If you're a federal employee who started before 1987, you may have had the choice to switch from CSRS to FERS, or you're still under CSRS. If you started after 1987, you're in FERS. Either way, understanding what separates the two systems reveals a lot about what your retirement will actually look like.
The short version: CSRS is a richer, more self-contained defined benefit. FERS is a three-legged stool designed around the assumption that you'll also have Social Security and TSP. Neither is obviously better -- the right answer depends on your specific situation -- but the math is worth knowing.
The benefit formula
CSRS uses a tiered multiplier: 1.5% for the first five years of service, 1.75% for the next five, and 2.0% for every year after that. A 30-year CSRS employee's annual pension is roughly 56.25% of their high-3 average salary.
FERS uses a flat 1.0% multiplier for most retirees, or 1.1% if you retire at 62 or later with at least 20 years of service. A 30-year FERS employee retiring at 62 earns 33% of their high-3. That's roughly 40% less than the equivalent CSRS pension.
The gap looks brutal in isolation. But FERS employees also receive Social Security (CSRS employees generally don't) and can contribute to the TSP with a government match (CSRS employees get no government match). The three components together are designed to reach a similar total retirement income -- but only if Social Security is substantial and TSP contributions have been maximized.
The COLA difference
This is where CSRS wins decisively. CSRS retirees receive the full CPI-W increase every year with no cap. In years with 7% inflation, CSRS retirees get 7%.
FERS retirees get a reduced COLA: if CPI is 2% or below, they get the full amount. If CPI is between 2% and 3%, they get exactly 2%. If CPI exceeds 3%, they get CPI minus one percentage point. At 7% CPI, FERS retirees get 6%. At 5%, they get 4%.
The cumulative effect over 25 years is significant. At 3% average inflation, a $40,000 CSRS pension grows to $81,000 in nominal terms. The equivalent FERS pension (assuming the 2% COLA every year at 3% CPI) grows to $65,000. The CSRS retiree is $16,000 ahead by year 25 on the pension alone. Add the periods of higher inflation like 2021-2023, and the gap widens further.
FERS COLAs also don't begin until age 62. If you retire at 57 under FERS, your pension is frozen in nominal terms for five years before any inflation protection starts. That's roughly 15% of purchasing power lost before your first COLA even arrives, at 3% inflation.
Social Security integration
CSRS employees don't pay into Social Security during their federal service and generally don't receive Social Security from that work. If they have private-sector Social Security credits, the Windfall Elimination Provision (WEP) historically reduced those benefits. The Government Pension Offset (GPO) historically reduced spousal and survivor Social Security benefits for CSRS retirees. Both WEP and GPO were fully repealed effective January 5, 2025 under the Social Security Fairness Act. CSRS retirees with Social Security credits from other work now receive their full earned benefit.
FERS employees pay full Social Security taxes and receive full Social Security benefits (subject to normal rules). For a federal employee with 30 years of federal service and some private-sector history, the Social Security benefit at 67 might be $1,800-$2,400/month. That's a significant addition to the FERS pension that CSRS retirees don't have.
TSP and the match
Both FERS and CSRS employees can contribute to the Thrift Savings Plan. FERS employees receive an automatic 1% employer contribution plus a 4% match on their contributions (up to 5% total). CSRS employees receive no government contribution or match on their TSP contributions, making it substantially less valuable for them.
A FERS employee who contributes the full 5% to TSP over a 30-year career, earning average market returns, can accumulate $400,000-$700,000 in TSP depending on salary level. That's a meaningful supplement to the smaller FERS pension. CSRS employees who didn't contribute to TSP (many didn't, since it wasn't the primary retirement vehicle) have only the pension.
The actual comparison
For a federal employee with a $100,000 high-3 salary and 30 years of service:
- CSRS pension at retirement: ~$56,000/year with full CPI COLA from day one
- FERS pension at 62: $33,000/year with partial COLA from age 62
- FERS Social Security at 67: ~$22,000/year with full CPI COLA
- FERS TSP at 65 (annuitized or drawn at 4%): ~$20,000-$28,000/year
Total FERS income at full retirement: $75,000-$83,000/year, with most components growing with inflation. Total CSRS: $56,000/year, fully indexed. FERS wins on total income if TSP was funded and Social Security is substantial. CSRS wins if the federal employee has minimal private-sector SS credits, didn't maximize TSP, or values the simplicity of one fully-indexed income source.
The FERS Supplement: bridging the gap to 62
FERS employees who retire before age 62 under immediate or voluntary early retirement may qualify for the FERS Supplement, a monthly payment from OPM designed to approximate what the retiree would receive from Social Security at 62 based on their federal service. The supplement fills the income gap between FERS retirement and when Social Security becomes available.
