A civil union in Illinois versus a marriage comes down to one trade-off: inside the state the two give you the same rights, but a civil union is not recognized by the federal government and often not by other states, while a marriage is recognized everywhere. If federal taxes, Social Security, immigration, estate planning, or the possibility of moving matter to you, marriage is the stronger legal choice. If none of those apply and you prefer the civil union for personal reasons, Illinois law protects you the same way at the state level.
Civil unions became available in Illinois on June 1, 2011 under the Religious Freedom Protection and Civil Union Act (750 ILCS 75/). Illinois legalized same-sex marriage effective June 1, 2014, and the U.S. Supreme Court’s Obergefell v. Hodges decision made it a nationwide right the following year. Illinois kept civil unions on the books anyway, so couples still have a real choice to make.
What’s Identical Inside Illinois
Under 750 ILCS 75/20, a party to a civil union is entitled to the same legal obligations, responsibilities, protections, and benefits that Illinois law gives to spouses. That language sweeps across statutes, administrative rules, and common law. Everywhere Illinois law says “spouse,” “family,” “next of kin,” or “married,” civil union partners are included without having to be separately named.
In day-to-day terms, that means civil union partners have hospital visitation and medical decision-making authority, next-of-kin status for emergency notifications, inheritance rights under Illinois probate law (including the spousal share if a partner dies without a will), and shared responsibility for family expenses the way spouses are jointly liable.
Civil unions in Illinois are open to both same-sex and opposite-sex couples, and the eligibility rules track marriage closely: both parties must be at least 18, neither can already be in a marriage or civil union, and close family members are barred from entering one together. There is no legal advantage to choosing a civil union over a marriage within Illinois. The state treats them the same.
Where a Civil Union Falls Short
This is the part that costs people money and legal protection. The federal government does not treat a civil union as a marriage, and most other states don’t either.
Federal Taxes
The IRS has stated plainly that individuals in civil unions are not considered married or spouses for federal tax purposes. Civil union partners cannot file federal returns as married filing jointly or married filing separately. Each partner files as single or, if eligible, head of household. This often produces a higher combined tax bill than married couples pay and blocks access to deductions and credits that use married status as a threshold.
Social Security
Social Security is more forgiving. The SSA classifies civil unions as non-marital legal relationships, but it will pay retirement, disability, and survivor benefits to a civil union partner when two conditions are met: the civil union was valid where it was established, and the laws of the state where the number holder is domiciled would let the civil union partner inherit a spousal share of personal property if the number holder died without a will. Because Illinois gives civil union partners full inheritance rights, an Illinois civil union generally meets both tests.
The SSA uses the date the couple entered the civil union as the effective marriage date for duration requirements. Surviving spouse benefits require nine months; spousal benefits require one year.
Immigration
Federal immigration law defines family relationships in terms of “spouse.” USCIS limits immediate-relative green card eligibility to the spouse, unmarried child under 21, or parent of a U.S. citizen. A civil union partner does not qualify as a spouse here, so a U.S. citizen cannot sponsor a civil union partner for a green card the way a spouse could be sponsored. For binational couples, this alone is usually decisive.
Estate Taxes and Retirement Accounts
Married couples get the unlimited marital deduction for federal estate tax, so assets pass between spouses tax-free at death. Civil union partners don’t qualify. Employer-sponsored retirement plans governed by federal ERISA law may also not automatically recognize a civil union partner as a beneficiary the way they would a spouse. If you expect to leave meaningful assets to your partner, this gap matters.
Moving or Traveling to Another State
There is no federal rule requiring states to recognize civil unions from other states. Courts often honor a relationship valid where it was created, but a longstanding exception lets states refuse recognition on public policy grounds, and only a handful of states still maintain civil union frameworks of their own. If you relocate to a state without civil union laws, your partner may not be treated as next of kin in a medical emergency, and property rights that were automatic in Illinois may not carry over. Marriage is recognized in all 50 states and most countries.
Converting a Civil Union to a Marriage
If you’re already in a civil union and the federal gaps now concern you, Illinois gives you a direct path. Under 750 ILCS 75/65, civil union partners can apply for a marriage license and have the marriage solemnized under the standard process, provided they’re otherwise eligible to marry and the parties are the same as those in the civil union. The marriage license application fee is waived in that situation.
Once converted, the parties are no longer in a civil union. The marriage certificate’s date becomes the operative date going forward. For most couples weighing the two statuses today, conversion is the practical answer to the federal and portability problems.
Why Some Couples Still Choose a Civil Union
Illinois kept civil unions available after marriage equality for a reason: some couples want the state-level legal protection without the religious, cultural, or historical associations of marriage. Opposite-sex couples who object to marriage as an institution, and same-sex couples who built their relationship around a civil union before 2014 and don’t want to change the paperwork, both still use them. There’s no legal benefit to doing so, only a personal one, and it comes with the federal trade-offs above.
Dissolving Either One
Exit terms are the same. Under 750 ILCS 75/45, the dissolution provisions of the Illinois Marriage and Dissolution of Marriage Act (Sections 401 through 413) apply to civil unions. Grounds for dissolution, property division, support obligations, and related issues are handled identically to a divorce.
One useful detail: anyone who enters an Illinois civil union consents to Illinois court jurisdiction for any action related to it, even if one or both partners later move out of state. If your partner relocates to a state that doesn’t recognize the civil union at all, you can still file for dissolution in Illinois. A declaration of invalidity, which treats the union as if it never legally existed, is also available under the same standards used for marriages (Sections 301 through 306), covering situations like fraud, a prohibited relationship, or lack of capacity to consent.
Which One Should You Choose?
For most couples deciding today, marriage is the better legal container because it travels. It covers you at the state level the same way a civil union does, and it also covers you at the federal level and across state lines. A civil union makes sense when you specifically want the Illinois protections without the label of marriage and you’ve thought through what you’re giving up federally. If you’re already in a civil union and any of the federal issues above apply to your life, the fee-waived conversion is designed for exactly that situation.