No, there is no deduction for purchasing the buyback service credit in
the year that you pay for them.
Instead, when you retire, you will not
have to pay income tax on the portion of your retirement pay that
represents the amount you paid in,because that income has already been
taxed.
https://ttlc.intuit.com/questions/2945276-is-federal-employee-service-credit-buyback-expense-de...
