March 27, 2018 13:56 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 APRA? What is the difference between a PERF pension and a Defined Contribution (DC) account? How do I contact INPRS?