Roth 401(k) vs. Traditional 401(k) in 2026: Which One Should You Choose?

David earns $180,000 a year and maxes out his 401(k). For years, he'd been contributing entirely to the traditional pre-tax option because "that's what his advisor told him to do in his 40s."

Now he's 57. He's starting to think about RMDs, IRMAA, and what his tax bill will look like at 72 with $2 million sitting in a pre-tax account generating mandatory withdrawals he may not need.

"Should I have been doing Roth all along?" he asked.

Maybe. Maybe not. The right answer depends on the specific tax comparison between now and later — and it's more nuanced than most rules of thumb suggest.

The Core Logic: Now vs. Later

The Roth vs. traditional decision ultimately comes down to one question: will you pay a higher or lower tax rate when you withdraw the money?

The "other factors" are where the real planning happens.

Two SECURE 2.0 Changes That Favor Roth 401(k) in 2026

Change 1: No More RMDs from Roth 401(k)

This is significant. Before 2024, Roth 401(k) accounts were subject to Required Minimum Distributions — meaning even though you'd pay no tax on the withdrawals, you were still forced to take distributions.

SECURE 2.0 eliminated RMDs from Roth 401(k) accounts during the owner's lifetime, bringing them in line with Roth IRAs.

Why this matters:

• You can leave a Roth 401(k) untouched for decades longer
• The tax-free growth compounds without forced distributions
• Your estate passes more tax-efficient assets to heirs
• It reduces the "double taxation" problem of large traditional IRA RMDs

For anyone who doesn't plan to spend down their 401(k) in retirement, this alone shifts the math toward Roth.

Change 2: High-Income Catch-Up Must Be Roth (Starting 2026)

If you earn over $145,000 from the plan's employer, your catch-up contributions (including the enhanced 60–63 catch-up) must go into a Roth 401(k). This is a forced Roth contribution for high earners — but it also means more high earners are building Roth balances even if they weren't previously.

The Tax Bracket Comparison

Here's how to think about the actual numbers.

Current marginal rate: What rate will the pre-tax contribution save you today?

Expected retirement rate: What effective rate will you pay on withdrawals?

The retirement rate is harder to estimate because it depends on:

• Total income from all sources (Social Security, pensions, RMDs, part-time work)
• Whether the tax cuts in the Tax Cuts and Jobs Act are extended (currently set to partially sunset)
• IRMAA — high traditional IRA balances mean large RMDs, which drive Medicare premium surcharges
• State taxes in your retirement state vs. current state

When Traditional 401(k) Still Wins

• You're in the 32%, 35%, or 37% federal bracket now and expect to be in the 22% or 24% bracket in retirement
• You have strong evidence you'll move to a no-income-tax state in retirement
• You expect to spend down most of your portfolio and don't care about RMDs or estate efficiency
• You're within 5 years of retirement and won't benefit much from Roth's long-term compound advantage

When Roth 401(k) Wins

• You're in the 22% or 24% bracket now (historical norms suggest these are not the highest rates ever)
• You're concerned about future tax rate increases — rates could rise after 2025 TCJA sunset provisions
• You want to minimize future RMDs (reducing IRMAA exposure, keeping Medicare premiums low)
• You're more than 10 years from retirement and want maximum tax-free compounding
• You're in the 60–63 enhanced catch-up window and required to use Roth if you earn over $145,000
• You have other large pre-tax accounts and want diversification of tax exposure

The Split Contribution Strategy

Many advisors now recommend splitting contributions between traditional and Roth 401(k):

• Contribute enough to traditional to capture the tax saving at your current marginal rate
• Route remaining contributions to Roth to build tax-free flexibility

Example (single, $180,000 income, 24% bracket):

• First $100,000 of income: up to the 22% bracket ceiling
• Income above $100,000: in 24% bracket
• Pre-tax contributions that reduce income from 24% to 22%: strong case for traditional
• Additional contributions beyond that: Roth (no incremental traditional benefit at those income levels is compelling vs. future flexibility)

This isn't a formula — it's a starting framework. The specific numbers matter.

A Note on the Roth Conversion Alternative

If you've been contributing traditional for years and are now reconsidering, Roth conversions offer a way to shift balance without giving up the original tax deduction. The tax you pay on conversion (at your current rate) is the cost of future tax freedom.

For many people in David's situation — large pre-tax balances, approaching retirement — a series of targeted Roth conversions in the 22% bracket during early retirement may be more valuable than changing future contributions.

Both strategies — Roth contributions going forward, conversions of existing balances — can run simultaneously.

Connect with a retirement advisor to model your specific contribution strategy and how much of your 401(k) should be pre-tax vs. Roth.