Owe Taxes After Marriage? Why It Happens and How to Fix It

If you owe taxes after marriage, the culprit is almost always withholding, not a higher tax rate. When both spouses update Form W-4 to Married Filing Jointly without completing Step 2 for dual incomes, each employer’s payroll system treats your paycheck as if it were the household’s only income and applies the full joint standard deduction and joint tax brackets to it. Your spouse’s employer does the same thing. Together, you each get credit for the full joint deduction and the full joint brackets, so far too little tax comes out of each check. By April, the shortfall lands as a balance due.

How the W-4 Break Actually Happens

Before the wedding, if your W-4 was set to Single, your employer withheld based on the Single standard deduction ($16,100 for 2026) and Single bracket widths.¹ That was accurate for your situation. The moment you flip the W-4 to Married Filing Jointly, the payroll system starts applying the full $32,200 joint standard deduction and the wider MFJ brackets to your paycheck alone.²

Consider two spouses each earning $80,000. As singles, each employer withheld against $80,000 minus $16,100, using Single brackets. Combined, that covered the real tax bill. After both W-4s change to MFJ with nothing else adjusted, each employer withholds against $80,000 minus the full $32,200 joint deduction and uses the wider joint brackets. Each paycheck has dramatically less tax pulled out. Over a full year, the couple’s combined withholding can fall short of what they actually owe by several thousand dollars.

Your tax rate did not go up. Your withholding went down.

How to Fix Your Withholding

Step 2 of the W-4, labeled “Multiple Jobs or Spouse Works,” exists to solve exactly this. Both spouses should address it when both are employed.² There are three ways to do it.

Check the box in Step 2(c). Both spouses check this box on their own W-4s. It cuts the standard deduction and bracket widths in half at each job, which roughly restores Single-level withholding. It works cleanly when both jobs pay about the same. When the incomes are lopsided, it tends to over-withhold from the lower earner.

Use the IRS Tax Withholding Estimator. The online tool at irs.gov produces a specific extra dollar amount to enter on Line 4(c) of one spouse’s W-4. It is more precise than the checkbox and avoids the over-withholding that comes from the blanket approach.

Complete the Multiple Jobs Worksheet in Publication 505. This is the most manual option and the most flexible, especially if either spouse has self-employment income or other complications.³

If You Married Mid-Year and the Gap Is Already Large

Bumping up withholding on your remaining paychecks may not be enough to close the gap in time. Two catch-up moves help. First, put a large additional amount on Line 4(c) of one spouse’s W-4 to front-load withholding into the final paychecks of the year. Second, send estimated tax payments straight to the IRS using Form 1040-ES.⁴

For the 2026 tax year, estimated payments are due April 15, June 15, and September 15 of 2026, and January 15, 2027. You can skip the January payment if you file your return and pay in full by February 1, 2027.⁴

Your Wedding Date Sets Your Filing Status for the Whole Year

The IRS treats you as married for the entire tax year if you are married on December 31.⁵ A New Year’s Eve wedding files as married for the whole year; a January 2 wedding leaves you single for the year that just ended. That all-or-nothing rule is why late-year couples get blindsided. If both of you worked all year on Single W-4s and then switched to MFJ in the final weeks, there are not enough paychecks left to correct the withholding before the return is due. Early-year couples have more runway.

Where Marriage Really Does Raise Your Tax

Separate from the withholding problem, does the joint return itself produce more tax than two Single returns would have? For most dual-income couples earning under roughly $500,000 combined, the answer under current federal law is no, at least not from the tax brackets. Every MFJ bracket threshold from 10% through 35% for 2026 is exactly double the Single threshold, and the standard deduction is doubled the same way.¹ Two equal earners filing jointly owe the same federal income tax they would have owed on two Single returns.

The bracket penalty lives at the top. The 37% rate hits a Single filer at $640,600, so two singles would not cross it until their combined income exceeded $1,281,200. MFJ enters the 37% bracket at $768,700, roughly half a million dollars sooner.¹

Two Surtaxes That Kick In Sooner

Two surtaxes create real marriage penalties at ordinary income levels because their MFJ thresholds are not double the Single thresholds.

The Net Investment Income Tax adds 3.8% on investment income when modified AGI exceeds $250,000 for MFJ, versus $200,000 for singles.⁶ Two unmarried people could each earn $200,000 in investment income, $400,000 combined, before triggering it. A married couple hits it at $250,000.

The Additional Medicare Tax adds 0.9% on wages above $250,000 for MFJ, versus $200,000 for singles.⁷ Two spouses each earning $150,000 owe nothing as singles. Filing jointly, they owe 0.9% on $50,000.

Phase-Outs and Lost Head-of-Household Status

Combining two incomes on one return can push you past phase-outs that were fine on separate Single returns. The American Opportunity Tax Credit phases out between $160,000 and $180,000 of MAGI for MFJ filers.⁸ A spouse who claimed the full $2,500 credit on a $60,000 salary can lose it entirely once combined with a spouse earning $130,000.

A couple that previously included a Head of Household filer also loses that status after marriage. Head of Household brackets and its $24,150 standard deduction are more favorable than Single, and moving from one Head of Household filer plus one Single filer to a joint return can produce a net increase in tax.

State Brackets May Not Be Doubled

Even when federal brackets are perfectly doubled, your state’s may not be. Roughly 15 states have income tax brackets for married couples that are not double the single-filer thresholds, creating a state-level marriage penalty independent of your federal return. Fixing your federal W-4 will not repair a state shortfall. Most states have their own withholding form, and you may need to request additional state withholding separately. The pairing of a federal withholding gap with a state marriage penalty is how couples end up owing $4,000 or $5,000 when they expected a refund.

Avoiding an Underpayment Penalty

If your return shows a balance due of $1,000 or more, the IRS can add an underpayment penalty. You avoid it by hitting one of two safe harbors: your withholding and estimated payments covered at least 90% of the current year’s tax, or they covered 100% of the prior year’s tax (110% if your prior-year AGI exceeded $150,000).⁹

For newly married couples, the prior-year safe harbor is usually the easier one to hit. Your prior-year tax was calculated on your Single return. If your combined withholding this year at least matches what both of you paid individually last year, you meet the safe harbor even if the joint return shows a large balance due. The penalty is charged on the shortfall at the IRS’s quarterly interest rate, which was 7% in the first quarter of 2026 and dropped to 6% in the second.¹⁰

If the Bill Is Here and You Can’t Pay It All

You can apply online for a short-term payment plan of up to 180 days at no setup cost if you owe less than $100,000 including penalties and interest. For longer terms, a monthly installment agreement is available on balances up to $50,000, with setup fees from $22 to $178 depending on whether you use direct debit and whether you apply online or by phone.¹¹ Interest and penalties keep accruing on both, so paying faster costs less. Having a plan in place also stops the IRS from moving to collection, which is what actually matters once a surprise bill has arrived.

1
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments From the One Big Beautiful Bill
2
Internal Revenue Service. Form W-4 (2026) Employees Withholding Certificate
3
Internal Revenue Service. Publication 505 (2025), Tax Withholding and Estimated Tax
4
Internal Revenue Service. 2026 Form 1040-ES – Estimated Tax for Individuals
5
eCFR. 26 CFR 1.7703-1 – Determination of Marital Status
6
Internal Revenue Service. Topic No. 559, Net Investment Income Tax
7
Internal Revenue Service. Topic No. 560, Additional Medicare Tax
8
Internal Revenue Service. American Opportunity Tax Credit
9
Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty
10
Internal Revenue Service. Quarterly Interest Rates
11
Internal Revenue Service. Payment Plans; Installment Agreements