Pre-tax or Roth: how to actually decide

The only question that matters

Pre-tax and Roth are the same account with the tax bill moved to a different end. A pre-tax (traditional) 401(k) deferral comes out of your paycheck before income tax, grows tax-deferred, and is taxed as ordinary income when you withdraw it. A Roth deferral is taxed now, grows tax-free, and comes out tax-free if the distribution is qualified — generally after age 59½ and five years from your first Roth contribution to that plan (IRS — Roth comparison chart).

So the question "is Roth or pre-tax better?" has one honest answer: it depends on which tax rate is lower — the one you would pay now, or the one you will pay later. Everything written about age, career stage and "tax-free growth" is a proxy for that comparison. Get the two rates right and the decision mostly makes itself.

One boundary before we start. This page covers new money. Whether to convert money already sitting in a traditional account is a different decision with different math — that belongs to the Roth conversion guide and the conversion calculator.

Why the effective rate is the honest comparison

The two rates in the comparison are not the same kind of rate, and that asymmetry is where most advice goes wrong.

Today, you save your marginal rate. A pre-tax deferral comes off the top of your income, so every dollar you defer escapes tax at your highest bracket. A household in the 22% bracket saves 22 cents per dollar deferred.

In retirement, you pay your effective rate on those dollars. Pre-tax withdrawals are taxed from the bottom up: the first slice is covered by the standard deduction and taxed at 0%, the next slice at 10%, then 12%, and so on. Take a retired married couple in 2026 whose only income is $80,000 of traditional 401(k) withdrawals. After the $32,200 standard deduction, taxable income is $47,800: the first $24,800 is taxed at 10% and the remaining $23,000 at 12%, for a federal bill of $5,240 — an effective rate of 6.6%, even though their marginal bracket is 12% (IRS — 2026 inflation adjustments, Rev. Proc. 2025-32).

That couple deferred at 22% and withdraws at under 7%. Comparing marginal-to-marginal (22% versus 12%) understates the pre-tax advantage; comparing marginal-now to effective-later shows it properly. This is why many people with ordinary retirement incomes do better with at least some pre-tax money.

The caveat cuts the other way, and it is large. Other income stacks underneath your 401(k) withdrawals. Social Security, a pension, rental income or part-time work fill the 0% and 10% bands first, and your pre-tax withdrawals land on top of them — at a higher effective rate. Required minimum distributions can force large withdrawals in years you do not need them, and the RMD tax guide shows how quickly those push a household up a bracket. The honest effective rate is the rate on your pre-tax dollars, after everything else in your retirement income has been stacked first.

The math that surprises people: equal rates, equal money

If the two rates are the same, the choice does not matter at all. Taxing a contribution at 22% and then letting it grow is arithmetically identical to letting it grow and then taxing it at 22% — the order of multiplication does not change the product.

Illustrative only. The growth rate is an assumption, not a forecast; the equality holds at any growth rate as long as both accounts hold the same investments. Investments can lose value.

Three conclusions follow. First, "tax-free growth" is not an argument for Roth by itself — the pre-tax account grows just as fast; you simply own a smaller share of it. Second, the decision is purely a bet on rates: the last two rows show that the size of the gap between today's rate and tomorrow's decides the winner. Third, when the bet is close, the tie-breakers below are what actually decide it.

Tie-breakers that favor Roth

• No lifetime required minimum distributions. Since 2024, designated Roth accounts in 401(k) and 403(b) plans are no longer subject to RMDs while the owner is alive (SECURE 2.0 §325; IRS — RMDs). Pre-tax money must come out from age 73 whether you need it or not.
• Tax-free to heirs. Most non-spouse beneficiaries must empty an inherited account within ten years. Inherited pre-tax money arrives as taxable income — often during the heirs' own peak earning years. Inherited Roth money generally comes out tax-free (IRS Pub. 590-B).
• A hedge against higher future rates. Nobody knows the 2050 rate schedule. Paying tax at a known rate removes that uncertainty for the dollars involved, and many planners value that insurance even when the expected-value math is a coin flip.
• A larger effective contribution. The $24,500 deferral limit is the same for both types, but $24,500 of Roth money is $24,500 after tax. Its pre-tax equivalent at a 22% rate is about $31,400. If you are maxing the limit and would otherwise invest the tax savings in a taxable account, Roth shelters more.
• Lower MAGI in retirement. Qualified Roth withdrawals are not income, so they do not push up the taxable portion of Social Security or Medicare IRMAA surcharges. The guide to whether Roth withdrawals count as income covers which tests they stay out of.

