26 CFR § 31.3402(b)-1 - Percentage method of withholding.
(a) Percentage method of withholding. The amount of tax to be deducted and withheld from an employee's wages under the percentage method of withholding is determined based on the entry for the employee's anticipated filing status or marital status and other entries on the employee's withholding allowance certificate using the applicable percentage method tables and computational procedures set forth in the applicable forms, instructions, publications, and other guidance prescribed by the Commissioner issued with respect to the period in which wages are paid.
(b) Applicability date. The provisions of this section apply on and after October 6, 2020. Taxpayers may choose to apply this section on or after January 1, 2020 and before October 6, 2020. For rules that apply before October 6, 2020, see 26 CFR part 31, revised as of April 1, 2020.