Yes. A 401(k) does take money out of your paycheck. Once you’re enrolled, your employer withholds the contribution amount you chose—either a percentage of pay or a flat dollar figure—from each paycheck and deposits it into your retirement account before the money ever reaches your bank. Whether that deduction lowers the income tax withheld from the same paycheck depends on whether you’re contributing to a traditional or a Roth 401(k).
Traditional vs. Roth: When You Pay the Tax
Both types of 401(k) reduce your take-home pay by the same dollar amount. The difference is when the IRS gets its cut.
Traditional 401(k)
With a traditional 401(k), your employer subtracts your contribution from your gross pay before calculating federal income tax withholding. Your taxable wages for that pay period drop by the amount you contributed, and your year-end W-2 shows a lower federal taxable income figure.1Internal Revenue Service. 401(k) Plan Overview Most states follow the same treatment. You’ll owe income tax on the money later, when you withdraw it in retirement.
Roth 401(k)
Roth contributions work the other way around. Your employer calculates federal and state income tax withholding on your full gross pay first, then takes your Roth contribution out of what remains. Your W-2 reflects your entire salary as taxable income for the year, with no reduction for the Roth amount.1Internal Revenue Service. 401(k) Plan Overview The upside comes later: qualified withdrawals in retirement, including all investment growth, come out tax-free.
Social Security and Medicare Still Come Out
A common misconception is that traditional 401(k) contributions escape all payroll taxes. They don’t. Both traditional and Roth deferrals stay subject to Social Security tax (6.2% of wages up to the annual wage base) and Medicare tax (1.45% of all wages, plus an additional 0.9% on earnings above $200,000).2Internal Revenue Service. Retirement Plan FAQs Regarding Contributions – Are Retirement Plan Contributions Subject to Withholding for FICA, Medicare or Federal Income Tax
The practical effect on your paystub: a traditional 401(k) deduction cuts your federal (and usually state) income tax withholding, but the Social Security and Medicare lines stay the same as they would without the deferral.
How Much Can Come Out
Federal law caps how much of your paycheck you can defer into a 401(k) each year. For 2026, the employee contribution limit is $24,500.3Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500 This cap covers your combined traditional and Roth deferrals across every employer you work for during the year, not per plan.4Office of the Law Revision Counsel. 26 USC 402 – Taxability of Beneficiary of Employees Trust
If you’re 50 or older, you can add $8,000 in catch-up contributions for a personal limit of $32,500. Workers aged 60 through 63 get a larger catch-up of $11,250 under a SECURE 2.0 provision, bringing their cap to $35,750.3Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
How the Deduction Starts
Nothing comes out of your paycheck until you’re enrolled. That happens in one of two ways.
Active Enrollment
You submit a contribution election through your employer’s benefits portal or on a paper form, picking a contribution percentage or dollar amount and choosing traditional, Roth, or a split. Without that authorization, your employer can’t withhold retirement money from your wages.
Automatic Enrollment
Many employers auto-enroll new hires at a default rate. Under a qualified automatic contribution arrangement, the starting rate is typically 3% of pay, rising by one percentage point each year until it reaches at least 6%, with a cap of 10%.5Internal Revenue Service. Retirement Topics – Automatic Enrollment Under SECURE 2.0, most 401(k) plans set up after December 29, 2022, must auto-enroll eligible employees once the plan has been operating for three years. Businesses with fewer than 10 employees and older plans are exempt.
If you were auto-enrolled and don’t want to participate, you can opt out. Most plans let you pull back contributions made during the first 30 to 90 days without penalty. You can also stay in and adjust your rate up or down at any time.6Internal Revenue Service. Operating a 401(k) Plan
Changing or Stopping the Deduction
Your plan has to allow you to change your contribution amount at least once a year.7Internal Revenue Service. Mid-Year Changes to Safe Harbor 401(k) Plans and Notices In practice, most plans let you make changes any time through an online portal, and the change usually takes effect within one or two pay cycles. You can increase your rate, drop it, or stop contributing entirely. Stopping doesn’t remove you from the plan or touch the money already in your account. It just means nothing new comes out of future paychecks.
