California cohabitation law gives unmarried couples almost none of the automatic legal protections that come with marriage, no matter how long you live together. The state does not recognize common-law marriage, so a partner who shares a home, raises children, and builds a life with someone for twenty years still has no automatic right to property division, financial support, or inheritance if the relationship ends or one partner dies. If you want legal protection, you have to take an affirmative step: register as domestic partners, sign written agreements, or use estate planning documents to create the rights the law will not give you.
No Common-Law Marriage in California
California requires a marriage license and a ceremony for a legally valid marriage. Time spent living together, sharing finances, or presenting yourselves publicly as a couple does not create a marriage under state law. The practical consequence is blunt. Unless you formalize the relationship, the law treats you and your partner as two unrelated adults. You have no right to each other’s earnings, no claim on property the other person acquires in their own name, no standing to receive support if you break up, and no inheritance rights if one of you dies without a will.
Every protection described below exists because someone chose to create it — through registration, a contract, or an estate plan. Nothing here happens on its own.
Who Owns What If You Separate
California’s community property system, which splits assets acquired during a marriage equally between spouses, applies only to married persons and registered domestic partners.1California Legislative Information. California Family Code 760 – Community Property For everyone else, the default is simple and often harsh: whoever holds title owns it. A house in one partner’s name belongs to that partner. A car registered to one person is that person’s car. Money in one person’s account is that person’s money. It does not matter who paid, or how many years you contributed to the household.
Jointly titled property is divided according to how it’s held. Joint tenants each own an equal share. Tenants in common own whatever percentages they agreed to, and those shares can be unequal. When both partners are on a mortgage, both remain liable for the full debt regardless of who keeps the property after a breakup. Lenders do not adjust based on your separation.
Marvin Claims
The 1976 California Supreme Court decision in Marvin v. Marvin allows unmarried partners to make property claims based on contract law rather than family law.2Justia. Marvin v. Marvin The court held that unmarried couples are just as capable as anyone else of making enforceable agreements about their earnings and property. An express agreement — written or oral — to pool resources or share property can be enforced.
Proving an implied contract is much harder. Without an explicit agreement, a court will look at how the couple actually behaved. The classic scenario has one partner leaving a career to manage the household while the other builds income and assets. If the couple’s conduct suggests they intended to share what they built, a court may find an implied agreement and divide accordingly. But implied contract claims are expensive to litigate and difficult to win, because they turn entirely on circumstantial evidence.
One limit is firm. Any agreement that rests on a promise to provide sexual services is unenforceable. Marvin was clear that contracts between unmarried partners are valid only when they rest on legitimate financial arrangements.2Justia. Marvin v. Marvin
Financial Support After a Breakup
Unmarried partners have no automatic right to ongoing financial support after a split. The court-ordered spousal support available in divorce simply does not apply to you. What is sometimes called “palimony” is a breach of contract claim: you have to prove your partner agreed to support you, then broke that promise.
A written agreement is the strongest evidence. An oral promise can also be enforced under Marvin, but reconstructing one years after the fact is a steep climb. Courts will look at who earned what, who sacrificed what, whether promises of future support were made, and whether both partners relied on an understanding that one would take care of the other. Even with strong facts, the outcomes are unpredictable. If support after a breakup matters to you, a written cohabitation agreement is far more reliable than hoping a court will piece together your understanding from memory.
Inheritance When a Partner Dies
When someone dies without a will, California’s intestate succession laws control who inherits. Those laws give everything to legal relatives — surviving spouse or registered domestic partner first, then children, then parents, then siblings.3California Legislative Information. California Probate Code 6401 – Intestate Share of Surviving Spouse An unmarried, unregistered partner does not appear anywhere in that hierarchy. You could live with someone for thirty years and inherit nothing if they die without a will.
To make sure your partner inherits, you need a will or a living trust naming them as a beneficiary. A will goes through probate, which is public, takes time, and can be contested by family members. A revocable living trust avoids probate for assets transferred into it during your lifetime, which usually makes it the stronger tool for unmarried couples with meaningful assets.
One form of ownership transfers automatically at death: joint tenancy with right of survivorship. If you and your partner hold your home as joint tenants, the surviving partner becomes the sole owner the moment the other dies, bypassing probate for that asset. Everything else titled solely in the deceased partner’s name — bank accounts, vehicles, retirement funds — will still pass through intestate succession to blood relatives unless separate arrangements are in place.
Medical Decisions and Hospital Access
If your partner is incapacitated, you have no automatic legal authority to make medical decisions for them. Hospitals default to the next of kin hierarchy: spouse, adult children, parents, siblings. An unmarried partner falls outside that chain entirely.
Two documents solve this problem. An advance healthcare directive (also called a durable power of attorney for healthcare) lets your partner name you as the person authorized to make medical decisions if they cannot. A HIPAA authorization allows medical providers to share health information with you. Without both, a hospital can legally refuse to discuss your partner’s condition with you or let you participate in decisions.