The supplement is calculated by multiplying the retiree's years of FERS-covered civilian service, divided by 40, by their estimated Social Security benefit at age 62. A retiree with 30 years of FERS service who would receive $1,800 per month in Social Security at 62 receives approximately $1,350 per month in supplement (30 divided by 40 equals 0.75, times $1,800). It's a meaningful payment -- often $1,000 to $1,500 per month -- that partially offsets the FERS pension's lower annuity rate relative to CSRS.
The supplement is subject to the Social Security earnings test. In 2026, if you earn more than $24,480 from employment while collecting the supplement, it's reduced by $1 for every $2 of excess earnings. This can eliminate the supplement entirely for retirees who continue working after FERS retirement. The supplement is also not indexed for inflation -- it pays a fixed dollar amount from the retirement date until the retiree turns 62, when it stops entirely and actual Social Security begins.
CSRS has no equivalent supplement because CSRS-covered employees generally didn't contribute to Social Security through their CSRS service. CSRS retirees who take early retirement receive a reduced CSRS annuity immediately, with no bridge payment. This is one area where FERS genuinely advantages employees who retire before 62 -- the supplement converts what would otherwise be a years-long income gap into a manageable transition.
Survivor benefits: how FERS and CSRS compare
Both systems provide survivor annuities for surviving spouses, but the percentage and cost differ. Under FERS, the full survivor annuity is 50% of the employee's unreduced annual basic pay. A partial survivor option provides 25%. Electing the full survivor annuity reduces the retiree's own monthly annuity by 10%; the partial option costs 5%.
Under CSRS, the standard survivor annuity is 55% of the employee's unreduced CSRS annuity. A reduced option of approximately 25% is also available. The cost of the full 55% CSRS survivor annuity is a 10% reduction in the retiree's monthly benefit -- the same percentage reduction as FERS, but providing a slightly higher survivor percentage (55% versus 50%).
FERS has an important advantage for surviving spouses that CSRS doesn't: the surviving spouse may also qualify for Social Security survivor benefits on the federal employee's own Social Security record. FERS employees pay into Social Security throughout their federal career, building an independent SS earnings record. A FERS retiree's surviving spouse could collect both the FERS survivor annuity (50% of the FERS pension) and Social Security survivor benefits -- a combination that often substantially exceeds what the CSRS 55% survivor annuity provides alone. The total survivor income package under FERS, when Social Security survivor benefits are included, is frequently larger than the CSRS alternative.
Federal Employee Health Benefits in retirement
FEHB coverage in retirement is available to both FERS and CSRS employees who meet the five-year enrollment requirement. Retirees pay the same premium share as active employees -- roughly 28% of the total premium, with OPM covering the remaining 72%. This subsidy makes FEHB one of the most valuable components of the federal retirement package. Premium for a comprehensive family plan at the 28% employee share can be $400 to $700 per month -- a fraction of what equivalent private coverage costs for a retiree on the open market.
FEHB coverage continues for your lifetime in retirement and doesn't vary between FERS and CSRS. At 65, federal retirees can coordinate FEHB with Medicare. Enrolling in both Part A (usually premium-free) and Part B ($202.90 per month standard premium in 2026) creates a layered coverage structure where Medicare pays first and FEHB covers remaining costs. For retirees with ongoing healthcare needs, this coordination produces very low out-of-pocket costs. Whether Part B is worth the premium depends on your health status, the specific FEHB plan you're enrolled in, and how aggressively the plan covers costs when it's primary.
Creditable service: what counts and what doesn't
Both FERS and CSRS count creditable service toward retirement eligibility and annuity calculation. Creditable service includes: time in a covered federal civilian position, military service (with a deposit paid), certain Peace Corps and AmeriCorps service, and time in certain temporary positions. What doesn't count without action: military service where no deposit was paid, refunded prior federal service, and non-covered employment.
Military service deposits deserve particular attention. Federal employees who served in the military before their civilian career can purchase credit for that military service. For FERS, the deposit is 3% of basic military pay received during the period, plus interest if paid after the third year of federal employment. For CSRS, the cost is 7% of military pay, reflecting the higher CSRS contribution rate. The decision to purchase requires comparing the deposit cost against the resulting pension increase -- typically 1% per year of purchased service under FERS, applied to your high-3 average salary.
Military retirees receiving military retired pay face a specific complication: the same years of military service can't typically count for both military retirement and civilian pension service credit unless the military retiree waives their military retired pay for the period being purchased. Waiving military retired pay to get civilian credit can make sense in some cases (particularly when the civilian pension benefit is higher) but requires careful analysis of both retirement systems. An OPM retirement counselor and a military benefits specialist should both be consulted before making that decision.
