You may have heard the expression that a check isn't worth the paper it's printed on if the signer doesn't have any money in his account to cover it. A similar premise can apply to prenuptial agreements. A prenup is a contractual agreement entered into between potential spouses prior to marriage, ironing out details of property ownership, inheritances and financial responsibilities in advance of the wedding. If an agreement doesn't meet the letter of the law in the state where it's entered into, it may be worthless.
A major requirement of prenuptial agreements is full disclosure by both parties. You must tell your future spouse the entire extent of your financial situation, including assets, income and debts. She must do the same. A prenup can be challenged as unconscionable without full disclosure, because it's not fair or equitable for a spouse to sign away rights to something she does not know exists or to take responsibility for debts she's not aware of. In some states, like New Jersey, a prenuptial agreement is only valid if both future spouses attach complete schedules of everything they own and owe before the wedding.
Evidence of Coercion
It's an ironclad rule that prenups must be entered into voluntarily and without coercion by either spouse. Neither of you can browbeat or threaten the other into signing. A common requirement in some states is that you must sign the agreement a specified period of time before your wedding. How much time varies by state, but if you sign a prenup just a few days before you tie the knot, your spouse might challenge it by raising the argument that you told her the wedding she'd already paid for was off unless she did so.
Separate Legal Counsel
Most states prohibit you and your spouse from sharing the same attorney when you negotiate and sign a prenuptial agreement. A lawyer is his client's advocate. He's charged with getting the best deal possible for the spouse who has retained him. Getting the best deal for you might mean shortchanging your spouse or vice versa, so ethically and legally, you cannot use the services of the same attorney. If you and your spouse don't use independent legal counsel, your spouse could probably challenge the agreement. One spouse's lawyer can draw up the agreement, then the other spouse can take a copy to her own attorney for review.
The Passage of Time
Most state courts acknowledge that the terms of a prenuptial agreement can be lopsided, giving an advantage to one spouse or the other. This does not necessarily make an agreement unconscionable or unfair. If things change drastically with the passage of time, however, what was reasonable at the time you married might become grossly inequitable. For example, if your spouse suffers a debilitating and permanent injury that prohibits her from being able to provide for herself, she might be able to challenge your prenup if it includes a waiver of spousal support or alimony. It would be unconscionable to resign her to a life of abject poverty because she signed the agreement in better days. Likewise, if you promised her several thousand dollars in alimony every month in case of divorce, but over the years your thriving business has failed or become obsolete, you may be able to challenge the prenup on the basis that your financial situation has changed through no fault of your own.