Cohabitation agreement: what it is, and what to put in yours

A cohabitation agreement is a contract between two people who live together that sets out their property and financial arrangements:¹ who owns what, how you share costs, and what happens to it all if you split up. Unmarried couples sign one because the rules that divide property in a divorce are written for spouses. In California, for example, the state’s family law statutes don’t govern how property acquired during an unmarried relationship is divided; those disputes are left to the courts.²

That leaves a gap. Without an agreement, a breakup can turn into an argument about who paid for what and what you each meant years ago, settled by whatever your state’s courts allow. Writing it down while you’re happy is the whole idea.

They can be, but each state sets its own conditions.^2,3,4

The landmark case is Marvin v. Marvin, decided by the California Supreme Court in 1976. It held that courts should enforce express contracts between unmarried partners, unless sex is explicitly part of the bargain. Even without an express contract, the court said, judges can look at how a couple behaved to find an implied agreement, a partnership or some other shared understanding, and can use fairness remedies when the facts call for it.²

The court’s reasoning answers a question a lot of couples have: do unmarried partners have rights? In California, not marital ones, but you don’t need to be treated as if you were married to have your deals enforced. The court said unmarried partners should be treated like any other unmarried people when it comes to contracts and fairness.²

Relying on an implied agreement means asking a judge to reconstruct, years later, what you both meant. A written one saves everybody the guesswork.

Other states add formalities. Minnesota enforces the property and money terms of a live-in couple’s agreement only if it’s written and signed by both partners, and only after the relationship ends.³ Without one, Minnesota courts must dismiss claims to a partner’s earnings or property that are based on having lived together.⁹ New Jersey won’t enforce a promise of support between unmarried partners unless it’s in writing, signed, and made with independent legal advice for both people.⁴

So the same handshake understanding could be enforceable in California and dismissed in Minnesota.^2,9 Before you rely on an agreement for anything big, a family lawyer in your state can tell you what it needs to hold up.

No. Living together, by itself, doesn’t create a common-law marriage, no matter how long it lasts.⁶ A common-law marriage is a marriage without a license or ceremony, and most states have abolished new ones.⁶

According to the Social Security Administration’s digest of state laws (last revised in 2023), a new common-law marriage can still be formed only in Colorado, Iowa, Kansas, Montana, Oklahoma, Rhode Island, Texas, Utah and the District of Columbia.⁵ Utah is phasing its version out: under a 2026 law, a court there can recognize one only if someone files a petition before May 5, 2027.¹⁰ New Hampshire recognizes one only in a narrow case: after one partner dies, if the couple had lived together, acknowledged each other as spouses and been known as married for three years.⁵

Where it still exists, it takes more than a shared address. Texas, for example, looks for an agreement to be married, living together in Texas as spouses, and telling others you’re married.⁵ And once a common-law marriage exists, it’s a real marriage: in Texas, it doesn’t end just because time passes or you stop living together.⁵ Some states that abolished it still honor common-law marriages formed before a cutoff, such as Pennsylvania (on or before January 1, 2005) and South Carolina (before July 24, 2019).⁵ If you live, or used to live, in a state on either list and aren’t sure where you stand, that’s a question for a local family lawyer, not a calendar.

One more gap worth knowing about: if one of you dies without a will, state inheritance laws generally pass property to a spouse, children and other relatives,¹¹ and an unmarried partner isn’t in that usual line. A cohabitation agreement isn’t a will, so estate planning is its own conversation.

The core is property and money: what each of you brings, what you buy together, how you share costs, and what happens to all of it if you break up. Here’s a checklist of topics worth settling.

Not sure what a fair split of costs looks like for the two of you? Our money questions for couples are a good way to find out before you put anything in writing.

1. 1

   Talk before you draft

   Go through the table above one topic at a time, over a few evenings if you need to. The conversation is most of the work.

2. 2

   Make your lists

   Each of you writes down what you’re bringing in: furniture, savings, the car, any debts. Photos of receipts for big items help later.

3. 3

   Write down what you decided

   Topic by topic, in sentences you both understand. If you can’t explain a line to each other, it isn’t finished.

4. 4

   Check your state’s rules

   A family lawyer can tell you what your state needs for it to count, like a signed writing in Minnesota or independent advice for promises of support in New Jersey.^3,4

5. 5

   Sign, keep copies, set a review date

   Once a year works, or whenever something big changes: a home, a baby, a new job, a wedding.

Kids are a separate matter. Even a prenup can’t lower child support or settle custody, because support is the child’s right and courts keep the final say on a child’s best interests,¹² so if you have or plan to have children together, talk to a family lawyer about parentage, custody and support.

A prenup is for couples about to marry and takes effect at the wedding;¹² a cohabitation agreement is for partners who live together without marrying.^1,2 The 2012 model law for prenups was deliberately written not to cover cohabitation agreements.¹²

If you later marry, marriage brings its own legal rules. Some couples sign one document that works as both; the model law treats the parts triggered by marriage as a premarital agreement and leaves the cohabitation parts with whatever force they have for the time you lived together.¹² Either way, a wedding is a natural moment to have a lawyer look at what you signed. Our guide to what a prenup is covers the marriage side.

Before you rely on one for anything big, because what makes an agreement enforceable differs from state to state.^3,4 A lawyer is especially worth it if:

• You’re buying a home together, or one of you owns the place you’ll share.
• There’s a big gap between you in income, savings or debt.
• One of you will cut back on paid work to care for kids or the home.
• Either of you owns a business or expects an inheritance.
• You want a promise of support to hold up. In New Jersey, it isn’t binding without independent legal advice for both of you.⁴
• You live in, or might move to, a state that still lets couples form a common-law marriage.⁵
• You have or plan to have children together.

Some couples each hire their own lawyer so both sides get independent advice, which New Jersey requires for promises of support.⁴ If cost is a worry, ask whether a lawyer can review a draft you’ve written together rather than starting from scratch.

What you’re paying for is local knowledge: which formalities your state requires, which terms a court there might not enforce, and whether the agreement lines up with your lease, your deed and any will.

No. A relationship contract like The Couples Contract isn’t legally binding, so it can’t do a cohabitation agreement’s job, but it covers the daily life a legal agreement leaves out.

Think of it this way: a cohabitation agreement is about who owns the couch. The Couples Contract, which isn’t legally binding, is about who vacuums it. It walks you through chores, who pays for what day to day, family and friends, time together and time alone, who walks the dog, even what happens if one of you gets a job in another city. You fill it in together, compare answers and sign it, knowing the only thing it binds you to is the conversation.

Start with our questions to ask before moving in together, then decide what belongs in a legal agreement and what belongs in a relationship one.