Your prenup cannot touch your 401(k)

This is the most expensive thing people get wrong about prenuptial agreements, and it is not a drafting problem — no wording fixes it. A prenup cannot waive a spouse’s rights in an employer retirement plan, because the person signing it is not yet a spouse. Federal law says so in one sentence, and two federal courts have handed entire accounts to surviving spouses whose prenups said otherwise.

Read the last clause again. Timing is not the defect. Even a prenup signed inside the technical window fails, because the signature belongs to a fiancé, and a fiancé is not a spouse.

What the spouse actually has

If one of you has a 401(k), a 403(b), a pension or any other employer plan governed by ERISA, the other spouse has two federal rights that exist whatever the plan documents or the prenup say:

• The survivor annuity. A married participant’s benefit is paid, by default, in a form that continues to the surviving spouse — the qualified joint and survivor annuity, and, if the participant dies first, the qualified pre-retirement survivor annuity.
• Default beneficiary status. In a plan like a 401(k), the spouse is the beneficiary unless the spouse has consented, in the required form, to somebody else.

Those rights can be given up. They just cannot be given up before the wedding.

The four things a valid waiver needs

• An actual spouse, signing after the marriage. The statute requires consent by “the spouse of the participant”; the words “after the marriage” are not in it. That timing rule comes from the regulation quoted above and from the cases — and the Second Circuit expressly reserved judgment on whether a pre-marriage signature would be fatal if it were the agreement’s only defect.
• In writing, consenting to the participant’s election.
• Naming the beneficiary or the benefit form, and acknowledging the effect of the waiver. A general “I give up any rights I may have” does not do it.
• Witnessed by a plan representative or a notary public. Not a friend, not the other spouse, not a colleague.

The four elements and the acknowledgment requirement: ERISA §205(c)(2), 29 U.S.C. §1055(c)(2)(A)(i)–(iii), read on uscode.house.gov, 27 September 2026. Specificity: Treas. Reg. §1.401(a)-20, Q&A-31 and Q&A-32, read on eCFR the same day — note the regulation is stricter than the statute, requiring the specific non-spouse beneficiary to be named in every case and, for a joint and survivor annuity, the particular optional form as well. §1055(c)(2)(B) sets out the circumstances in which no consent is needed at all.

What happens when people get it wrong

• The Second Circuit, 1992. An antenuptial agreement was held not to waive ERISA survivor benefits: it did not designate a beneficiary and did not acknowledge the effect of the waiver. The court applied the regulation above directly.
• A federal court in Florida, 1994. Two documents were offered as the waiver and both failed. The plan’s own spousal consent form — Merrill Lynch’s “Basic Retirement Plan New Participant Form” — was too vague to disclose what was being given up (it said only that the spouse gave up “rights I may have under the Plan and applicable law”), and its witnessing was invalid: the notary space was blank, and nobody shown to be a plan representative had witnessed the consent. The amendment to the prenuptial agreement failed for a different reason again — it did not designate a beneficiary, as 29 U.S.C. §1055(c)(2)(A)(ii) requires. The surviving spouse took the entire account balance.

Hurwitz v. Sher, 982 F.2d 778 (2d Cir. 1992) · Lasche v. George W. Lasche Basic Retirement Plan, 870 F. Supp. 336 (S.D. Fla. 1994). Both read in the reporter text, 27 September 2026.

So what can the prenup do?

Two useful things, and it is worth writing both in:

• Create an obligation to sign the real consent. A clause promising that, within a set number of days of the marriage, each party will execute the plan’s own spousal consent form, is enforceable between the two of you.
• Provide a remedy if they do not. An indemnity, or a dollar-for-dollar offset elsewhere in the agreement, so the promise has teeth.

What it cannot do is bind the plan. The plan administrator is not a party to your agreement and will not read it.

IRAs play by different rules

The survivor-annuity provisions sit in a part of ERISA that expressly does not apply to individual retirement accounts. No federal spousal-consent requirement, no notary rule, no plan form. In a common-law state, an IRA owner can usually name anyone as beneficiary without a signature from their spouse; the custodial agreement and state law decide it.

In the nine community property states — Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington and Wisconsin — the analysis flips. Community property principles can give a spouse an ownership interest in contributions made during the marriage, and custodians routinely ask for spousal consent before a non-spouse is named. This is one of the few places a prenup’s community-property opt-out does real work on a retirement account, because federal law does not preempt it the way it does for employer plans.

29 U.S.C. §1051(6) · Boggs v. Boggs, 520 U.S. 833 (1997) · IRS Publication 555.

And the designation beats everything anyway

Even where a waiver is valid, there is a second failure waiting. The plan pays whoever is named on its own form. The Supreme Court settled this in 2009: an administrator follows the plan documents, and an outside waiver document does not override them. The Court preferred, in its words, the virtues of an uncomplicated rule to inquiries about what anyone intended.

And if you are counting on divorce to clean this up — many states have a statute that automatically revokes an ex-spouse’s beneficiary designation on divorce. For an employer retirement plan, that statute is preempted and does not apply. An ex-spouse can still collect a 401(k) years after the divorce because nobody changed the form.

Kennedy v. Plan Administrator for DuPont Savings & Investment Plan, 555 U.S. 285 (2009) · Egelhoff v. Egelhoff, 532 U.S. 141 (2001).

What to actually do

• Before the wedding: put the obligation in the prenup — each party will sign the plan’s spousal consent within, say, 30 days of the marriage — with a remedy if they do not.
• After the wedding: get the consent form from the plan administrator, not from a lawyer’s precedent file. Fill in the named beneficiary. Sign it in front of a notary or a plan representative. Keep a stamped copy.
• The same week: update every beneficiary designation — 401(k), IRA, life insurance, annuities, payable-on-death accounts — and keep the confirmations.
• At 35, and after any job change: re-check the plan consent. New employer means a new plan and a new form.
• At divorce: the only ERISA-sanctioned way to move plan money is a qualified domestic relations order. Get one drafted and accepted by the plan; do not rely on the decree alone.

Keep reading

• The prenup and death — the elective share in all fifty states, homestead, and what else a prenup forgets
• What a prenup needs to cover — and what your state already protects
• “What am I not thinking about?”
• Prenups and postnups — the four ways one fails

Regulations, statutes and cases read at their official or primary sources on 21 September 2026 and linked above. General information about how these federal rules work, not advice about your plan or your agreement. Plan terms differ; ask your plan administrator for its own consent form. If a rule here has moved, tell us.