(a) Increases in withholding—(1) In general. In addition to the tax required to be deducted and withheld in accordance with the provisions of section 3402, the employee may request, after September 30, 1981, that the employer deduct and withhold an additional amount from the employee's wages. The employer must comply with the employee's request, except that the employer shall comply with the employee's request only to the extent that the amount that the employee requests to be deducted and withheld under this section does not exceed the amount that remains after the employer has deducted and withheld all amounts otherwise required to be deducted and withheld by Federal law (other than by section 3402(i) and this section), State law, and local law (other than by State or local law that provides for voluntary withholding). The employer must comply with the employee's request in accordance with the time limitations of § 31.3402(f)(3)-1 (relating to when withholding exemption certificate takes effect). The employee must make his request on Form W-4 as provided in § 31.3402(f)(5)-1 (relating to form and contents of withholding exemption certificates), and this Form W-4 shall take effect and remain effective in accordance with section 3402(f) and the regulations thereunder.

(2) Increases in withholding based on additional income. (i) The employee may request that the employer add an additional amount to the employee's wages and that the employer deduct and withhold an additional amount of income tax resulting from this addition under the computational procedures prescribed by the Commissioner in forms, instructions, publications, and other guidance for the calendar year for which the withholding allowance certificate claiming an additional amount to add to the employee's wages is furnished;

(ii) The employee may request that the employer deduct and withhold additional amounts of income tax resulting from the employee selecting higher withholding rate tables on the withholding allowance certificate;

(iii) The employer must comply with the employee's request under paragraph (a)(1)(i) or (ii) of this section, except that the employer shall comply with the employee's request only to the extent that the amount that the employee requests to be deducted and withheld under this section does not exceed the amount that remains after the employer has deducted and withheld all amounts otherwise required to be deducted and withheld by Federal law (other than by section 3402(i) and this section), State law, and local law (other than by State or local law that provides for voluntary withholding); and

(iv) The employer must comply with the employee's request in accordance with the time limitations in § 31.3402(f)(3)-1. The employee must make the request on Form W-4 as provided in § 31.3402(f)(5)-1 (relating to form and contents of withholding allowance certificates), and this Form W-4 shall take effect and remain effective in accordance with section 3402(f) and § 31.3402(f)(4)-1.

(3) Amount deducted treated as tax. The amount deducted and withheld pursuant to paragraphs (a)(1) and (2) of this section shall be treated as tax required to be deducted and withheld under section 3402.

(b) Applicability date. The provisions of paragraphs (a)(2) and (3) of this section apply on and after October 6, 2020. Taxpayers may choose to apply paragraphs (a)(2) and (3) this section on or after January 1, 2020 and before October 6, 2020.