The Thrift Savings Plan compounds daily. Every business day, the TSP recalculates what your account is worth, and whatever your money earned that day, whether interest in the G Fund or price appreciation in the stock and bond funds, becomes part of the base that earns the next day’s return. The mechanism differs by fund, but the frequency is the same across all of them.
Daily Interest in the G Fund
The Government Securities Investment Fund invests in special nonmarketable U.S. Treasury securities issued exclusively for the TSP, with principal and interest guaranteed by the U.S. government.1The Thrift Savings Plan (TSP). G Fund Because of that guarantee, the G Fund’s share price never drops. On a slow day your balance can sit flat, but it will not move backward.
The interest rate is set once a month, not once a day. Treasury calculates it as the weighted average yield of all outstanding Treasury securities with four or more years to maturity, measured on the last day of the previous month.2Office of the Law Revision Counsel. 5 USC 8438 – Investment of Thrift Savings Fund That monthly rate is then applied to the fund each business day. Interest credits daily, immediately becomes part of your balance, and starts earning the next day. The rate resets monthly; the compounding is daily.
The practical result is a return comparable to long-term Treasury bonds paired with the ability to redeem on any business day without risk to principal.1The Thrift Savings Plan (TSP). G Fund No commercial product offers the same combination.
Daily Share Price Changes in the C, S, I, and F Funds
The stock and bond funds do not pay “interest” in the G Fund sense. They hold pools of securities whose market value moves throughout each trading day. After the close, the TSP’s managers total each fund’s holdings, subtract accrued administrative expenses, and divide by the number of outstanding shares. That figure is the day’s share price.3The Thrift Savings Plan (TSP). Share Price Calculation
Each fund tracks an index. The C Fund mirrors the S&P 500.4The Thrift Savings Plan (TSP). C Fund The S Fund covers small- and mid-cap U.S. stocks outside the S&P 500. The I Fund tracks the MSCI ACWI IMI ex USA ex China ex Hong Kong Index.5The Thrift Savings Plan (TSP). I Fund The F Fund follows a broad U.S. bond index. When the underlying securities rise, so does the share price, and every share you own is worth more.
The compounding here works through price. Today’s closing price becomes tomorrow’s starting point. A 0.1% gain today, followed by another 0.1% tomorrow, layers the second day’s growth on the already-higher price. Over a career, that daily layering is where most of the growth comes from. The same mechanism runs in reverse on down days, which is the tradeoff for higher long-term expected returns.
Dividends, Interest, and Capital Gains Are Reinvested Automatically
Companies held in the C and S Funds pay dividends. Bonds in the F Fund pay interest. In an outside brokerage account, those payments might land in a cash balance and sit idle until you reinvest them. The TSP folds them in on the same day. Dividends, interest, capital gains, and securities lending income are all credited to the fund each business day and roll directly into the share price.3The Thrift Savings Plan (TSP). Share Price Calculation
You never see a separate dividend payment or a cash balance waiting to be deployed. Every dollar of income is already working toward the next day’s growth. You also do not receive 1099-DIV forms for these internal transactions while the money stays in the plan.3The Thrift Savings Plan (TSP). Share Price Calculation Tax reporting begins when you take a withdrawal, not before.
Lifecycle Funds Compound Daily and Rebalance Daily
If your money sits in one of the Lifecycle (L) Funds, it is spread across the five individual funds according to a target allocation that shifts gradually toward conservative holdings as the target retirement date approaches. The L Funds adjust their target mix every quarter.6The Thrift Savings Plan (TSP). Lifecycle Funds
Less well known: the L Funds also rebalance at the end of every trading day. Market movement pushes the actual mix away from the target during the day, and the TSP automatically buys and sells across the five underlying funds to bring it back in line.6The Thrift Savings Plan (TSP). Lifecycle Funds Your daily compounding continues normally inside each underlying fund; the rebalancing simply keeps your risk exposure consistent.
The L Income Fund, for people already drawing down, holds the most conservative mix with heavy weight in the G and F Funds.7The Thrift Savings Plan (TSP). L Income Further-dated L Funds lean harder on the stock funds. New enrollees who take no action are placed in the age-appropriate L Fund by default.
How New Contributions Join the Compounding Cycle
TSP contributions come out of your paycheck each pay period, which is biweekly for most federal employees.8The Thrift Savings Plan (TSP). Contribution Types Once your agency processes payroll and the money reaches the TSP, it buys shares at that day’s price. From that point forward, those shares participate in whatever daily price changes or interest accruals apply to your fund.
New FERS employees are automatically enrolled at 5% of basic pay unless they change or stop contributions.9The Thrift Savings Plan (TSP). Implementation of 5 Percent Automatic Enrollment Percentage for Thrift Savings Plan The agency contributes an automatic 1% of basic pay whether or not the employee contributes, plus matching contributions of up to another 4%, for a maximum agency contribution of 5%.8The Thrift Savings Plan (TSP). Contribution Types Every one of those dollars starts compounding the day it lands in your account.
What Slows Compounding Down
Daily compounding is only as strong as the balance actually working for you. A few features of the plan can quietly reduce that base.
Expense Ratios
Fees come out of the fund’s assets before the daily share price is set, so you never see them on a statement, but they still reduce what compounds. For 2025, each individual TSP fund charged between 0.033% and 0.034% in net administrative expenses. The L Funds run from 0.030% to 0.034%.10The Thrift Savings Plan (TSP). Expenses and Fees On a $100,000 balance, that is roughly $34 a year. Compared with commercial mutual funds charging 0.50% to 1.00% or more, the drag on compounding is small.
TSP Loans
A TSP loan pulls money out of the invested balance and stops it from compounding until you pay it back. You repay yourself with interest set at the G Fund rate from the month before you requested the loan, fixed for the life of the loan. The interest goes back into your account rather than to a lender, but the borrowed dollars miss whatever the stock funds earned during repayment. In a year when the C Fund returns 10% and the G Fund rate is 4%, every borrowed dollar effectively gave up six percentage points of growth. There are two loan types: a general purpose loan with a $50 processing fee and a primary residence loan with a $100 fee.11The Thrift Savings Plan (TSP). TSP Loans
Interfund Transfer Limits
Moving money between funds does not restart the compounding clock; your balance stays invested through the transfer. But the TSP caps how often you can shift. You get two interfund transfers or reallocations each calendar month that can move money into any combination of funds. After those first two, any additional transfers during the same month can only move money into the G Fund. If you hold both a civilian and a uniformed services TSP account, the two-transfer limit applies to each account separately.12The Thrift Savings Plan (TSP). How to Change Your TSP Investments The rule is designed to discourage short-term market timing.
The core answer stays simple. Every business day, the TSP prices your funds, credits any earnings, and hands you a slightly different starting point for tomorrow. Left alone through a full career, that daily cycle is what turns steady contributions into a retirement balance.