Yes, traditional 401(k) contributions are pre-tax: the money is taken out of your paycheck before federal income tax is calculated, which lowers your taxable income for the year. Roth 401(k) contributions work the other way around. You pay income tax on your full salary first, and then the contribution goes into the account. The choice between the two decides whether you get the tax break now or in retirement.
What “Pre-Tax” Actually Means on Your Paycheck
When you elect traditional 401(k) contributions, your employer diverts part of your salary into the plan before calculating federal income tax withholding.1Office of the Law Revision Counsel. 26 USC 401 – Qualified Pension, Profit-Sharing, and Stock Bonus Plans Your taxable income drops dollar for dollar. Earn $70,000, contribute $10,000, and the IRS treats your federal taxable income as $60,000 for the year. If the reduction pushes you into a lower marginal bracket, the tax savings grow.
Most states with an income tax treat pre-tax 401(k) contributions the same way, so your state taxable income usually falls as well.
One thing pre-tax status does not change: Social Security and Medicare taxes. FICA is withheld on your full salary, including the amount you defer.2Internal Revenue Service. Topic No. 424, 401(k) Plans That applies whether you choose traditional or Roth. The “pre-tax” label refers to income tax only.
How Roth 401(k) Contributions Differ
Roth 401(k) contributions are after-tax. Your employer withholds federal and state income tax on your full salary, and then the contribution goes into a designated Roth account.3Office of the Law Revision Counsel. 26 USC 402A – Optional Treatment of Elective Deferrals as Roth Contributions A $10,000 Roth contribution does not lower your taxable income for the year. You pay tax on that money at your current rate.
The payoff comes later. Qualified withdrawals in retirement, including every dollar of investment growth, are completely tax-free. Two conditions have to be met: the Roth account must have been open for at least five tax years, and you must be at least 59½.4Internal Revenue Service. Retirement Plans FAQs on Designated Roth Accounts The five-year clock starts on January 1 of the tax year you made your first Roth contribution to that plan. Roth funds rolled in from a previous employer’s plan can carry the earlier clock over.
How Each Type Is Taxed When You Withdraw
The pre-tax choice reverses at retirement. Traditional 401(k) distributions are taxed as ordinary income in the year you take them.5Internal Revenue Service. 401(k) Resource Guide – Plan Participants – General Distribution Rules Withdraw $40,000, and the full $40,000 gets added to your taxable income. Both your original contributions and all the investment earnings are taxable, because neither was taxed on the way in.
Qualified Roth 401(k) distributions are tax-free, contributions and growth alike, because the income tax was paid up front.4Internal Revenue Service. Retirement Plans FAQs on Designated Roth Accounts If a Roth withdrawal fails the five-year or age-59½ test, the earnings portion loses its tax-free status.
Any taxable distribution paid directly to you rather than rolled over to another retirement account is subject to a mandatory 20% federal income tax withholding.5Internal Revenue Service. 401(k) Resource Guide – Plan Participants – General Distribution Rules Your final tax bill may end up higher or lower, but that withholding is automatic.
What About the Employer Match?
Employer matching contributions have historically gone into a pre-tax account regardless of whether your own contributions were traditional or Roth.6Internal Revenue Service. Retirement Topics – Contributions The SECURE 2.0 Act now lets employers deposit matching contributions directly into your Roth account if the plan document permits it.7Internal Revenue Service. SECURE 2.0 Act Impacts How Businesses Complete Forms W-2 Most employers still use the traditional pre-tax method.
What that means in practice: even if you contribute 100% to a Roth 401(k), the match sitting alongside your Roth balance is likely pre-tax money that will be taxed when you withdraw it. Check your plan documents or a recent statement to see how your match is being treated.
Employer matches also often vest on a schedule. Leave before you are fully vested and you forfeit the unvested portion. Your own contributions, traditional or Roth, are 100% yours from day one.
Traditional or Roth: How to Think About the Choice
The core question is where you expect your tax rate to be higher: today or in retirement.
Traditional contributions favor you if your current marginal rate is higher than the rate you expect to pay on withdrawals later. You take the deduction now, at the steeper rate, and pay tax later at the lower rate. This is the common case for people in their peak earning years who expect a lower income in retirement.
Roth contributions favor you if your current rate is lower than what you expect later, or if you want a pool of retirement money that will not add to your taxable income when you draw it down. Roth also has a structural advantage on the back end: Roth 401(k) accounts are exempt from required minimum distributions during the account owner’s lifetime under the SECURE 2.0 Act.8Internal Revenue Service. Retirement Plan and IRA Required Minimum Distributions FAQs Traditional balances trigger RMDs starting at age 73.
You do not have to pick one or the other. Most plans that offer a Roth option let you split contributions between traditional and Roth, subject to a combined annual limit set by the IRS. Splitting hedges the bet: some of your retirement income comes out taxable, some tax-free, and you keep flexibility over which bucket to draw from each year.
One practical note before you set your election: if your employer matches, contribute at least enough to your traditional or Roth account to capture the full match. The pre-tax versus after-tax question matters, but forgoing free money to optimize your own tax treatment usually costs more than it saves.