Cohabitation Agreement: What It Covers and Why It Matters

What Is a Cohabitation Agreement?

A cohabitation agreement is a legally binding contract between two people who live together outside of marriage. Sometimes called a living together agreement, a non-marital contract, or a "no-nup," it sets mutual expectations for how property, money, and day-to-day responsibilities will be managed during the relationship and, if necessary, after it ends.

This type of agreement is best suited for committed, long-term partners who share some combination of income, expenses, debt, or a home. Washington Law Help recommends creating one when partners live together, plan to stay together long term, and share financial responsibilities. That said, cohabitation agreements aren't limited to romantic partners. Friends or family members who share a household and financial obligations can use them too.

The agreement doesn't need to be complicated, but it does need to be clear. At its core, it answers one question: if circumstances change, what happens to the things we share?

What Does a Cohabitation Agreement Cover?

A cohabitation agreement can address nearly any financial or property issue that matters to both partners. The specific terms will depend on your situation, but here are the provisions couples most commonly include:

• Housing: Whether one or both names will be on the lease or deed, who pays the mortgage or rent, and who stays in the home if the relationship ends
• Household expenses: How rent, utilities, insurance, groceries, and other bills are divided
• Separate vs. joint property: Which assets each partner brought into the relationship (separate property) and which items purchased together are considered shared
• Shared purchases: How jointly bought items like furniture, electronics, or vehicles are handled
• Debt responsibility: Who is responsible for debts incurred before cohabitation and debts taken on together during the relationship
• Post-separation support: Whether a higher-earning partner will provide any financial support to the other partner after a breakup, and for how long
• Pets: Who assumes responsibility for any pets if the relationship ends
• What happens if a partner dies: Whether the surviving partner retains ownership of shared property, often addressed through joint tenancy with rights of survivorship

Many couples also draft related documents alongside the agreement, including healthcare directives and powers of attorney, so each partner can make medical decisions for the other in an emergency.

What a Cohabitation Agreement Cannot Include

Courts will not enforce provisions that violate state law. Child support and custody arrangements are determined by courts based on the child's best interests, regardless of what partners agree to privately. Any clause that explicitly rests on a promise of sexual services will also render that portion of the agreement unenforceable.

Why Unmarried Couples Need a Cohabitation Agreement

In the vast majority of U.S. states, moving in together does not automatically create legal rights or obligations between partners. Unlike marriage, cohabitation does not trigger rules around property division, financial support, or inheritance. If you and your partner split up or one of you dies without a will, the law in most states treats you as legal strangers.

That legal gap matters more now than ever. Between 1980 and 2018, the number of unmarried partners living together in the U.S. nearly tripled from 6 million to 17 million. About 70% of first marriages among women under 36 began with premarital cohabitation lasting an average of 32 months. Millions of couples are building shared financial lives without the automatic legal framework that marriage provides.

A cohabitation agreement fills that gap deliberately. It's a way for partners to have honest conversations about money, expectations, and long-term plans. As Michael C. Cotugno, Esq., Managing Partner of Neptune Legal, puts it: "Understanding a partner's relationship with money, their historical experiences of abundance or scarcity, their anxieties tied to financial stability, or their personal definitions of success, allows for a deeper, more empathetic understanding of them as a whole individual."

State Exceptions to Keep in Mind

Washington State is a notable outlier. There, courts can require property distribution when a long-term cohabitation ends, even without a written agreement. However, the rules for cohabitants are still less favorable than those for married couples. In states that recognize common-law marriage (such as Colorado, Iowa, Kansas, Montana, and others), a cohabitation agreement's "no-marriage" statement can be especially important to clarify that both partners do not intend to create a legal marriage by living together.

Cohabitation Agreement vs Prenup: What's the Difference

The core difference is straightforward: a prenup governs a marriage, while a cohabitation agreement governs an unmarried relationship. They serve a similar purpose (financial clarity between partners), but they operate under different legal frameworks and kick in at different times.

