A TSP Roth conversion can be one of the most effective tax-planning strategies available to federal employees. By converting money from your Traditional TSP to your Roth TSP, you pay taxes now in exchange for the potential for tax-free qualified withdrawals in retirement.
Since the feature became available on January 28, 2026, federal employees have completed nearly 31,000 in-plan Roth conversions totaling approximately $684 million, showing just how much interest there is in the strategy.
Key Takeaways
- A TSP Roth conversion creates taxable income in the year you convert.
- The income taxes cannot be paid from your TSP account. They must be paid with funds from another source.
- Large conversions can increase your taxable income enough to affect Medicare’s Income-Related Monthly Adjustment Amount (IRMAA).
- Many federal employees find the best opportunity for Roth conversions is after retirement but before required minimum distributions begin.
The Tax Rule Many Federal Employees Miss
The biggest surprise for many federal employees is how TSP Roth conversion taxes are paid.
When you convert Traditional TSP money to Roth, the amount converted is added to your taxable income for that year. However, the tax bill cannot be paid using TSP assets. Instead, you’ll need enough cash in a savings account or another non-retirement source to cover the taxes when they come due.
Without sufficient liquid funds, even a Roth conversion that looks attractive on paper may not make financial sense.
A Simple Example
Suppose you convert $50,000 from your Traditional TSP to your Roth TSP while you’re in the 22% federal tax bracket.
That conversion could generate approximately $11,000 in federal income taxes, and that money must come from outside your TSP account. State income taxes, if applicable, could increase the total tax bill even further.
Timing Matters
A Roth conversion isn’t just about how much you convert. When you convert can be just as important.
Converting a large balance during your highest-earning working years could push you into a higher tax bracket or increase your Medicare premiums later through the Income-Related Monthly Adjustment Amount (IRMAA), which is based on income from two years earlier.
For many federal employees, the most favorable conversion window occurs after retirement but before required minimum distributions (RMDs) begin. Those years often come with lower taxable income, allowing conversions to be completed at a lower overall tax cost.
Is a TSP Roth Conversion Right for You?
A TSP Roth conversion can be an excellent long-term strategy, but it isn’t automatically the right choice for everyone. Your current tax bracket, available cash, expected retirement income, Medicare considerations, and future tax outlook all play a role in the decision.
A Federal Retirement Consultant (FRC®) can help you evaluate whether a TSP Roth conversion fits your overall retirement strategy and determine the most tax-efficient time to convert. No cost. No obligation.
Frequently Asked Questions:
Can I pay TSP Roth conversion taxes from my TSP?
No. Taxes generated by a TSP Roth conversion must be paid using money outside your TSP account.
When is the best time to do a TSP Roth conversion?
Many federal employees benefit most by converting after retirement but before required minimum distributions begin, when taxable income may be lower. The right timing depends on your individual financial situation.
Can a TSP Roth conversion increase Medicare premiums?
Yes. A large Roth conversion increases your taxable income for the year, which may increase future Medicare IRMAA premiums if your income exceeds the applicable thresholds.
