December 04, 2017 16:09 Updated Follow “Creditable service” is the amount of time that can be counted when we calculate your monthly PERF or TRF retirement benefit. Related articles What is service credit? When can I retire from PERF or TRF? What is the difference between a PERF pension and an Annuity Savings Account? What is APRA? How do I contact INPRS?