Traditional vs. Roth 401(k): The Tax Difference

The core difference

A traditional 401(k) and a Roth 401(k) can sit inside the very same plan, offered by the very same employer, invested in the very same funds. The only thing that differs is the tax treatment of your contribution:

• Traditional 401(k): contributions are deducted from your paycheck before income tax is calculated, lowering your taxable income today. The entire balance — contributions and all growth — is taxed as ordinary income when you withdraw it in retirement.
• Roth 401(k): contributions are made after income tax has already been withheld, so there's no upfront deduction. If the withdrawal is "qualified" (see below), both your contributions and all the growth come out completely tax-free.

What makes a Roth 401(k) withdrawal “qualified”

A Roth 401(k) distribution is tax-free only if it satisfies both of these conditions:

1. At least five tax years have passed since your first Roth contribution to that plan (the "five-year rule"), and
2. You are at least 59½, disabled, or deceased (in which case the rule applies to your beneficiary).

If you withdraw before meeting both conditions, the earnings portion of the distribution is taxable, and may be subject to the 10% early withdrawal penalty on top of that. Note that the five-year clock for a Roth 401(k) is tracked separately from the five-year clock on a Roth IRA — rolling a Roth 401(k) into a Roth IRA can, in some cases, let you count against whichever clock started earlier.

Employer matching is always pre-tax by default

The SECURE 2.0 Act gave employers the option to let employees choose to have employer contributions treated as Roth as well. If your plan offers this, the matched amount is included in your taxable income in the year it's contributed (since your employer is effectively paying you money that you're choosing to have taxed now), but it then grows and can be withdrawn tax-free under the same rules as your own Roth contributions. This is an employer-plan option, not a right — check whether your plan has adopted it.

Which one lowers your tax bill more?

This is a projection question, not a legal one, and the honest answer is "it depends on your future tax bracket" — which nobody can know for certain. As a general (not universal) rule of thumb people use:

• If you expect to be in a lower tax bracket in retirement than you are now, a traditional 401(k)'s upfront deduction is often more valuable.
• If you expect to be in a similar or higher bracket later — or you simply want to lock in today's known tax rate on the dollars you're saving — a Roth 401(k) can make sense.
• Many savers split contributions between both to diversify their future tax exposure.

This page describes the mechanics only; it isn't personalized advice, and a tax professional can model your specific situation.

Required minimum distributions

As of the SECURE 2.0 Act, Roth 401(k) balances are no longer subject to required minimum distributions during the original account owner's lifetime — that requirement was eliminated starting in 2024, bringing Roth 401(k)s in line with how Roth IRAs have always worked. Traditional 401(k) balances are still subject to RMDs. See required minimum distributions for the current starting age.