CSRS vs FERS: the full differences in pension, COLA, Social Security and TSP
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Published November 1, 2026 · By the OnPAR Federal Retirement Education editorial team · Last reviewed Nov 2026
Short answer: CSRS is the older federal retirement system: a bigger pension, no Social Security from federal work and no TSP match. FERS, which covers most employees hired since 1984, has three parts: a smaller pension, Social Security and the TSP with agency contributions of up to 5%. Since the Social Security Fairness Act (signed January 5, 2025), the WEP and GPO cuts that hit many CSRS retirees no longer apply to benefits payable for January 2024 and later (SSA).
CSRS vs FERS at a glance
| CSRS | FERS | |
|---|---|---|
| Pension formula | 1.5% x High-3 for each of the first 5 years, 1.75% for the next 5, 2% for each year over 10 | 1% x High-3 per year, or 1.1% if you retire at 62+ with 20+ years |
| Maximum pension | 80% of High-3 (plus sick leave credit) | No set cap |
| Employee contribution | 7.0% | 0.8%, 3.1% (FERS-RAE) or 4.4% (FERS-FRAE) |
| Social Security from federal work | No | Yes |
| TSP agency contributions | None | 1% automatic plus matching, up to 5% total |
| Retire before 55 (early out) | Cut 2% a year under 55 | No age cut |
| COLA | Full CPI-W, at any age | "Diet" COLA, generally from age 62 |
| FERS Supplement | n/a | Yes, from MRA to 62 if you qualify |
Sources: OPM CSRS computation, OPM FERS computation, 5 U.S.C. 8339, 5 U.S.C. 8415, 5 U.S.C. 8432(c), our contribution rates guide.
The pension formula
CSRS (OPM, 5 U.S.C. 8339): 1.5% of your High-3 for each of the first 5 years, plus 1.75% for each of the next 5, plus 2% for each year over 10. The maximum is 80% of High-3 plus sick leave credit, which OPM says generally affects only people with more than 41 years 11 months of service.
FERS (OPM, 5 U.S.C. 8415): 1% of High-3 per year of service, or 1.1% if you are 62 or older at separation with 20 or more years.
Both use the same High-3: your highest average basic pay over any 3 consecutive years, not counting overtime or bonuses.
When you can retire
| CSRS | FERS | |
|---|---|---|
| Optional (immediate) | 62 with 5 years, 60 with 20, 55 with 30 | 62 with 5, 60 with 20, MRA with 30, MRA with 10 (reduced) |
| Early out / discontinued service | 50 with 20, or any age with 25 | 50 with 20, or any age with 25 |
| Deferred | 62 with 5 years | 62 with 5, MRA with 30, MRA with 10 |
Sources: OPM CSRS eligibility, OPM FERS eligibility. FERS MRA is 55 to 57, depending on birth year. MRA+10 is cut 5% a year under 62 unless you have 20 years and start at 60 or later. See MRA+10 and VERA early outs and VSIP buyouts.
Reductions to watch
- CSRS under 55: cut by 1/6 of 1% for each month under 55 (2% a year), except for disability and special provisions (OPM).
- Survivor benefit: a full CSRS spouse survivor annuity costs 2.5% of the first $3,600 plus 10% of the rest. Under FERS, a 50% survivor benefit costs 10% of your annuity and a 25% benefit costs 5% (OPM CSRS, OPM FERS).
COLAs
CSRS gets the full CPI-W increase at any age. FERS gets a reduced formula and, for most regular retirees, only from age 62. For the COLA effective December 1, 2026, OPM announced 3.6% for CSRS and 2.6% for FERS. Full details: FERS vs CSRS COLA 2027.
Social Security, WEP and GPO
CSRS employees don't pay Social Security tax on federal pay, so CSRS pensions are "non-covered." SSA says the Social Security Fairness Act ended WEP and GPO, and December 2023 was the last month they applied. That raises benefits for some CSRS retirees and their spouses. If you never applied for Social Security because of WEP or GPO, SSA says you may need to file an application now, and the date you apply can affect when benefits start (SSA).
Which one am I in?
Check the retirement plan entry on your SF-50, or ask HR. If you transferred from CSRS to FERS, your annuity has a CSRS component and a FERS component, each computed under its own rules (OPM). See how to get your SF-50s from eOPF.
Run your numbers with our FERS retirement calculator.
Questions and answers
What is the main difference between CSRS and FERS?
CSRS is a larger pension without Social Security or a TSP match. FERS combines a smaller pension, Social Security, and the TSP with agency contributions of up to 5% of pay.
How is the CSRS pension calculated?
OPM says 1.5% of High-3 for each of the first 5 years, 1.75% for the next 5, and 2% for each year over 10, up to 80% of High-3 plus sick leave credit.
How is the FERS pension calculated?
OPM says 1% of High-3 per year of service, or 1.1% if you retire at 62 or older with at least 20 years.
Does WEP or GPO still reduce CSRS retirees' Social Security?
No. SSA says the Social Security Fairness Act ended WEP and GPO; December 2023 was the last month they applied.
Do CSRS and FERS get the same COLA?
No. CSRS gets the full CPI-W increase at any age. FERS gets a reduced formula, generally from age 62. For Dec 1, 2026 OPM announced 3.6% CSRS and 2.6% FERS.