Roth vs Traditional 401(k) and IRA

Traditional cuts your tax now, Roth cuts it later. The 2026 limits, the new mandatory Roth catch-up, and the costs the tax-rate question misses.

"Roth or Traditional?" sounds like a tax-code puzzle. It is really one question with two answers, and the whole thing turns on when you would rather pay the tax. This spoke sits under the Retirement hub.

The short version is easy. The part almost every explainer leaves out is that your tax rate is not the only thing riding on the answer — and between 60 and 65, it is not even the expensive part.

The core trade

• Traditional (401(k) or IRA): you deduct the contribution now and pay ordinary income tax on every dollar you withdraw later. Tax break today.
• Roth: you contribute after-tax dollars now, and qualified withdrawals later are tax-free. Tax break later.

Same money, two different bets on your own future tax rate.

Side by side

The differences that actually change a decision, rather than the ones that fill a chart:

Three rows there are worth stopping on.

The 401(k) limit is shared. $24,500 is the total across Roth and pre-tax deferrals, not each. Same for the IRA limit across Roth and traditional IRAs. Choosing Roth does not buy you more room.

The super catch-up replaces, it does not stack. At 60 to 63 you get $11,250 instead of $8,000, not in addition to it. That takes a 50-year-old's ceiling of $32,500 to $35,750 — a real increase, but not the two-catch-ups-added-together figure some articles print. The catch-up planner works out yours.

Roth accounts no longer have lifetime RMDs — including in a 401(k). Roth IRAs never did. Designated Roth 401(k) and 403(b) accounts stopped in 2024 under SECURE 2.0. The IRS states it plainly: the RMD rules "do not apply to Roth IRAs or Designated Roth accounts while the owner is alive." Note that several IRS explainer pages still carry the pre-2024 language. The RMD FAQ is the one that is current.

The case for paying tax now

Roth wins when the rate you avoid later is higher than the rate you pay today.

• You expect a higher rate in retirement. Common for younger savers, people early in their careers, and anyone with a large pre-tax balance that will eventually be forced out as RMDs.
• You want no RMDs. A traditional balance gets pulled out on the government's schedule starting at 73 or 75, whether you need the money or not. Roth money has no such deadline, which is the single most underrated feature of the account.
• You want a lever on your own taxable income later. A Roth withdrawal does not raise the income figures that drive ACA subsidies, Medicare surcharges, or how much of your Social Security gets taxed. That flexibility has a dollar value, and it is largest in exactly the years the next section is about.
• You think tax rates rise. Nobody knows. But paying a known rate today beats a guess if the guess is bad.

The case for paying tax later

Traditional wins when today's rate is the higher one.

• You are in your peak earning years and will drop into a smaller bracket once the salary stops.
• The deduction is worth more than the exemption. A dollar deducted at a high marginal rate is a real, immediate, certain saving. Roth's benefit is a forecast.
• You will retire into a low-income window. If you stop work at 60 and have several years before Social Security and RMDs begin, you may be able to pull that money out — or convert it — at a much lower rate than you deducted it at. That window is the whole basis of the Roth conversion ladder.

Since you are guessing about future tax law and your own future income, the honest answer is that nobody knows for sure. Which is why the default at the end of this page is a hedge, not a winner.

From 2026, high earners cannot make the catch-up pre-tax

This is new, and it catches people out.

If your prior-year Social Security (FICA) wages from the employer sponsoring your plan exceeded $150,000, SECURE 2.0 requires your catch-up contributions for 2026 to be Roth. Pre-tax is not an option for that portion.

Two details matter. The wage test is per plan-sponsoring employer, not per household and not on your total income — so someone with no FICA wages from that employer (a self-employed partner, for instance) is not caught by it. And the widely quoted $145,000 is the statutory base figure, not the live number: it is indexed, and Notice 2025-67 raised it. Final regulations arrived as T.D. 10033.

If you earn too much for a Roth IRA

An article about Roth versus Traditional that never mentions this has a hole in the middle of its own topic: you may not be allowed to contribute to a Roth IRA at all.

Direct Roth IRA contributions phase out between $153,000–$168,000 for single filers and $242,000–$252,000 for married couples filing jointly. Above the top of your range, the amount you can contribute is zero.

Two things to know:

• A Roth 401(k) has no income limit. If your plan offers one, that door stays open at any income. For most high earners this is the answer, and it is boring, which is why it gets less attention than the next bullet.
• The backdoor Roth — making a non-deductible traditional IRA contribution and converting it — is not blocked by the income limits, because conversions have no income limit. But it is governed by the pro-rata rule, and this is where people get hurt.

