Can employees who switched from CSRS to FERS receive blended or dual benefits, and how are they computed?
Executive summary
Employees who move from CSRS to FERS do not get a single “blended” new pension that erases the prior CSRS credits; instead, retirement pay is determined by which portions of service are covered under each system and the applicable formulas for each period (CSRS basic annuity rules for CSRS service; FERS basic annuity, Social Security and TSP for FERS service) [1] [2]. Guidance and computations hinge on whether the employee elected FERS coverage on return to service, had less than five years of non‑CSRS service, or holds CSRS Offset status — all facts stressed in OPM and retirement guides [1] [3].
1. What “switching” means on the record — not a single merged pension
When an employee “switches” from CSRS to FERS during a federal career, personnel and payroll records divide total federal service into CSRS‑covered service and FERS‑covered service; each portion is governed by its own computation rules rather than creating one blended annuity formula that treats all years the same [1] [2]. OPM guidance says if you had less than five years of non‑CSRS civilian service at the time you became covered by FERS, all your CSRS service may be converted to FERS service only if you remain in FERS — but that conversion is procedural and based on specific conditions, not an automatic “blend” of benefits [1].
2. Two distinct computations: how CSRS and FERS pieces are calculated
CSRS uses a defined‑benefit formula tied to years of service and a “high‑3” average salary; FERS provides a basic annuity (also using high‑3 rules), Social Security coverage, and TSP accumulation [2] [4]. In practice a person with mixed service will receive CSRS annuity amounts for CSRS‑covered periods and FERS annuity amounts (plus Social Security and TSP outcomes) for FERS‑covered periods — each computed under the system’s specific formula and then coordinated administratively [2] [4].
3. The CSRS Offset and returning employees: special mechanics that look like “dual” benefits
Employees who are CSRS Offset (a hybrid that includes Social Security) earn retirement credits under both CSRS and Social Security; their CSRS annuity is reduced, or “offset,” by the Social Security benefit attributable to the overlapping federal service [3]. The FedWeek and OPM materials note returning employees can be offered a choice between CSRS Offset or FERS after a break in service — that choice determines whether they ultimately have portions of career covered by both regimes and how benefits are coordinated [3].
4. Military and prior service analogies — true dual pensions exist but are distinct cases
Federal workers with prior military retirement sometimes choose to keep a separate military pension and a civilian FERS or CSRS annuity rather than making a deposit to coordinate service into FERS; that creates two pensions paid separately [5]. FedSmith’s coverage of the military Blended Retirement System underscores that “dual” pensions are possible when one benefit comes from military service and one from civilian service — but that is a different administrative situation than simply switching from CSRS to FERS during a civilian career [5].
5. Practical implications: contributions, Social Security, and COLAs differ
Contribution histories matter. CSRS employees historically contributed a higher share of pay into the civil service fund and did not pay Social Security taxes, while FERS employees pay Social Security taxes and different civil‑service contribution rates depending on hire date — these contribution differences change future benefit levels and interaction with Social Security [6] [3] [7]. Cost‑of‑living treatment also diverges: FERS COLAs are subject to caps and age rules that differ from CSRS, so mixed‑service retirees must expect varying COLA treatments for the portions of their annuity derived from each system [8] [9].
6. What the sources don’t say and next procedural steps
Available sources do not give a line‑by‑line numeric worked example for every possible mixed‑service permutation; computation depends on precise hiring/coverage elections, breaks in service, and any deposits made [1] [2]. For a definitive figure employees must obtain an OPM annuity estimate or use a detailed calculator from FedWeek and ask HR to produce service history and cost estimates before deciding on deposits or coverage elections [10] [1].
Sources used: OPM/benefits administration guidance and federal retirement explainers [1] [2] [3], FERS/CSRS comparisons and practical notes [4] [6] [7], and reporting on military/civilian dual pensions [5].