Roth 401(k) vs Traditional 401(k)
Roth 401(k) vs Traditional 401(k)
A Roth 401(k) combines the contribution ceiling of a 401(k) ($23,500 in 2024) with tax-free growth like a Roth IRA. The trade-off is the same: no current-year deduction, but tax-free withdrawals in retirement. Choose Roth if you believe you will earn similar or higher income in retirement; choose Traditional if you expect lower income or value current tax relief.
Key takeaways
- Roth 401(k) contributions are after-tax and do not reduce current taxable income, but all growth is tax-free and withdrawals are tax-free.
- The $23,500 annual limit (2024) applies to combined Traditional and Roth contributions; you cannot max out both.
- Roth 401(k)s are subject to Required Minimum Distributions (RMDs) starting at age 73; Roth IRAs have no lifetime RMDs.
- The decision between Traditional and Roth 401(k) mirrors the IRA decision: marginal rate now versus marginal rate in retirement.
- High earners should prioritize capturing employer match in Traditional form (free tax savings), then split additional contributions based on expected retirement income.
The mechanics: same contribution limit, split between types
If your employer offers both Traditional and Roth 401(k) options, you choose how to allocate your contributions between them. The annual limit of $23,500 (2024) is a combined cap. You could contribute $15,000 Traditional and $8,500 Roth, or $23,500 all-Roth, or any split that totals $23,500. You cannot contribute $23,500 to Traditional and another $23,500 to Roth.
This differs from IRAs, where you can max out both a Traditional IRA and a Roth IRA in the same year if income permits (total $7,000 each in 2024, but their limits are separate from each other). With 401(k)s, the unified limit forces a choice: Traditional or Roth, or a split.
The Roth 401(k) contribution is made after-tax. Your paycheck is reduced, but the contribution does not reduce your taxable income. If you contribute $500 per paycheck to a Roth 401(k), your taxable income stays the same, but your take-home is reduced by $500 (plus any applicable payroll taxes, which still apply to Roth contributions). You sacrifice more immediate cash flow but gain tax-free withdrawal rights later.
In contrast, a Traditional 401(k) contribution reduces both your taxable income and your take-home by approximately the same amount (adjusted for the tax savings). A $500 contribution to Traditional at a 24% marginal rate reduces taxable income by $500 and take-home by approximately $380 ($500 minus the $120 tax savings).
Why high earners often choose Roth 401(k)
High earners frequently choose Roth 401(k) contributions for a simple reason: they cannot deduct Traditional IRA contributions (income phase-out), and they are locked out of direct Roth IRA contributions (income limit). Roth 401(k) contributions have no income limits. A software engineer earning $300,000 can contribute the full $23,500 to a Roth 401(k) with no restrictions.
For this engineer, the choice is straightforward: contribute to a Roth 401(k) rather than Traditional. The engineer likely earns $200,000+ in retirement (substantial assets, high-income withdrawals), so the Traditional deduction is not valuable (expecting high marginal rate in retirement anyway). The Roth provides tax-free growth and withdrawal, which is superior.
A household where both spouses earn high incomes and have access to Roth 401(k)s might contribute $47,000 per year ($23,500 each) to Roth. Over 30 years at 7% growth, this compounds to approximately $4.7 million in tax-free retirement assets. The couple pays tax on contributions upfront but receives tax-free withdrawal rights forever. This is a powerful long-term wealth structure.
Roth 401(k) RMDs: a trap and a workaround
Unlike Roth IRAs, Roth 401(k)s are subject to Required Minimum Distributions (RMDs) starting at age 73. If you have $2 million in a Roth 401(k) at 73, you must begin withdrawing a percentage each year based on life-expectancy tables, just like a Traditional 401(k).
This is a meaningful disadvantage compared to a Roth IRA, which has no lifetime RMDs. For someone planning to leave money untouched for decades or pass it to heirs, a Roth 401(k) RMD obligation is friction.
However, there is a workaround: if you retire and no longer work for the employer sponsoring the Roth 401(k), you can roll the Roth 401(k) into a Roth IRA. The conversion itself is tax-free (you are moving after-tax Roth money to after-tax Roth money). Once in a Roth IRA, the RMD obligation disappears for your lifetime.
Example: You retire at age 65 with a $1.5 million Roth 401(k) at your former employer. You roll it to a Roth IRA. You can now leave the $1.5 million untouched until your death, and it grows tax-free for 20+ years without forced withdrawals. At your death, heirs inherit the Roth IRA and can continue tax-free growth (under current rules, though SECURE Act provisions are complex for non-spouse heirs).
This rollover eliminates the RMD trap. Many retirees with Roth 401(k)s should plan to roll them to Roth IRAs immediately upon separation from the employer. There is no tax or penalty; it is a straightforward administrative move.
Account-type matching strategy
For households juggling multiple account types, a practical strategy is:
-
Contribute enough to Traditional 401(k) to capture the full employer match. Match is free money and typically tax-deductible when earned, so capture it in Traditional form to get the tax deduction.
-
If you are high-income and expect similar income in retirement, fill remaining 401(k) capacity with Roth 401(k). This enables tax-free growth at high income levels, which Roth IRAs block via income limits.
-
If you are moderate-income and expect lower retirement income, add more to Traditional 401(k) after capturing the match. The current-year deduction is more valuable when you expect lower brackets later.
-
Max out backdoor Roth IRA if available ($7,000 per person, 2024, no income limit). This provides more Roth growth capacity without RMD risk.
Example for a high-earning couple:
- Both earn $200,000 combined; employer offers 50% match on first 6% of salary.
- Both contribute 6% to Traditional 401(k) to capture match (employer match is also Traditional).
- Both contribute remaining 401(k) capacity ($13,500 each) to Roth 401(k).
- Both execute backdoor Roth IRAs ($7,000 each).
- Total annual tax-free account funding: $47,000 (Roth 401(k) $27,000 + backdoor Roth $14,000) + $6,000 Traditional employer match.
Over 30 years, this strategy shelters substantial sums in tax-free accounts while capturing free employer money.
Decision flowchart
Next
Roth 401(k)s and backdoor Roths are tools for high savers. But all employees, regardless of income, should prioritize one thing above all: capturing their employer match. The next article clarifies why matching money is the highest-return investment most people will encounter.