Roth vs. Traditional TSP (and the Roth Conversion Question)
Most federal employees have a traditional TSP balance, a Roth TSP balance, or both — and in retirement, the difference between them drives your tax bill for decades. Understanding which is which, and the much-discussed "Roth conversion" strategy, is one of the higher-leverage things you can learn before you retire.
The core difference
| Traditional TSP | Roth TSP | |
|---|---|---|
| Contributions | Pre-tax (you got a deduction) | After-tax (already taxed) |
| Growth | Tax-deferred | Tax-free |
| Qualified withdrawals | Taxed as ordinary income | Tax-free |
| Lifetime RMDs | Yes, generally from age 73 | No (eliminated starting 2024) |
In plain terms: with traditional, you deferred the tax and you'll pay it as you withdraw; with Roth, you already paid the tax and qualified withdrawals come out clean. That elimination of Roth TSP required minimum distributions is recent and significant — your Roth balance can now keep growing untouched for life if you don't need it.
Why this matters so much in retirement
Every dollar you pull from traditional TSP is taxable income — and it stacks on top of your pension, your FERS supplement, and eventually Social Security. Large traditional balances can push you into higher tax brackets, increase how much of your Social Security is taxed, and even raise your Medicare premiums (IRMAA). Roth dollars don't do any of that. The mix between the two is a lever, not just a label.
The Roth conversion question
"Roth conversion" means moving money from a traditional (pre-tax) account to a Roth (after-tax) account — paying the tax now, on purpose, so it grows tax-free afterward. The appeal: the years between retirement and the start of RMDs and Social Security are often a low-income window where you can convert at a relatively low tax rate, instead of being forced to withdraw later at a higher one.
This is a tax-planning decision — get it right
Whether, when, and how much to convert depends on your current and future tax brackets, your other income, your time horizon, and your goals for heirs. Convert too much in a year and you can spike your own tax bill and Medicare premiums; convert too little and you miss the low-rate window. There's no one-size answer, and this is squarely a job for a qualified tax professional — not a rule of thumb and not a sales pitch. Our role is to show you the moving parts, not tell you what to do.
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