The TSP mutual fund window is an optional feature inside the Thrift Savings Plan that lets federal employees and uniformed service members invest in roughly 5,000 outside mutual funds beyond the core G, F, C, S, and I funds.1Federal Retirement Thrift Investment Board. Facts About the TSP’s Mutual Fund Window You need at least $40,000 in your TSP account to qualify, your first transfer must be at least $10,000, and total window holdings are capped at 25% of your TSP balance. Fixed fees run $132 a year before you place a single trade, plus $28.75 per buy or sell, which is why the window only pays off for participants with a clear reason to diversify beyond the core lineup.
Who Can Use It
Two balance thresholds control access. Your total TSP account must hold at least $40,000, and your initial transfer into the window must be at least $10,000 while staying at or under 25% of your total TSP balance.2The Thrift Savings Plan (TSP). Mutual Fund Window The $40,000 floor exists because a $10,000 transfer out of a $40,000 account hits the 25% ceiling exactly.
After the first transfer, you can move more money in, but window holdings can never exceed 25% of your overall TSP balance at the moment of any new transfer.3eCFR. 5 CFR Part 1601 Subpart F – Mutual Fund Window If market gains push your window balance above 25%, you won’t be forced to sell. You just can’t add more until the ratio drops back under the cap. Transfers have to be in whole dollar amounts; percentages aren’t allowed.
What You Can and Can’t Buy
The window includes about 5,000 mutual funds across roughly 300 fund families, including Fidelity, T. Rowe Price, and Vanguard.1Federal Retirement Thrift Investment Board. Facts About the TSP’s Mutual Fund Window That covers asset classes the core TSP funds don’t reach: emerging markets, commodities, real estate, sector equity, socially responsible strategies, and bond categories outside the Bloomberg U.S. Aggregate index tracked by the F Fund.
Congress limited the window to mutual funds only. Individual stocks, individual bonds, ETFs, options, futures, margin trading, and cryptocurrency are all prohibited by law.4Federal Register. 5 CFR 1601 – Mutual Fund Window Participants sometimes expect a full brokerage account, and this is not that. Each listed fund comes with a prospectus you can pull up before buying, and the platform lets you search by ticker, fund family, or other criteria.2The Thrift Savings Plan (TSP). Mutual Fund Window The window interface is separate from your main TSP dashboard.
What It Costs
Three fixed charges apply to every window user:
- Annual administrative fee of $37, which covers TSP overhead so non-users don’t subsidize the program.2The Thrift Savings Plan (TSP). Mutual Fund Window
- Annual maintenance fee of $95 for continued access to the window account.2The Thrift Savings Plan (TSP). Mutual Fund Window
- Per-trade fee of $28.75 every time you buy or sell shares inside the window.2The Thrift Savings Plan (TSP). Mutual Fund Window
Those charges are flat, so a $500 trade and a $50,000 trade cost the same $28.75. Small, frequent trades will eat returns quickly. Simply keeping the account open runs $132 a year before any activity.
On top of the TSP’s fees, each mutual fund carries its own expense ratio, deducted from fund returns, and some share classes carry front-end or back-end sales loads. The TSP doesn’t waive fund-level charges, so read each prospectus before buying.2The Thrift Savings Plan (TSP). Mutual Fund Window Core TSP funds have historically run at a fraction of a basis point, so the cost gap is real and it compounds.
Opening the Account and Moving Money
Enrollment happens entirely online through the My Account portal at tsp.gov. After logging in, you open the window option and sign an acknowledgment of risk before your first transfer can process.3eCFR. 5 CFR Part 1601 Subpart F – Mutual Fund Window The acknowledgment covers the higher fees, the 25% cap, and the different risk profile of window investments. No paper forms.
Getting money in takes two steps. First, transfer from your core TSP holdings into the window. The money lands in a sweep money market fund, not directly into whatever mutual fund you picked.3eCFR. 5 CFR Part 1601 Subpart F – Mutual Fund Window From the sweep account, you search for a fund, review the prospectus, and submit a buy order. Selling reverses the process: proceeds return to the sweep account, and from there you can reinvest or transfer cash back to core TSP funds.
Fund transfers and reallocations are capped at two per calendar month combined, and that limit covers movement in either direction between core funds and the window.2The Thrift Savings Plan (TSP). Mutual Fund Window Buying and selling mutual funds inside the window, once your money is already there, doesn’t count against that limit.
Loans and Withdrawals Don’t Work Directly From the Window
This trips up a lot of participants. You cannot take a loan, hardship withdrawal, age-based withdrawal, or any other distribution directly from money in the mutual fund window.3eCFR. 5 CFR Part 1601 Subpart F – Mutual Fund Window To access those dollars, you first sell your mutual fund shares, then transfer the proceeds back to core TSP funds, and only then can you request a withdrawal or loan.
That sequence takes time. Between selling shares, waiting for settlement, transferring back, and processing the actual withdrawal request, you’re looking at days or longer. If you’re approaching retirement or expect to need a TSP loan, a large window balance becomes a bottleneck. Size your window holdings with that timeline in mind.