Why couples make one

Almost always because a fact changed. The reasons cluster into a short list, and recognizing your own on it is more useful than a definition.

  • One of you started a business, or a business one of you owns became worth something.
  • An inheritance arrived, or a share in family property did, and the couple want to be clear about how it is treated.
  • One of you left paid work, cut hours, or moved for the other's career, and the household wants that recognized while both of you still agree what happened.
  • It is a second marriage and the estate plan has been rewritten, and the agreement is the instrument the new plan depends on.
  • A prenup was discussed before the wedding and never finished, usually because time ran out.
  • The couple's finances changed enough that the arrangement they assumed no longer describes them.
  • One of you is taking on significant debt, or is about to.

The estate-planning reason is the one most often overlooked and the one this corpus can say most about. In Colorado a waiver of a marital right has to sit inside a premarital or marital agreement to be enforceable at all, so a couple redoing their estate plan there may find the agreement is not optional if the plan depends on a waiver.

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Not simply a prenup signed later

A postnup is widely described as a prenup made after the wedding. That is right about the content and may be wrong about everything else, and the difference is not a technicality.

Before a wedding, two people are negotiating at arm's length and each is free to walk away. After it, they are already married, they may already owe each other duties that the law regards as significant, and one of them may be giving something up without receiving anything in return. States have taken different views about what that changes: some apply the same statutory framework to both, some apply a different or additional standard to agreements made during a marriage, and the question of what each person receives in exchange arises in a way it does not before a wedding.

Sahvelo has not read any state's enforceability standard for agreements made during a marriage, so it does not tell you whether yours applies the same test. What it will not do is repeat the reassuring version. Ask directly: does this state judge an agreement made during our marriage by the same standard as one made before it, and is there anything it requires that a prenup would not have needed?

What the statutes read here do show is that on specific estate-side provisions the two are treated alike. New York's waiver of the right of election is effective whether executed before or after the marriage, and the statute says so in a list of things that do not affect it. Florida's rule about marrying after making a will is defeated by a prenuptial or postnuptial agreement, named together. Colorado's probate code speaks of premarital and marital agreements as a single category. Three states, three provisions, and the same structural answer: on these, afterward is not too late.

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What it still cannot do

Every limit that applies to an agreement made before a wedding applies to one made after it, and one of them becomes more tempting to ignore because the couple is already married.

  • It does not settle custody, parenting time or child support. Those are decided on a child's interests when the question arises, and states commonly provide that a child's right to support cannot be adversely affected by such an agreement.
  • It does not bind a creditor who was not a party to it. Allocating a debt between spouses decides who reimburses whom, not who the lender may pursue.
  • It does not move an asset. The deed decides the house, the beneficiary form decides the account, the plan document decides the retirement plan.
  • It does not, by itself, redirect an employer retirement plan. That still takes the plan's own spousal consent, in writing and witnessed. The one advantage here is that a married couple can actually sign it, which two engaged people cannot.
  • It does not replace a will. Without one, intestacy decides everything the agreement did not.

The fourth item is the one place where being already married helps rather than complicating things. A spousal consent on an employer plan is given by a spouse, so a couple doing this after the wedding can complete the agreement and the consent in the same sitting. It is worth doing them together, because the consent is the step that gets forgotten when they are separated by months.

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Sahvelo gives information drawn from statutes, agency guidance and official forms. It is not legal advice for your particular situation. Terms & disclaimer.

What changes where you live

Three states read at source, on the narrow question of whether an agreement made after the wedding can do the estate-side job. None of them is read on what it takes to enforce one.

Does this state's provision work for an agreement signed after the wedding?

The answer in 3 states

  • New York

    Yes, on the waiver of the right of election, and the statute makes the point in a list rather than by implication. A spouse may waive or release the right during the other's lifetime, and the waiver is effective in accordance with its terms whether it was executed before or after the marriage of the spouses, whether it is unilateral or bilateral in form, and whether it was executed with or without consideration. That last item is worth noticing on this page specifically: the absence of consideration is one of the things most often raised about agreements made during a marriage, and for this particular waiver New York removes it as an objection. The requirement that remains is the formality: in writing, subscribed by the maker, and acknowledged or proved in the manner New York requires for recording a conveyance of real property. What New York requires of the wider agreement the waiver sits inside is governed by the Domestic Relations Law and is not read here.1

