The Roth TSP vs. Traditional TSP decision determines whether you pay taxes on your retirement savings now or later. Getting this choice right can mean tens of thousands of dollars in tax savings over retirement.

The TSP (Thrift Savings Plan) is the federal government’s tax-advantaged retirement savings program. It offers both a traditional (pre-tax) option and a Roth (after-tax) option under one account. The right answer depends on your current tax bracket, expected retirement income, and how long you plan to keep the money invested.

This guide compares the tax treatment of each TSP option side by side, covers the 2026 contribution limits, and explains which scenarios favor one over the other.

How the Traditional TSP Works for Federal Employees

Traditional TSP contributions come out of your gross pay before federal and state income taxes. This reduces your taxable income in the year you contribute, so you pay less in taxes today.

According to TSP.gov, withdrawals from taxable traditional TSP balances are generally taxed as ordinary income when distributed. That includes both your contributions and any investment earnings.

If you’re covered by FERS, all agency automatic contributions (1% of basic pay) and agency matching contributions go into your traditional TSP balance. This applies regardless of whether you designate your own contributions as Roth. Every FERS employee will build some traditional balance even if they contribute 100% to Roth.

Traditional TSP balances are subject to required minimum distributions. Under the SECURE 2.0 Act, participants born between 1951 and 1959 must begin taking RMDs at age 73. Those born in 1960 or later must start at age 75.

Tax Treatment of Your Roth TSP Contributions

Roth TSP contributions come out of your pay after federal and state income taxes. You pay taxes on the money upfront, but qualified withdrawals of both contributions and earnings are completely tax-free in retirement, according to TSP.gov.

A withdrawal qualifies as tax-free when two conditions are met. At least five years must have passed since January 1 of the year you made your first Roth TSP contribution. You must also be at least age 59½, permanently disabled, or deceased.

Effective January 1, 2024, the SECURE 2.0 Act exempts Roth TSP balances held by the original account owner from required minimum distributions. You can leave Roth TSP balances invested indefinitely, and qualified withdrawals stay tax-free. For estate planning and managing taxable income in later retirement, that’s a significant edge.

Roth TSP vs. Traditional TSP: Side-by-Side Comparison

The following table summarizes the key differences between Roth TSP and Traditional TSP across the factors that matter most to federal employees.

2026 TSP Contribution Limits and SECURE 2.0 Changes

The IRS set the 2026 elective deferral limit for TSP contributions at $24,500. This limit applies to your combined total of traditional and Roth contributions.

Employees age 50 and older can contribute an additional $8,000 in catch-up contributions, for a combined total of $32,500. If you turn 60, 61, 62, or 63 during 2026, you qualify for an enhanced catch-up limit of $11,250 under Section 109 of the SECURE 2.0 Act, bringing your maximum to $35,750.

A critical new rule took effect in 2026. Under Section 603 of the SECURE 2.0 Act, participants whose prior-year wages from TSP-eligible federal positions exceeded $150,000 (the indexed IRS threshold for 2025 wages) must make catch-up contributions as Roth contributions. TSP payroll systems generally apply this once you reach the $24,500 regular limit. Confirm the treatment with your payroll office.

This mandatory Roth catch-up rule affects many GS-14s, GS-15s, and SES employees in higher-locality areas. The threshold is based on Medicare wages in Box 5 of the prior-year W-2.

FERS employees should also remember that agency matching contributions are calculated per pay period, not annually. According to TSP.gov, you must contribute at least 5% of your basic pay each pay period to receive the full 4% agency match. Hit the annual limit early, and your agency match stops for the rest of the year.

When the Traditional TSP Is the Stronger Choice

The traditional TSP offers the greatest advantage when your current marginal tax rate is higher than the rate you expect in retirement. Late-career federal employees in GS-14 or GS-15 pay grades who plan to retire into a lower bracket fit this profile. So do employees relocating to a no-income-tax state like Florida or Texas, and those within a few years of retirement who want to maximize their current deduction.

Federal Pension Advisors, a retirement planning firm specializing in federal employee benefits, often works with employees in this situation to model the long-term tax impact of each allocation strategy.

Why Lower-Bracket Employees May Prefer Roth TSP

The Roth TSP tends to deliver the greatest long-term value when your current tax rate is lower than what you expect in retirement. Early-career and mid-career federal employees in GS-7 through GS-12 pay grades who anticipate promotions fit this profile. So do employees who believe federal tax rates may rise, and those who want to minimize required minimum distributions.

Roth TSP contributions also help manage two often-overlooked retirement costs. Qualified Roth withdrawals don’t count as taxable income, so they won’t increase the portion of your Social Security benefits subject to taxation. They also won’t push your modified adjusted gross income above the thresholds that trigger Medicare IRMAA surcharges.

