The Thrift Savings Plan (TSP) announced officially last week that starting in January 2026 TSP participants will be able to convert their money in traditional TSP (pre-tax) balance to a Roth TSP (after-tax) balance, called a “TSP Roth in-plan conversion.”
Participants who don’t have a TSP Roth balance their TSP account can create one.
“If you’re considering doing a Roth in-plan conversion, we strongly recommend that you consult a tax advisor to start planning how it would affect your taxable income and estimate how much you may need to pay in taxes,” the TSP wrote in the announcement.
“When you convert pre-tax money from your traditional TSP balance, your Roth in-plan conversion amount will become part of your taxable income for the year,” the TSP said. “This means that you’ll pay income tax on the conversion amount based on your income tax rate. You must pay the income tax on the conversion amount using personal funds from another source, such as a savings account. You cannot use part of the conversion amount in your TSP account to pay taxes.”
The TSP is also developing a calculator that will investors estimate the effects of converting traditional funds to Roth funds in a TSP account.
Additional helpful resources on the TSP Roth option:
Roth vs. Traditional TSP: Which One Should You Choose? by Ed Zurndorfer
Exploring the TSP Roth Conversion Strategy Reduce Your Tax Obligation in Retirement (video from Chris Kowalik)
Traditional and Roth TSP contributions (information on TSP.gov)
Summary of the Thrift Savings Plan (booklet)
Tax Rules about TSP Payments (booklet)