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Roth 401(k) contributions are taxed today, but qualified withdrawals can be received free of federal income tax. Understanding the timing of the tax can help you understand how a Roth 401(k) differs from a traditional pre-tax 401(k).
The central Roth benefit is the different timing of taxation: contributions are made with after-tax dollars, while qualified distributions can generally come out without federal income tax.
When a distribution satisfies the Roth qualified-distribution requirements, both contributions and associated earnings can generally be excluded from gross income.
Investment growth inside the Roth account is not taxed annually simply because the account increases in value. Qualified distributions can generally exclude those earnings from income.
Having both pre-tax and Roth retirement savings can provide different tax treatments when retirement income is eventually withdrawn.
Roth 401(k) participation does not have the income limitation that applies to direct Roth IRA contributions.
Roth 401(k) contributions share the 401(k) elective-deferral limit with traditional 401(k) contributions, rather than using the much smaller IRA contribution limit.
If your employer offers both options, you may be able to divide your elective deferrals between traditional pre-tax and designated Roth contributions, subject to applicable limits and plan rules.
The biggest difference is not whether taxes exist. It is largely when the tax treatment occurs.
Taxes generally apply to the Roth contribution in the year you earn the income.
Eligible pre-tax elective deferrals generally receive tax treatment when contributed, with taxable distributions later.
The example below illustrates the tax treatment concept. It is not a prediction of investment returns or future tax rates.
Imagine $10,000 is contributed to a Roth 401(k) and, over time, the account grows to $25,000.
“Tax-free” does not mean every withdrawal is automatically tax-free. Roth 401(k) earnings generally receive tax-free treatment when the distribution is qualified.
One reason people compare Roth and traditional contributions is that the tax rate today may differ from the tax rate that applies to future taxable retirement income.
Roth contributions are included in gross income when made. Qualified distributions can generally be excluded from gross income.
Traditional pre-tax contributions generally receive tax-deferred treatment, while taxable distributions generally create income later.
The tax impact depends on factors such as taxable income, filing status, deductions, other retirement income, future tax law and the specific plan and distribution circumstances.
Use this simple illustration to compare the contribution amount with an illustrative tax rate. This is not a tax calculation or tax advice.
At a 22% illustrative rate, $10,000 of Roth contributions would correspond to $2,200 of illustrative income tax on the contribution. Qualified future Roth withdrawals are generally excluded from gross income.
If your plan permits Roth contributions and matching contributions, your employer may use Roth deferrals when calculating its match.
Your Roth contribution is included in your income for tax purposes in the year of the contribution.
If the plan formula permits it, Roth deferrals can be used when determining the matching contribution.
Employer matching contributions generally cannot be deposited directly into the designated Roth account under the IRS rules.
Understanding the conditions for qualified distributions is just as important as understanding the Roth tax benefit itself.
A qualified distribution generally requires the applicable five-taxable-year period to have been satisfied.
A distribution can generally qualify when made on or after age 59½, provided the applicable five-year requirement is also met.
Qualified-distribution rules also recognize certain distributions after death or on account of disability.
A nonqualified distribution may result in taxable earnings, and an additional 10% tax may apply to taxable amounts in some early-distribution situations.
Roth 401(k) owners are generally not required to take lifetime RMDs from designated Roth accounts while alive under current rules.
Roth contributions do not generally reduce current federal taxable income like traditional pre-tax elective deferrals can.
The 2026 employee elective-deferral limit for a 401(k) is $24,500. Traditional and Roth 401(k) elective deferrals share this limit. Catch-up contributions may provide additional room for eligible participants.
Designated Roth contributions are included in gross income when contributed.
Earnings can generally be withdrawn tax-free when the distribution is qualified.
Roth 401(k) participation itself is not subject to the Roth IRA income limitation.
Roth and traditional elective deferrals count toward the same applicable employee deferral limit.
A plan may calculate an employer match using Roth deferrals, while the employer contribution is maintained separately.
Roth and traditional accounts can provide different tax treatments for future retirement withdrawals.
Explore the rest of the Roth 401(k) cluster for contribution, withdrawal, employer-match and comparison topics.
Compare Roth and traditional 401(k) treatment, then explore the contribution and retirement calculators on 401k.blog.
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