If your plan uses automatic escalation, your rate can climb on its own each year unless you actively pick a different number. Check your paystub after each plan anniversary so the deduction still fits your budget.
Employer Matching Doesn’t Come From Your Paycheck
If your employer matches contributions—say, 50 cents for every dollar you defer up to 6% of salary—that match is not deducted from your paycheck. It’s a separate deposit your employer makes into your 401(k) account. You won’t see a matching line on your paystub, and the match doesn’t affect your gross or net pay. Cutting your own deferral below the match threshold means giving up money your employer would otherwise pay you.
Loan Repayments Are a Second Paycheck Deduction
If your plan permits loans and you borrow from your 401(k), the repayments also come out of your paycheck as their own deduction. You can borrow up to the lesser of $50,000 or half your vested balance, and the loan generally has to be repaid within five years in substantially equal payments made at least quarterly (home purchase loans can run longer).8Office of the Law Revision Counsel. 26 USC 72 – Annuities; Certain Proceeds of Endowment and Life Insurance Contracts Most employers set up automatic payroll withholding for repayments, so you’ll see a second retirement-related line on your paystub alongside your regular contribution.
Loan repayments are made with after-tax dollars whether your account is traditional or Roth. If a paycheck can’t cover a scheduled repayment—because of reduced hours, unpaid leave, or a pay cut—the missed payment can push the loan into default. A defaulted loan that isn’t fixed becomes a deemed distribution, meaning the IRS treats the outstanding balance as taxable income for that year.9Internal Revenue Service. Plan Loan Failures and Deemed Distributions If you’re under 59½, an additional 10% early withdrawal penalty may apply. To avoid default, you can make a lump-sum payment for the missed installments or ask your plan administrator to reamortize the loan at a higher payment going forward.10Internal Revenue Service. 401(k) Plan Fix-It Guide – Participant Loans Dont Conform to the Requirements of the Plan Document and IRC Section 72(p)
Checking Your Paystub and W-2
Your paystub is the quickest way to confirm the right amount is coming out. Look in the deductions section for a line labeled “401(k),” “Retirement,” or a similar abbreviation. Many payroll systems list traditional and Roth deductions on separate lines. A loan repayment shows up as its own line item. Each deduction usually shows both the current-period amount and a year-to-date total, which helps you track progress toward the annual limit.
At year-end, your W-2 reports 401(k) activity in Box 12 using letter codes. Code D means traditional (pre-tax) deferrals; Code AA means designated Roth contributions.11Internal Revenue Service. Common Errors on Form W-2 Codes for Retirement Plans Checking these codes against your final paystub of the year is a simple way to catch payroll errors before you file.
Plan fees generally don’t appear on your paystub. Investment expense ratios come out of your investment returns, and administrative or individual service fees are deducted from your account balance rather than your wages.12U.S. Department of Labor. A Look at 401(k) Plan Fees
What If Too Much Comes Out
If your paycheck deductions push you past the $24,500 employee limit for 2026—easy to do if you switch jobs mid-year and both employers withhold contributions—the excess is included in your taxable income for the year it was contributed. To avoid being taxed on the same money twice, notify your plan administrator and have the excess (plus any earnings on it) distributed back to you by April 15 of the following year.13Internal Revenue Service. Consequences to a Participant Who Makes Excess Deferrals to a 401(k) Plan The deadline doesn’t move even if you file a tax extension.
Miss April 15 and the excess stays in the plan, then gets taxed a second time when you eventually withdraw it in retirement. You don’t get any basis credit for the amount already taxed, so there’s no way to recover the double tax later.13Internal Revenue Service. Consequences to a Participant Who Makes Excess Deferrals to a 401(k) Plan If you hold multiple jobs in the same year, track your combined year-to-date deferrals and dial back your contribution rate at one employer before you hit the cap.