The core difference between a civil union and a marriage is federal recognition: a civil union gives you most of the same rights as marriage inside a state that recognizes it, but the federal government does not treat civil union partners as spouses, which changes how you are treated for taxes, Social Security, pensions, immigration, and federal workplace protections. Marriage also travels; civil unions largely do not.
Where Civil Unions Still Exist
Civil unions were created as a legal alternative for same-sex couples who could not marry. After the Supreme Court’s 2015 decision in Obergefell v. Hodges, most states that had offered civil unions either stopped issuing new ones or converted existing civil unions into marriages.1Legal Information Institute (LII) / Cornell Law School. Obergefell v. Hodges Today, roughly five states still maintain civil union statutes, and a similar number offer domestic partnerships with varying levels of protection. Some are open to both same-sex and opposite-sex couples; others are not. If your state does not offer civil unions, marriage is the only legally recognized option available to you.
How Each Union Is Formed and Ended
Marriage follows the same basic template everywhere: you apply for a license, an authorized officiant conducts a ceremony, and witnesses are present. The ceremony can be religious or secular, but some form of solemnization is required in every state.
Civil union formation varies more. In some states the process closely mirrors marriage, with a license from the county clerk and an officiant. Other states allow a streamlined process where the couple can essentially self-certify without a traditional ceremony. You receive a certificate of civil union rather than a marriage certificate.
Ending each union looks similar within a state that recognizes both. Marriage ends through divorce; a civil union ends through dissolution. One partner files a petition, the court divides property and debts, and custody and support are set if children are involved. The grounds are typically the same, usually irretrievable breakdown or a period of separation.
The complication comes when a couple formed a civil union in one state and later moved to a state that does not recognize civil unions. A court generally cannot dissolve a legal relationship it does not acknowledge. Some issuing states let former residents return to file for dissolution regardless of where they live now; others impose residency requirements that could mean moving back for six months to a year before filing. A couple can end up legally bound in a union no court where they live will dissolve. That problem does not arise with marriage, which is recognized nationwide.
State-Level Rights Are Largely the Same
Within a state that recognizes civil unions, the legal protections are designed to mirror marriage. Partners can co-own property, inherit from each other if one dies without a will, and make medical decisions on each other’s behalf. Hospital visitation, health-care proxy status, and the ability to contest or renounce a partner’s will generally apply to civil union partners the same way they apply to married spouses.
Spousal privilege, the rule preventing one partner from being forced to testify against the other, is one area where equivalence is not guaranteed. Some civil union states explicitly extend it; federal courts generally limit it to married couples.2Legal Information Institute. Spousal Privilege In a federal-court matter, do not assume you have the same protection a married couple would.
The Federal Recognition Gap
Under the Respect for Marriage Act, which updated federal law in 2022, a person is treated as married for federal purposes only if the union is recognized as a “marriage” under the law of the state where it was entered.3Office of the Law Revision Counsel. 1 USC 7 – Marriage Civil unions do not meet that definition, no matter how many state-level rights they carry. That single rule drives most of what follows.
Federal Taxes
Civil union partners cannot file federal income taxes jointly. The IRS does not treat individuals in civil unions or domestic partnerships as married, so each partner files as single or, if independently eligible, as head of household. A civil union partner cannot be claimed as a dependent for head-of-household purposes, even if that partner has no income.4Internal Revenue Service. Answers to Frequently Asked Questions for Registered Domestic Partners and Individuals in Civil Unions Married couples, by contrast, can choose to file jointly, which often lowers the combined bill.
Estate and Gift Taxes
Married spouses benefit from the federal unlimited marital deduction, which allows any amount of property to pass between them during life or at death without federal gift or estate tax.5Legal Information Institute (LII) / Cornell Law School. Marital Deduction Civil union partners do not qualify. When one partner in a civil union dies, the survivor’s inheritance above the federal estate tax exemption is taxable, and large lifetime gifts between partners count against the gift tax exclusion. For couples with significant assets, this gap alone can cost hundreds of thousands of dollars.