One practical consideration: your cohabitation agreement can include a clause stating what happens if you eventually marry. Some couples specify that the agreement terminates upon marriage (at which point a prenup would govern). Others choose to carry certain terms forward. Either way, addressing the question upfront prevents ambiguity.

Are Cohabitation Agreements Legally Enforceable?

Yes, courts in most states will enforce a cohabitation agreement as an ordinary contract, provided it meets basic requirements. The landmark 1976 California case Marvin v. Marvin established the foundational precedent: contracts between unmarried partners are enforceable as long as they don't explicitly rest on a promise of sexual services. Since then, most states have followed suit.

The general requirements for enforceability are:

1. Written and signed. Oral or implied agreements are much harder to enforce and are not recognized in some states.
2. Voluntary. Both partners must sign without coercion or duress.
3. Fair terms. Courts may refuse to enforce agreements that are unconscionable or heavily one-sided.
4. Lawful provisions. No terms can violate state law (such as predetermined child custody or support).
5. Not based on sexual consideration. The agreement must be grounded in financial and property arrangements, not a sexual relationship.

If the agreement involves real property (a home or land), notarization and proper titling add an extra layer of reliability. Some states require notarization for agreements affecting real estate to be enforceable.

State-by-State Variation

Enforceability does vary. Some states enforce only written or express agreements between cohabitants; a few have historically been reluctant to enforce cohabitation contracts at all. California has one of the most comprehensive bodies of law for enforcing these agreements, while other states are still developing their approaches. This is one reason independent legal counsel matters: an attorney familiar with your state's rules can flag any requirements specific to your jurisdiction.

Cohabitation Agreement Templates vs Working With a Lawyer

Templates for cohabitation agreements are widely available online, and for straightforward situations, they can be a reasonable starting point. However, a template's enforceability depends entirely on whether it meets your state's legal requirements and addresses your specific circumstances.

Here's where the distinction matters:

A qualified attorney adds the most value when your situation involves real property, significant shared assets, income disparity, or children from prior relationships. They can also negotiate terms on your behalf and make sure the agreement is structured to hold up in your state.

Neptune offers a lawyer-led online approach where each partner can choose an independent attorney from the Neptune network. Having independent counsel on each side helps ensure both partners' interests are represented and strengthens the agreement's enforceability.

For simpler arrangements (two renters splitting bills with no major shared assets), a well-researched template reviewed by a single attorney may be sufficient. The key is knowing when complexity requires more.

How to Create a Cohabitation Agreement

Creating a cohabitation agreement is less about paperwork and more about honest conversation. Here's a practical framework:

Step 1: Disclose Your Finances

Before drafting anything, both partners should share a full picture of their financial situation: income, savings, debts, and any property they own. Full disclosure is a fairness requirement that also builds trust.

Step 2: Discuss and Decide on Key Terms

Use this checklist as a conversation guide:

• [ ] Whose name goes on the lease or deed?
• [ ] How will rent or mortgage payments be split?
• [ ] How will household bills and groceries be divided?
• [ ] What property does each partner consider separate?
• [ ] How will jointly purchased items be handled?
• [ ] Who is responsible for pre-existing debts?
• [ ] Will either partner provide support if the relationship ends?
• [ ] Who keeps the home if you separate?
• [ ] Who takes responsibility for pets?
• [ ] Do you want healthcare directives or powers of attorney?
• [ ] What happens to this agreement if you marry?

Step 3: Draft the Agreement

Put your decisions in writing. Whether you start from a template or work with an attorney from the beginning, the document should be clear, specific, and organized.

Step 4: Review With Independent Counsel

Each partner should ideally have their own attorney review (or help draft) the agreement. Independent representation for both sides significantly strengthens enforceability and makes sure neither partner's interests are overlooked.

Step 5: Sign, Date, and Notarize

Both partners should sign the agreement using their legal names. Having a witness present is helpful. If the agreement covers real property, notarization is strongly recommended and may be required in your state. Each partner should keep a signed copy.

Step 6: Revisit and Update

A cohabitation agreement isn't a "set it and forget it" document. Major life changes (a new home purchase, a child, a significant shift in income) are good reasons to review and update the terms together.