Prenuptial Agreements in Illinois: A Practical Guide and Checklist

Most people who search for a prenup in Illinois have the same four questions: what can it actually do, will it hold up, how far ahead do we need to start, and what do we have to hand over. This guide answers those in plain language, then gives you the document checklist we send our own clients. It is written by the attorneys at LaRocque Law, a family law firm in Chicago's West Loop that drafts and negotiates prenuptial and postnuptial agreements across Cook, DuPage, and Will Counties.

What a prenuptial agreement is

A prenuptial agreement, called a premarital agreement in the Illinois statute, is a written contract two people sign before they marry that takes effect when the marriage does. Illinois adopted the Uniform Premarital Agreement Act, so the rules for what a prenup can cover and when a court will enforce one are set by state law and apply the same way in every county.

Without a prenup, the Illinois Marriage and Dissolution of Marriage Act decides what happens to your property and income if you divorce, and maintenance is set by a statutory formula. A prenup replaces those default rules with ones you chose.

What to include in a prenup

An Illinois prenup can address:

Property you each bring into the marriage, and whether it stays non-marital no matter how it is titled or used later.

Income and property acquired during the marriage, including whether it is treated as marital, non-marital, or split by some other rule.

A business or professional practice: who owns it, how its growth during the marriage is treated, and how it is valued if the marriage ends.

Retirement accounts and the growth on them.

Maintenance (what many people still call alimony): whether it will be paid, waived, or set at a defined amount and duration.

Debt: who is responsible for what each of you brings in and what is borrowed during the marriage.

An expected inheritance or family gift, and how it is protected.

What happens on death, which matters if either of you has children from a prior relationship or wants to protect a family asset.

One thing a prenup cannot do is decide anything about children. Parenting time, allocation of parental responsibilities, and child support are decided by the court based on the child's best interests at the time, and no agreement signed before the children exist changes that.

What makes a prenup enforceable in Illinois

A prenup has to be in writing and signed by both parties. Beyond that, Illinois courts refuse to enforce an agreement in two situations: the spouse challenging it did not sign voluntarily, or the agreement was unconscionable when it was signed and that spouse did not receive fair and reasonable disclosure of the other's property and debts, did not waive disclosure in writing, and did not otherwise have adequate knowledge of the finances.

In practice, almost every prenup fight is about how the agreement was signed rather than what it says. The questions a judge asks years later are simple. Did each person know what the other owned and owed? Did each have a real chance to get their own lawyer? Was anyone under pressure? An agreement built so the answers are yes, yes, and no is very hard to attack. That means:

Full disclosure from both sides, attached to the agreement as financial schedules. Skipping disclosure to save time is the most common way a prenup fails.

Independent counsel. One lawyer cannot represent both of you. Illinois does not require your fiancé to hire an attorney, but an agreement where both sides had counsel is far harder to challenge, and we strongly recommend it.

Time. Illinois has no statutory deadline, and courts have enforced agreements signed close to the wedding when the other spouse had received the draft earlier, consulted a lawyer, and negotiated changes. But the closer to the ceremony you sign, the more the rest of the record has to carry.

Notarization is not required in Illinois. We notarize every agreement we draft anyway. It costs nothing and removes an argument.

When to start

The honest answer is: the more time, the better. A few months before the wedding gives both of you room to gather documents, get independent advice, and negotiate without the wedding date doing the negotiating for you. There is no legal minimum, and if your wedding is close, call us. When our schedule permits we can get a prenup done in a week. We do not recommend it, because an agreement signed in a hurry is an agreement that is easier to challenge later.

What a prenup costs in Illinois

Cost depends on complexity and on how much negotiation happens with the other side's attorney. LaRocque Law handles prenuptial agreements for a flat fee quoted at the consultation that covers as many revisions as it takes to finish. If your fiancé's attorney sends back three rounds of changes, the number does not move. What drives cost up at most firms is negotiation time, so two people who have already talked through the big decisions before they meet with counsel tend to pay less and finish faster.

