Retiring with $1 million? This 401(k) tax trap could cost you big

A married couple, both age 73, has about $1.5 million saved in a traditional 401(k), and they also receive Social Security income. Their taxes look reasonable while both are alive. The problem begins after one spouse dies because the surviving partner keeps the same income but pays higher taxes. This situation is often ignored in retirement planning discussions, even though it can cost thousands of dollars each year.

At age 73, retirees must take Required Minimum Distributions (RMDs) from their 401(k). The IRS rule uses a factor of 26.5, which means a $1.5 million 401(k) creates about $56,600 in first-year withdrawals, as reported by 24/7WallSt. If the couple also gets $30,000 in Social Security, their total income becomes around $86,600. Because this income is above $44,000 for married couples, up to 85% of their Social Security becomes taxable.

401(k) RMD tax example

About $25,500 of Social Security is added to taxable income. After using the 2026 standard deduction of $32,200 for married couples, taxable income falls to about $49,900. This puts them in the 12% tax bracket, leading to an estimated federal tax bill of roughly $5,500, which seems manageable. When one spouse dies, the survivor must file taxes as single instead of married. The standard deduction drops sharply from $32,200 to $16,100 for single filers. With the same income, taxable income rises to about $66,000.

Single filer tax jump

The 22% tax bracket for single filers starts at $50,401 in 2026. Around $15,600 of income now gets taxed at the higher 22% rate. The federal tax bill increases to about $9,200. That means roughly $3,700 more taxes each year on the same income, as noted by 24/7WallSt. The gap gets bigger over time because RMD withdrawals increase as retirees age. Investment growth can also push required withdrawals even higher each year.

Medicare IRMAA income risk

This increases the amount taxed at higher rates for the surviving spouse. Medicare costs can also rise due to IRMAA surcharges tied to income. In 2026, IRMAA starts at $218,000 income for married couples but only $109,000 for single filers. This means the single filer reaches the higher Medicare cost threshold much sooner. Once income crosses $109,000, Medicare Part B surcharges add about $1,148 per year.

The married couple would not face this until their income reached $218,000. The tax and Medicare penalty happens even though income stays the same. This issue often affects women more because they statistically live longer than men. Many widows inherit retirement accounts and the higher tax burden without planning for it, as cited by 24/7WallSt. Experts say retirees should model what happens if one spouse dies within 5 to 10 years. These projections often show higher taxes for the surviving spouse.

Roth conversion tax strategy

One strategy is converting part of a traditional 401(k) into a Roth account before RMDs begin. This can lower future required withdrawals and reduce taxable income later. Roth conversions between ages 60 and 72 can sometimes be taxed at lower 12% rates. Timing matters because large conversions can raise Medicare premiums later due to the two-year lookback rule. Another strategy is using Qualified Charitable Distributions (QCDs) from retirement accounts.

The 2026 QCD limit is $111,000 per person. QCDs count toward RMDs but do not increase taxable income, as noted by 24/7WallSt. This can reduce both taxes and Medicare surcharges. Advisors can also help balance Roth conversions and QCDs to stay below IRMAA thresholds. Overall, the “widow’s tax penalty” can quietly reduce retirement income by thousands each year.

FAQs

Q1. Why do taxes increase after one spouse dies with a 401(k)?

Taxes increase because the surviving spouse files as single, gets a smaller deduction, and may move into higher tax brackets.

Q2. How can retirees reduce the 401(k) widow tax penalty?

They can use strategies like Roth conversions or charitable distributions to lower future taxable income.