VERA and VSIP: how they interact with FERS and CSRS
Voluntary Early Retirement Authority reduces the age and service requirements for immediate retirement during authorized workforce reductions. Under VERA, FERS employees with at least 25 years of service at any age, or at least 20 years of service at age 50 or older, can retire with an immediate annuity. CSRS employees can retire with 25 years at any age or 20 years at age 50 or older under VERA authority.
For FERS employees who take VERA before their Minimum Retirement Age (MRA), the pension begins immediately but the FERS Supplement doesn't start until MRA. If you're 47 with 25 years of service and your MRA is 57, that's a 10-year gap with no supplement. The pension pays from day one, but without the SS bridge that closes most of the CSRS-FERS income gap for employees who retire between MRA and 62.
Voluntary Separation Incentive Pay -- a separate cash payment of up to $25,000 -- is often offered alongside VERA as an additional inducement to leave. VSIP is taxable income in the year received. For employees choosing between accepting VERA/VSIP and staying, the net present value of the pension years gained by retiring earlier must be weighed against the pension years of additional accrual forfeited by leaving. A 30-year CSRS career at 2.5% per year produces a 75% annuity. A 28-year career produces 70%. Two years of additional service is worth 5 percentage points of final salary -- permanent, for life -- and should be weighed against the value of VSIP and early retirement.
The full income comparison with present value framing
The income numbers earlier in this comparison ($75,000 to $83,000 per year for FERS versus $56,000 for CSRS at the example service level) don't tell the complete story. Timing matters. Under FERS, income arrives in stages: the basic annuity at retirement, the FERS Supplement if retiring before 62, Social Security beginning at 62 or later, and TSP income drawn according to your chosen strategy. Under CSRS, income arrives immediately at a higher starting rate with full CPI indexing from day one.
Use the FERS retirement calculator to project income at multiple retirement ages, including supplement eligibility and Social Security interaction. Use the Social Security calculator to model the optimal Social Security claiming age alongside the FERS annuity -- the FERS Supplement stops at 62 regardless of whether you claim SS, and the claiming decision at 62 versus 70 can affect lifetime benefits by $100,000 or more depending on longevity. Use the pension income tax calculator to model the after-tax income from each system. FERS income is distributed across three sources -- pension, Social Security, TSP -- with different tax treatments and different state exemption rules. CSRS income is concentrated in a single fully-taxable pension stream. After state and federal taxes, the gap between the two systems often looks different from the pre-tax comparison.
MRA+10 and the postponed retirement option
Federal employees have four retirement categories most commonly discussed: standard immediate, early voluntary (VERA), deferred, and disability. There's a fifth option -- MRA+10 -- that gets less attention and is frequently misunderstood. If you leave federal service after reaching your Minimum Retirement Age with at least 10 years of creditable service, you can claim a reduced immediate annuity rather than waiting for a deferred benefit starting at 62.
The MRA itself ranges from 55 to 57 depending on birth year. Employees born before 1948 have an MRA of 55. Those born between 1953 and 1964 have an MRA of 56. Born in 1970 or later, your MRA is 57. The MRA+10 reduction is 5% for every year you're under 62 at the annuity start date -- that's 5/12 of 1% per month. Claiming at 57 with 10 years of service produces a 25% permanent reduction. The reduction stays in place for life; it doesn't recalculate at 62.
The postponed retirement option partially addresses this. Instead of accepting the reduced annuity immediately, you can separate from service and delay claiming until a later date when the penalty is smaller or gone. Postponing until age 60 with at least 20 years of service eliminates the reduction entirely. Waiting until 62 eliminates it regardless of service credit. Each month of postponement reduces the penalty proportionally.
The cost of postponing is real: no annuity income and no federal health benefits through FEHB during the gap period. Unlike a full immediate retirement where FEHB coverage continues into retirement, a postponed retirement breaks the coverage chain. Employees who postpone need either savings or alternative income to bridge the period between separation and annuity start. Comparing the income forgone during postponement against the higher lifetime annuity depends on both the benefit amounts and how long you expect to collect.
TSP matching: the three-layer structure
The Thrift Savings Plan employer contribution structure is central to FERS's total compensation. There are three separate layers, not one.
First: an automatic 1% contribution. OPM credits 1% of your basic pay to the TSP every pay period whether you contribute anything or not. This happens automatically from day one. It vests after three years of federal service (two years for congressional employees).
