26 U.S.C. § 6096: Designation by individuals

Every individual (other than a nonresident alien) whose income tax liability for the taxable year is $3 or more may designate that $3 shall be paid over to the Presidential Election Campaign Fund in accordance with the provisions of section 9006(a). In the case of a joint return of husband and wife having an income tax liability of $6 or more, each spouse may designate that $3 shall be paid to the fund. For purposes of subsection (a), the income tax liability of an individual for any taxable year is the amount of the tax imposed by chapter 1 on such individual for such taxable year (as shown on his return), reduced by the sum of the credits (as shown in his return) allowable under part IV of subchapter A of chapter 1 (other than subpart C thereof). at the time of filing the return of the tax imposed by chapter 1 for such taxable year, or at any other time (after the time of filing the return of the tax imposed by chapter 1 for such taxable year) specified in regulations prescribed by the Secretary. Funds which become available under the Presidential Election Campaign Fund Act of 1966 [this section and section 971 et seq. of former Title 31, Money and Finance] shall be appropriated and disbursed only after the adoption by law of guidelines governing their distribution. Section 6096 of the Internal Revenue Code of 1986 [formerly I.R.C. 1954] shall become applicable only after the adoption by law of such guidelines. Guidelines adopted in accordance with this section shall state expressly that they are intended to comply with this section.”