Allowable service
Primary source
Verbatim text below is from the Electronic Code of Federal Regulations (eCFR), a public-domain U.S. government work. Always verify the current version with the eCFR before relying on it for any legal matter.
Full Text
(a) Service credit deposits are not allowed for training periods prior to actual enrollment.
(b) Service credit deposits can only be made for satisfactory volunteer and volunteer leader service.
(c) Annuitants enrolling as a volunteer or volunteer leader are not to be deemed reemployed annuitants. Service as a volunteer or volunteer leader performed after retiring under a CSRS or FERS retirement is not creditable serviced for retirement purposes.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.