TSP C Fund: what's actually inside it
Officially the Common Stock Index Investment Fund. Large-capitalization US company stocks. Tracks the S&P 500.
504 holdings · expense ratio 0.048% · top 10 = 39.1% · concentration score 31.7/100 · holdings as of 2026-09-30
Top 25 holdings
| # | Holding | Weight | |
|---|---|---|---|
| 1 | NVDA | 8.38% | |
| 2 | AAPL | 7.37% | |
| 3 | MSFT | 5.78% | |
| 4 | AMZN | 3.71% | |
| 5 | GOOGL | 3.07% | |
| 6 | AVGO | 2.53% | |
| 7 | GOOG | 2.45% | |
| 8 | META | 2.43% | |
| 9 | MU | 1.82% | |
| 10 | TSLA | 1.52% | |
| 11 | AMD | 1.52% | |
| 12 | BRK-B | 1.41% | |
| 13 | LLY | 1.40% | |
| 14 | JPM | 1.33% | |
| 15 | XOM | 1.02% | |
| 16 | JNJ | 0.97% | |
| 17 | V | 0.91% | |
| 18 | INTC | 0.91% | |
| 19 | WMT | 0.70% | |
| 20 | ABBV | 0.70% | |
| 21 | MA | 0.68% | |
| 22 | PLTR | 0.65% | |
| 23 | CSCO | 0.64% | |
| 24 | LRCX | 0.62% | |
| 25 | AMAT | 0.62% |
Sector split
Overlap with the other TSP funds
The question a federal employee can actually act on: holding two of these, how much is the same underlying company?
| Paired with | Overlap | Effective Funds (50/50) |
|---|---|---|
| TSP I Fund | 0.8% | 2.0 |
| TSP S Fund | 0.1% | 2.0 |
| TSP F Fund | 0.1% | 2.0 |
What has changed
Between July 2026 and September 2026, from 3 months on record:
| July 2026 | September 2026 | Change | |
|---|---|---|---|
| Largest holding | NVDA7.6% | NVDA8.4% | +0.8pp |
| Top 10 holdings | 37.6% | 39.1% | +1.4pp |
| Positions published | 504 | 504 | no change |
One point per month, taken from the issuer's published holdings file. Tracking began July 2026 — figures from before then were not retained.
Frequently asked
What does the TSP C Fund actually hold?
The C Fund — officially the Common Stock Index Investment Fund — tracks the S&P 500. The Thrift Savings Plan does not publish a holdings list and does not file SEC form N-PORT, so this page shows the 504 positions of VOO, which tracks the same index, as of 2026-09-30. The largest position is NVDA at 8.4%, and the top ten are 39.1% of the fund.
Is this the TSP's real holdings data?
No, and that distinction matters. It is a labelled proxy: a different fund tracking the same index, not the C Fund itself. VOO tracks the same index, so its published holdings are the closest available picture of what the C Fund owns. Index funds tracking the same benchmark hold nearly identical portfolios, so the picture is close — but the weights are VOO's, not the TSP's, and the TSP has never published its own.
How much do the TSP funds overlap each other?
The C Fund overlaps the I Fund 0.8% by weight — I Fund 0.8%, S Fund 0.1%, F Fund 0.1%. Overlap is the sum of the smaller weight in each fund over every holding both own, computed from the proxy holdings described above.
Why isn't the G Fund shown?
The G Fund — officially the Government Securities Investment Fund — is deliberately absent. It holds non-marketable US Treasury securities issued only to the TSP, which are not traded anywhere and have no market equivalent. Showing it through a bond fund would misrepresent an instrument whose defining feature is that its principal cannot fall.
Most federal employees hold more than the TSP
A TSP account is rarely the whole picture — there is often an IRA, a spouse's 401(k), or a brokerage account alongside it. Paste them all together to see the real overlap between your C Fund and everything else you own, and your own Effective Funds number. Free, no account, nothing stored.
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How it overlaps the other TSP funds
TSP C Fund shown via VOO, holdings as of 2026-09-30. The TSP publishes no holdings of its own. Weights are fractions of the fund. Diagnostics, not advice.