Second: dollar-for-dollar matching on your first 3% of contributions. For every dollar you contribute up to 3% of basic pay, the government matches it. At $80,000 annual salary, contributing $2,400 draws $2,400 in matching contributions.
Third: 50-cent matching on the next 2% of contributions. Contributions between 3% and 5% of basic pay earn a 50-cent match per dollar contributed. Contributing the full 5% of basic pay captures the complete matching structure: 3% dollar-for-dollar plus 1% from the partial match, plus the automatic 1%, equals 5% from OPM when you contribute 5% yourself.
Contributing less than 5% means leaving government money unclaimed. At $80,000 per year, contributing 3% instead of 5% costs $800 annually in forgone matching. Over 25 years with 6% average investment returns, that's roughly $55,000 in uncaptured retirement wealth. The match is the closest thing in the federal government to a guaranteed return -- the only question is how much of it you capture. All employer contributions vest at the same three-year mark as the automatic 1%.
High-3 salary: what counts and when it matters
The FERS annuity uses your high-3 average salary -- the mean of your three highest consecutive years of basic pay. "Basic pay" is specifically defined: it excludes overtime, performance bonuses, awards, allowances, and most other compensation beyond your base rate. For General Schedule employees, locality pay is included in basic pay and counts toward the high-3.
For most employees, the high-3 comes from the final three years because that's typically when pay is highest. That's not always true. An employee who took a voluntary demotion, moved from a high-cost-of-living locality to a lower one, or accepted a lower-graded position may have had higher basic pay in earlier years. Calculate it explicitly rather than assuming the final three years are the peak.
Retirement timing can affect the high-3 calculation. An employee who retires six months into a new pay period captures six months at the new rate and six months at the prior rate for that year. Staying through a within-grade step increase, or timing retirement to capture a full year at a higher step, can meaningfully affect the high-3 and the annuity it generates. At the GS-14 level in a high-locality area, the difference between step 9 and step 10 is $5,000 to $7,000 annually. Compounded over a 25-year retirement, a higher high-3 from strategic timing adds substantial lifetime income.
The FERS supplement
FERS employees who retire with an immediate annuity before age 62 and meet the service requirements may receive the FERS annuity supplement. It approximates the Social Security benefit you'd receive at 62 based on your federal service earnings alone, bridging the income gap between retirement and your first eligibility date for Social Security.
The calculation divides your years of creditable federal service by 40 and multiplies by your estimated Social Security benefit at 62 from federal earnings only. An employee with 30 years of service and an estimated $1,800 per month SS benefit at 62 receives a supplement of $1,350 per month -- 30/40 times $1,800, or $16,200 per year. That's real bridge income for employees retiring before 62.
The earnings test applies to the supplement. Outside earnings above the annual exempt amount ($24,480 in 2026) trigger a withholding of $1 in supplement for every $2 earned above the threshold. A retired federal employee working part-time at $42,000 per year loses approximately $8,760 annually in supplement income. The supplement can effectively disappear for employees who continue working at high earnings after retirement.
The supplement stops at 62 completely. It doesn't convert into a Social Security payment and SSA has no record of it. At 62, you separately decide whether to claim your own Social Security based on your full earnings history from all employment combined. These are independent decisions. Use the FERS retirement calculator to project total income at multiple retirement ages including the supplement, TSP distributions, and the point when Social Security starts. Use the Social Security calculator to model the optimal claiming age given the FERS annuity and any other income sources. Use the pension income tax calculator to model after-tax income across all three FERS income sources -- the annuity, Social Security, and TSP withdrawals -- which carry different federal tax treatment and qualify for different state exemptions.
Deferred retirement
Employees who leave federal service before reaching their MRA but with at least 5 years of service have a third path: deferred retirement. At 62, you can claim a full annuity based on your service credit and high-3 salary at the time you separated. No reduction applies if you wait until 62. The benefit doesn't grow with inflation during the waiting years, and there's no COLA until it starts, but it's a guaranteed defined benefit income stream for the rest of your life.
Deferred retirement does not preserve FEHB coverage. You lose federal health insurance when you leave service, and you generally can't re-enroll when the annuity starts unless you were continuously enrolled throughout the separation period and met specific requirements. Most employees who leave before retirement eligibility must find private insurance or use a spouse's plan until Medicare at 65. That gap is often the biggest practical cost of leaving federal service early with a deferred annuity as the only pension.
TSP assets remain yours regardless of your retirement category. The TSP stays invested, and you can leave it there until required minimum distributions begin at age 73. The combination of a small deferred annuity at 62, TSP distributions, and Social Security provides multiple guaranteed income sources for employees who left federal service mid-career -- a picture that's often stronger than expected once all three components are modeled together rather than separately.