A Roth 401(k) is funded with after-tax money, not pre-tax

When you contribute to a Roth 401(k), the money comes out of your paycheck after federal income tax has already been withheld. This is the opposite of a traditional 401(k), where contributions reduce your taxable income in the year you make them. With a Roth, you pay tax on the money now, at your current tax rate, and then the money grows tax-free inside the account.

The trade-off is straightforward: you give up a tax deduction today in exchange for tax-free withdrawals later. If you withdraw money from a Roth 401(k) in retirement—both the contributions you made and the earnings they generated—you owe no federal income tax on any of it, as long as you follow the withdrawal rules.

Your employer may offer both a traditional 401(k) and a Roth 401(k) as separate accounts. Some employers offer only one or the other. The choice between them depends on whether you expect to be in a higher or lower tax bracket in retirement than you are now.

Key Takeaways

  • Roth 401(k) contributions are taken from your paycheck after taxes, so they do not lower your taxable income this year.
  • Traditional 401(k) contributions are pre-tax and reduce your income tax bill in the year you contribute, but you pay tax on withdrawals in retirement.
  • Money withdrawn from a Roth 401(k) in retirement is tax-free if you meet the account age and withdrawal timing rules.
  • Your employer's plan may offer a Roth option, a traditional option, or both—you cannot create a Roth 401(k) on your own.

How Roth and traditional 401(k) contributions work side by side

If your employer offers both types, you can split your contributions between them in the same year. For example, you might put $10,000 into a traditional 401(k) and $10,000 into a Roth 401(k), as long as your total does not exceed the annual contribution limit set by the IRS (which changes each year). The traditional portion lowers your taxable income; the Roth portion does not.

The annual contribution limit applies to both accounts combined, not to each one separately. If the limit is $23,500 in a given year, that $23,500 is your ceiling across all 401(k)s you own, whether they are Roth, traditional, or a mix of both.

Your employer may also match your contributions. In most plans, employer matching goes into the same type of account you contributed to—if you put money into a Roth 401(k), the match typically goes into a Roth 401(k) as well. Check your plan documents or ask your benefits administrator to confirm how your employer's match works.

Tax impact in retirement: the real difference

The tax treatment in retirement is where the Roth and traditional 401(k) paths diverge most sharply. With a traditional 401(k), every dollar you withdraw is taxed as ordinary income at whatever your tax rate is that year. If you withdraw $50,000 from a traditional 401(k) in retirement, that $50,000 counts as income on your tax return.

With a Roth 401(k), withdrawals of your own contributions and earnings are tax-free in retirement, provided the account has been open for at least five years and you are at least 59½ years old (or meet another exception, such as disability). This means a $50,000 withdrawal from a Roth 401(k) adds nothing to your taxable income.

The Roth advantage grows larger if your tax rate rises between now and retirement. If you are in the 22% tax bracket today but expect to be in the 32% bracket in retirement, paying tax now at 22% and withdrawing tax-free later saves you money. The opposite is true if you expect your tax rate to drop in retirement.

Required minimum distributions and Roth 401(k)s

A traditional 401(k) requires you to begin taking withdrawals—called required minimum distributions (RMDs)—starting at age 73 (as of 2023, though this age may change). You must withdraw a calculated amount each year, whether you need the money or not, and you pay income tax on those withdrawals.

A Roth 401(k) also has RMDs during your lifetime. However, once the account passes to your heirs, the rules differ. Your beneficiaries must withdraw the money within a set timeframe, but they may owe income tax on the earnings portion of those withdrawals (though not on your original contributions). This makes a Roth 401(k) a more tax-efficient inheritance tool than a traditional 401(k) in many cases.

If you do not want to take RMDs from a Roth 401(k) during your own lifetime, you can roll it into a Roth IRA, which has no RMD requirement for the original account owner. This is a common strategy for people who do not need the money and want to let it grow longer.

Income limits and who can contribute to a Roth 401(k)

Unlike a Roth IRA, a Roth 401(k) has no income limits. No matter how much you earn, if your employer offers a Roth 401(k), you can contribute to it. This makes the Roth 401(k) valuable for high earners who are phased out of Roth IRA contributions.

You must have earned income from your employer to contribute—you cannot contribute if you are not working for that employer. Self-employed people can set up a Solo Roth 401(k) if they have self-employment income, but they still need actual income to contribute.

Common mistakes when choosing between Roth and traditional

One frequent error is assuming that a Roth 401(k) is always better because withdrawals are tax-free. In reality, the choice depends on your personal tax situation. If you are young and in a low tax bracket, a Roth may make sense. If you are near retirement and in a high tax bracket, a traditional 401(k) deduction might save you more money right now.

Another mistake is forgetting that employer matches typically go into the same account type you chose. If your employer offers a generous match, confirm whether it goes into a Roth or traditional account, because that affects the total tax picture of your contributions.

A third pitfall is not understanding the five-year rule. You cannot withdraw earnings from a Roth 401(k) tax-free until the account has been open for five years, even if you are over 59½. If you open a Roth 401(k) at age 60, you must wait until age 65 to withdraw earnings without penalty.

Frequently Asked Questions

Can I contribute to both a Roth 401(k) and a traditional 401(k) in the same year?

Yes, if your employer offers both. Your combined contributions to all 401(k)s cannot exceed the annual IRS limit, but you can split that limit between Roth and traditional accounts however you choose. For example, you could contribute $15,000 to a Roth 401(k) and $8,500 to a traditional 401(k) in the same year.

Do I pay taxes on Roth 401(k) contributions when I get paid?

No, but the money is taken from your after-tax paycheck. Your employer withholds federal income tax on your gross pay first, then deducts your Roth 401(k) contribution from what remains. This is different from a traditional 401(k), where the contribution itself reduces your gross taxable income.

What happens to a Roth 401(k) if I change jobs?

You can roll the Roth 401(k) into a Roth IRA at your new employer's plan, or into a Roth IRA you open yourself. Rolling it into a Roth IRA gives you more investment choices and eliminates RMDs during your lifetime. The five-year rule for earnings still applies, based on when you first opened any Roth account.

Is the employer match in a Roth 401(k) also tax-free in retirement?

The employer match itself goes into a Roth account if you contribute to a Roth 401(k), but the match is still subject to the five-year rule and age requirements for tax-free withdrawal. The match is treated the same as your contributions for tax purposes once it is in the account.

Should I choose Roth or traditional if I am not sure what my tax rate will be in retirement?

If you are uncertain, splitting contributions between both types can hedge your bet. You get some tax savings now from the traditional contribution and some tax-free growth from the Roth. This approach reduces the risk of choosing wrong, though it requires your employer to offer both options.