$900,000 Inherited 401(k): The 10-Year Tax Bomb Most Beneficiaries Miss Until Year 10

A 58-year-old daughter, still working and earning a six-figure salary, gets the call. Her 75-year-old mother has died, leaving behind a $900,000 traditional 401(k) with the daughter named as sole beneficiary. The grief is one problem. The IRS clock that just started ticking is another.

Under the SECURE Act, most adult children who inherit a parent’s 401(k) are now classified as non-eligible designated beneficiaries. That means the entire account must be emptied by the end of the tenth year after the original owner’s death. The old stretch strategy, where a 58-year-old could let an inherited account compound for 25 or 30 years and pull out tiny life-expectancy slices, is gone for this profile of beneficiary.

The wrinkle most beneficiaries miss

Here is the part that catches people: because the mother was already 75 and had begun her own required minimum distributions, the daughter cannot simply ignore the account for nine years and cash out in year ten. The IRS finalized this in 2024. When the original owner had already started RMDs, the beneficiary must take annual distributions in years one through nine based on the beneficiary’s single life expectancy, and the account still has to be at zero by year ten.

Annual withdrawals are required, and the account must still be emptied by year ten.

On $900,000, a 58-year-old’s first-year inherited RMD lands near $25,000 using the IRS Single Life Table. That is the floor. The daughter can take more, and almost always should, because of what happens to the leftover balance in year ten.

The tax bomb in year ten

Suppose the daughter takes only the minimum each year and the account grows at roughly the 4.5% currently available on a 10-year Treasury. By year ten, she is still staring at a balance well above $700,000 that must come out in a single tax year. Added on top of her salary, that distribution lands almost entirely in the 35% federal bracket, plus state tax. A six-figure earner in a state like California or New York can lose more than 45 cents on the dollar.

The smarter move, in most cases, is to spread the distributions evenly across all ten years. Roughly $90,000 a year on top of a $130,000 salary keeps the marginal rate at 24% for a single filer under current brackets, sparing the daughter the top-bracket cliff.

For a beneficiary who is already 65 and on Medicare, the cascade is worse. The 2026 IRMAA threshold kicks in at $109,000 of modified adjusted gross income for a single filer and $218,000 for a couple. A $90,000 inherited distribution layered on top of Social Security and a pension can push a retiree two or three IRMAA tiers higher, adding $1,150 to $6,900 per person in annual Medicare surcharges. The lookback is two years, so a big distribution in 2026 raises premiums in 2028.

Strategies that actually move the needle

Three steps are worth taking inside the first 90 days after the death.

1. Set up an inherited 401(k) or inherited IRA in the beneficiary’s name rather than the estate’s. Rolling the balance to an inherited IRA at the same custodian preserves creditor protection and gives the beneficiary control over investment mix during the ten-year window. Cashing the check directly forfeits the entire deferral and triggers tax on the full $900,000 in one year.
2. Model the ten-year tax curve before the first distribution. A fee-only CPA can map projected income, Social Security claiming age, and Medicare enrollment against the distribution schedule. If the beneficiary expects to retire inside the ten-year window, front-loading distributions during working years when other income drops can save tens of thousands. The reverse is also true: a beneficiary about to start a higher-earning job should accelerate distributions now.
3. Coordinate with the surviving spouse’s own retirement timeline. If the beneficiary is married and the spouse plans to convert traditional IRA money to Roth, stacking conversions on top of inherited distributions in the same year is a common and expensive mistake.

The ten-year clock does not pause for grief, market downturns, or job changes. It just runs.

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