42 U.S.C. § 432

The Secretary of the Treasury shall make available information returns filed pursuant to part III of subchapter A of chapter 61 of subtitle F of the Internal Revenue Code of 1986, to the Commissioner of Social Security for the purposes of this subchapter and subchapter XI. The Commissioner of Social Security and the Secretary of the Treasury are authorized to enter into an agreement for the processing by the Commissioner of Social Security of information contained in returns filed pursuant to part III of subchapter A of chapter 61 of subtitle F of the Internal Revenue Code of 1986. Notwithstanding the provisions of section 6103(a) of the Internal Revenue Code of 1986, the Secretary of the Treasury shall make available to the Commissioner of Social Security such documents as may be agreed upon as being necessary for purposes of such processing. For purposes of carrying out the return processing program described in the preceding sentence, the Commissioner of Social Security shall request, not less than annually, such information described in section 7529(b)(2) of the Internal Revenue Code of 1986 as may be necessary to ensure the accuracy of the records maintained by the Commissioner of Social Security related to the amounts of wages paid to, and the amounts of self-employment income derived by, individuals. The Commissioner of Social Security shall process any withholding tax statements or other documents made available to the Commissioner by the Secretary of the Treasury pursuant to this section. Any agreement made pursuant to this section shall remain in full force and effect until modified or otherwise changed by mutual agreement of the Commissioner of Social Security and the Secretary of the Treasury.