Visitation is separate. Medicare-participating hospitals must allow patients to designate any visitor they choose, including an unmarried partner, and those policies cannot discriminate based on the visitor’s relationship to the patient.4U.S. Department of Health & Human Services. FAQs on Patient Visitation at Certain Federally Funded Entities and Facilities Being allowed into the room, however, is not the same as having a say in what happens there.
Children Born to Unmarried Parents
When a married couple has a child, both spouses are automatically presumed to be legal parents. For unmarried couples, only the birth mother has automatic parental rights. The other parent must establish legal parentage separately.
The simplest route is a Voluntary Declaration of Parentage, typically offered at the hospital when the child is born. Both parents sign it, and once filed with the state, it carries the same legal weight as a court order.5California Courts. Parentage Case Introduction Parents can also sign it later. If parentage is disputed, either parent can file a parentage case in family court, where a judge may order genetic testing.
Once parentage is established, both parents are equally entitled to custody.6California Legislative Information. California Family Code 3010 – Custody of Minor Child This step is not just about the birth certificate. It is the legal foundation for custody, visitation, child support, and the child’s right to inherit from and receive benefits through both parents. A non-birth parent who skips it may have no standing to seek custody if the relationship falls apart.
Registering as Domestic Partners
California offers registered domestic partnership as an alternative to marriage, and it carries nearly identical legal weight under state law. Registered domestic partners receive the same rights, protections, benefits, responsibilities, and obligations as married spouses.7California Legislative Information. California Family Code 297.5 – Rights, Protections, and Benefits That includes community property, intestate inheritance, spousal support upon separation, and the right to dissolve the partnership through family court.
To register, both partners must be at least 18, not married to or in a domestic partnership with anyone else, not related by blood in a way that would prevent marriage, and capable of consenting.8California Legislative Information. California Family Code 297 – Domestic Partners You file a Declaration of Domestic Partnership with the California Secretary of State.9California Secretary of State. Domestic Partners Registry
Registration solves the state-law problem. It does not solve the federal one.
Federal Gaps Registration Does Not Close
Federal law does not treat domestic partners as spouses, so several protections stay out of reach even after you register.
Income Tax Filing
Unmarried partners must each file their federal return as Single, or as Head of Household if they support a qualifying dependent. Joint filing is not available.10Internal Revenue Service. Filing Status For couples with unequal incomes, that difference can cost real money each year.
Gift Tax
Married spouses can transfer unlimited amounts to each other without gift tax consequences. Unmarried partners cannot. Gifts above the annual exclusion require a gift tax return, and amounts above the lifetime exemption are taxable.11Internal Revenue Service. What’s New – Estate and Gift Tax This matters most when one partner pays the mortgage on a jointly owned home or funds a large purchase in the other’s name.
Social Security Survivor Benefits
If your partner dies, you have no claim to their Social Security survivor benefits. Those are available to surviving spouses who were married at least nine months before the worker’s death, and to ex-spouses from marriages that lasted at least ten years.12Social Security Administration. Who Can Get Survivor Benefits Cohabitation is not a substitute.
Inherited Retirement Accounts
A surviving spouse can roll a deceased partner’s IRA into their own account and continue tax-deferred growth. An unmarried partner inheriting an IRA is a non-spouse beneficiary and generally must draw down the entire account within ten years of the owner’s death, accelerating the tax bill.13Internal Revenue Service. Required Minimum Distributions for IRA Beneficiaries
Writing a Cohabitation Agreement
A cohabitation agreement is a written contract that defines your financial rights and obligations during the relationship and spells out what happens if you split. For unmarried couples who do not register as domestic partners, it is the single most important piece of legal protection available. It replaces the default rule — each person keeps whatever is titled in their name, with no support owed — with whatever arrangement actually reflects your relationship.
A well-drafted agreement typically covers:
- Separate property each partner owns coming into the relationship and wants to keep.
- Property acquired together, whether it will be owned jointly or separately, and in what proportions.
- How you will split rent or mortgage payments, utilities, groceries, and other household costs.
- Who is responsible for debts, especially credit cards and loans taken out during the relationship.
- Whether one partner will provide financial support to the other if the relationship ends, and for how long.
To be enforceable, the agreement must be in writing and signed by both partners, and both should disclose their assets and debts fully before signing.
One thing a cohabitation agreement cannot do is settle child custody or support in advance. Courts decide those issues based on the child’s best interests at the time of separation, and no private agreement between parents can override that authority. Custody and support for any children you have together will be handled through family court regardless of what your contract says.
The cost of having an attorney draft a cohabitation agreement is a fraction of what a Marvin claim costs to litigate after a breakup. Couples who skip this step because it feels unromantic tend to regret it most when the relationship ends and they discover how little the law protects them.