You can stop investments at any time, although if you are a Federal Employees Retirement System employee, remember that will mean that government matching contributions will shut off, too (the automatic contribution equal to 1 percent of salary will continue, though).
Ongoing investments can be changed in several ways. First, you can increase or decrease the amount being withheld from your pay. Second, you can change the way you allocate your investments among the TSP’s available funds. Third, you can change how much of your ongoing investments are going into traditional versus Roth balances. Those changes can be made at any time.
You also can move your existing account balance among the available funds through what is called an “interfund transfer” at any time with this exception: after two transfers in a month, any additional transfers may only move money into the government securities G Fund—even if one or both of the earlier transfers moved money only into that fund. Conversions of one type of balance to the other currently aren’t allowed.
In an interfund transfer, you choose a percentage of your account as of that date to allocate to each of the funds you choose. You can elect from any combination of the funds available.
If you have both traditional and Roth balances, any changes in ongoing allocations and any interfund transfers will apply equally to both types.