Estimated reading time: 10 minutes
The Roth 401k vs traditional 401k choice usually gets presented as a bet on whether tax rates will rise. I read it differently. As a CFP® and fee-only fiduciary, I plan around your personal bracket arc: the gap between the rate you pay on income today, at peak earnings, and the rate you will pay when you finally draw that money out in retirement.
That arc has a particular shape for the executive women I work with. Once you hold $1.5 million or more in investable assets, the pre-tax balance you are building today matures into required withdrawals and Medicare surcharges in your 70s. So the 2026 numbers below are inputs to one calculation: your marginal rate now versus your likely rate later. This post walks through both sides of it, including the new rule that forces many high earners into Roth contributions this year whether they chose them or not.
Table of contents
- What Is the Difference Between a Roth 401(k) and a Traditional 401(k)?
- The 2026 Contribution Limits
- Roth 401(k) vs Traditional 401(k): When Pre-Tax Wins, When Roth Wins
- The Bracket Arithmetic: A Worked Example
- Why High Earners Should Rarely Choose 100% Either Way
- What to Do This Week
- Frequently Asked Questions
- Sources
What Is the Difference Between a Roth 401(k) and a Traditional 401(k)?
A traditional 401(k) takes your contribution before tax: you exclude it from income now and pay ordinary income tax on every dollar you withdraw in retirement. A Roth 401(k) reverses the order: you contribute after-tax dollars today, and qualified withdrawals, including all the growth, come out tax free. Both share one combined contribution limit, which is $24,500 for 2026.
Beyond the tax treatment, the two behave identically day to day. Same investment menu, same payroll deduction, same plan. Changing your election is a form, and you can direct any percentage to each side. Also worth knowing: the Roth 401(k) has no income cap on contributions. Unlike a Roth IRA, which phases out at higher incomes, you can fund a Roth 401(k) on a $700,000 salary.
One wrinkle: employer matching dollars typically land in the pre-tax bucket unless your plan has adopted Roth matching. As a result, even someone who elects 100% Roth usually retires holding both tax treatments anyway.
The 2026 Contribution Limits
For 2026, you can defer up to $24,500 into a 401(k) in any mix of Roth and traditional. If you are 50 or older, you can add an $8,000 catch-up contribution, and at ages 60 through 63 the catch-up rises to $11,250. Then comes the change that surprises executives: if your 2025 Social Security wages from your employer exceeded $150,000, every catch-up dollar you contribute in 2026 must go in as Roth.
| 2026 limit | Amount | What it means for you |
|---|---|---|
| Employee deferral | $24,500 | Combined cap across Roth and traditional |
| Catch-up, age 50+ | $8,000 | Total of $32,500 if you are 50 or older |
| Catch-up, ages 60 to 63 | $11,250 | Total of $35,750 in those four years |
| Mandatory Roth catch-up | 2025 wages over $150,000 | All 2026 catch-up dollars must be Roth |
Treasury finalized the Roth catch-up requirement in September 2025 under the SECURE 2.0 Act, and it took effect January 1, 2026. Because the test looks only at wages from the employer sponsoring your plan, a mid-2025 job change can leave your catch-up unrestricted for one more year. I made a video walking through exactly this rule: If You Earn Over $150K and You’re Still Making Catch-Up Contributions, Watch This First.
Two related strategies sit outside these limits, and I keep them out of this post deliberately. After-tax contributions above the $24,500 line belong to the mega backdoor Roth conversation, and moving existing IRA dollars to Roth belongs to Is a Roth IRA Conversion Right for You. Meanwhile, if you are still deciding whether maxing out is the right move this year, start with Should I Max Out My 401(k).
Roth 401(k) vs Traditional 401(k): When Pre-Tax Wins, When Roth Wins
Pre-tax wins when your marginal bracket today is higher than the bracket you expect in retirement. Roth wins when that order flips, or when your pre-tax balance is already large enough that future required withdrawals will set your retirement bracket for you. Because most executive women I meet sit between those poles, the honest answer is usually a percentage rather than a pure election.
| Dimension | Traditional 401(k) | Roth 401(k) |
|---|---|---|
| Tax break timing | Deduction now; contribution excluded from 2026 income | No break now; qualified withdrawals tax free |
| Tax on withdrawals | Ordinary income tax on every dollar | Zero on qualified withdrawals |
| RMDs | Required beginning at age 73 | None during your lifetime (2024 onward) |
| The bracket bet | You expect a lower bracket in retirement | You expect an equal or higher bracket later |
| Best-fit profile | Peak earner in the 32% to 37% bracket with a moderate pre-tax balance | Saver with a large pre-tax balance, or in a temporarily low-income year |
The RMD row deserves emphasis. Since 2024, Roth 401(k)s no longer require lifetime distributions, a SECURE 2.0 change that removed the old reason to roll them into a Roth IRA. Traditional balances, however, must start paying out at 73 whether you need the income that year or not.
The Bracket Arithmetic: A Worked Example
Here is the arithmetic with real 2026 numbers. Dana is a hypothetical composite: 54, a chief marketing officer, married filing jointly, with $460,000 of taxable income. For 2026, the 32% bracket for joint filers runs from $403,551 to $512,450, so her contributions come off the top at 32%. A $24,500 pre-tax deferral saves her $7,840 in federal tax this year.
Now project the withdrawal side. Suppose her retirement taxable income lands around $250,000, inside the 24% joint bracket in 2026 terms. Pulling that same $24,500 out at 24% costs $5,880. Deduct at 32, repay at 24: the pre-tax choice wins by $1,960 per year of contribution, before state taxes. So far, traditional looks obvious.
