Illinois joins many of other states in upholding the Uniform Premarital Agreements Act, which states that a prenuptial agreement between two spouses is a valid way of dividing assets even if (in most cases) it contradicts current state law, such as with the division of property or distribution of assets. The state of Illinois makes two exceptions where it won't uphold a prenuptial agreement: if one of the parties did not voluntarily sign the agreement or if one of the parties was not aware of the other party's full financial history and didn't waive their right to know this information. 

A prenuptial agreement is most often designed to protect assets, and as previously stated, is only valid when all income and assets are disclosed. Additionally, many people use prenuptial agreements to make sure that their family will be protected and any assets will pass to them and not to a potential “second family” should one of the partners get remarried or start another family. People also use prenuptial agreements to include lifestyle standards, information about property, art, jewelry, etc. 

In Illinois, it's not required for either party to use an attorney to create their prenuptial agreement; however, if it gets to the point where the couple tries to divorce and the prenup is in question, one thing a judge will often look at is if the individuals involved had adequate legal counsel during the process of creating their prenuptial agreement.  Typically, courts are far more willing to throw out a prenuptial agreement when a fiancé lacked legal representation or when the fiancé was not made fully aware of his or her rights with regard to the prenup.  Unfairness of a prenup, or unconscionability, isn't enough to invalidate it. 

Unconscionability has been defined as “an absence of meaningful choice on the part of one of the parties together with contract terms which are unreasonably favorable to the other party... A contract is unconscionable when it is improvident, totally one sided or oppressive.” When an Illinois court looks at this type of situation, it considers under what circumstances the prenup was signed – not what circumstances have arisen since. The court asks whether or not the agreement was unconscionable at the time it was enacted. 

Illinois also makes provisions for duress and coercion. In order to be valid, a prenup must have been voluntarily signed by both parties. The Illinois Supreme Court defines duress as “a condition where one is induced by a wrongful act or threat of another to make a contract under circumstances which deprive [the individual] of the exercise of free will.”