Illinois: A-
Statutes
IUPAA 750 ILCS 10/1
Separate Property
All assets can remain separate property, avoiding costly divorce settlements. Joint assets and debts titled in both names are split 50/50 as marital property.
Unconscionability at Execution Only
Courts review unconscionability only at signing, not at enforcement. Changed circumstances during marriage will not invalidate a valid prenup.
Unconscionability Standard
A prenup is invalid only if unconscionable at execution AND signed without fair financial disclosure (or written waiver) AND the challenging party lacked knowledge of the other's finances. All three required—unconscionability alone insufficient. Even highly one-sided agreements are upheld.
Spousal Support Undue Hardship Minimum
Complete waivers of spousal support are enforceable. However, courts may override the waiver if it would cause undue hardship due to circumstances not reasonably foreseeable at execution. We believe “undue hardship” means slightly above a public assistance threshold, though may be higher for wealthier spouses.
Timing
No statutory deadline exists, but attorneys recommend at least one month before. We recommend signing 60+ days before the wedding with 2-3 weeks review time to reduce challenge risk. Reach out to an attorney 4-6 months before the wedding with your PerfectPrenup draft.
Independent Counsel
Not required if waived in writing. However, independent counsel dramatically strengthens enforceability if challenged.
Financial Disclosure
"Fair and reasonable disclosure" of property and financial obligations required, or can be waived in writing (both included). Illinois requires only "fair and reasonable" disclosure, not "full" disclosure. Written waivers (included) make agreements nearly unbreakable.
High Burden to Challenge
Only two defenses allowed: involuntary execution, or unconscionability with inadequate disclosure. Challenging party bears burden of proof. Fraud, duress, and coercion must be proven—allegations alone insufficient.
Child Support
Child support and custody clauses are unenforceable and could undermine the entire agreement. Do not include.
Case Law
In re Marriage of Iqbal, 11 N.E.3d 1 (Ill. App. 2d Dist. 2014)
Postnuptial agreement struck down as substantively unconscionable—required living by Islamic law, banned calling police without counselor approval, and forfeited rights for violations.
In re Marriage of Chamberlain, 2024 IL App (unpublished)
Postnuptial agreement invalidated—cognitively-impaired spouse recovering from medical crisis signed without independent counsel; both procedurally and substantively unconscionable. Attorney representation helps marginal cases, and both spouses must have mental capacity to understand agreement.
In re Marriage of Hightower, 358 Ill. App. 3d 165 (2005)
Property and maintenance agreements binding unless unconscionable—established Illinois's strong pro-enforcement presumption without requiring express findings of fairness.
In re Marriage of Amyette, 2023 IL App (3d) 200195
Undue hardship defined as "mathematically demonstrable" likelihood of "homelessness or life in sub-standard housing"—near-destitution required for relief from spousal support waivers.
In re Marriage of Prill, 2021 IL App (1st) 200516
"Not fair does not equal unconscionable"—all presumptions favor validity; mere unfairness insufficient without both absence of meaningful choice AND unreasonably favorable terms.
In re Marriage of Woodrum, 2018 IL App (3d) 170369
"Fair and reasonable" disclosure requires only sufficient knowledge to understand rights waived, not full asset disclosure—wife's claim failed despite incomplete schedules; had two weeks and reasonable general knowledge.
In re Marriage of Heinrich, 2014 IL App (2d) 121333
Invalidation requires both unconscionability AND inadequate disclosure—parties who sign without reading are bound; unfairness alone insufficient.
In re Marriage of Murphy, 834 N.E.2d 56 (Ill. App. 3d Dist. 2005)
Agreements without fraud, duress, or coercion are valid—must guarantee equitable settlement; challenging party bears burden with evidence, not allegations.
In re Marriage of Barnes, 324 Ill. App. 3d 514 (4th Dist. 2001)
Wife earning $24K divorced husband earning $250K (90% disparity); $10K annual alimony cap (4% of income) upheld—no undue hardship where not destitute or requiring public assistance.
In re Marriage of Drag, 762 N.E.2d 1111 (Ill. App. 3d Dist. 2002)
Contract interpretation rules apply to prenups—general contract law principles govern, not special family law scrutiny.