Does a Spouse Automatically Inherit a 401(k)?

Yes. Under federal law, a spouse does automatically inherit a 401(k): the Employee Retirement Income Security Act (ERISA) makes the surviving spouse the default beneficiary of the entire vested balance, regardless of what the beneficiary form or the will says.¹ The only way to change that outcome is a written waiver signed by the spouse after the marriage and witnessed by a notary or plan representative. Prenuptial agreements do not count, and a beneficiary form naming someone else without a valid waiver is legally void.

The Federal Default Rule

ERISA, strengthened by the Retirement Equity Act of 1984, requires that a deceased participant’s entire vested 401(k) benefit be payable to the surviving spouse.¹ This is not a suggestion the participant can quietly override. If someone logs into their plan portal and names a child, sibling, or new partner without proper spousal consent on file, the plan administrator is still obligated to pay the surviving spouse. The federal rule overrides state inheritance laws, probate procedures, and anything written in a will or trust.²

One detail catches families off guard. A plan can require that the participant and spouse have been married for at least one year before the automatic survivor protection applies.² If the participant dies inside that first year, a new spouse may not be entitled to the balance under the automatic rule. The plan’s Summary Plan Description will tell you whether that one-year provision is in effect.

When Someone Else Can Inherit Instead

A married participant can direct their 401(k) to someone other than their spouse, but only if the spouse signs a written waiver that meets ERISA’s requirements. Three elements have to be present:

Written consent that names the alternate beneficiary, or that allows the participant to designate one without further approval.
An acknowledgment showing the spouse understands the financial effect of giving up the balance.
A signature witnessed by either a notary public or an authorized plan representative.

Miss any of the three and the waiver fails.¹ Plan administrators who pay a non-spouse without a valid waiver on file face personal liability, and a plan that consistently ignores spousal consent risks losing its tax-qualified status.³ Because the risk falls on the administrator, plans tend to be strict. If anything looks off, they default to paying the spouse.

Why a Prenuptial Agreement Doesn’t Override the Rule

This is where many estate plans quietly fail. Couples often include 401(k) assets in a prenup and assume it settles the question. It doesn’t. Federal regulations are explicit that consent to waive 401(k) rights signed before marriage is not valid, because the person signing is a fiancé, not a spouse. Only a spouse can waive spousal rights under ERISA.

The reasoning is mechanical. The statute grants rights to a “spouse,” and before the ceremony neither party holds that legal status, so neither party has any ERISA right to waive. A prenup signed one hour before the wedding still fails the test. Federal courts have upheld this consistently, including in cases brought by children from prior marriages who tried to enforce prenuptial waivers and lost.

The practical fix is simple and often overlooked: the prenup should require the new spouse to sign a separate 401(k) waiver on the plan’s own consent form immediately after the wedding. That post-marriage waiver, properly witnessed, is what actually redirects the money. Without it, the prenup’s 401(k) provisions are unenforceable and the surviving spouse inherits the full balance no matter what the couple agreed to before the ceremony.

Divorce and an Ex-Spouse Still Listed on the Form

Divorce is where people most often lose money they expected to inherit. ERISA tells the plan administrator to follow the plan documents and the beneficiary designation on file. If an ex-spouse is still listed when the participant dies, many plans will pay the ex-spouse, and a current partner or the children may have no way to recover the money.

The Supreme Court confirmed this in Egelhoff v. Egelhoff (2001), ruling that ERISA preempts state laws that try to automatically revoke an ex-spouse’s beneficiary status upon divorce.⁴ Some plans include their own automatic revocation provision, and those plan-level provisions are enforceable. Many plans don’t. The only reliable move after a divorce is to file a new beneficiary designation with the plan administrator right away.

If a divorce settlement awards part of one spouse’s 401(k) to the other, that division is only enforceable through a Qualified Domestic Relations Order. A QDRO is a court order that directs the plan administrator to pay a share of the benefits to an “alternate payee,” usually the former spouse.⁵ Without a valid QDRO, the plan cannot legally pay anyone but the participant or the named beneficiary, no matter what the divorce decree says. This step gets missed, sometimes for years.

Same-Sex Spouses and Domestic Partners

After the Supreme Court’s 2013 decision in United States v. Windsor, the Department of Labor clarified that “spouse” under ERISA includes anyone in a same-sex marriage legally recognized under any state’s law, regardless of where the couple currently lives.⁶ A same-sex surviving spouse has the same automatic 401(k) rights as any other.

