Getting married changes your tax. It does not change your withholding — that keeps running on whatever you told your employer when you were hired, until you tell them something else.
For most couples the mismatch is small and shows up as an unexpected refund. For two-earner couples it can go the other way, and a bill in April is a worse surprise than a refund.
Why marrying breaks your withholding
Your employer works out withholding from Form W-4 as though the job it is paying you for is your household's only income. That assumption is roughly right for a single person with one job. It is wrong in two different ways once you marry.
If only one of you works, withholding is now too high. You are entitled to the wider joint brackets and the doubled standard deduction, and the payroll system does not know it. A single earner on $130,000 pays $8,694 a year less once married — and without a new W-4, that whole amount is withheld anyway and returned to you the following year.
If you both work, the problem inverts. Each employer applies a full set of low brackets to its own job, so between them they apply those cheap bands twice. Your actual return applies them once, to your combined income. Two jobs that each look correctly withheld can add up to a household that is under-withheld.
What to do
- Work out the size of the change. The calculator gives you the annual difference between filing jointly and staying unmarried. That is the amount your withholding is now wrong by, before anything else changes.
- Submit a new W-4 to each employer. Change the filing status to Married filing jointly. This is the step almost everyone remembers.
- If you both work, handle the second job. This is the step almost everyone forgets, and it is the one that causes April bills. Form W-4 offers three ways: tick the checkbox in Step 2(c) on both W-4s if the two jobs pay similarly, use the IRS Tax Withholding Estimator, or use the worksheet on the form. The checkbox is the simplest and is designed for roughly equal incomes.
- Claim dependants once, not twice. Step 3 is per household, not per job. Both of you entering the same children doubles the credit your employers assume and under-withholds you by that amount.
- Check a payslip afterwards. Multiply the new federal withholding by the number of pay periods left in the year, add what has already been withheld, and compare against what you expect to owe.
Time it against your wedding date
Marital status for an entire tax year is set by your status on 31 December. Marry on 30 December and you file jointly for that whole year, on income earned when you were single — so the withholding mismatch covers twelve months, not two days. Marry on 2 January and none of it applies until the following year.
If you are marrying late in the year, that makes updating the W-4 more urgent, not less: there are few pay periods left to correct twelve months of withholding. See how your wedding date changes your taxes.
If the change is a penalty, not a bonus
Couples with children on modest incomes can find marrying increases their federal tax, sometimes substantially — two earners on $25,000 each with two children pay $3,599 a year more, almost all of it lost Earned Income Tax Credit. If that is you, the W-4 change matters more than it does for anyone else, because that money is not currently being withheld from anybody.
Either increase withholding using the extra-withholding line in Step 4(c), or set the money aside yourself. Doing neither means finding it in April. The EITC marriage penalty explains where the figure comes from.
Also worth doing
- Tell the Social Security Administration if either of you changed name — the IRS matches the name on your return against their records, and a mismatch delays processing.
- Update your address with the IRS and with each employer if you have moved.
- Revisit any health-insurance subsidy. Premium tax credits are calculated on household income, and marriage changes the household.
This is general information, not tax advice. The calculator models federal income tax on wage income only, so it cannot tell you your full withholding target — the IRS Tax Withholding Estimator can, and it accounts for income this site deliberately ignores.
Every figure on this page is computed by the same engine as the calculator, against tax year 2026 figures from IRS Rev. Proc. 2025-32. Change the inputs there to see your own numbers.