Roth TSP vs Traditional TSP: Which Wins for an E-5 or O-3 in 2026?

The only question that matters: your rate now vs. your rate later

Traditional TSP contributions skip tax today and are taxed as ordinary income when withdrawn. Roth TSP contributions are taxed today and withdrawn tax-free (after age 59 1/2 and five years). If the same dollars face the same rate at both ends, the two produce identical after-tax balances. So the decision reduces to one comparison: is your marginal federal rate higher now, or when you withdraw?

For service members that comparison is unusually lopsided, for two reasons that do not apply to civilians:

1. A large share of military compensation is already untaxed. BAH and BAS are excluded from federal income tax, so taxable income is basic pay plus a few special pays, which lands most enlisted members and many company-grade officers in the 12% bracket.
2. Retirement income for a careerist stacks. A BRS pension (2% x years of service x High-3 average) is fully taxable, arrives at 38 to 45, and sits on top of a civilian salary, which routinely puts a retired O-5 or E-8 in the 22% or 24% bracket for decades.

Where an E-5 and an O-3 actually sit in the 2026 brackets

2026 figures (Rev. Proc. 2025-32): standard deduction $16,100 single, $32,200 married filing jointly; the 12% bracket covers $12,400 to $50,400 of taxable income single ($24,800 to $100,800 MFJ) and the 22% bracket $50,400 to $105,700 single ($100,800 to $211,400 MFJ). Basic pay is approximate; check your grade and years of service on the DFAS pay table.

The E-5 pays an effective federal rate of 7.3% on basic pay; the married O-3 pays 6.6%. Neither will see rates that low again once a pension and a civilian paycheck stack. The single O-3 is the interesting case: a traditional contribution saves 22 cents on the dollar today, roughly a comfortable retirement's rate, so the tie-breakers below decide it. Check where your own basic pay lands, including a working spouse's income, in the tax bracket explainer.

Worked example: the E-5, 10% for 32 years

Same member as the TSP calculator's worked example: 26 years old, $3,900 a month basic pay, L Fund at an assumed 6.5% return, contributing until 58 (32 years). To compare fairly, hold take-home pay equal, not the contribution:

• Traditional: $4,680 a year into the TSP; the 12% deduction refunds $562, so take-home falls by $4,118.
• Roth: $4,118 a year into the TSP (the same $4,118 hit to take-home; $562 goes to the IRS instead).

The 32-year compounding factor at 6.5% is ((1.065^32 - 1) / 0.065) = 100.05.

• Traditional balance at 58: $4,680 x 100.05 = $468,234, all of it taxable on withdrawal.
• Roth balance at 58: $4,118 x 100.05 = $412,046, none of it taxable.

Read the table as a bet on your future bracket. For Roth to lose, this E-5 needs a retirement marginal rate below 12%, which in 2026 terms means under $50,400 of taxable income as a single filer with no pension and no other job; not the profile of someone who saved 10% of pay for 32 years. And the government's 5% (automatic 1% plus 4% match) always lands in the traditional balance, so a member who goes 100% Roth still has a taxable bucket to absorb the low brackets in retirement. To see how the match and your own rate combine into a projected balance, run your own numbers in the Military TSP Contribution calculator.

The single O-3 case, and why it is closer

Rerun the method for the single O-3 at 22%: $8,040 traditional versus an equal-take-home Roth of $8,040 x 0.78 = $6,271, from age 28 to 58 (30 years, factor 86.37 at 6.5%).

• Traditional: $8,040 x 86.37 = $694,415 pre-tax. After 22%: $541,644. After 24%: $527,755. After 12%: $611,085.
• Roth: $6,271 x 86.37 = $541,626 tax-free.

At a 22% retirement rate it is a dead heat; at 24% Roth wins by about $13,900; at 12% traditional wins by about $69,500. So the single O-3's answer hinges on career path. An officer who leaves at 8 years with no pension and retires on modest income leans traditional. One who serves 20 years to O-5 draws a BRS pension of 40% of High-3 (roughly $50,000 a year, taxable) on top of a civilian salary, locking in 22% to 24% for life; that officer leans Roth, and should go Roth in any year they marry (the married O-3 above is back at 12%).

