What is the difference between Roth and traditional 401(k) contributions?

Traditional (pre-tax): contributions reduce your taxable income now; you pay taxes when you withdraw in retirement. Roth (after-tax): contributions are taxed now; withdrawals in retirement are tax-free including growth. The total amount of money in your account is the same — the difference is when you pay taxes.

Should I choose Roth or traditional?

Choose traditional if you expect lower tax rates in retirement than now (common for peak earners). Choose Roth if you expect higher tax rates in retirement than now (common for early career), if you want tax-free income in retirement, or if you want to hedge against future tax rate changes. Many advisors recommend a split — contribute to both to diversify your tax exposure.

What if I do not know what my tax rate will be in retirement?

You probably do not know. For this reason, many financial planners recommend tax diversification — holding both pre-tax (traditional) and post-tax (Roth) assets. This gives you flexibility to draw from different buckets in retirement based on your tax situation at that time, which may be favorable in some years and not others.

Is there an income limit for Roth 401(k)?

No income limit for Roth 401(k) contributions — this is different from Roth IRA, which has income limits. Anyone with access to a Roth 401(k) through their employer can contribute regardless of income. Roth IRA contributions in 2026 phase out at $150,000–$165,000 (single) and $236,000–$246,000 (MFJ).

Can I contribute to both Roth and traditional in the same year?

Yes. You can split contributions between Roth and traditional within your 401(k), as long as the combined total does not exceed the annual limit ($23,500 in 2026). For example: contribute $12,000 to traditional and $11,500 to Roth. You can also hold both a traditional IRA and a Roth IRA, subject to their respective rules.

Should I Contribute to Roth or Traditional 401(k)?

The Only Question That Matters

The Roth vs. traditional choice is fundamentally about when you pay taxes:

Traditional: pay taxes later (in retirement) on both the original contribution and all growth
Roth: pay taxes now on the contribution; all growth and withdrawals are tax-free

If your tax rate will be lower in retirement → traditional saves more money overall. If your tax rate will be higher in retirement → Roth saves more money overall. If your tax rate stays the same → they produce identical outcomes.

The Math

Mathematically, if tax rates are the same, Roth and traditional are equivalent. Here is a simplified illustration:

$10,000 to invest, 25% tax rate, 7% growth for 30 years:

Option	After-Tax Contribution	Growth	Withdrawal	Taxes at Withdrawal	Net
Traditional	$10,000 pre-tax	$76,123	$76,123	25% = $19,031	$57,092
Roth	$7,500 after-tax	$57,092	$57,092	$0	$57,092

Equal results, assuming equal tax rates.

The difference emerges only when the current rate and future rate diverge.

Who Benefits from Roth

Early Career, Lower Income Now

A 25-year-old in the 22% bracket who expects to be in the 24–32% bracket at peak earning years has a strong argument for Roth contributions now — paying 22% taxes today rather than 32% later.

Roth IRA Eligibility

Roth IRA contributions are only available under the income limits ($150,000–$165,000 single, $236,000–$246,000 MFJ in 2026). High earners lose access to Roth IRA contribution. A Roth 401(k) — available regardless of income — may be the primary way high earners access Roth benefits.

Desire for Tax-Free Income in Retirement

Roth distributions do not count as taxable income. For retirees managing income to control Medicare premium tier, tax bracket on Social Security benefits, or RMD impacts, having a Roth bucket to draw from tax-free has substantial planning flexibility value.

No Required Minimum Distributions (Roth IRA)

Roth IRAs are exempt from required minimum distributions (RMDs). Roth 401(k)s currently follow RMD rules, but can be rolled to a Roth IRA to avoid them. For people who want to let assets continue compounding beyond age 73, Roth IRAs avoid the forced withdrawal requirement that applies to traditional accounts.

Who Benefits from Traditional

Peak Earners

Someone in the 32–37% bracket now who expects to draw down retirement income at a 22% effective rate is clearly better off deferring taxes. The traditional 401(k) generates a larger tax deferral benefit when current rates are high.

State Tax Considerations

High state income tax states (California, New York, New Jersey at 9–13%) add substantial weight to the traditional argument during working years. If retirement will occur in a lower- or no-income-tax state, the benefit of deferring is amplified.

Immediate Cash Flow

Traditional contributions reduce your tax bill now. A $1,000 traditional contribution in the 24% bracket reduces your current year tax by $240. For people with tight cash flow, the traditional tax break today is a tangible benefit.

The Diversification Argument

For most people, the actual answer is: both.

You do not know what tax rates will look like in 20–30 years. Tax law changes, you may have unexpected income in retirement, Social Security and RMDs can push you into higher brackets than anticipated. Holding both traditional (pre-tax) and Roth (post-tax) retirement assets gives you options at withdrawal time to optimize your tax situation in any environment.

Practical split for uncertainty:

Contribute to traditional 401(k) for the tax break now
Fund a Roth IRA separately (if income eligible)
Or split contributions: 50/50 or 2/3 traditional + 1/3 Roth within the 401(k)

Simplified Decision Guide

Situation	Recommendation
Early career, lower income	Lean Roth
Mid-career, moderate income, uncertain future rate	Split or Roth IRA + traditional 401(k)
Peak earner, high bracket now	Lean traditional
High income, over Roth IRA limit	Roth 401(k) for Roth access
Want flexibility in retirement withdrawals	Split or hold both