Taking money out of a 401k does not affect your Social Security benefits in the way most people fear: your monthly check will not shrink. Social Security calculates your benefit from your earnings history alone, and 401k distributions are not earnings. What withdrawals can do is make more of your benefit taxable and push you into higher Medicare premium brackets, so the real question isn’t whether your check changes but how much of it you get to keep.
The Earnings Test Does Not Count 401k Money
If you claim Social Security before full retirement age and keep working, the Social Security Administration can temporarily withhold part of your benefit through the earnings test. In 2026, the threshold is $24,480. For every $2 you earn above it, $1 in benefits is withheld until you reach full retirement age.1Social Security Administration. 2026 Cost-of-Living Adjustment (COLA) Fact Sheet
The word that matters is “earned.” The earnings test counts wages from a job and net self-employment income. It does not count 401k distributions, pension payments, annuities, interest, or dividends.2Social Security Administration. Will Withdrawals From My Individual Retirement Account Affect My Social Security Benefits? A large 401k withdrawal will not trigger the earnings test.3Social Security Administration. Receiving Benefits While Working
Your benefit amount itself is calculated from your highest 35 years of indexed earnings. The SSA reviews each new year of wages to see whether it ranks among that top 35, and if so, recalculates your benefit upward. Retirement account withdrawals never enter that calculation.4Social Security Administration. Benefit Calculation Examples for Workers Retiring in 2026
How Withdrawals Make Your Benefits Taxable
Your 401k won’t shrink the check, but it can shrink what you keep after taxes. The mechanism runs through what the IRS calls “combined income” (sometimes called provisional income) under 26 U.S.C. § 86. The formula: take your adjusted gross income, add any tax-exempt interest, then add half of your annual Social Security benefit. That total decides what percentage of your benefits the IRS treats as taxable.5Office of the Law Revision Counsel. 26 USC 86 – Social Security and Tier 1 Railroad Retirement Benefits
Traditional 401k withdrawals are taxed as ordinary income and flow straight into your AGI. Every dollar you pull raises your combined income, and once you cross a threshold, more of your Social Security check gets pulled into taxable territory. This is the double effect that catches retirees off guard: the withdrawal is taxed, and it also triggers additional tax on benefits they assumed were tax-free.
The Combined Income Thresholds
The thresholds have not been adjusted for inflation since 1993, so more retirees cross them every year:
- Single filers, $25,000 to $34,000: up to 50% of benefits become taxable.
- Single filers, above $34,000: up to 85% of benefits become taxable.
- Married filing jointly, $32,000 to $44,000: up to 50% of benefits become taxable.
- Married filing jointly, above $44,000: up to 85% of benefits become taxable.
- Married filing separately and living with your spouse: the base amount is zero, so benefits are taxable from the first dollar of combined income.
“Up to 85%” is not a tax rate. It means up to 85% of your benefit amount is added to your taxable income and taxed at your regular bracket. A retiree in the 22% bracket with 85% of a $24,000 annual benefit taxable would owe roughly $4,488 in additional federal tax on that Social Security income alone.
Withholding From Your Social Security Check
Social Security doesn’t automatically withhold federal tax. If you expect your combined income to make benefits taxable, you can request voluntary withholding at 7%, 10%, 12%, or 22% through your my Social Security account or by calling 1-800-772-1213.7Social Security Administration. Request to Withhold Taxes Without it, you may owe a lump sum at filing or face underpayment penalties.
Traditional Versus Roth: The Account Type Changes Everything
The impact on your Social Security tax bill depends heavily on which 401k you draw from.
A Traditional 401k was funded with pre-tax dollars. Every dollar you withdraw counts as ordinary income and lands in your AGI, which feeds the combined income formula and can drag more of your Social Security into the taxable range.
A Roth 401k was funded with after-tax dollars. Qualified distributions are completely tax-free. To qualify, you must be at least 59½ and the account must have been open for at least five years. Because qualified Roth withdrawals never appear in AGI, they don’t factor into the combined income calculation and don’t make Social Security benefits any more taxable.6Internal Revenue Service. Social Security Income FAQs That makes Roth balances especially useful for retirees trying to stay under the combined income thresholds.
