My understanding is that the general purpose of both post- and pre- nuptial agreements is the same, and the main difference is that the timing of when they are signed.

But are there legal differences between what can be covered in the agreements? Specifically, are there things that postnuptial agreement cannot have that prenuptial can, (aside from things related to marriage annulment, presumably, since you can't annul a marriage that's already valid)?

  • (my layman's understanding is that, of course, you can legally put anything you want into an agreement - question is, what of that is legally enforceable).
    – user0306
    Commented Dec 26, 2016 at 23:50
  • Annulment is retroactive, and can certainly be applied to a marriage previously considered valid. The rest of your question is based on a premise that differences could exist. Why do you think that is the case?
    – user4657
    Commented Dec 27, 2016 at 0:47
  • @Nij - I don't have any reason to think differences exist, and would be quite happy with well-argued answer showing they don't. Which is why I phrased the question as "are there" and not "what are" :)
    – user0306
    Commented Dec 27, 2016 at 1:17
  • A "post-nup" might be able to ratify an otherwise voidable marriage, or a marriage whose existence is not clear, in a common law marriage jurisdiction. A pre-nup might be able to avoid certain liabilities for a spouse's debt that arise by operation of law and might otherwise attach upon marriage and isn't unilaterally avoidable after that point, such as liability for debts incurred for premarital necessities.
    – ohwilleke
    Commented Dec 27, 2016 at 2:03
  • A "post-nup" could also validate a prior pre-nup that was itself invalid because a spouse was a minor at the time of the marriage, because the formalities weren't complied with, or because there wasn't proper financial disclosure the first time.
    – ohwilleke
    Commented Dec 27, 2016 at 2:10

1 Answer 1


I can't think of anything regarding the marriage contract that is illegal to agree to within a marriage but that is legal to agree to prior to a marriage.

However, I can think of plenty of stipulations that it would be hard to imagine a reasonable person accepting once they're in a marriage, but that they would reasonably agree to in order to enter a marriage.

E.g., supposing that "if x then I forfeit my marital right to y" is a legal nuptial agreement. For any such x and y I can imagine that clause occurring in a prenuptial agreement. And it would be enforceable under contract law because I suspect that marriage is a form of consideration.

But after the marriage has been established, why would anyone unilaterally forfeit a right? I can only think of twothree reasons:

  1. The forfeit is mutual: I.e., both spouses agree to an identical clause. Or, the spouses agree to substantially equal clauses. (E.g., one spouse forfeits y if x, and the other forfeits b if a; where a·b ≈ x·y.)

  2. One spouse requires the contract as a condition of continuing the marriage. However, I am dubious that this scenario is enforceable. I.e., if I one day say to my spouse, "I'm divorcing you unless you agree to give up your marital right to y," I have a suspicion that such an "agreement" might not withstand an artful legal challenge for several reasons: The consideration I'm offering is something I already pledged. This is like demanding a contract renegotiation once a counterparty has undertaken work. It seems like something that would be ripe for estoppel.

  3. (Thanks to @ohwilleke for noting this one:) The spouse forfeiting a right stands to gain something in exchange. E.g., in order for one spouse to receive an inheritance, the other must disclaim any right to it should the marriage later be dissolved. The spouse is not forfeiting a right already enjoyed, and in consideration of the postnuptial agreement will (potentially) enjoy extra wealth within the marriage.

  • 1
    It actually happens all the time. For example, a wife may forfeit a right to a minimum inheritance at death from her husband and to give up marital property rights in appreciation in gifts and inheritances upon divorce, because doing so is necessary for her inlaws to feel comfortable leaving a substantial inheritance to her husband. Another time would be when one spouse has creditor problems.
    – ohwilleke
    Commented Dec 27, 2016 at 2:07
  • @ohwilleke - I should have provided for the scenario you mention in which there is objective consideration provided for the forfeit. Just added that to the list. The case of debt avoidance seems analogous.
    – feetwet
    Commented Dec 27, 2016 at 2:28

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