How the Thrift Savings Plan Works: BRS Matching, Contribution Limits, and Fund Options
The exact BRS government matching formula, 2026 IRS contribution limits, vesting rules, and TSP fund performance data — sourced directly from TSP.gov and 37 U.S.C. § 354.
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What the TSP Is
The Thrift Savings Plan (TSP) is a defined-contribution retirement savings plan for federal employees and uniformed service members, established under the Federal Employees Retirement System Act of 1986 (5 U.S.C. Chapter 84). It functions identically to a 401(k) in the private sector: contributions are invested in index funds, grow tax-deferred (or tax-free in the Roth option), and are withdrawn in retirement. As of 2024, the TSP held approximately $845 billion in assets across 7 million accounts.
The Blended Retirement System and Government Matching
All service members who entered military service on or after January 1, 2018 are automatically enrolled in the Blended Retirement System (BRS) under 37 U.S.C. § 354. Those who entered before that date and did not opt in during the 2018 opt-in window remain on the legacy High-3 system, which provides no government TSP matching.
Under BRS, the government makes two types of contributions to your TSP:
Government Contribution Structure (Per TSP.gov)
The matching formula, published directly on TSP.gov, works as follows for each biweekly pay period:
| Your Contribution (% of Basic Pay) | Auto 1% Contribution | Agency Match | Total Government Contribution |
|---|---|---|---|
| 0% | 1% | 0% | 1% |
| 1% | 1% | 1% | 3% |
| 2% | 1% | 2% | 5% |
| 3% | 1% | 3% | 7% |
| 4% | 1% | 3.5% | 8.5% |
| 5% | 1% | 4% | 10% |
The matching formula is: dollar-for-dollar on the first 3% of basic pay you contribute, plus $0.50 per dollar on the next 2%. Contributing 5% or more captures the full 4% match plus the automatic 1%, for a total government contribution of 5% of basic pay. Contributing less than 5% leaves free money on the table.
The automatic 1% contribution begins after 60 days of service and is subject to a 2-year vesting period — you must complete 2 years of service to keep it if you separate before then. The matching contributions vest immediately.
2026 IRS Contribution Limits
The IRS sets annual limits on how much you can contribute to your TSP. For 2026, per TSP.gov:
| Limit Type | 2026 Amount | Who It Applies To |
|---|---|---|
| Elective Deferral Limit | $24,500/year | All participants under age 50 |
| Catch-Up Contribution Limit | +$8,000/year | Ages 50-59 and 64+ |
| Higher Catch-Up Limit (SECURE 2.0) | +$11,250/year | Ages 60-63 only |
| Annual Additions Limit | $72,000/year | Total including all contributions |
Government matching contributions do not count toward the $24,500 elective deferral limit. They do count toward the $72,000 annual additions limit.
TSP Fund Options and Historical Performance
The TSP offers five individual index funds and a series of Lifecycle (L) funds. As of the 10-year period ending December 31, 2024 (per TSP.gov fund performance data):
| Fund | Index Tracked | 10-Year Avg Annual Return |
|---|---|---|
| C Fund | S&P 500 | ~12.6% |
| S Fund | Dow Jones U.S. Completion TSM | ~9.8% |
| I Fund | MSCI EAFE (international) | ~5.6% |
| F Fund | Bloomberg U.S. Aggregate Bond | ~1.6% |
| G Fund | Special U.S. Treasury securities | ~2.4% |
The L Funds (Lifecycle funds) automatically shift from aggressive to conservative allocations as the target retirement date approaches. The L 2050 Fund had a 10-year average annual return of approximately 9.5% as of December 31, 2024. Past performance does not guarantee future results.
Traditional vs. Roth TSP
You can contribute to a Traditional TSP (pre-tax contributions, taxed on withdrawal) or a Roth TSP (after-tax contributions, tax-free qualified withdrawals). The $24,500 limit applies to the combined total of both. Government matching contributions always go into the Traditional TSP regardless of your election, per 5 U.S.C. § 8432.
For most junior enlisted members in lower tax brackets, the Roth TSP is generally advantageous because contributions are taxed now at a lower rate, and all future growth is tax-free. This is not tax advice — consult a financial advisor for your specific situation.
The Cost of Not Contributing 5%
For an E-4 with 4 years of service earning approximately $2,844/month in basic pay (2026 DFAS), contributing only 3% instead of 5% means forgoing $28.44/month in government matching ($2,844 x 1%). Over a 20-year career, that uncaptured match — compounded at 7% annually — equals approximately $14,700 in lost retirement savings. Contributing at least 5% is the single highest-return financial action available to BRS-enrolled service members.
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