OPM administers the FERS basic annuity, which counts as taxable income. Social Security provides a second taxable stream. Adding large traditional TSP withdrawals and RMDs on top of those two sources can push you into a higher tax bracket. A Roth TSP balance gives you a tax-free withdrawal source that doesn’t compound this problem.

The Split Contribution Strategy: Using Both

Many federal employees find the most effective approach is contributing to both options at the same time. This strategy, sometimes called tax diversification, gives you flexibility to draw from either balance depending on your taxable income needs in any given year.

In a year when your pension and Social Security already place you near the top of your bracket, you could draw exclusively from the Roth balance to avoid the next bracket. In a lower-income year, you might withdraw more from the traditional balance to take advantage of deductions or a lower effective rate.

Federal Pension Advisors recommends modeling your projected retirement income from all three FERS pillars (the basic annuity, Social Security, and the TSP) before committing to a single contribution strategy.

How the Roth In-Plan Conversion Option Works

Starting in 2026, TSP participants can transfer money from their traditional TSP balance to their Roth TSP balance through Roth in-plan conversions. According to TSP.gov, the converted amount is taxed as ordinary income in the year of conversion. All future growth and qualified withdrawals from that converted balance are tax-free.

This option is most valuable during lower-income years. Consider the gap between leaving federal service and starting Social Security or pension payments. Because a conversion increases taxable income for the year, it may also affect tax brackets, Medicare IRMAA, and Social Security taxation.

You must pay the tax on the conversion from outside funds, not from your TSP balance. You must also satisfy any RMD requirement for the year before converting.

Making Your Roth TSP vs. Traditional TSP Decision

Revisit the Roth TSP vs. Traditional TSP choice as your career progresses and tax law evolves. Early-career employees in lower tax brackets generally benefit most from Roth contributions. Late-career employees in peak earning years often benefit most from traditional contributions. Many employees in between benefit from a split strategy.

Whatever your situation, contribute at least 5% of your basic pay every pay period to capture the full FERS agency match. According to TSP.gov, the agency match is worth up to 4% of your basic pay, in addition to the 1% automatic agency contribution. It’s deposited every pay period only if you’re actively contributing at least 5%.

Federal Pension Advisors can help you model the long-term tax impact of your Roth-to-traditional allocation based on your pay grade, years of service, and retirement timeline. A personalized projection across all three FERS income pillars is the most reliable way to determine which TSP strategy keeps more of your money working for you.

Frequently Asked Questions

Can I contribute to both the Roth TSP and Traditional TSP at the same time?

Yes. You can split your contributions between Roth and Traditional TSP in any proportion. The combined total can’t exceed the 2026 IRS elective deferral limit of $24,500, or $32,500 with standard catch-up contributions for employees age 50 and older. Change your allocation at any time through your agency’s payroll system.

Do I pay taxes on Roth TSP withdrawals in retirement?

Qualified Roth TSP withdrawals are completely tax-free, including both your contributions and all investment earnings. To qualify, you must be at least age 59½, and at least five years must have passed since January 1 of the year you made your first Roth TSP contribution. Non-qualified withdrawals may owe taxes on the earnings portion only.

Does my agency match go into my Roth TSP if I choose Roth contributions?

No. According to the Federal Retirement Thrift Investment Board, all agency automatic contributions and matching contributions go into your traditional TSP balance. This applies regardless of how you designate your own employee contributions. Every FERS employee will accumulate a traditional balance from agency deposits even if they contribute exclusively to the Roth TSP.

Are Roth TSP accounts subject to required minimum distributions?

No. Under the SECURE 2.0 Act, Roth TSP balances are exempt from required minimum distributions during the original account owner’s lifetime, effective January 1, 2024. Only the traditional TSP balance counts toward your annual RMD. This exemption lets you keep Roth savings invested indefinitely while qualified withdrawals remain tax-free.

When should a federal employee choose Traditional TSP over Roth TSP?

The Traditional TSP is generally the stronger choice when your current marginal tax rate is higher than the rate you expect in retirement. This commonly applies to late-career employees in GS-14 or GS-15 grades, employees within five years of retirement, and those planning to relocate to a no-income-tax state. Each situation requires individual analysis.

Do high earners have to make Roth catch-up contributions in 2026?

Yes. Under SECURE 2.0 Section 603, participants whose prior-year wages from TSP-eligible positions exceeded $150,000 (the indexed threshold for 2025 wages) must make catch-up contributions as Roth. TSP payroll systems generally apply this once you reach the $24,500 regular limit. The threshold is based on Medicare wages in Box 5 of the prior-year W-2.