Federal Employees: TSP and FERS Basics

Federal civilian employees hired since January 1, 1984 participate in the Federal Employees Retirement System (FERS), a three-legged stool of (1) a defined-benefit annuity, (2) Social Security, and (3) the Thrift Savings Plan. Used to its limits the package replaces approximately 70–80% of pre-retirement income for a career employee, more than most private-sector defined-contribution plans. Used as the default-enrolled federal worker tends to, it leaves substantial value on the table.

The TSP: federal 401(k) with a critical match structure

The Thrift Savings Plan is the federal-employee defined-contribution plan, authorized under 5 U.S.C. §§8401–8479. It is administered by the Federal Retirement Thrift Investment Board.

• Employee deferral limit: Same as §402(g) — $23,500 in 2025, plus $7,500 catch-up (50+) or $11,250 super catch-up (60–63).
• Agency contributions:
  • Agency Automatic 1%: Paid to every FERS employee regardless of employee contribution.
  • Agency Matching: Dollar-for-dollar on first 3%, then 50 cents on next 2%. Maximum match = 4% of salary; combined with the automatic 1% = 5% of salary in agency money.
• Critical contribution rule: The match applies to each pay period. An employee who maxes out the $23,500 by mid-year loses the match on the remaining pay periods. To capture the full match, divide $23,500 by the number of pay periods (26) = $904 per pay period. Higher contributions cap out before year-end, forfeiting match.
• Fund choices: G Fund (government securities), F Fund (fixed income index), C Fund (S&P 500), S Fund (small/mid cap), I Fund (international developed). Lifecycle funds (L funds) blend these to target retirement dates.
• Expense ratios: Among the lowest in the world, approximately 4.8 basis points across all funds (2024). The expense advantage compounds to roughly $30,000–$60,000 over a 30-year career versus a typical retail mutual fund.
• Roth TSP available since 2012. Same $23,500 limit applies in combination.

The FERS defined-benefit annuity

FERS basic annuity is calculated as:

Annuity = high-3 average salary × years of service × multiplier

• Standard multiplier: 1.0%.
• Enhanced multiplier for those retiring at age 62+ with 20+ years of service: 1.1%. (11% formula advantage for waiting from 60/61 to 62.)
• Law enforcement, firefighters, air traffic controllers: 1.7% for first 20 years, 1.0% thereafter.

Eligibility: Minimum Retirement Age (MRA, 57 for those born 1970+) with 30 years of service; age 60 with 20 years; age 62 with 5 years. "MRA+10" allows retirement at MRA with 10–29 years of service but the annuity is reduced 5% per year under age 62.

The FERS supplement

Employees who retire before age 62 with eligibility for an immediate, unreduced annuity (e.g., MRA + 30 years) receive a FERS Annuity Supplement equal to an estimated Social Security benefit at age 62 attributable to FERS service. It bridges the income gap between separation and Social Security eligibility. Subject to the Social Security earnings test if the retiree works after MRA. Terminates at age 62 regardless of when Social Security is actually claimed.

Worked example: 30-year FERS career

GS-14 retiring at age 60 with 30 years of service. High-3 salary: $160,000. Standard multiplier 1.0%.

• FERS basic annuity: $160,000 × 30 × 0.01 = $48,000 per year.
• FERS supplement (estimated): approximately $19,000 per year (varies by SS earnings history), until age 62.
• TSP (max contribution + 5% agency, 30 years, 7% real return): approximately $2,400,000.
• Social Security at age 67 (FRA): roughly $36,000 per year.
• Combined replacement at 67+: $48,000 FERS + $36,000 SS + 4% × $2,400,000 TSP draw ($96,000) = $180,000, or 112% of high-3 salary.

The replacement ratio overshoots in part because the TSP balance, fully funded, dwarfs the defined-benefit annuity at career end.

Common mistakes

• Front-loading TSP contributions and forfeiting match. The most common federal-employee mistake. Spread evenly across 26 pay periods.
• Defaulting to the L 2050 fund in mid-career. Default enrollment selects the closest target-date L fund; many career employees never reconsider.
• Retiring at 61 instead of 62 with 20+ years. The multiplier jumps from 1.0% to 1.1% at age 62 with 20 years — a permanent 10% lift to every future annuity payment for one additional year of service.
• Failing to roll old federal service to FERS via deposit/redeposit. Prior CSRS service can be credited toward FERS retirement eligibility and amount with a deposit; the IRR (Individual Retirement Record) audit at retirement is the last chance.
• Misunderstanding the FERS supplement. It is income-tested (Social Security earnings test, not SS taxation rules) and ends at 62. A retired federal employee taking a private-sector consulting role may lose much or all of the supplement.
• Forgetting FEHB at retirement. Federal Employee Health Benefits enrollment for 5 continuous years prior to retirement is required to carry the benefit into retirement — the most valuable post-retirement benefit in U.S. employment.

Sources

• 5 U.S.C. §§8401–8479, FERS: law.cornell.edu §§8401–8479
• OPM FERS Information: opm.gov/retirement-center/fers-information/
• TSP, official site: tsp.gov
• OPM Pamphlet RI 90-1, FERS Handbook for Personnel and Payroll Offices: opm.gov RI 90-1
• Federal Retirement Thrift Investment Board, annual reports: frtib.gov

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