The state of Tennessee requires renewal of nursing assistant certificates every two years. To renew a CNA certificate you must provide proof of eight hours of paid CNA employment within the last two years. The following documents qualify as valid proof of employment for certified nursing assistants: a pay stub, a payroll printout, or a notarized attestation form. One of the valid documents must be submitted to the Tennessee Nurse Aide Registry along with a completed employment verification form for approval and subsequent renewal of your certification.