  • Colorado

    Yes as a category, and in Colorado the agreement is not merely permitted but required. Any affirmation, modification or waiver of a marital right or obligation made on or after 1 July 2014 is unenforceable unless it is contained in a premarital or marital agreement enforceable under part 3 of article 2 of title 14. The phrase names both kinds together, so an agreement made during the marriage is within the permitted vessel. The consequence for a couple redoing an estate plan is direct: if the plan depends on one spouse giving up a marital right, Colorado gives them one place to put it and a will or trust is not that place. Everything then turns on the agreement being enforceable under title 14, which Sahvelo has not read, so this page states nothing about what Colorado requires of such an agreement.2

  • Florida

    Yes, on the provision read here, which is the one about marrying after making a will. Where a person marries after making a will and the spouse survives them, the surviving spouse takes the share they would have received had there been no will, unless provision has been made for, or waived by, the spouse by prenuptial or postnuptial agreement, or the spouse is provided for in the will, or the will discloses an intention not to provide for them. The two kinds of agreement are named together in the same clause, so a couple who married without dealing with this can still deal with it. Note what this does not tell you: it says a postnuptial agreement can defeat this particular claim, and says nothing about what Florida requires before enforcing one, or about Florida's separate elective-share regime, neither of which is read here.3

Sahvelo has read all three of these states at their own sources. Another state's rule may differ, and we would rather say that than generalize.

Questions people ask about this

  • We got married without a prenup. Is it too late?

    Not for the estate-side work in the states read here. New York's waiver of the right of election works whether executed before or after the marriage. Florida's provision about marrying after making a will names prenuptial and postnuptial agreements together. Colorado's probate code treats premarital and marital agreements as one category and, on a waiver of a marital right, as the only permitted one. What Sahvelo cannot tell you is whether your state judges an agreement made during a marriage by the same standard it applies to one made before, because no state's standard is read here. That is the question to ask first.132

  • Is a postnup harder to enforce than a prenup?

    Sahvelo does not know, for any state, and will not guess. It is a real question rather than a technicality: before a wedding each person can walk away, and afterward they cannot, which is why states have taken different views about what an agreement made during a marriage requires. Some apply the same framework, some apply something additional, and what one person receives in exchange arises in a way it does not beforehand. Ask counsel in your state directly, and treat any general answer that does not name your state as not an answer.

  • I just inherited something. Should we do this now?

    It is one of the ordinary reasons couples make one, and doing it while both of you are relaxed about it is better than doing it while you are not. Two things are worth establishing at the same time. Whether an inheritance stays separate under your state's rules is a question about the state and about what happens to the money afterward, because keeping it in a separate account and mixing it into a joint one are not the same act. And an agreement is not the only document involved: if the point is that this should eventually reach your children rather than your spouse, the will, any trust and the beneficiary forms all have to say so too.

  • We are working through a serious financial disagreement. Is this a good idea?

    It can be, and it can also be the wrong instrument at the wrong moment. Some couples use an agreement to settle a specific question that has become corrosive, and find the clarity useful. What is worth watching for is whether both of you are actually in a position to negotiate. An agreement one person signs to end an argument, or under pressure, is both unfair and less likely to survive being tested later. Each of you having your own advice matters more here than usual, and if one of you does not feel free to say no, that is the thing to address first.

  • My state is not one of the three. What do I ask?

    Two questions, and the second is the one that decides it. Does this state permit an agreement made during a marriage to deal with the rights we want it to deal with, including a surviving spouse's claim on an estate? And does this state judge such an agreement by the same standard as one made before a wedding, or does it require something more? Sahvelo asserts nothing about the states it has not read.

Where this sits in the process

Related

Sources

Three states, on the narrow question of whether an agreement made after the wedding works. None on what it takes to enforce one.

  1. N.Y. EPTL §5-1.1-A(e) (waiver or release of right of election)

    New York: the waiver works whether executed before or after the marriage, and with or without consideration.

    nysenate.gov Checked 2026-08-13

  2. C.R.S. §15-11-213 (waiver of right to elect and of other rights)

    Colorado: premarital and marital agreements named together, as the only permitted vessel.

    leg.colorado.gov Checked 2026-08-19

  3. Fla. Stat. §732.301 — pretermitted spouse

    Florida: prenuptial and postnuptial agreements named together in the same clause.

    flsenate.gov Checked 2026-08-13

  4. 29 U.S.C. §1104(a)(1)(D) — the duty to act in accordance with plan documents

    Federal: the plan fiduciary follows the plan's own documents.

    uscode.house.gov Checked 2026-08-13

  5. 29 U.S.C. §1055 — survivor annuities and the spousal consent requirement

    Federal: the spousal consent, which a married couple can actually sign.

    uscode.house.gov Checked 2026-08-13

Sources last reviewed 2026-09-09. Where a source is marked pending re-verification, the page says so wherever the claim appears.