10/26/2026
Workers whose tax filing status changes during 2026 from married filing jointly to single or head of household have until December 1, 2026, to hand their employer a new Form W-4 for 2027. That is the IRS rule in Publication 505, the agency’s guide to tax withholding and estimated tax. A change that happens late in the year gets more time: the deadline is 10 days after the change if that date falls after December 1.
The W-4 is the form that tells payroll how much federal income tax to hold back from each paycheck. A divorce or the death of a spouse changes the tax a worker owes, and a paycheck set up for a joint return can end up taking out too little for the year ahead. Anyone whose status changed this year, and who is still working, has to decide whether payroll already has the right form.
