Traditional 401(k) deferrals generally postpone federal income tax until withdrawal; designated Roth 401(k) deferrals are taxed in the year you contribute. Qualified Roth withdrawals can exclude earnings from income, but they must meet specific timing and qualifying-event rules.
How traditional and Roth 401(k) contributions are taxed
A traditional 401(k) deferral generally is not included in your current federal income-tax wages. The IRS says it is generally excluded from W-2 box 1 and not subject to income-tax withholding when contributed. It is still generally subject to Social Security and Medicare taxes. See the IRS guidance on 401(k) plans.
A designated Roth 401(k) deferral is made after federal income tax. The IRS says your gross income for the contribution year is higher than it would have been if you had made only pre-tax salary deferrals. A designated Roth account is part of an employer plan; it is not a Roth IRA. The IRS describes designated Roth accounts in 401(k), 403(b), and governmental 457(b) plans.
Traditional vs. Roth 401(k): the tax differences
| Tax question | Traditional 401(k) | Designated Roth 401(k) |
|---|---|---|
| When is the contribution generally included in federal income? | Generally when distributed, rather than in current income when deferred. | In the year contributed. |
| How are contributions treated when withdrawn? | Pre-tax deferrals and related earnings are generally taxable. | Contributions are not taxed again when withdrawn. |
| How are earnings treated when withdrawn? | Generally taxable as part of the distribution. | Excluded from income if paid as part of a qualified distribution; earnings in a nonqualified distribution are generally included in gross income. |
| Do account owners have lifetime required minimum distributions? | Account owners generally must begin required minimum distributions at age 73. | Owners are not required to take lifetime withdrawals from designated Roth 401(k) accounts; beneficiaries are subject to distribution rules. |
These are general federal rules, not a forecast of which option will produce the lower tax bill for you. The IRS explains the contribution and withdrawal treatment in its pages on Roth accounts in retirement plans and 401(k) plans.
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How 401(k) withdrawals are taxed
Traditional 401(k) withdrawals
Pre-tax salary deferrals and the earnings associated with them are generally taxable when withdrawn. The tax is postponed, not eliminated. Distribution circumstances can also affect whether additional tax applies.
Qualified Roth 401(k) withdrawals
To receive qualified-distribution treatment, a designated Roth distribution generally must be made after a five-taxable-year participation period and after you reach age 59½, die, or become disabled. The five-year period starts on the first day of the tax year in which you first made designated Roth contributions to the plan. Special rules can apply to certain direct rollovers from another plan. When a distribution qualifies, Roth contributions are not taxed again and the earnings are excluded from income. The IRS details these rules in its designated Roth account FAQs.
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Nonqualified Roth withdrawals
A Roth withdrawal that does not meet the qualified-distribution rules is not automatically tax-free. The earnings portion is generally included in gross income, and separate early-distribution rules may apply depending on the circumstances. The IRS outlines those rules and exceptions in its 401(k) distribution guide.
How to decide between traditional and Roth deferrals
The core decision is when you prefer to pay federal income tax: generally later on traditional deferrals, or in the contribution year on Roth deferrals. The rules alone cannot establish which choice will leave you with a lower lifetime tax bill. That depends on your tax circumstances over time, along with plan and jurisdiction details.
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- Compare the current tax cost of Roth contributions with the later taxation of traditional withdrawals.
- Consider whether you can meet the Roth qualified-distribution conditions before relying on tax-free treatment of earnings.
- Do not assume age or income alone makes one option universally better; the result depends on individual circumstances.
The federal rules here do not determine state tax treatment, personal tax outcomes, or the features of your employer’s plan. A tax professional or fiduciary financial planner can help apply the rules to your circumstances.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Required minimum distributions and 401(k) taxes
The IRS says account owners generally begin required minimum distributions at age 73. Owners are not required to take lifetime withdrawals from designated Roth accounts in 401(k) and 403(b) plans, but beneficiaries remain subject to distribution rules. This lifetime-owner exception should not be assumed to settle a beneficiary’s requirements or every plan-specific distribution question. See the IRS page on required minimum distributions.
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