July 03, 2019 16:54 Updated Follow There are several things that factor into the final cost of extra service. We suggest you read Buying Extra Service Credit if you are a member of PERF or TRF. For other funds, . Related articles Do you accept credit cards? I was a substitute teacher. How can I add this service to my account? How many years of creditable service must I have in order for my spouse or child to receive a survivor benefit from PERF? If I become disabled during my employment, am I protected from termination? What is Hero's Honor?