Can Unmarried Couples File Jointly? Common Law and Filing Status

Unmarried couples cannot file a joint federal tax return. The Married Filing Jointly status is reserved for couples who are legally married under state law on the last day of the tax year, and the IRS follows that state-law determination.¹² The one narrow exception is common law marriage, still recognized in about a dozen states. Everyone else files as Single or Head of Household, and shared finances need to be handled with that in mind.

Why Joint Filing Requires a Legal Marriage

Federal law authorizes joint returns for a “husband and wife,” and the IRS looks to state law to decide whether two people qualify. If your state considers you unmarried on December 31, so does the IRS. A domestic partnership, a cohabitation agreement, or years of living together do not change that answer at the federal level.

The gap between filing jointly and filing as two singles isn’t the standard deduction itself. For 2026, married couples filing jointly get $32,200, and two single filers get $16,100 each, which adds to the same amount.³ The real difference shows up when one partner earns far more than the other. Married couples can effectively shift income into lower brackets on a joint return. Two single filers cannot.

The Common Law Marriage Exception

If you live in a state that recognizes common law marriage and you meet its requirements, the IRS treats you as legally married. You can file jointly, make spousal IRA contributions, and use every other benefit married couples get. The requirements vary by state, but generally include mutual intent to be married, living together, and holding yourselves out publicly as a married couple.

States that currently allow new common law marriages are Colorado, Iowa, Kansas, Montana, Oklahoma, Rhode Island, South Carolina, Texas, Utah, and the District of Columbia. New Hampshire recognizes common law marriage only after one partner’s death. Alabama, Florida, Georgia, Indiana, Ohio, Pennsylvania, and a few others still honor common law marriages formed before their cutoff dates but no longer permit new ones.

Two common misconceptions cause problems. Living together for a certain number of years does not, by itself, create a common law marriage in any state. And common law marriage isn’t a legal relic — it’s alive in roughly a dozen jurisdictions and creates real tax obligations. Sort this question out before you file. Claiming joint status when you don’t qualify and missing it when you do are both costly.

If You Move to a Non-Recognizing State

A common law marriage validly formed in a recognizing state stays valid for federal tax purposes even if you later move to a state that requires a ceremony. The IRS has held this position since Revenue Ruling 58-66.⁴ A couple who established common law marriage in Colorado can keep filing jointly after moving to California.

Domestic Partnerships and Civil Unions Don’t Qualify

Registered domestic partners and civil union partners are not married for federal tax purposes. They cannot file a joint federal return, and they cannot use Married Filing Separately either.⁵ Each partner files as Single, or as Head of Household if they qualify. Some state tax systems let domestic partners file jointly on the state return, but the federal return still has to be filed individually. Partners domiciled in California, Nevada, or Washington face an added community property layer and typically need Form 8958 to split income between their separate federal returns.⁶

Which Filing Status Each Partner Uses

The default status for an unmarried person is Single, which applies if you’re unmarried on December 31 and don’t qualify for anything better.⁷

Head of Household is the better choice when you can claim it. For 2026 it comes with a $24,150 standard deduction versus $16,100 for Single, plus wider tax brackets.³ To qualify you must be unmarried on the last day of the year, pay more than half the cost of keeping up your home, and have a qualifying person, usually a dependent child, living with you for more than half the year.² Your partner does not count as a qualifying person, even if you claim them as a dependent.⁵

When each partner has their own child from a prior relationship, both partners can potentially file as Head of Household on separate returns, each based on their own qualifying child. Married couples cannot replicate that.

Claiming Your Partner as a Dependent

You can sometimes claim a partner as a dependent under the qualifying relative rules. Your partner doesn’t have to be an actual relative; anyone who lives with you as a member of your household for the whole year can qualify if they meet the other tests.⁸ The requirements:

Your partner lives with you for the entire calendar year as a member of your household.
Your partner’s gross income is under the annual threshold, which is $5,300 for 2026.
You provide more than half of your partner’s total support for the year.
Your partner is not filing a joint return with someone else.