One boundary worth naming: withdrawals from either account taken before age 59½ generally carry an additional 10% tax on top of any regular income tax owed, with limited exceptions.8Internal Revenue Service. Retirement Topics – Exceptions to Tax on Early Distributions
Required Minimum Distributions Force the Issue
Even if you’d rather leave your Traditional 401k alone to keep Social Security tax-free, the IRS eventually forces withdrawals. Required minimum distributions start at age 73 under the SECURE 2.0 Act, and the age moves to 75 beginning in 2033.9Internal Revenue Service. Retirement Plan and IRA Required Minimum Distributions FAQs10Fidelity. SECURE Act 2.0 – What the New Legislation Could Mean for You
RMDs apply whether or not you’ve claimed Social Security. They grow with your account balance and life expectancy, and because Traditional RMDs count as ordinary income, they push combined income up and drag more of your benefit into taxable range. Retirees who delayed claiming until 70 for a larger check often discover that RMDs starting at 73 create a surprisingly heavy tax bill.
You can delay only your very first RMD, pushing it to April 1 of the year after you turn 73. Every RMD after that is due December 31. If you push the first one into the following year, you’ll take two RMDs that year, which can spike your combined income and make a much larger share of your Social Security taxable.11Internal Revenue Service. IRS Reminds Retirees: April 1 Final Day to Begin Required Withdrawals From IRAs and 401(k)s Miss an RMD entirely, and you owe a 25% excise tax on the amount you should have taken, dropping to 10% if you correct the shortfall within two years.12Internal Revenue Service. Retirement Topics – Required Minimum Distributions (RMDs)
Starting in tax year 2024, Roth 401k balances are exempt from RMDs during the account owner’s lifetime, so they can keep growing without forced withdrawals or the Social Security tax consequences that come with them.10Fidelity. SECURE Act 2.0 – What the New Legislation Could Mean for You
Medicare Premiums Are the Second Hit
The tax bite on Social Security gets most of the attention, but 401k withdrawals also drive Medicare premiums. Medicare Part B and Part D include an income-related monthly adjustment amount (IRMAA) for higher-income retirees, based on modified adjusted gross income from two years earlier. A large Traditional 401k withdrawal in 2024 shows up on your 2026 premium.13Medicare.gov. 2026 Medicare Costs
In 2026, single filers with modified AGI above $109,000 (or $218,000 for married filing jointly) pay higher Part B premiums. The standard 2026 Part B premium is $202.90 per month. A retiree who crosses into the first IRMAA bracket ($109,001–$137,000 single or $218,001–$274,000 joint) pays $284.10 monthly for Part B plus an extra $14.50 for Part D. At the top bracket ($500,000+ single or $750,000+ joint), Part B climbs to $689.90 and Part D adds $91.00 on top of the base plan premium.14Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles
Because IRMAA uses a two-year lookback, a one-time large withdrawal or Roth conversion can raise your premium two years later even if your income drops back down. Certain life-changing events (retirement, death of a spouse, divorce) let you file Form SSA-44 to have your IRMAA recalculated using more recent income.15Social Security Administration. Medicare Income-Related Monthly Adjustment Amount – Life-Changing Event A large 401k withdrawal on its own does not qualify.
Softening the Tax Hit
The lever retirees actually control is which account they draw from and when. A few strategies stand out.
Blend Traditional and Roth withdrawals. Pulling from a Roth first keeps combined income lower because qualified Roth distributions don’t touch AGI. If you have both, you can take just enough from the Traditional side each year to stay below a combined income threshold.
Consider Roth conversions in the gap years. Between retirement and age 73, some retirees convert portions of their Traditional 401k to a Roth IRA. The conversion is taxable now, but it shrinks future RMDs and the income spike that comes when RMDs and Social Security overlap. You pay tax at a potentially lower rate today to avoid higher combined income later.
Watch the two-year IRMAA window. If you’re planning a large withdrawal or conversion, check whether it lands in a year that will raise your Medicare premium two years later. Spreading conversions across several years can keep each year below the next IRMAA bracket instead of blowing past it in one.
Set up voluntary withholding on your Social Security check if you know your combined income will make benefits taxable, and rerun the combined income calculation each year once RMDs and Social Security are both flowing.