How 401k Withdrawals Are Taxed After Retirement

Money you take out of a traditional 401k after retirement is taxed as ordinary income in the year you receive it, at 2026 federal rates that run from 10% to 37%. That is the core of how 401k withdrawals are taxed after retirement, but it isn’t the whole bill. Required minimum distributions, Social Security, Medicare premiums, and state taxes all react to what you pull out, and the order and size of your withdrawals can change the total by thousands of dollars.

Traditional 401k Withdrawals Are Ordinary Income

Any amount distributed from a qualified employees’ trust is taxable to the person who receives it, in the year they receive it.¹ Your contributions went in before tax and the growth was never taxed, so the IRS treats the full withdrawal as income you’re earning for the first time.

Your 401k income doesn’t sit in its own tax bucket. It stacks on top of Social Security, pensions, part-time work, rental income, interest, and dividends, and the combined total sets your bracket. For 2026, a single filer pays 10% on the first $12,400 of taxable income, then 12% up to $50,400, 22% up to $105,700, 24% up to $201,775, 32% up to $256,225, 35% up to $640,600, and 37% above that.² Married couples filing jointly get wider brackets.

This is where lump sums hurt. Pull $200,000 in a single year to buy a house or clear a mortgage and the whole amount lands in that year’s taxable income, easily reaching the 32% or 35% bracket at the top. Spreading the same total over several years usually produces a lower combined tax bill.

Roth 401k Money Comes Out Tax-Free When Qualified

A Roth 401k works in reverse. Contributions were taxed going in, so qualified withdrawals, including all the growth, come out with no federal income tax. To qualify, you must be at least 59½ and the account must have been open at least five taxable years. The five-year clock starts on January 1 of the first year you made a designated Roth contribution to the plan.³

If a withdrawal isn’t qualified, your original contributions still come out tax-free (you already paid tax), but the earnings portion is taxed as ordinary income.⁴

One change matters for retirement planning. Starting in 2024, Roth 401k accounts are no longer subject to required minimum distributions during the owner’s lifetime, so the money can keep growing tax-free for as long as you live.⁵

Required Minimum Distributions on the Traditional Side

The IRS won’t let a traditional 401k sit untouched forever. Under SECURE 2.0, the age you must begin RMDs depends on when you were born:

Born January 1, 1951 through December 31, 1959: RMDs begin at age 73.
Born on or after January 1, 1960: RMDs begin at age 75.

Final regulations placed the 1959 birth year under the age-73 threshold after earlier confusion.⁵

Each year’s RMD equals your December 31 balance from the prior year divided by a life expectancy factor from the IRS Uniform Lifetime Table. A separate table applies if your sole beneficiary is a spouse more than ten years younger.⁶ The divisor shrinks with age, so the required percentage grows over time.

Your first RMD carries a small grace period: the deadline is April 1 of the year after you reach your RMD age. Using that extension is often a mistake. Pushing the first RMD into the following year means taking two RMDs in the same calendar year, which can lift you into a higher bracket and trigger Medicare surcharges.⁷ Every RMD after the first is due by December 31.

Still Working Past Your RMD Age

If you’re still on the payroll past your RMD age, you may be able to delay RMDs from your current employer’s 401k until April 1 of the year after you actually retire. Three conditions all have to be met: you’re still actively working, you don’t own more than 5% of the business, and the plan allows the delay.⁸ It only covers the current employer’s plan. Old 401k accounts and IRAs are not included.

Penalty for Missing an RMD

Taking less than the required amount triggers an excise tax equal to 25% of the shortfall. Correct it quickly and the penalty drops to 10%. The correction window closes at the earlier of an IRS notice of deficiency, an IRS assessment, or the last day of the second tax year after the year the penalty was imposed.⁹ On a $50,000 shortfall, that’s a $7,500 difference.

What the Plan Withholds Before You See the Money

The tax you eventually owe and the tax withheld at distribution aren’t always the same number. How the payment is structured determines the withholding.

Lump Sums and Other Eligible Rollover Distributions

Any distribution you could roll into an IRA or another qualified plan but choose to take as cash is subject to a mandatory 20% federal withholding. You can’t elect a lower rate or opt out. Form W-4R lets you elect higher, not lower.¹⁰ If your actual bracket is higher than 20%, you’ll owe the difference when you file.

Direct the same distribution to an IRA or another employer plan through a trustee-to-trustee transfer and the 20% withholding doesn’t apply, because the money never reaches your hands.¹¹ On a $100,000 distribution, that’s $20,000 in immediate cash flow.

Periodic Payments

Regular installments are withheld more like wages. The plan administrator uses Form W-4P and applies withholding based on your filing status and adjustments.¹² If you don’t submit a W-4P, the default treats you as single with no adjustments, which often over-withholds.

RMDs

RMDs are not eligible rollover distributions, so the mandatory 20% doesn’t apply.¹¹ The default withholding on an RMD is 10%, adjustable from 0% to 100% on Form W-4R. If an RMD is your main source of withholding, setting it higher can prevent a large balance due in April.

How 401k Withdrawals Can Make Social Security Taxable

A 401k distribution doesn’t just get taxed on its own. It can pull your Social Security benefits into the tax base too. The IRS uses “provisional income,” which equals half your Social Security benefits plus all other taxable income (including 401k distributions) and tax-exempt interest.