The income limit disqualifies most partners. Even modest part-time wages will push someone past $5,300. But if your partner is a full-time student, staying home with children, or out of work for most of the year, the deduction can be worth pursuing. Claiming a partner as a dependent qualifies you for the Credit for Other Dependents, worth up to $500.

Splitting a Shared Mortgage

Co-owning a home creates a reporting wrinkle. The lender sends one Form 1098 to one borrower, but both partners may deduct the share of mortgage interest and property taxes they actually paid.⁹ The partner who received the 1098 reports their portion on Schedule A, line 8a. The other partner reports their share on line 8b as home mortgage interest not reported on Form 1098, naming the person who did receive it. A paper filer should attach a short explanation of how the interest was split.

None of this helps unless you itemize. If your share of the mortgage interest plus your other itemized deductions doesn’t clear $16,100 for 2026, the standard deduction beats itemizing and the split doesn’t matter. Run the numbers both ways.

Which Parent Claims the Children

Only one parent can claim a shared child as a dependent. The Child Tax Credit, Earned Income Tax Credit, and Child and Dependent Care Credit tied to that child cannot be split across two returns.¹⁰ If both parents claim the same child, the IRS applies these tie-breaker rules in order:¹¹

If only one of the two people claiming the child is a parent, the parent wins.
If both are parents, the child goes to whichever parent the child lived with for more nights.
If the nights are equal, the child goes to the parent with the higher adjusted gross income.

The custodial parent can voluntarily release the dependency claim by signing Form 8332, which transfers the Child Tax Credit to the other parent. Head of Household status, the Earned Income Tax Credit, and the Child and Dependent Care Credit stay with the custodial parent no matter what Form 8332 says.¹²

Gift Tax Between Partners

Married spouses can transfer unlimited amounts to each other tax-free through the marital deduction. Unmarried partners have no equivalent. Paying your partner’s mortgage, buying them a car, or adding them to the title of a home you own can all be treated as taxable gifts.

For 2026, you can give up to $19,000 per person per year with no gift tax reporting.³ Anything above that requires filing Form 709, though no actual gift tax is due until you exceed the $15 million lifetime exclusion.¹³ The filing obligation still matters, because unreported gifts above the annual exclusion can create penalties later.

The scenarios that trip couples up are ordinary ones. One partner covers the whole mortgage on a jointly titled home. One partner pays all the household bills while the other saves. If the excess passes $19,000 in a year, the IRS treats it as a gift, and most couples never think about it until an audit or a breakup surfaces the issue.

When Filing Separately Actually Helps

The unmarried tax picture isn’t uniformly worse. The Earned Income Tax Credit tests eligibility against each filer’s income, and two unmarried partners with children can sometimes claim a larger combined EITC than they could if they were married filing jointly, because a lower-earning partner’s qualifying child claim isn’t dragged into a higher joint income calculation.¹⁴ Certain income-based phase-outs also hit married couples at thresholds that aren’t quite double the single amount, producing the classic marriage penalty for two high earners. Unmarried couples sidestep that entirely.

1
Office of the Law Revision Counsel. 26 U.S. Code 6013 – Joint Returns of Income Tax by Husband and Wife
2
Internal Revenue Service. Publication 501 (2025), Dependents, Standard Deduction, and Filing Information
3
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments From the One, Big, Beautiful Bill
4
Internal Revenue Service. Revenue Ruling 2013-17
5
Internal Revenue Service. Answers to Frequently Asked Questions for Registered Domestic Partners and Individuals in Civil Unions
6
Internal Revenue Service. Publication 555, Community Property
7
Internal Revenue Service. Filing Status
8
Internal Revenue Service. Dependents
9
Internal Revenue Service. Other Deduction Questions 2
10
Internal Revenue Service. Claiming a Child as a Dependent When Parents Are Divorced, Separated or Live Apart
11
Internal Revenue Service. Tie-Breaker Rule
12
Internal Revenue Service. Dependents
13
Internal Revenue Service. What’s New – Estate and Gift Tax
14
Internal Revenue Service. Earned Income and Earned Income Tax Credit (EITC) Tables