Thrift Savings PlanThe C Fund is the Thrift Savings Plan’s large-company U.S. stock fund. It tracks the S&P 500 — roughly the 500 largest publicly traded U.S. companies — and over the last twenty years it has been the best-compounding of the five core TSP funds.
For most federal employees it is the single most important holding in the plan. It is also the one that fell 36.99% in 2008.
The C Fund returned 11.01% a year over 2006–2025, turning $10,000 into $80,821.11 — the highest of the five core funds. It paid for that with a 36.99% loss in 2008 and an 18.13% loss in 2022. Highest long-run return, third-deepest single-year loss, behind the I and S funds.
What the C Fund actually holds
The C Fund is an index fund tracking the S&P 500. When you own it you own a slice of the largest American companies, weighted by size, which in practice means the biggest names dominate the result. It covers large-cap U.S. stocks only — no small companies (that is the S Fund) and nothing outside the United States (the I Fund).
Does the C Fund have a ticker symbol?
No. TSP funds are internal to the plan, are not publicly traded, and have no ticker. People search for a “C Fund ticker” because the fund tracks the S&P 500, and any S&P 500 index fund or ETF tracks the same index — but you cannot buy the C Fund itself outside the TSP, and it is not the same as buying an S&P 500 ETF in a brokerage account. The formal name you will see on TSP paperwork is the Common Stock Index Investment Fund.
What the C Fund costs
TSP administrative expenses are among the lowest of any retirement plan in the country, and the TSP publishes a net expense ratio for every fund each year. We do not print a figure here, because our data source covers returns rather than the fee schedule and we only publish numbers we can point to — check the current published net expense ratio for the C Fund on tsp.gov. What matters for a decision is the ranking: TSP costs are low enough that they are almost never the reason to choose one of these funds over another. Choose on risk and role instead.
Risk profile: the reliable engine, with real teeth
Seventeen of the twenty years in the table below were positive, six were gains above 24%, and three were losses. The losses were not small: −36.99% in 2008, −18.13% in 2022, −4.41% in 2018. A federal employee with a large balance in 2008 watched more than a third of it disappear inside twelve months, and the recovery took years, not months.
That is the honest trade. The C Fund produced the best twenty-year result of the five funds, and it required you to sit through the worst two calendar years of the period without selling.
C Fund annual returns, 2006–2025
| Year | C Fund return |
|---|---|
| 2006 | 15.79% |
| 2007 | 5.54% |
| 2008 | -36.99% |
| 2009 | 26.68% |
| 2010 | 15.06% |
| 2011 | 2.11% |
| 2012 | 16.07% |
| 2013 | 32.45% |
| 2014 | 13.78% |
| 2015 | 1.46% |
| 2016 | 12.01% |
| 2017 | 21.82% |
| 2018 | -4.41% |
| 2019 | 31.45% |
| 2020 | 18.31% |
| 2021 | 28.68% |
| 2022 | -18.13% |
| 2023 | 26.25% |
| 2024 | 24.96% |
| 2025 | 17.85% |
Calendar-year returns for the C Fund, January 2006 through December 2025. Click a column heading to sort — sorting by return is the fastest way to see the best and worst years. Source: Portfolio Visualizer export used for the Retirement Edge TSP backtest.
2008, 2020 and 2022 — the C Fund in the three stress tests
2008: −36.99%. Its worst year of the period. The G Fund returned +3.75% and the F Fund +5.45% in the same year, which is the entire case for holding some fixed income.
2020: +18.31%. A strong calendar year that hides a violent February–March crash. The number belongs to investors who held through it; anyone who sold in March did not get it.
2022: −18.13%. A rate-driven decline in which the F Fund fell too (−12.83%), so a conventional stock-and-bond mix offered less shelter than expected.
Who the C Fund suits — and who it does not
It suits you if you have a decade or more before you need the money and you want the core growth holding of the TSP. Across this twenty-year period it was the largest single position in many growth-oriented TSP allocations.
It does not suit you if you are close to retirement with no fixed-income ballast, or if a 35% paper loss would make you move your entire balance to the G Fund at the bottom. In that case the problem is the allocation, not the fund.
The other TSP funds
- S FundSmall and mid-cap U.S. stocks · 9.53%
- I FundInternational stocks · 5.91%
- F FundU.S. investment-grade bonds · 3.41%
- G FundGovernment securities · 2.85%
- All five, side by sideThe TSP funds hub
The part a table cannot tell you
How much of the C Fund to hold, and when that should change, is the actual question. Our TSP allocation by age guide gives a decade-by-decade framework, you can pressure-test any mix in the TSP Calculator, and the TSP Edge model portfolio is a rules-based monthly update built from these same five funds — research you choose to act on, with most months saying nothing needs to change.