Roth 401(k) vs. Traditional 401(k): How the Tax Timing Changes Your Paycheck and Retirement

Many workers see two 401(k) choices on an enrollment form and treat them as two different savings plans. They are not. A Roth 401(k) and a traditional 401(k) are two tax versions of the same workplace retirement account. The money can go into the same investment funds in the same plan. The difference is when tax is paid: now, with a Roth account, or later, with a traditional account.

How a traditional 401(k) works

With a traditional 401(k), contributions come out of pay before income tax is figured. That lowers taxable income in the year the money is put in. The money then grows without yearly tax on dividends or gains inside the account. Tax is due when the money is taken out in retirement, and withdrawals are taxed as ordinary income in that year.

That timing can help a worker who pays tax at a higher rate now than in retirement. It can hurt in the opposite case. A large withdrawal in one retirement year can also push that year’s income into a higher tax bracket. Federal law also requires most owners of traditional 401(k) accounts to start required minimum distributions at an age set by law. That age has risen in steps and depends on birth year, so workers should check the rule that applies to them.

How a Roth 401(k) works

With a Roth 401(k), contributions come out of pay after income tax has been paid. There is no tax break in the year the money is put in. The trade is at the other end. Qualified withdrawals in retirement are free of federal income tax, and that includes earnings if the account has been held at least five years and the owner is at least 59 and a half, or another qualifying event applies.

Unlike a Roth IRA, a Roth 401(k) has no income limit for contributions. A worker can use one only if the employer’s plan offers it. Since 2024, Roth 401(k) accounts are no longer subject to required minimum distributions during the owner’s lifetime. That change lets an owner leave the money in the account longer if the plan allows it.

What stays the same in both accounts

Both accounts are tied to an employer plan. Both take contributions from pay, often as a percentage the worker picks. Many employers match part of what a worker puts in, but match rules vary by plan, and workers should check plan documents for how matching money is taxed. The Internal Revenue Service sets a combined limit on employee contributions each year, and that limit can change from year to year. Withdrawals before age 59 and a half may be taxed and may face a 10 percent additional tax, with exceptions set by law. The rules for early withdrawals differ by account type and by whether the money is contributions or earnings.

Comparison table

	Traditional 401(k)	Roth 401(k)
What it is	A workplace retirement account funded with pre-tax pay	A workplace retirement account funded with after-tax pay
Who qualifies or gets it	Workers whose employer plan offers a traditional option	Workers whose employer plan offers a Roth option, with no income limit for contributions
Costs	No tax break is lost up front, but tax is due on withdrawals in retirement, and investment fees in the plan still apply	Tax is paid up front, so take-home pay is lower for the same contribution, and investment fees in the plan still apply
Pros	Lowers taxable income in the contribution year, and may suit a worker who expects a lower tax rate in retirement	Qualified withdrawals in retirement are free of federal income tax, and no required minimum distributions apply during the owner’s lifetime
Cons	Withdrawals are taxed as ordinary income, and required minimum distributions apply at the age set by law	No tax break in the contribution year, and the option is available only if the employer’s plan offers it

Verdict: which fits which case

Choose a traditional 401(k) if the tax break now matters most, or if a lower tax rate in retirement looks likely. The lower taxable income this year is the main gain, and the tax bill arrives later. Choose a Roth 401(k) if paying tax now looks cheaper than paying it later, or if tax-free withdrawals in retirement and no required minimum distributions during the owner’s lifetime matter more than a break this year. Many workers split contributions between the two when a plan allows it, and that split spreads the tax risk across both periods. Either choice beats leaving the money out of the plan, because the account, the match where one is offered, and the years of growth do most of the work either way.

Explainer based on program rules published by the Internal Revenue Service and the U.S. Department of Labor.