Prenups and postnups are not the same

A postnuptial agreement covers the same ground after the wedding. People tend to treat the two as interchangeable. They are not. Once you are married, you owe each other a higher duty of good faith, and Illinois courts examine postnups closely for unconscionability: whether each spouse had a meaningful chance to consult their own lawyer, whether there was pressure or overreaching, whether the financial information was complete, and whether the terms are unusually one-sided. An agreement signed as the price of reconciliation, by a spouse without a lawyer, is exactly the kind courts set aside. If you are already married and considering an agreement, it is worth reading our prenuptial and postnuptial agreements page before you sign anything.

Illinois prenup document checklist

This is the checklist we give clients. A prenup is only as strong as the financial disclosure behind it, so each of you needs a documented picture of what the other owns, owes, and earns. Gather complete, current copies with all schedules and statements. If you are not sure whether something belongs, include it.

Before you start: do not transfer, sell, retitle, close, or materially change any asset or account in anticipation of the agreement without talking to your attorney first.

Identification and marriage information. Wedding date and location. For any prior marriage, the judgment of dissolution, annulment order, or death certificate. Any existing premarital, postnuptial, separation, cohabitation, or property agreement.

Income and employment. Federal and state tax returns for the past two years with all schedules (W-2s, 1099s, K-1s). Three most recent pay stubs. Employment agreement, offer letter, bonus plan, deferred compensation or equity compensation documents, or partnership agreement. Documentation of expected bonuses, commissions, stock awards, or distributions, and of any self-employment, consulting, trust, or rental income.

Assets and accounts. Most recent statements for every checking, savings, brokerage, and investment account. Statements or plan summaries for 401(k), 403(b), IRA, Roth IRA, pension, and deferred compensation plans. Stock options, RSUs, or other equity. For any real estate: deed, most recent mortgage statement, property tax bill, purchase documents, and any appraisal. Vehicle titles and loans. Cryptocurrency, digital assets, collectibles, and other significant personal property. Life insurance declarations and cash value. Trust agreements and anything concerning an expected inheritance or gift.

Business and professional interests. Formation documents, operating agreement, shareholder or partnership agreement, buy-sell agreement. Business tax returns for two years and year-to-date financials. Balance sheet, profit and loss, cap table. Any recent valuation, offer, or financing documents.

Debts. Most recent statements for mortgages, home equity loans, credit cards, student loans, auto loans, business loans, and lines of credit. Guarantees, co-signed obligations, judgments, tax liabilities, pending claims, or bankruptcy. Current child support or maintenance orders, including any arrearage.

Estate planning. Current will, trust, and powers of attorney. Beneficiary designations for retirement accounts and life insurance. Any property settlement from a prior marriage that still affects you.

A short written summary. Anything you own, owe, or earn that the documents do not show; anything you expect to receive by gift, inheritance, or family trust; property you intend to keep separate; any planned purchase, sale, refinance, or business transaction before the wedding; and the specific things you want the agreement to address.

Frequently asked questions

Are prenups enforceable in Illinois?

Yes, when they are done right. Illinois enforces premarital agreements under the Uniform Premarital Agreement Act. The ones that fail were signed under pressure, without disclosure, or with terms so one-sided a court will not enforce them.

Can a prenup waive maintenance in Illinois?

Yes. A prenup can provide for maintenance, set it at a defined amount and duration, or waive it. Our Illinois maintenance calculator shows what the guideline number would be without a waiver.

Can a prenup cover child custody or child support?

No. Those are decided by the court based on the child's best interests at the time. Any provision that tries to fix them in advance is unenforceable.

Do both of us need a lawyer?

Illinois does not require it, but one lawyer cannot represent both of you, and an agreement where each side had independent counsel is far harder to challenge. We strongly recommend it.

How much does a prenup cost in Illinois?

It varies with complexity and negotiation. We quote a flat fee at the consultation that covers all revisions.

Can we sign a prenup after the wedding?

Not a prenup. An agreement signed after the wedding is a postnuptial agreement, which Illinois recognizes but reviews more strictly.

Ready to start?

If you are getting married in Cook, DuPage, or Will County and want an agreement drafted to be enforced, schedule a consultation. We will tell you what it should cover, what the flat fee is, and how quickly it can be done properly. Our prenuptial and postnuptial agreements page explains how we handle them.