26 CFR § 31.3402(l)-1 - Determination and disclosure of marital or filing status.
(a) In general. An employer shall apply the applicable percentage method or wage bracket method withholding tables corresponding to the marital status or filing status that the employee selects on a valid withholding allowance certificate as set forth in forms, instructions, publications, and other guidance prescribed by the Commissioner.
(b) Employee's filing status. An employee will be treated as single unless the employee selects head of household or married filing jointly filing status on a valid withholding allowance certificate. Employees may select a filing status other than single, subject to the following conditions:
(1) The employee may select head of household filing status on the employee's withholding allowance certificate only if the employee reasonably expects to be eligible to claim head of household filing status under section 2(b) and § 1.2-2(b) of this chapter on the employee's income tax return.
(2) The employee may select married filing jointly filing status on the employee's withholding allowance certificate only if paragraph (d) of this section applies to the employee and the employee reasonably expects to file jointly a single return of income under subtitle A of the Code with the employee's spouse. If an employee is married and expects to file a separate return from the employee's spouse, the employee must select single or married filing separately filing status on the employee's withholding allowance certificate.
(c) Change in filing status -
(1) In general. Unless paragraph (c)(2) of this section applies, the employee must within 10 days furnish the employer with a new withholding allowance certificate if the employee's filing status changes -
(i) From married filing jointly (or qualifying widow(er)) to head of household, married filing separately, or single; or
(ii) From head of household to married filing separately or single.
(2) Exception. If the employee's filing status changes in the manner described in paragraph (c)(1)(i) or (ii) of this section, but the total effect of the changes together with other changes affecting the employee's anticipated tax liability under subtitle A does not result in an amount of tax to be deducted and withheld from the employee's wages for the taxable year that is less than the employee's anticipated tax liability under subtitle A, the employee is not required to furnish a new withholding allowance certificate within 10 days. However, the employee must furnish a new withholding allowance certificate to take effect the following calendar year by the later of December 1 of the calendar year in which the employee's filing status changes, or within 10 days of such change.
(d) Determination of marital status. For the purposes of section 3402(l)(2) and paragraph (b) of this section, paragraphs (d)(1) and (2) of this section shall be applied in determining whether an employee is a single person or a married person:
(ii) Either the employee or the employee's spouse is, or on any preceding day within the same calendar year was, a nonresident alien unless the employee has made or reasonably expects to make an election under section 6013(g) in the time and manner prescribed in § 1.6013-6(a)(4) of this chapter.
(iii) The employee's spouse died during one of the two taxable years immediately preceding the current taxable year and, on the basis of facts existing at the beginning of such day, the employee reasonably expects, at the close of the taxable year, to be a surviving spouse as defined in section 2 and § 1.2-2(a) of this chapter. The employee must reasonably expect to file an income tax return claiming qualifying widow(er) status.
(e) Applicability date. The provisions 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. For rules that apply before October 6, 2020, see 26 CFR part 31, revised as of April 1, 2020.