How Does a 401(k) Withdrawal Affect Your Tax Return?

A 401(k) withdrawal affects your tax return by adding to your taxable income for the year you take it. If it comes from a traditional pre-tax 401(k), the full distribution is taxed at your ordinary income rate, and if you’re younger than 59½ the IRS usually tacks on a 10% early withdrawal penalty. That extra income can push you into a higher bracket, shrink credits tied to your adjusted gross income, and even raise your Medicare premiums two years later. A qualified Roth 401(k) withdrawal, by contrast, comes out tax-free.1Internal Revenue Service. 401(k) Resource Guide – Plan Participants – General Distribution Rules

How a Traditional 401(k) Withdrawal Adds to Your Income

Traditional 401(k) contributions went in before taxes, so the IRS collects when the money comes out. The distribution is added to your wages and other income for the year and taxed at your ordinary rate. There’s no capital gains treatment, even for growth that came from stock investments inside the plan.2Internal Revenue Service. 401(k) Resource Guide – Plan Participants – 401(k) Plan Overview

For 2026, single-filer federal brackets run:3Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026

  • 10% up to $12,400
  • 12% from $12,401 to $50,400
  • 22% from $50,401 to $105,700
  • 24% from $105,701 to $201,775
  • 32% from $201,776 to $256,225
  • 35% from $256,226 to $640,600
  • 37% over $640,600

A withdrawal stacks on top of the income you already have. Someone earning $90,000 in wages who takes a $30,000 distribution pays 22% on the part that stays inside the 22% bracket and 24% on the piece that crosses $105,700. Married couples filing jointly get wider bands, but the stacking works the same way.

The other effect is quieter. Distribution income raises your adjusted gross income, and AGI drives eligibility for the child tax credit, education credits, ACA marketplace subsidies, and other benefits. A withdrawal that looks manageable on its face can knock you out of something you were counting on.

The 10% Early Withdrawal Penalty

Take money from a traditional 401(k) before age 59½ and the IRS adds a 10% penalty to the taxable portion, on top of the regular income tax. A $20,000 early withdrawal for someone in the 22% bracket runs roughly $4,400 in income tax plus $2,000 in penalties, leaving about $13,600 in hand.4Office of the Law Revision Counsel. 26 USC 72 – Annuities; Certain Proceeds of Endowment and Life Insurance Contracts

Hardship withdrawals aren’t a way around this. Even if your plan permits a hardship distribution for an immediate financial need, the amount is still taxable income and the 10% penalty still applies unless a separate exception covers you.5Internal Revenue Service. 401(k) Plan Hardship Distributions – Consider the Consequences

Exceptions That Waive the Penalty

Several situations remove the 10% penalty while leaving the distribution taxable as ordinary income:6Internal Revenue Service. Retirement Topics – Exceptions to Tax on Early Distributions

  • Rule of 55: leaving your job during or after the year you turn 55 lets you take penalty-free withdrawals from that employer’s plan. Roll the funds to an IRA first and you lose this exception.
  • Total and permanent disability, certified as expected to result in death or last indefinitely.
  • Payments to an ex-spouse under a qualified domestic relations order (QDRO), taken directly from the plan.
  • Substantially equal periodic payments (SEPPs) set up using one of three IRS-approved methods and continued for the longer of five years or until age 59½. Breaking the schedule early triggers a retroactive penalty on all prior payments.7Internal Revenue Service. Substantially Equal Periodic Payments
  • Unreimbursed medical expenses above 7.5% of AGI, even if you don’t itemize.8Internal Revenue Service. Publication 502 (2025) – Medical and Dental Expenses
  • Distributions after a physician certifies a terminal illness.

SECURE 2.0 added more exceptions for plan years beginning after December 31, 2023:

  • Birth or adoption of a child, up to $5,000, repayable within three years.
  • Domestic abuse victims, up to the lesser of $10,500 (the 2026 inflation-adjusted limit) or 50% of the vested balance.9Internal Revenue Service. 2026 Amounts Relating to Retirement Plans and IRAs, as Adjusted
  • Emergency personal expenses, one withdrawal of up to $1,000 per calendar year, self-certified, with three years to repay if you choose.

Each exception waives only the 10% penalty. The withdrawal itself is still ordinary income on your return.

Roth 401(k) Withdrawals

Roth 401(k) contributions were made with after-tax dollars, so the treatment on the way out is different. The question is whether your distribution is “qualified.”10Internal Revenue Service. Retirement Topics – Designated Roth Account

A qualified distribution comes out entirely tax-free and penalty-free, earnings included. Two conditions must both be met: you’re 59½ or older (or the distribution follows disability or death), and at least five tax years have passed since your first Roth 401(k) contribution to that plan. The five-year clock starts on January 1 of the year of that first contribution.

If either condition fails, the distribution is non-qualified. Your original contributions still come back tax-free, but the earnings portion is taxed as ordinary income and hit with the 10% penalty if you’re under 59½. And Roth 401(k) rules do not let you pull “contributions first” the way a Roth IRA does. Every non-qualified withdrawal is treated as a proportional mix of contributions and earnings. Take $5,000 when the account holds $9,400 in contributions and $600 in earnings, and $4,700 comes out tax-free while $300 is taxable, with the penalty applied to that $300 if no exception covers you.11Internal Revenue Service. Retirement Plans FAQs on Designated Roth Accounts

Moves That Don’t Show Up as Income

Not every 401(k) transaction is taxable. A direct rollover, where the plan administrator sends your funds straight to another 401(k) or an IRA, produces no taxable income because you never receive the money.12Internal Revenue Service. Rollovers of Retirement Plan and IRA Distributions

If the check is instead made out to you, the plan must withhold 20% for federal tax before it leaves. You then have 60 days to deposit the full original amount (including the withheld 20%, which you’d need to replace out of pocket) into a qualifying account. Miss the 60 days and the entire distribution becomes taxable income, plus the 10% penalty if you’re under 59½.

