If you get married any time in December, taxes for that year are filed as a married couple, because the IRS looks only at your marital status on December 31. A wedding on December 30 counts the same as one in January as far as the full year’s return is concerned. You and your spouse will file either a joint return covering both of your incomes for the whole year, or two separate married returns. Filing as Single is no longer an option.
The December 31 Rule
Federal law looks at one date: the last day of the tax year. If you hold a valid marriage certificate on December 31, you are considered married for all of that year’s tax purposes, even if the ceremony happened that same afternoon.1Office of the Law Revision Counsel. 26 USC 7703 – Determination of Marital Status The reverse is also true: a divorce finalized on or before December 31 treats you as unmarried for the whole year.
The IRS follows state law to decide whether a marriage is valid. If the state where you married recognizes it, so does the IRS, including common-law marriages in states that still allow them. The one exception to the December 31 rule involves a spouse who dies during the year; marital status is then set as of the date of death, and the surviving spouse can still file jointly for that final year.2eCFR. 26 CFR 1.7703-1 – Determination of Marital Status
Your Two Choices
Once you are married on December 31, you have two filing statuses available. Married Filing Jointly (MFJ) combines both spouses’ income, deductions, and credits onto a single Form 1040. Married Filing Separately (MFS) means each spouse files their own return reporting only their own income and deductions. Head of Household exists on paper as a third option, but it requires that your spouse not have lived in your home for the last six months of the year, which rules it out for essentially every December newlywed still living with their spouse.3Internal Revenue Service. Publication 501 (2025), Dependents, Standard Deduction, and Filing Information
Most couples file jointly because the math almost always favors it. The joint return has three structural advantages built into the tax code: a larger standard deduction, wider brackets, and access to credits that MFS filers lose entirely.
Standard Deduction and Brackets
For the 2026 tax year, the standard deduction for couples filing jointly is $32,200. Each spouse filing separately gets $16,100. The deduction totals the same if both spouses take the standard amount, but the brackets diverge. The 22% bracket starts at $100,800 for joint filers and at just $50,400 for those filing separately.4Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 The same pattern holds up the ladder. When two spouses earn similar incomes, bracket compression on separate returns can push the couple’s combined tax bill noticeably higher.
Credits You Lose by Filing Separately
The bracket difference is annoying. The credit restrictions are worse.
- The American Opportunity Tax Credit and the Lifetime Learning Credit are completely unavailable to MFS filers.5Office of the Law Revision Counsel. 26 USC 25A – American Opportunity and Lifetime Learning Credits
- You cannot deduct any student loan interest if your filing status is MFS.6Internal Revenue Service. Topic No. 456, Student Loan Interest Deduction
- The Child and Dependent Care Credit is generally unavailable to MFS filers.7Internal Revenue Service. Topic No. 602, Child and Dependent Care Credit
- The Earned Income Tax Credit is reachable on an MFS return only if you had a qualifying child living with you more than half the year and either lived apart from your spouse for the last six months or were legally separated under a written agreement. For a couple who married in December and still live together, that exception does not apply.8Internal Revenue Service. Who Qualifies for the Earned Income Tax Credit (EITC)
- The income phase-out for Roth IRA contributions on an MFS return runs from $0 to $10,000, so any meaningful income blocks a direct Roth contribution.9Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
A few other restrictions compound the pain. If one spouse itemizes deductions, the other must also itemize, even if their total deductions fall below the standard deduction amount.10Internal Revenue Service. Itemized Deductions, Standard Deduction The capital loss limit drops from $3,000 per return on a joint filing to $1,500 per spouse on separate returns.11Internal Revenue Service. Topic No. 409, Capital Gains and Losses Filing separately should be treated as the exception requiring a specific reason, not a default choice.
When Filing Separately Still Makes Sense
Protecting Yourself From a Spouse’s Tax Problems
When you file jointly, both spouses are liable for the entire tax bill, including penalties and interest the IRS adds later. The agency can pursue either spouse for the full amount, even if the error belonged entirely to the other person. This “joint and several liability” is the biggest legal risk of a joint return.12Office of the Law Revision Counsel. 26 USC 6015 – Relief From Joint and Several Liability on Joint Return
If your new spouse has a history of unfiled returns, unreported income, or outstanding tax debt, filing separately keeps you off their ledger. Each spouse is responsible only for the tax on their own return. For December marriages where you may not yet have full visibility into your partner’s financial past, that protection can be worth the higher tax cost.
Income-Driven Student Loan Repayment
Couples where one or both spouses carry federal student loans on an income-driven repayment plan face a real trade-off. On a joint return, your IDR payment is based on combined household income. Filing separately means only the borrower’s individual income counts toward the payment calculation.13Federal Student Aid. 4 Things to Know About Marriage and Student Loan Debt For a couple where the non-borrower earns significantly more, this can reduce monthly loan payments by hundreds of dollars. Run the numbers both ways: compare the extra tax from filing separately against twelve months of lower loan payments.
Community Property States Add Complexity
Couples who live in Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, or Wisconsin face an extra wrinkle when filing separately.14Internal Revenue Service. Publication 555 (12/2024), Community Property Community property laws treat income earned during the marriage as belonging equally to both spouses. An MFS couple in one of these states must split their combined community income down the middle and report each half on their own return, using Form 8958.15Internal Revenue Service. About Form 8958, Allocation of Tax Amounts Between Certain Individuals in Community Property States
For a December wedding, the community property split typically applies only to income earned from the wedding date through December 31, since pre-marriage income is usually separate property. The allocation still adds paperwork and can eliminate much of the perceived benefit of filing separately. In these states, the MFS calculation is worth doing carefully or handing to a tax professional.
What To Do Before Year-End and First Filing
A December wedding triggers a few administrative steps that directly affect the return you will file in the spring.
The IRS matches the name and Social Security number on every return against Social Security Administration records. If you change your last name but file under the new name before updating it with the SSA, your return may be delayed or your refund held. Use your former name on your tax return until the SSA update is complete.16Internal Revenue Service. Name Changes and Social Security Number Matching Issues
You should give your employer a new Form W-4 within 10 days of getting married.17Internal Revenue Service. Tax To-Dos for Newlyweds to Keep in Mind For a December wedding, the W-4 change will mostly affect withholding for the following year, but filing promptly avoids under-withholding surprises once your first full married year begins.
If either spouse receives advance Premium Tax Credit payments through a health insurance marketplace plan, marriage changes the household income used to calculate that credit. Report the marriage to the marketplace promptly. If you don’t update your information and your combined household income is higher than what was originally estimated, you may owe back some or all of the advance credit when you reconcile on Form 8962 at tax time.18Internal Revenue Service. Premium Tax Credit (PTC) Overview
Changing Your Mind After You File
If you file separately and later realize a joint return would have been cheaper, you have three years from the original due date of your separate return to amend to a joint return using Form 1040-X. The reverse is not true. Once you file a joint return and the filing deadline passes, you generally cannot amend to separate returns.19Internal Revenue Service. Publication 504 (2025), Divorced or Separated Individuals This asymmetry matters for a first-year married couple weighing their options: filing separately first and switching to joint later preserves both choices, while filing jointly locks you in.