Convert $50,000 Inside a 401(k) and the Plan Can’t Withhold a Dollar of Tax From It. All $50,000 Lands in the Roth and the Bill Comes in April. Convert the Same $50,000 From an IRA and the Custodian Offers to Withhold, Which Is the Trap
The path you choose for a Roth conversion determines whether tens of thousands of dollars actually land inside the account or quietly drain away before conversion even completes, and the two paths work in opposite directions for reasons most retirement…
Converting pre-tax retirement savings to a Roth raises a withholding question that trips people up: how much federal tax is withheld depends on whether the money comes from a 401(k) or an IRA. The tax you owe on the conversion itself is the same either way, and what changes is how much is withheld up front, which can make the April bill look very different.
Under federal law, a rollover from a pre-tax account to a Roth IRA adds to gross income any amount that would be includible were it not part of a qualified rollover contribution. The section 72(t) early distribution tax does not apply to the converted amount. The difference between the two paths is how and when you pay the tax.
Where the Convertible Money Sits by Age
The Federal Reserve’s Distributional Financial Accounts put the money in question mostly in the hands of people near retirement. As of 2026 Q2, families ages 55 to 69 held about $8.5 trillion in defined contribution benefits. That’s 49.5% of families’ total, and families ages 40 to 54 held another 33.1%.
Older families have also built up a larger share of these assets over time. People 70 and up held 2.3% of these assets in 1989 Q3, and that share reached 9.4% in the latest quarter. The Fed data covers defined contribution benefits by age, and the largest pre-tax balances sit with families ages 55 to 69.
Why a 401(k) Conversion Arrives With No Withholding
Inside an employer plan, a traditional-to-Roth move is called an in-plan Roth rollover. According to the IRS, “There is no income tax withholding required on an in-plan Roth direct rollover.” IRS guidance also clarified that you cannot voluntarily withhold on these rollovers. Converting $50,000 this way places the full amount into the designated Roth account.
You then settle the tax on your return. For 2026, the 22% rate applies to single taxpayers earning over $50,400, and the 24% rate starts over $105,700.
If the entire conversion falls into the 22% bracket, it adds $11,000 in federal tax. If it lands in the 24% bracket, the added tax is $12,000.
IRS Publication 575 notes that when a rollover creates taxable income, the taxpayer “may have to increase your withholding or make estimated tax payments.” In practice, the money for the tax comes from somewhere outside the converted balance. That usually means electing higher withholding from your paycheck or making quarterly estimated payments.
How the IRA Withholding Default Changes the Outcome
An IRA conversion counts as a nonperiodic distribution. Under federal law, the payer “shall withhold from such distribution an amount equal to 10 percent” unless the owner opts out. That opt-out applies on a distribution-by-distribution basis, and custodians typically collect it on Form W-4R. If the default stays in place on a $50,000 conversion, $5,000 goes to the IRS, and $45,000 reaches the Roth IRA.
The withheld money is treated as a distribution that was never converted. Conversion guidance from Wells Fargo (NYSE:WFC | WFC Price Prediction) notes that someone who chooses withholding to pay the taxes and is under age 59 1/2 may owe the additional tax on that portion. At 10%, the extra cost on $5,000 is $500, on top of regular income tax. The $5,000 also never grows tax-free inside the Roth.
The default withholding also falls short of the full bill. At the 22% rate, a $11,000 liability set against $5,000 withheld leaves $6,000 still owed in April.
Side-by-Side Comparison of the Two Conversion Paths
| Item | 401(k) In-Plan Conversion | IRA Conversion, Default Withholding |
|---|---|---|
| Federal withholding | None | 10% unless waived |
| Amount reaching the Roth | $50,000 | $45,000 |
| Extra tax on withheld amount, under 59 1/2 | Not applicable | $500 |
| Tax still owed at 22% | $11,000 | $6,000 |
Rule Changes to Watch Before Converting
IRA withholding is avoided when the withholding election is set to zero, so the full amount converts and you pay the tax from cash outside the account. Owners already past 59 1/2 avoid the additional tax. Even so, any amount withheld for them still leaves the Roth permanently. Timing matters too, and the low-tax years between the last paycheck and the first required withdrawal are often the cheapest window to run one (we sized up that window in a free Roth guide here: The Roth Window).
Rules for how rollovers are processed may change. In Notice 2026-49, released August 12, 2026, the Treasury Department and the IRS said they are considering guidance to standardize rollover procedures. One idea is a safe harbor that lets the distributing trustee reasonably conclude no withholding is needed on the rollover contribution. That proposal addresses rollovers between plans, while the 10% default on IRA-to-Roth conversions remains in the statute.
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David Beren has been a Flywheel Publishing contributor since 2022. Writing for 24/7 Wall St. since 2023, David loves to write about topics of all shapes and sizes. As a technology expert, David focuses heavily on consumer electronics brands, automobiles, and general technology. He has previously written for LifeWire, formerly About.com. As a part-time freelance writer, David’s “day job” has been working on and leading social media for multiple Fortune 100 brands. David loves the flexibility of this field and its ability to reach customers exactly where they like to spend their time. Additionally, David previously published his own blog, TmoNews.com, which reached 3 million readers in its first year. In addition to freelance and social media work, David loves to spend time with his family and children and relive the glory days of video game consoles by playing any retro game console he can get his hands on.
