Published
Sep 21, 2026
Last Updated
Sep 21, 2026
TSP Mutual Fund Window: What Federal Employees Need to Know in 2026
The TSP Mutual Fund Window (MFW) is an optional investment option within the Thrift Savings Plan (TSP). The TSP is the federal government's tax-advantaged retirement savings program for federal employees and uniformed service members. It lets you invest up to 25% of your TSP balance in publicly available mutual funds.
You need at least $40,000 in your total TSP account to be eligible for the Mutual Fund Window. Your initial transfer must be at least $10,000 and cannot exceed 25% of your total TSP balance. You'll also pay added annual and per-trade fees that don't apply if you stick to the TSP's five core funds.
Core TSP funds do not have the MFW's separate annual and per-trade fees. That's because the MFW adds platform and trading fees on top of each mutual fund's own expense ratio.
The window provides access to mutual-fund strategies and asset classes that aren't directly available through the five core TSP funds, such as sector-specific funds, actively managed bond strategies, or emerging-market small caps.
This guide from Federal Pension Advisors, a retirement planning firm specializing in federal employee benefits, covers eligibility, costs, and current participation data. Use it to weigh whether the window fits your plan.
What Is the TSP Mutual Fund Window?
The MFW is an investment option within your TSP account. It lets you invest a portion of your balance in publicly available mutual funds through a third-party brokerage platform.
Once you transfer money in, it's no longer invested in the core TSP funds. Instead, you select mutual funds available on the platform. Before making changes to your investment mix, it's also important to understand TSP allocation risk and how different investment choices may affect your retirement strategy. The MFW is maintained separately from the five core TSP funds within the TSP structure.
The Federal Retirement Thrift Investment Board (FRTIB) is the independent federal agency that administers the TSP. FRTIB publishes MFW fund-count data periodically. As of December 31, 2024, the most recent figure it has published, 4,765 mutual funds were available through the MFW.
The window doesn't permit exchange-traded funds (ETFs), individual stocks, or individual bonds. It's mutual funds only.
The MFW was built for participants seeking strategies the TSP's five core index funds don't directly provide.
Who Is Eligible to Use the TSP Mutual Fund Window
TSP.gov's mutual fund window page sets out the eligibility rules. You need at least $40,000 in your total TSP account to be eligible. You can't invest more than 25% of your total account balance in the window at any time.
Your initial fund transfer into the window must be at least $10,000. It can't exceed 25% of your TSP balance on the day you transfer.
If market performance pushes your window balance above the 25% ceiling, you generally can't add more to the window until the balance falls below the limit.
If you hold more than one TSP account, such as a civilian account and a uniformed services account, eligibility rules and fees apply separately to each. You'd need to open a separate MFW account for each.
How the Mutual Fund Window Works
- Confirm eligibility. Your total TSP balance must be at least $40,000.
- Transfer funds. Move at least $10,000 from your core TSP funds into the window.
- Land in a sweep account. Your transferred money starts in a money market mutual fund inside the window.
- Select mutual funds. Choose from the available lineup and place trades.
- Monitor the 25% cap. Ongoing transfers can't push your window balance above 25% of your total TSP account.
Fund transfers into the MFW count toward your monthly TSP transfer limit. You get two interfund transfers per month. After that, you can only move money into the G Fund.
TSP Mutual Fund Window Fees
Fees matter. They're a central factor in deciding whether the window makes sense for your balance.
TSP.gov's published fee schedule sets the MFW annual fee at $150. That breaks down into a $95 maintenance fee and a $55 administrative fee. Both fees come directly out of your core TSP account, not the window itself.
FRTIB redetermines the $55 portion every three years based on actual program expenses, so it can shift over time. Check TSP.gov for the current amount before you budget around it.
Every trade inside the window, whether you're buying or selling a mutual fund, carries a $28.75 transaction fee on top of the annual fee.
On a $10,000 window balance, the $150 annual fee alone equals roughly 1.5% of that balance, before trading costs or fund expense ratios. As your balance grows, the fixed annual fee represents a smaller percentage of your assets. Frequent trading can also increase costs, because each trade carries a transaction fee. For investors approaching or entering retirement, it is also important to consider how account costs and investment decisions can affect long-term portfolio sustainability and [TSP risks after early retirement].