A 401(k) loan isn’t a taxable event either, as long as it follows the rules: up to the lesser of $50,000 or 50% of your vested balance, repaid within five years with at least quarterly payments (longer for a primary home purchase).13Internal Revenue Service. Retirement Topics – Plan Loans But default changes everything. If you miss payments or leave the job without repaying, the outstanding balance is treated as a deemed distribution: taxable income, and subject to the 10% penalty if you’re under 59½.14Internal Revenue Service. Hardships, Early Withdrawals and Loans

How It Actually Appears on Your Return

Your plan administrator issues Form 1099-R to you and the IRS for any distribution of $10 or more. Expect it by early February.15Internal Revenue Service. About Form 1099-R

Box 1 shows the gross distribution. Box 2a shows the taxable amount, which for a traditional 401(k) is usually identical to Box 1. Box 4 shows federal tax already withheld, which credits against your total tax the same way wage withholding does. Box 7 carries a distribution code:16Internal Revenue Service. Instructions for Forms 1099-R and 5498 (2025)

  • Code 1: early distribution, no known exception.
  • Code 2: early distribution, exception applies (such as a QDRO).
  • Code 7: normal distribution after age 59½.
  • Code G: direct rollover, non-taxable.

The Box 1 amount goes on the pensions and annuities line of Form 1040, with the Box 2a taxable amount next to it. If your 1099-R shows Code 1 but you qualify for an exception the plan didn’t know about (Rule of 55, medical expenses, one of the SECURE 2.0 provisions), you claim the exception on Form 5329 by entering the appropriate code, which removes the 10% penalty from the calculation.17Internal Revenue Service. Instructions for Form 5329 (2025)

Required Minimum Distributions Starting at 73

Once you turn 73, the IRS requires you to withdraw a minimum amount from your traditional 401(k) each year. Your first RMD is due by April 1 of the year after you turn 73; each later one is due by December 31. Many plans let you delay RMDs while you’re still working for the sponsoring employer.18Internal Revenue Service. Retirement Topics – Required Minimum Distributions (RMDs)

Missing an RMD carries a 25% excise tax on the shortfall. Take the missed amount within two years and the penalty drops to 10%. You can request a full waiver on Form 5329 with a written explanation of the reasonable error and the fix.19Internal Revenue Service. Retirement Plan and IRA Required Minimum Distributions FAQs

Each RMD is ordinary income. If you delay the first one to April 1, you’ll still owe the second by December 31 of that same year, and doubling up can push you into a higher bracket.

Ripple Effects: Medicare and Social Security

Distribution income doesn’t stop at your tax bill. It flows into two calculations that matter for retirees.

Medicare Part B and Part D premiums are income-tested. If your modified adjusted gross income clears certain thresholds, you pay a surcharge called IRMAA. For 2026, it starts at $109,000 for individuals and $218,000 for married couples filing jointly. MAGI here is AGI plus tax-exempt interest.20Social Security Administration. POMS HI 01101.010 – Modified Adjusted Gross Income (MAGI) The catch is the timing: IRMAA uses your tax return from two years earlier, so a large 2024 withdrawal drives your 2026 premiums. The lowest surcharge adds $81.20 per month to Part B; at the top tier (individual MAGI of $500,000 or more), the Part B surcharge reaches $487 per month.21Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles

A withdrawal can also make more of your Social Security taxable. The formula adds your AGI, any nontaxable interest, and half of your Social Security benefits. For single filers, benefits start becoming taxable above $25,000, and up to 85% can be taxed above $34,000. For joint filers, the thresholds are $32,000 and $44,000. These numbers were set in 1983 and 1993 and have not been indexed to inflation.22Social Security Administration. Income Taxes on Social Security Benefits Qualified Roth 401(k) distributions don’t count in this formula.

State Income Tax

Most states tax 401(k) distributions as ordinary income at their own rates, which reach as high as 13.3%. Roughly a dozen states either have no income tax or specifically exempt retirement plan distributions, and some tax them only in part depending on age or amount. State withholding rules also vary: some require withholding whenever federal tax is withheld, others let you opt out, and no-income-tax states withhold nothing. If you moved during the year, the state where you’re a legal resident on the distribution date generally has the taxing authority.

Don’t Let the 20% Withholding Fool You

The 20% mandatory withholding on a lump-sum distribution sounds like a lot, but it often isn’t. In the 24% or 32% bracket you’ll owe more than that, and the 10% penalty (if it applies) is on top. Add state tax and the gap gets wider.1Internal Revenue Service. 401(k) Resource Guide – Plan Participants – General Distribution Rules

The IRS expects tax to be paid across the year. If your total withholding doesn’t cover at least 90% of this year’s liability or 100% of last year’s, you can face an underpayment penalty even after paying the full bill at filing. For a large mid-year withdrawal, you can ask the plan to withhold more than the default 20%, or make quarterly estimated payments to close the gap.23Internal Revenue Service. Topic No. 306, Penalty for Underpayment of Estimated Tax

The most useful thing you can do before pulling money is run the numbers first. Add the withdrawal to your projected income, look up your combined federal and state rate, and factor in the 10% penalty if it applies. Treat the 20% withheld at the source as a deposit, not the final bill.