TSP Roth in-plan conversions: the new 2026 feature, explained
For the first time in the plan’s history, you can move traditional TSP money into your Roth balance without rolling it out to an IRA first. It launched quietly on January 28, 2026, and it hands federal employees a genuine tax-planning lever they never had. It also comes with four rules that catch people out: no withholding, no undo, a $500 floor, and a 26-per-year ceiling. Here’s how it actually works — and how to spread the tax hit.
1. What actually changed
The Federal Retirement Thrift Investment Board published its final rule on January 15, 2026, and the feature went live January 28, 2026, under authority granted by the SECURE 2.0 Act of 2022. You’ll find it in My Account on TSP.gov.
Before this, a fed who wanted to convert pre-tax retirement money usually had to move it out to an IRA first — leaving the TSP’s very low costs behind and adding a rollover step where mistakes happen. Now the whole transaction stays inside the plan. Both pre-tax and tax-exempt traditional balances are eligible, including employee contributions, agency contributions, and earnings.
2. The rules that actually matter
| Rule | What it means |
|---|---|
| 26 per calendar year | Matches biweekly pay periods — enough to ladder conversions all year |
| $500 minimum | Per conversion; a $500 minimum balance must remain in each contribution type |
| Taxable in year of conversion | Added to ordinary income at your marginal rate |
| No withholding | You must pay the tax from outside funds |
| Irreversible | No recharacterization — once done, it’s done |
The 26-per-year allowance is more useful than it first looks. It’s what makes a genuine ladder possible inside the plan: convert in measured pieces as the year unfolds, and stop the moment you’ve used the tax room you meant to use.
3. The withholding trap
This is the detail that blindsides people. IRS guidance provides that withholding does not apply to a Roth in-plan conversion of an otherwise nondistributable amount, and the FRTIB confirmed participants cannot elect voluntary withholding either. So a $40,000 conversion generates a real tax bill with zero set aside against it. You pay from savings, a taxable brokerage account, or estimated tax payments — and if you can’t, you probably shouldn’t convert that much.
Paying the tax out of retirement assets undercuts most of the point of converting, because the dollars that leave to cover taxes stop compounding tax-free. The rule of thumb: if the outside cash isn’t there, size the conversion down until it is.
4. There is no undo
Once a conversion completes, it cannot be reversed. There’s no recharacterization for in-plan Roth conversions. Convert in January, then have a windfall in November that pushes you into a higher bracket — you’re still taxed on what you converted. Convert right before a sharp market drop, and you’ve paid tax on a value that has since evaporated.
Both scenarios argue for the same discipline: convert in partial amounts, and lean toward later in the tax year, when your income picture is far clearer than it was in January.
5. Plan your conversion ladder
Spreading a conversion across several years keeps each year’s income bump smaller. Model it here — and note the cash you’ll need on hand each year.
Your conversion
A planning estimate using a flat marginal rate. A real conversion can push you into a higher bracket and can affect IRMAA and the taxable share of Social Security. Not tax advice — model your actual return before converting.
6. The two five-year clocks
Converted balances follow the same qualified-distribution rules as your other Roth TSP money, and two separate five-year clocks are in play: one governing when earnings come out tax-free, and another governing penalty-free access to converted principal. They interact with your age and your retirement date, which means converting shortly before you plan to withdraw can produce an unpleasant surprise. If you’re close to needing the money, confirm exactly where you stand on both clocks first.
7. Who should — and who shouldn’t
Often a good fit: you’re in a temporarily low-income year; you want to shrink future RMDs (Roth TSP balances aren’t subject to them); you’re deliberately leaving heirs money that arrives tax-free; you have outside cash to pay the tax.
Often a poor fit: you’re in a peak earning year; you’d have to raid retirement assets to pay the tax; you expect a genuinely lower bracket in retirement; or you’ll need that specific money within a few years.
8. The federal timing window
Federal retirees have a structural advantage worth exploiting. There is often a stretch — after you retire, before Social Security and RMDs both switch on — when taxable income dips well below career levels. That trough is the natural home for conversions. If you retired under FERS before 62, that window can be several years wide.
The tactics for filling it deliberately are covered in depth in the Roth conversion window and the bracket-filling ladder — what’s new in 2026 is simply that you can now execute the whole thing without ever leaving the TSP.
9. FAQ
What is a TSP Roth in-plan conversion?
It lets you move money from your traditional (pre-tax and tax-exempt) TSP balance into your Roth TSP balance without taking the money out of the plan. The Federal Retirement Thrift Investment Board published its final rule on January 15, 2026, and the feature went live January 28, 2026, under authority from the SECURE 2.0 Act of 2022. Before this, a federal employee who wanted to convert pre-tax retirement money generally had to roll it out to an IRA first. Now the entire transaction happens inside the TSP, where costs are low and the funds stay familiar. You request it through My Account on TSP.gov.
How much tax will I owe on a TSP Roth conversion?
The amount you convert is added to your ordinary income for the year of the conversion, so you pay tax at your marginal rate on the full converted amount. The critical detail is that no tax is withheld. IRS guidance provides that withholding does not apply to a Roth in-plan conversion of an otherwise nondistributable amount, and the FRTIB confirmed participants cannot elect voluntary withholding either. That means you must pay the tax from outside money — savings, a taxable brokerage account, or estimated tax payments — rather than from the TSP itself. Paying the tax out of retirement assets defeats much of the benefit.
Can I undo a TSP Roth conversion?
No. Once a conversion is completed it cannot be reversed. There is no recharacterization option for in-plan Roth conversions, so if you convert in a year that turns out to be a high-income year, or the market falls sharply right after you convert, you are still liable for the tax on the amount you converted. This irreversibility is the strongest argument for converting in smaller partial amounts across several years rather than making one large conversion, and for waiting until late in the tax year when your income picture for that year is clearer.
How many conversions can I do, and is there a minimum?
Under the FRTIB final rule, participants may request up to 26 conversions per calendar year, a figure chosen to align with biweekly pay periods. Each conversion carries a $500 minimum, and a $500 minimum balance must be maintained in each contribution type. The generous number of allowed conversions is what makes a laddered strategy practical inside the TSP: rather than converting one large sum, you can convert repeatedly in measured amounts as your income picture for the year becomes clearer, stopping once you have used the tax room you intended to use.
Who benefits most from converting?
Conversions tend to favor people whose tax rate today is lower than the rate they expect later. For federal retirees, that often points to the window between retiring and the year required minimum distributions and full Social Security begin, when taxable income can dip temporarily. Other common motivations include reducing the size of future RMDs, since Roth TSP balances are not subject to them, and leaving heirs assets that come to them tax-free. Conversions are usually a poor fit if you are in a peak earning year, if you would have to pay the tax out of the retirement account itself, or if you expect a materially lower tax rate in retirement.
How do the five-year rules apply to converted money?
Converted balances follow the same qualified distribution rules as other Roth money in the TSP, and two separate five-year clocks matter. One governs when earnings on Roth balances can come out tax-free, and a second governs penalty-free access to converted principal. Because these clocks interact with your age and retirement date, converting shortly before you plan to withdraw can produce an unwelcome surprise. If you are close to needing the money, confirm exactly where you stand on both clocks before converting, and consider talking it through with a tax professional.