Combat-zone pay: Roth, every time

Pay earned in a designated combat zone is excluded from federal income tax under IRC section 112 (enlisted pay in full, officer pay up to the highest enlisted rate plus imminent danger pay). That changes the Roth math from "probably" to "always":

• Roth TSP from combat-zone pay is never taxed. Not going in, not on the earnings, not coming out. It is the only fully tax-free retirement contribution in the U.S. system.
• Traditional TSP from combat-zone pay is untaxed going in, but the earnings are taxed on withdrawal. The original dollars come back tax-free; decades of growth do not.

Numbers: the E-5 deploys for six months at a 50% election, contributing 6 x $3,900 x 50% = $11,700. At 6.5% for 30 years that grows by a factor of 6.61 to about $77,400. As Roth, all $77,400 is spendable. As traditional, the $65,700 of growth is taxed on withdrawal, about $14,450 at 22%. Two notes: traditional contributions from tax-exempt pay do not count toward the 2026 $24,500 elective deferral limit (only the $72,000 annual-additions limit), while Roth contributions from the same pay do. And matching stops if elective deferrals hit $24,500 before December, so spread a large Roth election across the year rather than front-loading it into a deployment.

Tie-breakers when the rates are close

When your current and expected retirement rates are within a couple of points, these secondary factors settle it, and most favor Roth:

• No RMDs on Roth TSP. SECURE 2.0 eliminated required minimum distributions from Roth employer plans, including Roth TSP, from 2024. Traditional balances face RMDs at 73.
• State taxes. Many states exempt military retirement pay but tax traditional TSP withdrawals; Roth removes that exposure.
• The $24,500 limit is effectively bigger in Roth. $24,500 of Roth is $24,500 spendable; $24,500 of traditional is $24,500 minus future tax.
• Roth catch-up rule. From 2026, SECURE 2.0 requires catch-up contributions ($8,000 at 50, $11,250 at 60 to 63) to be Roth if prior-year FICA wages exceeded $150,000; senior officers only, but one more push toward Roth.

The one factor favoring traditional: if you are at 22% or higher now and expect to retire early, before any pension, on modest income, the deduction today is worth more than tax-free growth. A 50/50 split is a legitimate hedge; myPay accepts separate traditional and Roth percentages. To turn the projected balance into yearly retirement income next to a pension, use the retirement calculator, and whenever you change your election, run your own numbers in the Military TSP Contribution calculator to confirm you still capture the full 5% match.

FAQ

Q: Does the BRS match go into Roth if I contribute Roth?
No. The automatic 1% and all matching go into your traditional balance regardless of your election, so you will always have some pre-tax money. Your own contributions can be any Roth/traditional split you set in myPay.

Q: What tax bracket is an E-5 in for 2026?
A single E-5 with about $46,800 of basic pay and no other taxable income has $30,700 of taxable income after the $16,100 standard deduction, inside the 12% bracket ($12,400 to $50,400). Federal tax is about $3,436, an effective 7.3% of basic pay, because BAH and BAS are excluded.

Q: Is Roth TSP always better for combat-zone pay?
Yes. Pay excluded under IRC section 112 was never taxed, and qualified Roth withdrawals are never taxed, so the contribution and all its growth are permanently tax-free. Traditional contributions from the same pay return the original dollars tax-free but tax every dollar of earnings.

Q: If I switch from traditional to Roth, does my take-home pay drop?
Yes, by your marginal rate times the contribution. An E-5 at 12% moving a $390 monthly (10%) contribution to Roth sees take-home fall about $47 a month; a single O-3 at 22% moving $670 a month sees a drop of about $147.

Q: Do Roth TSP withdrawals count toward the tax on my military pension or Social Security?
No. Qualified Roth withdrawals are excluded from adjusted gross income, so they do not push pension income into a higher bracket, raise the taxable share of Social Security, or trigger Medicare IRMAA surcharges. Traditional TSP withdrawals do all three.

Q: Can I contribute to both Roth TSP and a Roth IRA in 2026?
Yes. The 2026 TSP elective deferral limit of $24,500 and the IRA limit of $7,500 ($8,600 with the age-50 catch-up) are separate. The Roth IRA phases out from $153,000 single / $242,000 MFJ; the Roth TSP has no income limit.

Sources

• TSP.gov - Roth and traditional contributions
• TSP.gov - Contribution limits
• Military Compensation (militarypay.defense.gov) - Basic pay tables
• IRS - Combat zone tax exclusion (Publication 3, Armed Forces' Tax Guide)