"...Employees who are covered under the Federal Employees Retirement System (FERS) or the Civil Service Retirement System (CSRS) are eligible to receive credit towards retirement for their Peace Corps Volunteer service.
To do so, you must make a deposit for this period of service. While you are a Peace Corps Volunteer, no money is deducted from your monthly readjustment allowance for retirement. Your deposit is an amount equal to the money that would have been deducted and put into the retirement fund, plus any accrued interest..."