Postnuptial agreements, are contracts made between the husband and wife after the marriage. These contracts or agreements concern only the financial matters and may be enforceable at the time of divorce.
In cases where there is a postnuptial agreement and one of the parties dies intestate (without a will) Washington intestate laws supersede the postnuptial agreement. That is to say, postnuptial agreements are made with the intend of protecting assets in case the parties divorce, they do not take the place of will.
Postnuptial agreements is a relatively new concept and it does not have the amount of precedent to provide a solid ground for enforceability. In Washington State the courts have enforced postnuptial agreements provided they meet certain standards.