Traditional vs. Roth TSP

The choice between Traditional and Roth Thrift Savings Plan (TSP) contributions is really one choice: when you pay income tax on the money. Tax diversification means holding balances that get taxed differently when you withdraw them.

You can’t know your tax rate decades from now, or what tax law will look like then, and holding some of each is a hedge against that uncertainty. Everything else about the two accounts is detail hanging off that single idea.

Traditional contributions come out of your pay before tax. They lower your taxable income this year, grow without yearly tax, and are taxed as ordinary income when you withdraw them in retirement. In simple terms, you take the tax break now and settle up later.

Roth contributions are the mirror image: you pay tax on the money this year, before it goes in. In return, qualified withdrawals in retirement come out completely tax-free, including all the growth. You settle up now and owe nothing later.

Otherwise the two are the same. The funds you can hold are identical, and the contribution limit is shared.

The agency match works the same way no matter which you pick. Only the timing of the tax changes, and that timing is what makes the decision worth thinking through.

The Traditional TSP gives you a tax break today. Your contributions come out of your pay before income tax is figured, so they lower your taxable income for the year. The money then grows tax-deferred, meaning you owe no tax on the gains along the way.

The bill comes due when you withdraw. In retirement, every dollar you take from your traditional balance counts as ordinary income, taxed at whatever your rate is that year. You deferred the tax; you didn’t erase it.

This treatment helps most when your tax rate today is higher than it will be in retirement. A deduction taken at a high rate now can outweigh the tax you pay at a lower rate later, and many higher-earning, later-career employees are in that position.

Traditional balances also carry required minimum distributions. A required minimum distribution (RMD) is the minimum amount the IRS makes you withdraw each year once you reach a set age. The age is set in law and can change, so confirm the current figure in our assumptions. Keep in mind that traditional money is taxed on the way out, on a schedule you don’t fully control.

The Roth TSP flips the timing. You contribute money you’ve already paid tax on, so there’s no deduction this year. In exchange, qualified withdrawals come out entirely tax-free, including every dollar of growth your contributions earned.

A withdrawal counts as qualified only if it passes two tests. The IRS requires that five years have passed since your first Roth contribution, and that you’re at least age 59½. Death or disability also satisfy the second test, and if you meet both, the earnings are tax-free.

Miss the tests, and the growth portion of an early withdrawal can be taxed. Your own contributions remain yours, but the earnings lose the tax-free treatment. That’s why the five-year clock is worth starting early, even with small contributions, since the sooner it starts, the sooner your whole balance can qualify.

Roth helps most when your tax rate today is lower than you expect it to be later. You pay tax on the seed at today’s rate and let the harvest escape tax entirely (the seed is what you put in; the harvest is the growth). Early-career employees in a lower bracket are often in that spot. A further Roth advantage: Roth balances are no longer subject to RMDs during your lifetime.

Here’s the rule that surprises people. Agency contributions always go into your traditional balance, no matter how you direct your own. Even if you send every dollar of your own contribution to Roth, the agency match lands in traditional.

That means almost every contributing employee ends up holding both. Your Roth contributions build a Roth balance, while the match builds a traditional balance right alongside it. You get a head start on tax diversification without even choosing it.

The match doesn’t change the most important habit: contribute at least 5% of your pay to capture all of it. The match is a guaranteed return no fund can offer. Where your own share goes, Roth or traditional, is the second decision, made after you lock in the full match.

When you eventually withdraw, each balance follows its own rules. The traditional match and its growth are taxed as income, while your qualified Roth withdrawals are tax-free. The TSP tracks the two balances separately for exactly this reason, so the right tax treatment applies to each.

The whole decision turns on one comparison. Is your tax rate higher today, or will it be higher when you withdraw?

Traditional bets your rate is higher now, and Roth bets your rate is higher later. Neither bet can be known for certain in advance.

Early in a federal career, pay is often lower, so the tax rate is often lower too. Paying tax now through Roth can mean paying at a low rate and letting decades of growth come out tax-free. That’s the common argument for leaning Roth early on.

Later in a career, pay and tax rates are usually higher. Since a traditional deduction is worth more when your rate is high, many employees lean traditional during their peak-earning years. Your own path may not follow this pattern, and that’s fine.

We can’t tell you which way your rates will move. Tax law changes, careers change, and retirement income varies from person to person. What we can say is this: the choice is a forecast about tax rates, not a guess about the market. Name the forecast, and the decision gets clearer.

Because no one can predict future tax rates, holding both balances is itself a plan, called tax diversification. With money in both buckets, you choose which one to draw from each year in retirement, based on what’s most tax-efficient that year.

A retiree with only traditional money is exposed to every future rate increase on withdrawals. A retiree with only Roth gave up deductions that might have been valuable.

A mix gives you levers. In a high-income year, you can lean on tax-free Roth; in a low-income year, you can pull cheaper traditional dollars.

You may already be building both, since the match is always traditional. Adding Roth contributions of your own rounds out the mix. You don’t have to split evenly, since even a meaningful slice of each gives you flexibility you wouldn’t have with one alone.

Tax diversification won’t maximize any single outcome. If you knew future rates for certain, one pure choice would win. You don’t, so the mix trades a little upside for a lot of resilience. That’s the same logic behind diversifying investments, applied to taxes instead.

A few TSP rules trip people up, though the biggest ones are simple once you see them. The contribution limit is shared, the Roth TSP has no income limit, and the two balances follow different withdrawal rules.

Keep these specifics in mind as you set up your contributions:

One more point on changing your mind: updating your Traditional-or-Roth election changes only future contributions. Moving money already in your traditional balance takes a separate step: a Roth in-plan conversion, which the TSP added in early 2026. Converting is a taxable event, so the amount you convert counts as ordinary income that year.

Finally, watch the year-end limit. If you hit the shared limit early in the year, your contributions stop, and so does the match for the rest of the year. Spreading contributions evenly across all pay periods keeps the match flowing through December.

• Shared limit: the IRS elective deferral limit applies to your Traditional and Roth contributions combined, not to each separately.
• No income cap: unlike a Roth IRA, the Roth TSP has no income limit, so high earners can still contribute.
• Catch-up on top: at age 50 and older, the extra catch-up amount the IRS sets is room above the shared limit, not part of it, and that room is likewise shared across your Traditional and Roth balances.
• RMD difference: traditional balances have required minimum distributions; Roth balances no longer do during your lifetime.
• Same funds: the G, F, C, S, I, and L fund choices are identical in both balances.

The Traditional vs. Roth TSP choice is one decision about tax timing. Traditional gives a deduction now and taxes withdrawals later, while Roth taxes contributions now and makes qualified withdrawals tax-free.

The match is always traditional, so most feds already hold both (often without having planned it).

To set your own share, weigh where your tax rate is today against where you expect it to be in retirement. Lower now often points toward Roth, and higher now often points toward traditional. When you’re unsure, a mix hedges the question rather than betting it all one way.

Whatever you choose, capture the full 5% match first. Then set your Traditional-or-Roth split, and revisit it as your pay and tax picture change over a career. The decision isn’t permanent, and you can redirect future contributions at any time.

See how your TSP fits the rest of your plan with our free readiness score. The next lesson covers creditable service and buying back military time, which adds to the pension side of your retirement. To review how the funds inside each balance work, revisit how the TSP works.