If you get married any time in December, you and your spouse can file your federal taxes together for that entire year. The IRS looks at one date only: your marital status on December 31. A wedding on December 2 or December 31 has the same effect, and all of the income each of you earned during the year, including the months before the wedding, goes on one joint return if that’s what you choose.1Office of the Law Revision Counsel. 26 USC 7703 – Determination of Marital Status
How the IRS Decides You’re Married
Federal tax law defers to state law on whether a marriage is valid. If the state where you married recognizes it, the IRS does too. That includes common-law marriages in states that still allow them, provided you meet that state’s requirements.2eCFR. 26 CFR 1.7703-1 – Determination of Marital Status
The December 31 rule cuts both ways. Marry on December 31 and you’re married for the whole year. Finalize a divorce or legal separation by that same date and you’re treated as unmarried for the whole year. The one carve-out is a spouse who dies during the year: marital status is fixed at the date of death, and the surviving spouse can still file jointly for that final year.
Your Two Filing Options as a Newly Married Couple
Once you’re married on December 31, you have two choices on your federal return. Married Filing Jointly combines both spouses’ income, deductions, and credits on one Form 1040. Married Filing Separately means each spouse files their own return with only their own income and deductions.
Single is not an option. Head of Household is only available if you lived apart from your spouse for the last six months of the year, paid more than half the cost of your home, and had a qualifying child living with you for more than half the year.3Internal Revenue Service. Publication 501 (2025), Dependents, Standard Deduction, and Filing Information For a couple who just married in December and is living together, that status doesn’t apply.
Why Filing Jointly Almost Always Wins
The tax code is built to reward the joint return. Three things drive that.
A Much Larger Standard Deduction
For the 2026 tax year, the standard deduction for couples filing jointly is $32,200. If you file separately, each spouse gets $16,100.4Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 The totals match if neither spouse itemizes, but the brackets don’t line up the same way.
Wider Tax Brackets
Joint filers get bracket thresholds roughly double those of separate filers. For 2026, the 22% bracket starts at $100,800 for joint filers but at just $50,400 for spouses filing separately. When two spouses earn similar incomes, that compression can push the couple’s combined tax bill noticeably higher on separate returns.
Credits You Lose by Filing Separately
Filing separately closes the door on several common tax breaks.
- The American Opportunity Tax Credit and Lifetime Learning Credit are completely unavailable to separate filers.5Office of the Law Revision Counsel. 26 USC 25A – American Opportunity and Lifetime Learning Credits
- You cannot deduct student loan interest if your filing status is Married Filing Separately.6Internal Revenue Service. Topic No. 456, Student Loan Interest Deduction
- The Child and Dependent Care Credit is generally off-limits, with a narrow exception for spouses who qualify as deemed unmarried.7Internal Revenue Service. Topic No. 602, Child and Dependent Care Credit
- The Earned Income Tax Credit is unavailable to a separate filer unless a qualifying child lived with them for more than half the year and they either lived apart from their spouse for the last six months or were legally separated in writing. That doesn’t help a December-newlywed couple living together.8Internal Revenue Service. Who Qualifies for the Earned Income Tax Credit (EITC)
- Direct Roth IRA contributions phase out for separate filers over an income range of $0 to $10,000, which eliminates most working spouses.9Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
A few more restrictions add up. If one spouse itemizes, the other has to itemize too, even when their deductions come in below the standard amount.10Internal Revenue Service. Itemized Deductions, Standard Deduction The capital loss deduction drops from $3,000 on a joint return to $1,500 per spouse on separate returns.11Internal Revenue Service. Topic No. 409, Capital Gains and Losses Filing separately should be a specific choice for a specific reason, not the default.
When Filing Separately Still Makes Sense
Protecting Yourself From a Spouse’s Tax Problems
A joint return creates joint and several liability. Both spouses are responsible for the entire tax bill, plus any penalties and interest the IRS tacks on later, and the IRS can pursue either one for the full amount even when the error belonged entirely to the other.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 a full picture of your partner’s financial history, that separation can be worth the higher tax cost.
Income-Driven Student Loan Repayment
If one or both of you are on a federal income-driven repayment plan, the joint-versus-separate choice affects your monthly loan payment as well as your tax bill. A joint return puts combined household income into the IDR formula. A separate return lets the borrower use only their individual income.13Federal Student Aid. 4 Things to Know About Marriage and Student Loan Debt Where one spouse earns significantly more than the borrower, filing separately can cut monthly payments substantially. Do the math both ways: the extra tax from filing separately against twelve months of lower loan payments.
If You File Jointly and Your Spouse Has Old Debts
Two different relief programs exist, and they solve different problems.
Injured Spouse Relief
If you file jointly and your refund gets seized to pay your spouse’s past-due child support, defaulted student loans, or old tax debt, you are the injured spouse. Form 8379 asks the IRS to calculate and return your share of the refund. File it with your original return if you’re expecting the offset, or after the fact once a notice arrives.14Internal Revenue Service. Instructions for Form 8379 This is the more common situation for newlyweds who learn their partner had pre-marital debts subject to Treasury offset.
Innocent Spouse Relief
Innocent spouse relief covers a different problem: your spouse understated tax on a joint return, either by underreporting income or claiming deductions that didn’t hold up, and you had no reason to know. When the IRS later bills the couple, you can request relief under IRC Section 6015 to avoid paying tax attributable to your spouse’s errors.15Internal Revenue Service. Tax Relief for Spouses The bar is higher: you have to show you genuinely didn’t know and that holding you responsible would be unfair.
Community Property States Add a Wrinkle
Couples in Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, or Wisconsin have to deal with community property rules if they file separately.16Internal Revenue Service. Publication 555 (12/2024), Community Property Income earned during the marriage belongs equally to both spouses under state law, which means a separately filing couple must split their combined community income down the middle and report each half on their own return, using Form 8958.17Internal Revenue Service. About Form 8958, Allocation of Tax Amounts Between Certain Individuals in Community Property States
For a December wedding, the split usually applies only to income earned from the wedding date through December 31, since pre-marriage income is typically separate property. The allocation still adds paperwork and can wipe out much of the perceived benefit of filing separately. If you live in a community property state and are weighing separate returns, run the numbers carefully or bring in a tax professional.
Administrative Steps After a December Wedding
A few housekeeping items directly affect what happens when you file.
If either spouse is changing their last name, update Social Security first. The IRS matches every return against Social Security Administration records, and a mismatch can delay processing or hold up your refund. Until the SSA update goes through, file your return under your former name.18Internal Revenue Service. Name Changes and Social Security Number Matching Issues
Give your employer a new Form W-4 within 10 days of the wedding.19Internal Revenue Service. Tax To-Dos for Newlyweds to Keep in Mind A December wedding leaves little of the current year for a W-4 change to affect, but doing it promptly sets up correct withholding for your first full year of married filing.
If either spouse has a health insurance marketplace plan with advance Premium Tax Credit payments, report the marriage to the marketplace right away. Advance payments were calculated on the old household income and size. Skip the update and your combined household income may leave you owing back some or all of the advance credit when you reconcile on Form 8962.20Internal Revenue Service. Premium Tax Credit (PTC) Overview
Can You Change Your Mind Later?
In one direction, yes. If you file separately and 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.21Internal Revenue Service. Publication 504 (2025), Divorced or Separated Individuals
The other direction is largely blocked. Once you file jointly and the filing deadline passes, you generally cannot amend to separate returns. The narrow exception involves a personal representative for a deceased spouse acting within one year. The practical takeaway: if you’re on the fence, filing separately first preserves both choices, while filing jointly locks the decision in.