Core TSP Funds vs. the Mutual Fund Window
TSP Mutual Fund Window Advantages and Drawbacks
Potential advantages:
- Access to asset classes not available in the five core funds, such as sector-specific or actively managed strategies
- The flat annual fee represents a smaller percentage of assets on larger window balances
- Allows eligible participants to use mutual funds within the TSP rather than moving those assets to an outside IRA
Costs and constraints to weigh:
- The $150 annual fee plus $28.75 per trade can meaningfully erode returns on smaller window balances
- Duplicating an index a core fund already tracks adds cost without adding diversification
- Example: buying an S&P 500 mutual fund when the C Fund already tracks that index
- The 25% cap limits how much of your overall strategy the window can influence
Participation remains a small share of the overall plan. As of December 31, 2025, FRTIB's 2025 Annual Report to Congress recorded 8,624 funded MFW accounts holding $760 million in assets. On the same date, the plan held 7,298,608 total participant accounts and $1.073 trillion in total assets.
The Mutual Fund Window and Roth Conversions
The TSP introduced Roth in-plan conversions on January 28, 2026. If you hold investments through the Mutual Fund Window and are considering a Roth conversion, it’s important to understand the potential tax implications before taking action. You can also review AI tax advice for federal employees for additional considerations around using AI-generated tax information for federal retirement planning. Check the current process with TSP.gov or the ThriftLine first, and confirm eligibility requirements before you take action.
The 11 Lifecycle Funds, Updated
The TSP's core lineup includes 11 Lifecycle (L) Funds, built exclusively from the G, F, C, S, and I Funds. As of June 30, 2025, FRTIB added the L 2075 Fund and retired the L 2025 Fund, merging it into the L Income Fund. The specific L Fund lineup changes periodically even when the total count stays the same.
How Federal Pension Advisors Can Help You Decide
Whether the mutual fund window belongs in your retirement plan depends on several factors. These include your total TSP balance, your time horizon, and your FERS (Federal Employees Retirement System) or CSRS (Civil Service Retirement System) status. They also include how the added fees compare to the diversification you're seeking.
Federal Pension Advisors, a retirement planning firm specializing in federal employee benefits, helps federal employees weigh options like the mutual fund window against their core TSP allocation and retirement timeline. A federal retirement professional can help you evaluate the MFW alongside your broader TSP allocation and retirement timeline.
This article is intended to inform, not to serve as individualized investment advice.
Frequently Asked Questions
What is the TSP Mutual Fund Window?
The TSP Mutual Fund Window is an optional investment option within the Thrift Savings Plan that lets eligible participants invest up to 25% of their balance in outside mutual funds. It requires a $40,000 total TSP balance and a $10,000 minimum initial transfer, and it carries fees that don't apply to the core TSP funds.
How much does the TSP Mutual Fund Window cost?
Per TSP.gov's published fee schedule, the window carries a $150 annual fee in combined maintenance and administrative charges, plus $28.75 for every trade you place. These fees come out of your core TSP account. Mutual funds you select inside the window also carry their own expense ratios, on top of these platform costs.
Who is eligible for the TSP Mutual Fund Window?
You need a total TSP balance of at least $40,000 and must transfer a minimum of $10,000 to open a window account. You cannot invest more than 25% of your total TSP balance in the window at any time, and eligibility applies separately to each TSP account you hold.
Can I buy ETFs or individual stocks through the TSP Mutual Fund Window?
No, the mutual fund window only offers mutual funds. As of December 31, 2024, the most recent figure FRTIB has published, that totaled 4,765 funds. ETFs, individual stocks, and individual bonds are not available.
How many TSP accounts use the Mutual Fund Window?
As of December 31, 2025, FRTIB's Annual Report to Congress counted 8,624 funded MFW accounts holding $760 million in assets. On the same date, the plan held 7,298,608 total participant accounts and $1.073 trillion in total assets.
Is the TSP Mutual Fund Window worth it?
The answer depends on your balance, investment objectives, desired diversification, and the additional fees. The fixed annual fee represents a larger percentage of a smaller MFW balance, while the window may provide access to investment categories not available through the core TSP funds.
Disclaimer
This article is for informational and educational purposes only and does not constitute individualized investment, tax, or retirement advice. TSP rules, fees, investment options, and eligibility requirements may change. Review current information on TSP.gov or contact the ThriftLine before making investment or retirement decisions.
Get Updated
Subscribe to our weekly updates for the latest on retirement planning, federal benefits, exclusive webinars, and more!
Stuart Hunsicker
Stuart Hunsicker is a federal retirement specialist who helps federal employees understand how workplace policy changes, FERS, TSP, FEHB, and retirement benefits work together. He focuses on helping federal workers make informed retirement decisions based on current regulations and long-term financial planning.
Download Federal Retirement: Step-by-step Checklist
This comprehensive guide will help you understand your federal benefits, optimize your savings, and plan for a comfortable future.
Recent Post's
