New Mutual Fund Window in the Thrift Savings Plan

What is the TSP Mutual Fund Window?

Think of the mutual fund window as a separate investment “sub-account” inside your TSP. You move (transfer) money from your TSP core funds into the window, then buy and sell mutual funds inside that window.

This option was designed for people who want access to strategies the core TSP funds don’t directly cover (for example, certain sector funds or specialized bond funds). The tradeoff is higher costs and more moving parts.

What you can (and can’t) invest in

You can invest in:

• Mutual funds (thousands of choices)

You cannot invest in:

• ETFs
• Individual stocks
• Individual bonds
• Other publicly traded securities 

Eligibility rules of the mutual fund window

To open and use the mutual fund window, the big rules to know are:

• Your TSP balance must be at least $40,000 (so your initial transfer isn’t more than 25%).
• Your initial transfer must be at least $10,000. 
• You can’t invest more than 25% of your total TSP balance in the mutual fund window.

If market movement pushes your window balance above 25%, you typically can’t add more until you’re back within limits.

Mutual fund window fees and costs

Using the mutual fund window adds multiple layers of cost:

1) Annual fees (TSP window fees)

• $55 annual administrative fee (the regulation notes this fee is redetermined every three years)
• $95 annual maintenance fee
• Total: $150/year before you place a single trade

2) Trading fees

• $28.75 per trade (buying or selling funds in the window)

3) Mutual fund expense ratios (fund-level costs)

Every mutual fund you choose has its own internal expense ratio. These are often much higher than the core TSP index funds—especially if you drift into actively managed funds.

Why it matters

If you move $10,000 into the window, the $150/year in annual fees alone is a 1.5% “fee drag” on that slice of your portfolio—before trading fees and mutual fund expenses. If you trade more than once in a while, costs can climb fast.

Should you use the mutual fund window?

It could make sense to use the mutual fund window if:

• You have a large TSP balance and only plan to use the window for a specific, long-term allocation (not frequent trading)
• You’re intentionally adding exposure you can’t reasonably get with the core funds (and you understand the costs)

It likely doesn’t make sense to use the mutual fund window if:

• Your account is near the minimum requirements (fees are a much bigger percentage hit)
• You plan to trade frequently (the per-trade fee adds up fast)
• You’re mainly attracted by “more options,” but don’t have a clear reason for a specific fund/strategy

Mutual Fund Window FAQ 

1. Can I buy ETFs in the TSP mutual fund window?

No. The mutual fund window is mutual funds only—no ETFs, stocks, or bonds. 

2. What do I need to qualify?

Typically: at least $40,000 in your TSP, a $10,000 minimum initial transfer, and a 25% maximum allocation to the window. 

3. What are the annual mutual fund fees?

$55 annual administrative fee + $95 annual maintenance fee ($150 total), plus $28.75 per trade, plus the mutual funds’ internal expenses. 

4. Do TSP transfer limits still apply?

Yes—transfers back from the window count toward monthly limits (with the G Fund exception)