A pre-tax 401(k) takes money from your paycheck and puts it into an employer-sponsored retirement account before that contribution is included in your federal income-tax wages. The money generally remains subject to Social Security and Medicare taxes, and you generally pay income tax on pre-tax contributions and their investment earnings when they are distributed. In other words, a pre-tax 401(k) usually defers income tax rather than eliminating it.
How contributions work through payroll
If you are eligible for your employer’s plan, you elect to defer part of your compensation—often as a percentage of pay or a dollar amount. Your employer sends that amount to the 401(k), where you can invest it among the options the plan offers. The plan document determines matters such as eligibility, contribution procedures, investment choices, and when money can be accessed. The IRS explains the federal tax treatment of elective deferrals.
For federal income-tax purposes, a pre-tax deferral generally is not included in your Form W-2, box 1 wages for the year you contribute it. It is still included in wages subject to Social Security and Medicare taxes. So “pre-tax” refers to the timing of federal income tax on the contribution, not an exemption from every tax.
Example: deferring $100
If you defer $100 from pay, that $100 is generally excluded from federal income-tax wages for that year, while Social Security and Medicare taxes still apply. Your take-home pay does not necessarily fall by exactly $100: the reduction in income-tax withholding may offset part of the deferral, and the actual withholding effect depends on your circumstances and payroll settings. This is an illustration of tax treatment, not a guaranteed tax saving.
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How much you can contribute in 2026
For 2026, the IRS lists a basic 401(k) elective-deferral limit of $24,500, or 100% of compensation if that is less. Eligible participants may also be able to make catch-up contributions under applicable rules. The limit is annual and can change; check the IRS’s current contribution guidance for the rules that apply to you.
What happens to an employer match
A plan may add employer contributions tied to your deferrals, but a match is not guaranteed. Whether the employer contributes, how the match is calculated, and whether contributions are discretionary depend on the plan’s terms. Employer contributions may also be subject to a vesting schedule, which determines how much you keep if you leave the job. Review the plan document or ask the plan administrator for the match formula and vesting rules. The IRS’s 401(k) overview describes how plan features are governed by plan terms.
Pre-tax 401(k) versus Roth 401(k)
The main difference is when the contribution is taxed. A pre-tax contribution generally reduces federal income-tax wages in the contribution year, with tax generally due when the money is distributed. A designated Roth contribution is included in gross income in the year contributed; Roth contributions are not taxed again when withdrawn, and Roth earnings can be tax-free when the distribution is qualified. The IRS defines a qualified Roth distribution as one made at least five years after the first Roth contribution and after age 59½, on account of disability, or to a beneficiary after death. See the IRS guidance on Roth accounts in retirement plans.
Neither tax treatment is automatically better for everyone. The choice depends in part on whether you prefer to pay tax now or later and how your taxable income and circumstances may change. The plan’s contribution and investment terms also matter; the tax rules alone do not predict which option will be more favorable for you.
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What to expect when you withdraw money
Regular distributions and rollovers
Pre-tax 401(k) distributions are generally taxable unless the distribution qualifies for a rollover or another applicable treatment. A rollover to another eligible plan or a traditional IRA can defer tax on the amount rolled over when the rules are met. If an eligible rollover distribution is paid to you, the plan generally must withhold 20% from the taxable amount; a direct transfer from one plan to another or to an IRA has no withholding. Withholding is a payment toward taxes, not a determination of your final tax bill. Any taxable amount not rolled over is generally included in income. The IRS outlines these rules in its general distribution guidance.
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Early distributions
A taxable distribution before age 59½ may also be subject to an additional 10% tax unless an exception applies. Exceptions depend on the circumstances and account rules; hardship by itself does not automatically remove the additional tax. Your plan’s terms determine when you can take a distribution, including whether hardship withdrawals are available. Check the IRS list of exceptions to the additional tax on early distributions and confirm the rules for your situation.
Required minimum distributions
Under current IRS guidance, required minimum distributions (RMDs) from 401(k) plans generally begin at age 73. If the plan permits you to delay taking them until retirement, your first deadline generally is April 1 of the year after the later of the year you turn 73 or the year you retire; a plan can require distributions earlier. Later annual RMDs generally are due by December 31. RMDs are generally taxable except for amounts already taxed or otherwise tax-free. Timing can depend on retirement status, plan terms, and beneficiary rules, so consult the IRS’s RMD guidance and your plan administrator.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the federal rules do not settle
The rules above describe federal tax treatment. They do not establish state or local tax treatment, whether you qualify for a particular employer plan, or the terms of your plan. For a specific decision—especially a rollover, early distribution, or RMD—check the plan rules and consider advice suited to your tax circumstances.
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