It’s a terrible cliché in the business world: “The situation is fluid.” Marriages, too, are fluid situations—the state of a married couple does not remain static after the wedding. Finances change, children enter the picture, and a few extra cars wind up in the driveway.A prenuptial agreement exists to protect assets and lay out instructions for what should happen in the event of a divorce. But when the situation is fluid, a prenup may not cover everything. Postnuptial agreements serve the same purpose but are signed after the wedding. Take these suggestions forwhat to add to a postnuptial agreement.Child CustodyWhen you married, perhaps you didn’t plan to have children and never thought to account for child care, custody, or inheritances if the marriage should end in death or divorce. A postnuptial agreement can put into writing your wishes and desires for your shared children or children from a previous marriage who have become part of the family. A postnuptial agreement can address custody and visitation rights in the event of a divorce, leaving one fewer issue to negotiate in mediation or litigation.Division of PropertyNegotiating the division of property in a divorce can be one of the more difficult aspects of the process, particularly when years of marriage elide the spouses’ respective claims to their properties. A postnuptial agreement will allow spouses to more clearly define what is personal property and what is marital property. In Illinois, unlike states such as California, the state does not necessarily designate all property acquired during a marriage as eligible for division. Without the aid of a prenuptial orpostnuptial agreementinIllinois, property such as real estate, vehicles, furniture, and investments are reasonably considered to be marital property, and a judge would try to equitably assign those assets. Coming into such assets later in marriage may lead you to determine how specifically to allocate those in the event of a marriage’s dissolution.InheritanceA death in one spouse’s family can mean a financial windfall that a spouse may wish to protect as much as possible in a postnup. If a prenuptial agreement did not account for the unforeseen inheritance of a significant sum, you may wish to add this to determine how, if at all, to divide that money after marriage. If you do not make official specifications, the court will see this inheritance as marital property.Business OwnershipA change to the financial situation of your business, for better or worse, can put an item on your list ofwhat to add to a postnuptial agreement. This is particularly pertinent for small business owners who owned and operated a business before entering the marriage. That business may have begun to thrive since your marriage, or it may have failed. Either way, assets and liabilities exist now that did not exist before, and failing to outline them in a postnuptial agreement could spell trouble for continued entrepreneurship.