Social Security
Social Security survivor and spousal benefits are built around marriage, but civil union partners are not entirely locked out. The Social Security Administration has said that some individuals in non-marital legal relationships like civil unions may qualify if they meet certain requirements.6Social Security Administration. Do I Qualify for Benefits as a Spouse if I Am Now in, or the Surviving Member of, a Civil Union or Domestic Partnership? Those requirements are fact-specific, so eligibility is far less certain than a married spouse’s automatic entitlement.
Pensions and Retirement Plans
Federal pension law protects married spouses in ways it does not protect civil union partners. Under ERISA, defined benefit pension plans must offer a surviving spouse a qualified preretirement survivor annuity if the participant dies before retirement. The Department of Labor and IRS read “spouse” under ERISA to exclude domestic partners and civil union partners, even where state law treats those unions as equivalent to marriage.7Pension Benefit Guaranty Corporation. Domestic Partner Not Entitled to QPSA Benefit If your partner participates in a traditional pension plan and dies before retirement, you have no automatic federal right to a survivor benefit. The same gap applies to 401(k) plans, where married spouses are default beneficiaries by law.
Family Leave and COBRA
The Family and Medical Leave Act allows eligible employees to take unpaid leave to care for a spouse with a serious health condition. The Department of Labor defines “spouse” under the FMLA as a husband or wife recognized under state marriage law and explicitly states that individuals in civil unions and domestic partnerships are not spouses for FMLA purposes.8U.S. Department of Labor. Fact Sheet #28L – Leave Under the Family and Medical Leave Act When You and Your Spouse Work for the Same Employer If your civil union partner is seriously ill, your employer has no federal obligation to hold your job while you provide care.
COBRA works the same way. When a married employee loses a job, federal law gives the spouse an independent right to elect continued health coverage. A “qualified beneficiary” is defined to include the spouse of a covered employee, and civil union partners are not treated as spouses for this purpose.9GovInfo. 29 USC 1167 – Definitions and Special Rules Some employers voluntarily extend COBRA-like benefits to domestic partners, but they are not required to.
Immigration
The immigration system draws an especially hard line. USCIS does not recognize civil unions, domestic partnerships, or other non-marital relationships as marriages for immigration purposes.10USCIS. USCIS Policy Manual Volume 6, Part B, Chapter 6 – Spouses A U.S. citizen cannot sponsor a civil union partner for a family-based green card the way they can sponsor a spouse. The K-1 fiancé(e) visa, which allows a foreign partner to enter the U.S. and marry within 90 days, requires the couple to actually marry, not form a civil union.11U.S. Citizenship and Immigration Services. Visas for Fiancé(e)s of U.S. Citizens For a couple where one partner is not a U.S. citizen, a civil union provides essentially no immigration pathway.
Parental Rights
Within a state that recognizes civil unions, both partners generally have the same parental rights as married spouses: custody, guardianship, and authority over education and healthcare decisions. The risk arises when the family crosses state lines. A parent-child relationship established through a civil union in one state may not be recognized in a state without civil union laws, which can leave a non-biological parent without legal standing.
The most reliable way to protect parental rights across all jurisdictions is a court order establishing parentage. A confirmatory adoption, available in some states, is a streamlined path to an adoption decree confirming an existing parent-child relationship without the full home study process. Where confirmatory adoption is not available, a stepparent or second-parent adoption accomplishes the same goal with more paperwork. Every state is required to honor a valid court judgment from another state, so an adoption decree travels with the family in a way a civil union certificate may not.
Recognition Outside the United States
A valid U.S. marriage is generally recognized in most countries, though the State Department notes that recognition depends on each country’s own laws.12U.S. Department of State. Marriage – Travel.State.gov Civil unions have no comparable portability. Many countries have no equivalent status and will not recognize a U.S. civil union. Even countries that offer their own form of civil partnership may not recognize one formed under U.S. law. For couples who live or travel internationally, that gap can affect inheritance, hospital visitation, and emergency medical decisions. If international mobility matters to you, marriage is the only union that travels reliably.