Roth accounts use post-tax money, not pre-tax
A Roth IRA or Roth 401(k) is funded with money you have already paid income tax on. You do not get a tax deduction in the year you contribute. The tradeoff is that when you withdraw the money in retirement, you owe no federal income tax on the earnings — only the contributions themselves come out tax-free, because you already paid tax on them.
This is the opposite of a traditional IRA or traditional 401(k), where you contribute pre-tax dollars and reduce your taxable income in the year you contribute. You then pay income tax on withdrawals in retirement.
The choice between Roth and traditional comes down to whether you expect to be in a higher or lower tax bracket when you retire. If you think your tax rate will be lower later, traditional makes sense now. If you think it will be higher, or you want tax-free growth, Roth is the better bet.
Key Takeaways
- Roth contributions come from your after-tax paycheck, so you get no tax deduction in the year you contribute.
- Earnings in a Roth account grow tax-free, and you withdraw them tax-free in retirement if you follow the rules.
- Traditional accounts let you deduct contributions now but require you to pay tax on withdrawals later.
- Your income level may limit how much you can contribute to a Roth IRA, though Roth 401(k) contributions have no income cap.
How post-tax contributions work in practice
When you contribute to a Roth IRA, the money comes straight from your checking account after taxes have already been withheld. If you earn $50,000 and contribute $7,000 to a Roth IRA, you do not reduce your taxable income to $43,000. You still report $50,000 in income on your tax return, and you pay tax on all of it.
With a Roth 401(k) through your employer, the contribution is deducted from your paycheck, but it is deducted after payroll taxes are calculated. Your gross pay is still subject to federal income tax withholding, Social Security tax, and Medicare tax. The Roth 401(k) contribution does not lower any of those.
The IRS does not care that you already paid tax on the money. What matters is that you did, and that fact is recorded when you file your return. Years later, when you withdraw, the IRS knows the contribution was post-tax and does not tax it again.
The tax-free growth advantage
The real benefit of a Roth is not the contribution — it is what happens to your money while it sits in the account. Any interest, dividends, or investment gains inside a Roth grow without being taxed each year. In a regular taxable brokerage account, you would owe tax on those gains every year. In a Roth, you owe nothing until you withdraw.
And when you do withdraw in retirement, as long as you follow the rules, you owe no tax on any of it — not the contributions, not the earnings. A traditional account taxes you on the full withdrawal amount, including earnings you never paid tax on.
This is why Roth accounts are often better for younger workers who have decades for money to grow. The longer the money sits, the more earnings accumulate tax-free.
Income limits for Roth IRA contributions
The IRS limits who can contribute to a Roth IRA based on income. For 2024, if you file as single, you can contribute the full amount only if your modified adjusted gross income is below $146,000. The ability to contribute phases out between $146,000 and $161,000. Above $161,000, you cannot contribute to a Roth IRA at all.
These limits change every year. If your income is too high for a Roth IRA, you may still be able to use a Roth 401(k) through your employer, which has no income limit. You can also explore a backdoor Roth strategy, though that involves more steps and tax reporting.
Traditional IRAs and 401(k)s have no income limits, which is one reason higher earners sometimes use them instead.
Roth 401(k) versus Roth IRA
Both use post-tax money and offer tax-free growth, but they work differently. A Roth IRA is an individual account you open on your own. You can contribute up to $7,000 per year (or $8,000 if you are 50 or older). There is no income limit on earnings inside the account, and you can withdraw contributions anytime without penalty.
A Roth 401(k) is offered by your employer. You can contribute up to $23,500 per year (or $31,000 if you are 50 or older). There is no income limit. However, you cannot withdraw contributions before age 59½ without a penalty, just like a traditional 401(k).
If your employer offers a Roth 401(k), you can contribute to both a Roth IRA and a Roth 401(k) in the same year, as long as you have the income to cover both.
When to choose Roth over traditional
Roth makes the most sense if you expect to be in a higher tax bracket in retirement than you are now. This is often true for younger workers earning less early in their careers. It is also a good choice if you want to lock in current tax rates before they rise, or if you want withdrawals in retirement that do not count toward income thresholds that affect Medicare premiums or Social Security taxation.
Roth is less attractive if you need the tax deduction now to lower your current taxable income, or if you expect to be in a much lower tax bracket in retirement. Someone nearing retirement with high income might benefit more from a traditional 401(k) deduction today.
Many workers use both: a traditional 401(k) to reduce current taxes and a Roth IRA for tax-free growth on additional savings. The right mix depends on your situation and your guess about future tax rates.
Withdrawal rules and the five-year clock
With a Roth IRA, you can withdraw contributions anytime, tax-free and penalty-free. Earnings are different. You can withdraw earnings tax-free only if you are 59½ or older and the account has been open for at least five years. If you withdraw earnings before then, you owe income tax and a 10% penalty on the earnings portion.
A Roth 401(k) has stricter rules. You cannot withdraw contributions or earnings before 59½ without a penalty, even if the account is old. The five-year rule still applies to earnings. Some employers allow loans from a Roth 401(k), which is another way to access money without a withdrawal.
The five-year clock resets if you roll a Roth 401(k) into a Roth IRA, so timing matters if you are switching jobs.
Frequently Asked Questions
Do I pay taxes twice on Roth money?
No. You pay income tax once, when you earn the money. That tax is withheld from your paycheck or paid when you file your return. When you contribute to a Roth and when you withdraw in retirement, you do not pay tax again on the contributions themselves. Earnings are taxed once at withdrawal, but only if you withdraw before age 59½ or within five years of opening the account.
Can I deduct Roth contributions on my taxes?
No. Roth contributions are not deductible. You report them on your tax return for informational purposes, but they do not reduce your taxable income. This is the defining difference from a traditional IRA or 401(k), where the contribution itself lowers your income for the year.
What happens if I exceed the Roth IRA income limit?
If your income is above the limit, you cannot contribute to a Roth IRA that year. Some people use a backdoor Roth strategy: they contribute to a traditional IRA (which has no income limit) and then convert it to a Roth. This involves tax reporting and may trigger taxes if you have other traditional IRA balances, so consult a tax professional first.
Is a Roth 401(k) better than a Roth IRA?
Neither is universally better. A Roth 401(k) lets you contribute more money per year and has no income limit, but it locks your money until 59½. A Roth IRA has lower contribution limits and income restrictions, but you can withdraw contributions anytime. If your employer offers both, you can use them together.
Do I have to pay taxes on Roth withdrawals in retirement?
No, as long as you follow the rules. You must be 59½ or older and the account must be at least five years old. If both conditions are met, all withdrawals — contributions and earnings — are tax-free. If you withdraw early, you owe tax and penalties only on the earnings portion, not the contributions.