Traditional TSP or Roth TSP? Do the Math Before You Guess

Every new soldier gets handed the same form in their first week of processing: Traditional TSP or Roth TSP. Check a box, move on to the next station. Most guys check whatever their battle buddy checked. I didn't. I sat down with a calculator before I signed anything, and the answer I landed on wasn't the one I expected walking in.

The Question Nobody Explains Right

Traditional TSP takes your contribution out of your paycheck before taxes. You get a smaller tax bill today, but every dollar you pull out in retirement — contributions and every cent of growth — gets taxed as ordinary income. Roth TSP is the opposite: you pay tax on the money now, at today's rate, and every dollar you withdraw after 59½ comes out completely tax-free, growth included. Same fund menu, same C Fund I've put my own money in for years. The only thing that changes is when Uncle Sam gets his cut.

The Tax Bracket Math Most Soldiers Skip

Here's the calculation that actually matters: what tax bracket are you in today, and what bracket do you expect to be in when you pull the money out? Not what sounds impressive — what the IRS tables actually say.

Take an E-3 with under two years in, base pay around $2,700 a month, $32,400 a year. After the standard deduction, most of that lands in the 10% to 12% federal bracket. Put $150 a month into Traditional TSP and you save $18 to $22 a month in taxes today — real money, but not life-changing. Put that same $150 into Roth instead, and you pay that $18 to $22 now, in exchange for every dollar it grows into coming out untouched decades later.

Run $150 a month at an 8% average return for 30 years and you land around $224,000. Taxed on the way out of a Traditional account — even at a modest 15% blended rate in retirement — that costs you over $33,000. In Roth, that number is zero. The lower your bracket right now, the harder that math tilts toward Roth, because you're locking in today's cheap rate instead of gambling on tomorrow's.

The Match Always Goes Traditional — No Matter What You Pick

One detail trips up almost every soldier I talk to: your choice only applies to your own contributions. Under BRS, the government's automatic 1% and matching up to 4% always land in your Traditional balance, no matter which box you checked. Defer 5% of base pay and the service matches dollar-for-dollar on the first 3% and 50 cents on the dollar for the next 2% — up to 5% of your pay showing up for free. On $2,700 a month base pay, deferring 5% ($135) gets you roughly $135 in matching money right alongside it. That's a 100% return before the market does a single thing. Whatever you decide about Traditional versus Roth for your own money, get to at least 5% first. Leaving that match on the table isn't a tax strategy — it's just leaving money in the building.

Why I Picked Roth, and Why That's Not Universal Advice

I enlisted at 38 with $781,000 already sitting in index funds outside the military, built the boring way — S&P 500 only, never sold, never timed it. My TSP contributions are small next to that number, so I wasn't optimizing for a deduction today. I was optimizing for certainty. My base pay right now, in my first year in the Army, puts me in one of the lowest tax brackets I've seen since I was working three jobs after arriving in this country in 2008. I'd rather pay tax on that income at today's low rate than bet on what Congress does to tax brackets 20 years from now. That's why I checked Roth.

If you're a senior NCO or officer stacking bonuses and special pay in the 22% to 24% bracket, the math tilts the other way — Traditional's upfront deduction is worth more to you today, and you can diversify later. There's no universal right answer here, only the right one for your bracket and your timeline. If you haven't mapped out where a decision like this fits into the rest of your plan, that's exactly what I walk through in the military wealth path breakdown.

Don't check that box because your battle buddy did. Run your own numbers, pick the one that matches your bracket and your timeline, and then leave it alone for 20 years. Boring on purpose, relentless by design.