Everything engaged couples need to know about making a prenuptial agreement valid and enforceable in Illinois — in plain English, reviewed by attorney James Sexton, Esq.
Yes — prenuptial agreements are legal and enforceable in Illinois under the Illinois Uniform Premarital Agreement Act.
Illinois adopted the Uniform Premarital Agreement Act, codified at 750 ILCS 10, for agreements executed on or after January 1, 1990. A premarital agreement must be in writing and signed by both parties, and it is enforceable without consideration — the marriage itself is enough. It becomes effective on marriage. Because Illinois is an equitable-distribution state, where a judge otherwise divides marital property in whatever proportions the court finds just, a prenup is the tool that lets couples set those terms themselves.
An Illinois prenup is enforceable when it is written, signed, voluntary, and backed by fair financial disclosure — the challenger carries the burden of proving otherwise.
The agreement must be a written document signed by both parties. Oral premarital agreements are not enforceable in Illinois, and no consideration beyond the marriage is required.
Under 750 ILCS 10/7, an agreement fails if the challenging party proves they did not execute it voluntarily. Signing well before the wedding is the best insurance against a duress claim.
An agreement is unenforceable only if it was unconscionable when signed AND the challenger was not given fair and reasonable disclosure, did not waive disclosure in writing, and had no adequate knowledge of the other party's finances.
Spousal support can be modified or eliminated, but if the waiver later causes undue hardship in light of circumstances not reasonably foreseeable at signing, a court can order support to the extent needed to avoid that hardship.
| Governing statute | Illinois Uniform Premarital Agreement Act — 750 ILCS 10 |
|---|---|
| Property division | Equitable distribution |
| Notarization | Recommended (not required by statute) |
| Waiting period | None required — but sign well before the wedding |
| Spousal support | Can be modified or waived — subject to an undue-hardship override for unforeseeable circumstances |
See how Illinois's signing formalities compare in our prenup notarization requirements by state guide.
Illinois courts set aside prenups mainly when the agreement was signed involuntarily, or was unconscionable and made without fair financial disclosure.
Under 750 ILCS 10/7, the spouse challenging the agreement carries the burden of proof, and unconscionability is decided by the court as a matter of law based on the circumstances at signing. The other pressure point is the undue-hardship safety valve: even a valid support waiver can be partially overridden if enforcing it would cause hardship the couple could not reasonably have foreseen. Full disclosure, an early signing date, and reasonable terms are what make an Illinois prenup stick.
Trusted Prenup creates a state-specific Illinois prenuptial agreement online — built to meet the requirements above and designed by James Sexton, Esq. A traditional attorney typically costs $2,500–$10,000; this is a flat $599.
A guided questionnaire captures your assets, debts, and wishes — most couples finish in under 90 minutes.
We assemble a complete prenup built to meet your state's exact legal requirements.
Review with your partner, then sign online with notarization handled for you.
An attorney-drafted prenup in Illinois — especially in Chicago — commonly runs $2,500–$10,000 or more. Trusted Prenup creates a state-specific Illinois prenup online for a flat $599, with optional notarization and attorney-review add-ons.
No. 750 ILCS 10/3 requires only a written agreement signed by both parties. Notarization is still strongly recommended as proof the signatures are genuine, and it's available as an add-on.
Yes, but the challenger carries the burden. They must prove the agreement was signed involuntarily, or that it was unconscionable when signed and made without fair financial disclosure or a written waiver of disclosure.
Yes — Illinois allows couples to modify or eliminate spousal support entirely. The one caveat: if enforcing the waiver would cause undue hardship from circumstances not reasonably foreseeable at signing, a court can order support to the extent needed to avoid it.
No. Illinois is an equitable-distribution state, meaning a judge divides marital property in whatever proportions the court considers just — not automatically 50/50. A prenup lets you set the division yourselves instead.
Illinois has no statutory waiting period, but signing at least 30 days before the wedding undercuts any later claim of last-minute pressure. Trusted Prenup's online process makes it easy to finish well ahead of the date.
Yes — Illinois enforces properly executed prenuptial agreements regardless of how they were drafted. What matters is execution: a written agreement, voluntary signatures, full financial disclosure, and Illinois's signing formalities. The full picture is in are online prenups legally binding.
Trusted Prenup is not a law firm and does not provide legal advice. This guide is general information about Illinois law and not a substitute for advice from a licensed attorney about your situation.