Then run the part most calculators skip. Dana already holds $1.4 million pre-tax. Compounding at an assumed 6% for 19 years, that balance alone reaches roughly $4.2 million by age 73, even with no further contributions. Her first required withdrawal would be about $160,000 ($4.2 million divided by 26.5, the IRS life expectancy factor at 73). Stacked on Social Security and portfolio income, that forced income can push her right back into the 32% bracket she deducted against, and past the Medicare surcharge line as well. Consequently, her projected retirement bracket is a moving target that her own balance keeps raising.
Why High Earners Should Rarely Choose 100% Either Way
At the $1.5 million level and above, I recommend a deliberate split far more often than a pure election. A split hedges the bracket bet, and it builds a tax-free bucket you will want later for large one-time expenses, a car, a roof, a daughter’s wedding, without spiking that year’s taxable income.
Medicare is the quiet reason this matters. Your 2026 premiums are set by your 2024 income: the standard Part B premium is $202.90 per month, and surcharges begin once joint MAGI passes $218,000 ($109,000 for single filers). Traditional 401(k) withdrawals count toward that number every single year. Qualified Roth withdrawals stay out of it entirely. For a couple with large pre-tax balances, RMDs plus Social Security can lock in those surcharges for decades, which is why I model this interaction in my retirement tax playbook.
In practice, my framework runs like this. During 35% or 37% bracket years, tilt heavily pre-tax and let the mandated Roth catch-up do the tax-free building. During a 24% or lower year (a sabbatical, a business loss, the gap between retirement and RMDs), tilt hard toward Roth. In between, a split such as 70% traditional and 30% Roth keeps both buckets growing while you watch how the arc develops.
What to Do This Week
Pull your 2025 W-2 and check Box 3. If your Social Security wages passed $150,000, your 2026 catch-up contributions must be Roth. Confirm your plan offers a Roth option, because without one you cannot make catch-ups at all this year.
Find your true marginal bracket. Take taxable income from line 15 of your Form 1040 and place it in the 2026 tables. For joint filers, 32% starts above $403,550 and 35% above $512,450; for single filers, 32% starts above $201,775.
Estimate your age-73 pre-tax balance. Compound your current traditional balances to age 73 at a conservative return, then divide by 26.5 for a first-year RMD estimate. If that figure plus Social Security clears $218,000 jointly, your future bracket problem is already forming, so tilt new dollars toward Roth.
Set your 2026 election as a percentage split, then calendar a December review. A bonus, an equity vest, or a planned sabbatical can move your bracket, and your split should move with it before payroll closes the year.
Frequently Asked Questions
Should I split my 401(k) between Roth and traditional?
For most high earners, yes. A split hedges the gap between your bracket today and your bracket in retirement, which no one can forecast precisely. In 2026, all $24,500 of your deferral can be divided in any percentage. A common starting point in peak-earning years is a majority traditional with a meaningful Roth slice, adjusted whenever your income changes.
Do Roth 401(k)s have required minimum distributions?
No. Beginning with the 2024 tax year, SECURE 2.0 eliminated lifetime RMDs from designated Roth 401(k) accounts, matching the Roth IRA treatment. Traditional 401(k) balances still require distributions starting at age 73. Beneficiaries who inherit a Roth 401(k) do remain subject to post-death distribution rules, so the exemption applies during the owner’s lifetime only.
Does a Roth 401(k) have income limits?
No income limit blocks Roth 401(k) contributions. While Roth IRA eligibility phases out at higher incomes, a Roth 401(k) accepts the full $24,500 deferral for 2026 at any salary. The only income-based rule is the catch-up requirement: 2025 wages above $150,000 force your 2026 catch-up contributions, though never your regular deferrals, into Roth form.
What happens to my catch-up contributions in 2026 if I earned over $150,000?
If your 2025 Social Security wages from your current employer exceeded $150,000, every 2026 catch-up dollar ($8,000 at 50 plus, or $11,250 at ages 60 to 63) must be designated Roth. Many plans will convert your election automatically. However, if your plan offers no Roth feature, you cannot make catch-up contributions at all until it adds one.
Is a Roth 401(k) better than a traditional 401(k) for high earners?
Often, partially. A high earner in the 35% or 37% bracket usually benefits from pre-tax deferrals today. Yet once pre-tax balances grow large, future RMDs and Medicare surcharges erode that advantage, so adding Roth alongside traditional protects the later years. The stronger your balance sheet, the more the Roth share earns its place.
If you would like a second set of eyes on your own split before payroll closes out the year, book a free 15-minute Align Call. We will look at your bracket, your balances, and your 2026 election together. Whether we work together or not, you’ll walk away with clarity on your best next step.
Sources
- IRS: 401(k) limit increases to $24,500 for 2026, IRA limit increases to $7,500
- IRS Notice 2025-67: 2026 Amounts Relating to Retirement Plans and IRAs
- IRS: Treasury, IRS issue final regulations on the new Roth catch-up rule and other SECURE 2.0 Act provisions
- Federal Register: Catch-Up Contributions (Final Rule, September 16, 2025)
- IRS Revenue Procedure 2025-32: 2026 Inflation-Adjusted Tax Rate Tables
- IRS: Retirement Plan and IRA Required Minimum Distributions FAQs
- IRS Publication 590-B: Uniform Lifetime Table (Life Expectancy Factors)
- CMS: 2026 Medicare Parts A & B Premiums and Deductibles
All information is for educational purposes only and should not be considered financial, tax, or investment advice.