The pro-rata rule works like this. For tax purposes the IRS does not look at the one account you just funded. It aggregates all of your traditional, SEP and SIMPLE IRA balances and treats them as a single pot. Your after-tax basis is spread across the whole pot, so a conversion comes out proportionally taxable, no matter which account the money physically left. As Publication 590-B puts it: "Until all of your basis has been distributed, each distribution is partly nontaxable and partly taxable." Form 8606 does the arithmetic.

The practical consequence: if you have a large pre-tax rollover IRA sitting there, a backdoor Roth is mostly a taxable event, not a free one. A 401(k) balance is not counted in the pro-rata pot, which is why people sometimes roll an IRA into a 401(k) first. That is a real strategy with real trade-offs, and it is beyond this page.

The tax-rate question is not the whole cost

Most explanations stop at "compare your rate now and later." That is incomplete, and the gap is expensive.

Traditional withdrawals and Roth conversions raise your reported income. Roth withdrawals do not. Several things key off that income figure, and two of them have a price tag.

Before 65 — the ACA subsidy cliff. The enhanced premium tax credits expired on 31 December 2025. For 2026, household income one dollar over 400% of the federal poverty line forfeits your entire premium tax credit — not a slice of it, all of it. For a single person that line is $62,600. A conversion done "to be efficient" at 61 can cost the tax plus five figures of lost premium help. See health care before Medicare and the ACA bridge tool.

From 63 — Medicare IRMAA. Medicare surcharges use your income from 2 years earlier. So the return you file at 63 sets your premium at 65. Cross the first tier — $109,000 single, $218,000 joint — and it costs roughly $1,148 for that year, per person on Medicare. Higher incomes hit higher tiers, which cost considerably more.

Neither of these means "avoid conversions." It means the years between 60 and 65 are when the Roth question stops being theoretical and starts having a dollar value attached. The conversion cost checker prices all three effects together.

The senior deduction changes the bet — until it does not

This page is built on one premise: that you can compare today's rate with your retirement rate. The One Big Beautiful Bill Act made that comparison harder.

From 2025, people aged 65 and over get an extra deduction of $6,000 each — $12,000 for a couple where both qualify — available whether or not they itemise. It phases out at higher incomes and disappears entirely well before the top brackets.

Two honest caveats, both of which cut against building a plan around it:

1. It expires. The deduction is scheduled to end after 2028. A saver choosing Roth today on the strength of a lower retirement rate should not assume this deduction is still there when they retire. It requires an act of Congress to survive.
2. It is not "no tax on Social Security." The thresholds that decide how much of your benefit is taxed — combined income above $25,000 single, $32,000 joint — were not changed, and they have never been indexed. They are the same nominal dollars set in the 1980s and 1990s. Every year of inflation drags more retirees over them.

So: the senior deduction genuinely lowers the retirement tax rate for a stretch of years, which strengthens the Traditional case for someone retiring soon. It does nothing for someone retiring in 2040. Do not let a temporary deduction settle a permanent question.

The plain default: hedge

Because the future is unknowable, most people are best served by holding both. Not as a compromise, but as an asset: two tax pools let you choose, year by year, which dollars to take — filling a low bracket with traditional withdrawals, then topping up from Roth without touching your ACA or IRMAA figures. That is the mechanism behind a plain withdrawal plan, and you cannot use it if everything you own is in one bucket.

And before any of this: capture the full employer match. An instant 50–100% return beats the Roth-versus-Traditional question outright, and beats almost everything else in personal finance. Note that the match itself is pre-tax by default — a Roth match exists only if your plan chose to offer it, and it is taxable to you in the year it lands.

Key takeaways

• Traditional is a tax break now; Roth is a tax break later. Pick the one that avoids your higher rate.
• The 401(k) and IRA limits are shared across Roth and pre-tax. Choosing Roth buys no extra room, and the 60–63 super catch-up replaces the standard one rather than stacking on it.
• From 2026, a 50+ saver with prior-year wages over $150,000 from the plan sponsor must make the catch-up as Roth.
• High earners are phased out of direct Roth IRA contributions. The Roth 401(k) has no income limit; the backdoor route works but the pro-rata rule can make it expensive.
• Before 65 a conversion can cost your whole ACA credit; from 63 it raises your Medicare premium 2 years later. Model it in the conversion cost checker before you act.

Educational only — not financial or tax advice.