The choice between a Roth and traditional 401(k) hinges on whether you prefer paying taxes now on contributions (Roth) or deferring taxes until withdrawal (traditional). Both are employer-sponsored retirement plans with similar contribution limits, but they differ in tax treatment and long-term impact based on income level and future tax assumptions.
A traditional 401(k) allows pre-tax contributions, reducing taxable income in the year funds are deposited. Growth compounds tax-deferred, and withdrawals in retirement are taxed as ordinary income. For example, contributing $10,000 annually to a traditional 401(k) lowers your adjusted gross income by that amount in the contribution year.
A Roth 401(k) uses after-tax dollars. Contributions are made with income already taxed, so growth and qualified withdrawals are tax-free. If you contribute $10,000 annually to a Roth 401(k), you pay income tax on that amount upfront, but future gains and withdrawals are not subject to federal income tax.
Both plans allow investment in stocks, bonds, mutual funds, and target-date funds. Withdrawals before age 59½ incur a 10% penalty unless an exception applies. Early distributions from a traditional 401(k) are taxed as ordinary income; early Roth withdrawals are subject to a 10% penalty on earnings, though contributions can be withdrawn tax- and penalty-free.
Traditional 401(k)s offer immediate tax relief. A person earning $75,000 who contributes $10,000 to a traditional 401(k) reduces their taxable income to $65,000. Assuming a 22% marginal tax rate, this saves $2,200 in federal income tax that year.
Roth 401(k)s provide no upfront tax benefit. The same $75,000 earner pays $2,200 in federal taxes on the $10,000 contribution, then invests the after-tax amount. Over time, if the account grows to $500,000, withdrawals are entirely tax-free.
Eligibility for Roth 401(k) contributions is not income-limited, unlike Roth IRAs. Anyone with a qualifying 401(k) plan can contribute to a Roth 401(k), regardless of income. However, not all employers offer both options-some only provide traditional 401(k)s.
| Feature | Traditional 401(k) | Roth 401(k) |
|---|---|---|
| Contribution Type | Pre-tax | After-tax |
| Tax on Contributions | Not taxed when contributed | Already taxed |
| Tax on Growth | Deferred until withdrawal | Never taxed if qualified |
| Withdrawal Taxation | Ordinary income tax | No tax if qualified |
| Required Minimum Distributions (RMDs) | Yes, starting at age 73 | Yes, starting at age 73 |
| Income Limit for Participation | None | None |
Individuals in a lower tax bracket today compared to expected retirement tax rates typically benefit more from a traditional 401(k). A 30-year-old earning $50,000 with a projected retirement income of $60,000 may face a lower tax rate in retirement, making tax deferral advantageous.
Those expecting higher tax rates in retirement-such as someone in a high-income career with stable future earnings-may gain more from a Roth 401(k). A software engineer earning $150,000 today with a 32% marginal rate would pay $48,000 in federal taxes on $150,000. If they expect to be in a 24% bracket during retirement, the Roth's tax-free withdrawals offer net savings.
According to the Internal Revenue Service (IRS), the 2024 annual contribution limit for both plans is $23,000, with an additional $7,500 catch-up contribution for those aged 50 and older. These limits apply equally to both account types.
Many assume Roth 401(k)s are only for high earners. This is incorrect. The IRS sets no income cap for Roth 401(k) participation-anyone with access through their employer can contribute. The misconception likely stems from Roth IRA income limits, which do restrict eligibility.
Another error is believing that Roth accounts are always better due to tax-free growth. While tax-free withdrawals are valuable, the upfront tax cost can reduce initial capital. A 25% tax rate on a $10,000 contribution means only $7,500 is invested. If the account grows 5% annually, it takes nearly 14 years to break even on the tax paid versus a traditional 401(k) with the same growth and a 25% tax rate at withdrawal.
Some believe they must choose one or the other. Employers offering both options allow employees to split contributions. For example, allocating 5% to traditional and 5% to Roth 401(k) provides tax diversification-some income is taxed now, some later. This strategy can hedge against uncertain future tax policy changes.
Consider two employees at the same company, both earning $80,000 annually. They each contribute $10,000 to their 401(k) annually and retire at age 65 after 35 years. Assume a 7% average annual return and a 25% tax rate at withdrawal.
Traditional 401(k) Scenario: After 35 years, the account grows to $1,147,000. Withdrawals are taxed at 25%, leaving $860,250 after tax. Total tax paid: $286,750.
Roth 401(k) Scenario: The $10,000 annual contribution is made after-tax. With a 25% rate, $2,500 is paid in taxes each year, leaving $7,500 invested. The account grows to $860,250. Withdrawals are tax-free. Total tax paid: $87,500 (on contributions).
In this case, the Roth 401(k) results in $860,250 in spendable income, while the traditional 401(k) yields $860,250 after tax. The outcomes are equal because the tax rate remains constant. But if the retirement tax rate were 15%, the traditional 401(k) would yield $974,950 after tax-$114,700 more than the Roth.
I managed my own 401(k) allocation during my early career. I contributed 10% to a traditional 401(k) and 5% to a Roth 401(k) for five years. My income was $65,000, placing me in the 22% federal bracket. The Roth portion reduced my take-home pay by $1,100 annually, but by year five, it had grown to $42,000. When I left the job, I rolled both balances into a Roth IRA and traditional IRA, respectively. The Roth portion grew tax-free, and I accessed it without penalty after five years.
My advice: if your employer offers both, consider splitting contributions. This provides flexibility in retirement planning. If you're unsure, consult a fee-only financial advisor. The National Association of Personal Financial Advisors (NAPFA) provides a directory of certified professionals who charge transparent fees.
There is no universal answer to what is better Roth or traditional 401k. The optimal choice depends on current tax rate, expected future tax rate, income stability, and risk tolerance. High earners in low brackets may benefit from Roth; younger workers with rising incomes may gain from traditional. Those near retirement should assess their tax situation carefully.