A 62-year-old software engineer in Charlotte plans to retire next spring with roughly $1.2 million in his 401(k). He remarried in 2019, four years after finalizing a divorce that split the marital assets cleanly. What he has not done since 2004, when his employer first enrolled him in the plan, is open the beneficiary form. His ex-wife is still listed at 50%. His current wife is listed nowhere. If he dies tomorrow, roughly $600,000 walks out the door to a woman he has not spoken to in a decade.
Threads on r/legaladvice and r/humanresources are full of these stories. The pattern is always the same: divorce settled, life moved on, paperwork ignored. And in nearly every case, the money went exactly where the form said it should.
Why the Form Beats the Divorce Decree
A 401(k) is governed by federal law (ERISA), and ERISA has one hard rule: the plan administrator pays whoever is on the beneficiary designation form. The form controls, overriding both your will and your divorce decree.
The Supreme Court settled this in Kennedy v. Plan Administrator for DuPont Savings and Investment Plan in 2009. William Kennedy divorced Liv Kennedy, and the divorce decree explicitly waived her rights to his DuPont retirement plan. He never changed the beneficiary form. When he died, DuPont paid Liv the entire balance. His estate sued. The Court sided with DuPont unanimously. The plan administrator is required to follow the form, and a divorce decree does not override it.
Some states have “revocation on divorce” statutes that automatically strip an ex-spouse from beneficiary designations. ERISA preempts them for 401(k) plans. That state law protects your ex from being cut out of your life insurance in some jurisdictions, but it does nothing for the 401(k).
The Spousal Consent Trap Your New Marriage Just Created
A new marriage creates its own trap under ERISA. Under ERISA, a current spouse is automatically entitled to 100% of your 401(k) unless she signs a notarized waiver. So even if the engineer above updates his form tomorrow and names his three adult children from the first marriage as equal beneficiaries, that designation is legally void unless his current wife signs a spousal consent form witnessed by a plan representative or notary.
The reverse trap is worse. If he does nothing and dies, the plan administrator is legally required to pay the ex who is on the form, but the current wife can sue, claiming her ERISA spousal rights. The result is often a multi-year legal fight that eats six figures in attorney fees before anyone sees a dollar. On a $1.2 million account, litigation costs of $150,000 to $300,000 are typical.
The Tax Cost of the Wrong Heir
A surviving spouse who inherits a 401(k) can roll it into her own IRA and stretch withdrawals across her remaining lifetime. An ex-spouse gets the same treatment under most plans. Adult children, under the SECURE Act, must drain an inherited 401(k) within 10 years. If a 55-year-old daughter inherits $600,000 in her peak earning years, she is stacking those withdrawals on top of a six-figure salary, often pushing her into the 32% or 35% federal bracket plus state tax. A $600,000 inheritance can shrink to roughly $360,000 after taxes.
That math changes how you name contingent beneficiaries. Naming a spouse first and children as contingent (per stirpes, so grandchildren inherit a deceased child’s share) is standard. Naming a trust as beneficiary requires drafting that meets IRS “see-through” rules, or the 10-year clock accelerates to five.
Three Actions Before You File Retirement Paperwork
- Pull your current beneficiary designation from the plan portal today. Log into Fidelity, Vanguard, Empower, or whichever recordkeeper holds your 401(k). Screenshot the primary and contingent designations. If you cannot remember the last time you updated the form, you have not updated it recently enough.
- If you are remarried, get the spousal consent form notarized the same week you update the primary beneficiary. A designation naming anyone other than your current spouse is unenforceable without it. Plan administrators reject these forms routinely for missing notary seals.
- Name contingent beneficiaries with per stirpes language, and match them to your will and IRA designations. Mismatched forms across a 401(k), a rollover IRA, and a life insurance policy are the single most common reason estates end up in probate litigation. Fix all three in one sitting.
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