Eligibility vs. annuity: two different things
It's a common misconception that a refund permanently erases that service. It doesn't — those years still count toward whether you're vested and eligible to retire. What a refund actually costs you, if you never redeposit it, is the annuity credit: those years simply don't multiply into your pension's dollar amount.
Why the redeposit grows over time
The redeposit amount isn't frozen at whatever you were refunded — interest accrues from the date of the refund at OPM's variable rate. The longer you wait to redeposit, the more it costs, which is the same dynamic as a military buyback deposit. This calculator uses the same long-run ~4.5% rate assumption as FedHorizon's Military Buyback Calculator for that reason.
Not returning to federal service?
This calculator is specifically for someone who separated, took a refund, and came back (or plans to). If you're not returning, redeposit isn't the relevant question — your remaining creditable service (the years you didn't have refunded) may still qualify you for a deferred annuity. See the Deferred vs. Postponed Retirement Calculator for that path.
How this fits your full retirement timeline is one input. Your full report combines pension, supplement, survivor election, and FEHB into one decision.
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