Domestic partnerships and civil unions do not qualify. The DOL guidance excludes state-recognized relationships not called “marriage,” even when they carry equivalent rights.⁶ If you are in a domestic partnership or civil union rather than a legal marriage, you have no automatic ERISA right to your partner’s 401(k). Your partner would need to name you as beneficiary on the form, and if they later marry someone else, that spouse’s rights override your designation unless the new spouse signs a valid waiver.

When No Beneficiary Form Was Ever Filed

If a participant dies without ever submitting a beneficiary designation, the plan’s own default rules control. Almost every plan document lists the surviving spouse first, then children, then the estate. Because the plan document governs, these assets generally avoid probate.

Even without a form, you’ll still need to prove you are the surviving spouse. Expect to provide a certified marriage certificate and a certified death certificate. Common-law marriages recognized by the state where they were established are harder to document and often require sworn statements and supporting evidence like joint tax returns or shared property records. The plan’s Summary Plan Description spells out the default hierarchy and the claims process, and the administrator is required to give a potential beneficiary information about their rights.

What You Can Do With the Money You Inherit

Surviving spouses get distribution options no other beneficiary receives, and the choice can shape your tax bill for decades.

Roll It Into Your Own IRA

You can roll the inherited 401(k) into your own traditional IRA, or into a Roth IRA if the funds came from a designated Roth account. The IRS then treats the account as if it were always yours. You follow normal IRA rules, including required minimum distributions based on your own age. The tradeoff: if you’re under 59½ and pull funds out, you’ll owe the standard 10% early withdrawal penalty on top of income tax unless a separate exception applies.⁷

Keep It as an Inherited Account

You can also leave the funds in an inherited IRA or inherited 401(k). Distributions from an inherited account are not subject to the 10% early withdrawal penalty, whatever your age.⁸ That matters most for a younger surviving spouse who may need the money before 59½. You can spread distributions over your own life expectancy.

Delay Distributions

If your spouse died before their required beginning date for distributions, you can wait until the year they would have turned 73 to start taking money.⁹ That lets the account keep growing tax-deferred if you don’t need income immediately.

Non-spouse beneficiaries generally have to empty an inherited account within 10 years of the participant’s death. Surviving spouses are exempt from that 10-year rule.⁹ Distributions from an inherited pre-tax 401(k) count as ordinary income in the year you receive them. Roth 401(k) contributions come out tax-free, and Roth earnings are also tax-free if the account has been open for at least five years.

Accounts That Don’t Follow the Same Rule

Not every retirement account carries ERISA’s automatic spousal protection, and mixing up the rules can be costly.

IRAs. Individual Retirement Accounts are not governed by ERISA and do not require spousal consent to change beneficiaries under federal law. An IRA owner can name anyone as beneficiary at any time without their spouse’s knowledge. If you assume your spouse’s IRA is coming to you because the 401(k) would, you may be wrong. The exception is the nine community property states: Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin. In those states, each spouse holds an automatic 50% interest in assets acquired during marriage, which can include IRA contributions made with marital income. A surviving spouse there may have a legal claim to half the balance even without being named, though enforcing it can take legal action.

Solo 401(k) plans. A solo 401(k) covers a business owner with no employees, or just the owner and their spouse. The IRS says these plans follow the same rules as any other 401(k).¹⁰ The spousal consent and survivor benefit requirements under Section 401(a)(11) still apply, so the surviving spouse retains the automatic right to the full balance.² Solo plans are generally exempt from ERISA’s reporting and fiduciary rules because they don’t cover traditional employees, but that exemption doesn’t reach the spousal protections, which come from the tax code separately. A business owner who assumes their solo 401(k) is free of spousal consent is setting up a serious problem for their intended beneficiaries.

1
U.S. Department of Labor. FAQs About Retirement Plans and ERISA
2
Office of the Law Revision Counsel. 26 U.S. Code 401 – Qualified Pension, Profit-Sharing, and Stock Bonus Plans
3
Internal Revenue Service. Fixing Common Plan Mistakes – Failure to Obtain Spousal Consent
4
Legal Information Institute. Egelhoff v Egelhoff
5
U.S. Department of Labor. QDROs Under ERISA – A Practical Guide to Dividing Retirement Benefits
6
U.S. Department of Labor. Technical Release No. 2013-04
7
Internal Revenue Service. Safe Harbor Explanations – Eligible Rollover Distributions Notice 2026-13
8
Internal Revenue Service. 401(k) Resource Guide – Plan Participants – General Distribution Rules
9
Internal Revenue Service. Retirement Topics – Beneficiary
10
Internal Revenue Service. One-Participant 401k Plans