section 423 of this title and any benefits under section 402 of this title based on his wages and self-employment income was first required (in a continuous period of months), and in each third year thereafter, the Commissioner of Social Security shall redetermine the amount of such benefits which are still subject to reduction under this section; but such redetermination shall not result in any decrease in the total amount of benefits payable under this subchapter on the basis of such individual’s wages and self-employment income. Such redetermined benefit shall be determined as of, and shall become effective with, the January following the year in which such redetermination was made. (2) In making the redetermination required by paragraph (1), the individual’s average current earnings (as defined in subsection (a)) shall be deemed to be the product of— (A) his average current earnings as initially determined under subsection (a); and (B) the ratio of (i) the national average wage index (as defined in section 409(k)(1) of this title ) for the calendar year before the year in which such redetermination is made to (ii) the national average wage index (as so defined) for the calendar year before the year in which the reduction was first computed (but not counting any reduction made in benefits for a previous period of disability). Any amount determined under this paragraph which is not a multiple of $1 shall be reduced to the next lower multiple of $1. (g) Proportionate reduction; application of excess Whenever a reduction in the total of benefits for any month based on an individual’s wages and self-employment income is made under this section, each benefit, except the disability insurance benefit, shall first be proportionately decreased, and any excess of such reduction over the sum of all such benefits other than the disability insurance benefits shall then be applied to such disability insurance benefit. (h) Furnishing of information (1) Notwithstanding any other provision of law, the head of any Federal agency shall provide such information within its possession as the Commissioner of Social Security may require for purposes of making a timely determination of the amount of the reduction, if any, required by this section in benefits payable under this subchapter, or verifying other information necessary in carrying out the provisions of this section. (2) The Commissioner of Social Security is authorized to enter into agreements with States, political subdivisions, and other organizations that administer a law or plan subject to the provisions of this section, in order to obtain such information as the Commissioner may require to carry out the provisions of this section.