Tie-breakers that favor pre-tax

• The employer match is usually pre-tax regardless. Matching contributions go into the pre-tax bucket by default, so everyone who gets a match already owns some pre-tax money. SECURE 2.0 §604 lets plans offer Roth matching, but it is optional for the plan and the match becomes taxable to you in the year it is made.
• State-tax arbitrage. Deferring in a high-tax state and withdrawing after a move to a state with no income tax removes the state layer entirely. Pre-tax is the only way to capture that; Roth pays the state tax up front.
• The 0% band. Every retiree gets a standard deduction — $32,200 for married couples and $16,100 for single filers in 2026 — plus age-65 add-ons. Pre-tax dollars that fall inside it are never taxed. A retiree with no pre-tax money wastes that band every year.
• Qualified charitable distributions. From age 70½, IRA owners can give directly from their IRA to charity, tax-free, up to $111,000 in 2026 (IRS Notice 2025-67). QCDs are only worthwhile from pre-tax money, and 401(k) money must be rolled into an IRA first. If you give regularly, see the QCD limit for 2026.
• Lower AGI today. Pre-tax deferrals reduce adjusted gross income now, which can preserve credits, deductions and phase-outs tied to AGI in your working years.

The split: a decision table by bracket

Because the future is uncertain, the most defensible strategy for most households is tax diversification: owning both buckets so you can choose each year which one to draw from. Pre-tax money fills the low brackets cheaply; Roth money covers the years when another taxable dollar would cost too much — a large one-off expense, a year near an IRMAA threshold, or the years after a spouse dies and filing status changes to single.

Bracket thresholds: IRS, Rev. Proc. 2025-32. The lean is a starting point, not a rule; state tax and the tie-breakers above can move it.

The high-bracket rows rely on one habit: take the deduction now at 32% or more, then move money to Roth in the low-income window between retirement and Social Security or RMDs, when conversions can happen at 10% or 12%. That sequencing is what a Roth conversion ladder is built on. A split does not have to be 50/50 either — a common approach is to set the percentage so that projected pre-tax balances will roughly fill the standard deduction and the 12% bracket in retirement, and send everything beyond that to Roth.

Roth 401(k) vs traditional 401(k): side by side

If your plan offers both, the Roth or traditional 401k choice is the same rate comparison as above, applied inside one plan. Searches for Roth vs regular 401k usually mean exactly this: the "regular" 401(k) is the pre-tax (traditional) side, and the Roth side is a designated Roth account in the same plan, with the same investment menu and the same deferral limit. What differs is the tax treatment at each end and a handful of rules that follow from it.

Sources: IRS Roth comparison chart; IRS designated Roth accounts; IR-2025-111.

Read the table as a list of tie-breakers, not a verdict. In a Roth 401k vs traditional 401k decision, two rows settle most cases: the tax on the way in and the tax on the way out, which is the bracket table above. The rest matter at the margin. The absence of RMDs and the shared dollar limit favour Roth if you are maxing out; the AGI reduction favours pre-tax if an income-tested credit or deduction is in play this year.

A 401(k) choice also does not close the IRA door. Workplace plan coverage has no effect on whether you can contribute to a Roth IRA; only your modified AGI does, as our guide to having a Roth IRA and a 401(k) at the same time explains, with the two limits side by side.

Roth 401(k) specifics for 2026

• No income limit. A Roth IRA phases out between $153,000 and $168,000 of modified AGI for single filers and $242,000 to $252,000 for joint filers in 2026. A Roth 401(k) has no income test at all, which makes it the main Roth door for high earners (IRS — designated Roth accounts).
• One shared limit. The 2026 elective deferral limit is $24,500, combined across pre-tax and Roth. Catch-ups add $8,000 at age 50 and over, or $11,250 at ages 60 to 63 (IRS — 2026 limits, IR-2025-111).
• Separate five-year clock. Each Roth 401(k) has its own five-year period for qualified distributions, starting with your first Roth deferral to that plan. Rolling to a Roth IRA brings the IRA's clock instead.
• After-tax room above the limit. Some plans accept after-tax contributions up to the $72,000 total additions limit and let you convert them inside the plan — the "mega-backdoor Roth." The mechanics are in the in-plan Roth conversion guide.

The mandatory Roth catch-up rule

The status as of September 2026: the statute originally applied from 2024, but the IRS granted an administrative transition period through the end of 2025 (IRS Notice 2023-62). The requirement is in effect for 2026. Final regulations were published on 16 September 2025 (Federal Register — catch-up contributions); they generally apply to taxable years beginning after 31 December 2026, and for 2026 plans must follow a reasonable, good-faith interpretation of the statute.

Three practical points. The test uses FICA wages (Box 3 of your W-2) from that employer, so someone with no FICA wages from the plan sponsor — a self-employed partner, for example — is outside it. (Self-employed readers deciding between pre-tax and Roth in a SEP now have a Roth option too; see SEP IRA contribution limits for 2026.) If your plan does not offer a Roth option, it cannot accept catch-ups from affected employees at all. And the rule applies only to the catch-up; your base $24,500 can still be pre-tax, Roth or any mix.

A five-minute way to decide

1. Find your marginal bracket today from last year's return, adding any state income tax rate.
2. Estimate retirement income — Social Security, pensions, rental income — and see how much room it leaves in the standard deduction and the 10% and 12% brackets. That room is where pre-tax money is taxed lightly.
3. Pick your row in the bracket table, then adjust for the tie-breakers that apply to you: heirs, charitable giving, a planned move, or an existing pre-tax balance already large enough to fill the low brackets.
4. Always capture the full employer match, whichever type you choose.
5. Revisit the split each year. A raise, a job change, a marriage or a lower-income year can move you into a different row.