For single filers, up to 50% of Social Security benefits become taxable once provisional income exceeds $25,000, and up to 85% become taxable above $34,000. For joint filers, the thresholds are $32,000 and $44,000.¹³ These thresholds have never been indexed to inflation, so most retirees with meaningful 401k income exceed them.

That creates a hidden marginal rate. An extra $1,000 from your 401k can also pull up to $850 of previously untaxed Social Security into the taxable column. For someone in the 22% bracket, the effective rate on that $1,000 withdrawal can approach 40%. Small changes in how much you take out matter more here than most people expect.

Medicare Premiums and the Two-Year Lookback

Large 401k withdrawals can also raise your Medicare Part B and Part D premiums through the Income-Related Monthly Adjustment Amount, or IRMAA. Medicare uses your modified adjusted gross income from two years earlier, so 2026 premiums are set from your 2024 return.¹⁴

The standard 2026 Part B premium is $202.90 per month. Surcharges begin above $109,000 for single filers and $218,000 for joint filers, escalating through five tiers:

$109,001–$137,000 single / $218,001–$274,000 joint: $81.20 monthly Part B surcharge.
$137,001–$171,000 / $274,001–$342,000: $202.90 surcharge.
$171,001–$205,000 / $342,001–$410,000: $324.60 surcharge.
$205,001–$499,999 / $410,001–$749,999: $446.30 surcharge.
$500,000 or more / $750,000 or more: $487.00 surcharge.

Part D carries separate surcharges at the same income thresholds. Combined annual cost at the top tier exceeds $6,900 per person.¹⁴

The two-year lag catches new retirees. A big final-year 401k distribution or company stock cash-out shows up in Medicare premiums two years later. If you’ve had a life-changing event such as retirement, work stoppage, or death of a spouse, you can ask Medicare to use your current, lower income by filing Form SSA-44 with the Social Security Administration.

Employer Stock in Your 401k: Net Unrealized Appreciation

If your 401k holds stock in the company you worked for, a rule called net unrealized appreciation can shift much of the tax from ordinary income rates to long-term capital gains rates. Instead of rolling the whole account into an IRA, you take an in-kind distribution of the employer stock into a taxable brokerage account. You pay ordinary income tax on the stock’s original cost basis in the year of distribution. The appreciation (the NUA) is taxed at long-term capital gains rates whenever you sell.¹

The rate spread is meaningful. The top 2026 ordinary rate is 37%; the top long-term capital gains rate is 20%. On $500,000 of appreciation, that gap is over $80,000 in federal tax.

The rules are strict. The distribution has to qualify as a lump-sum distribution triggered by reaching age 59½, separating from service, death, or disability. The entire vested balance has to move within a single tax year, with the stock going in-kind to a taxable account and the rest able to roll to an IRA. NUA covers only employer securities, not mutual funds that hold company stock. And once the employer stock rolls into an IRA, the NUA option is gone for good.

State Taxes on 401k Withdrawals

State treatment varies widely. Some states impose no personal income tax at all. Others exempt retirement income specifically or shield a set dollar amount each year. The rest tax 401k distributions as ordinary income, with top rates that can exceed 13%. State legislatures adjust these rules often, and many states offer targeted deductions or credits for residents above a certain age.

The State You Left Can’t Tax You

Federal law blocks a former state from taxing your retirement withdrawals. Under 4 U.S.C. § 114, no state may impose income tax on the retirement income of someone who is not a resident or domiciliary of that state.¹⁵ The protection covers 401k plans, IRAs, 403(b) plans, 457 plans, and government pensions. If you retire in one state and move to another, only your new state of residence can tax your withdrawals.

If You Retire Before 59½

Withdrawals from a 401k before age 59½ normally add a 10% additional tax on top of ordinary income tax.¹⁶ For early retirees, the most useful exception is the Rule of 55: if you leave your job during or after the year you turn 55, distributions from that employer’s 401k plan aren’t hit with the 10% penalty.¹⁷ Ordinary income tax still applies. The exception covers only the plan at the employer you separated from, not old 401ks or IRAs. For certain public safety employees, including federal law enforcement officers, firefighters, and air traffic controllers, the age drops to 50.

1
Office of the Law Revision Counsel. 26 USC 402 – Taxability of Beneficiary of Employees Trust
2
Tax Foundation. 2026 Tax Brackets and Federal Income Tax Rates
3
Internal Revenue Service. Retirement Plans FAQs on Designated Roth Accounts
4
Internal Revenue Service. Roth Comparison Chart
5
Congressional Research Service. Required Minimum Distribution (RMD) Rules for Original Owners of Retirement Accounts
6
Internal Revenue Service. Retirement Topics – Required Minimum Distributions (RMDs)
7
Charles Schwab. RMD Reference Guide
8
Fidelity. Making Sense of RMDs
9
Office of the Law Revision Counsel. 26 USC 4974 – Excise Tax on Certain Accumulations in Qualified Retirement Plans
10
Internal Revenue Service. 2026 Form W-4R
11
Internal Revenue Service. Pensions and Annuity Withholding
12
Internal Revenue Service. 2026 Form W-4P
13
Office of the Law Revision Counsel. 26 USC 86 – Social Security and Tier 1 Railroad Retirement Benefits
14
Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles
15
Office of the Law Revision Counsel. 4 USC 114 – Limitation on State Income Taxation of Certain Pension Income
16
Office of the Law Revision Counsel. 26 USC 72 – Annuities; Certain Proceeds of Endowment and Life Insurance Contracts
17
Internal Revenue Service. Retirement Topics – Exceptions to Tax on Early Distributions