As an outside trainer, I maintain the following items on my PC indefinitely:
Record of Training
Pics 'n permits (digital versions)
Invoices
Actual test copies that I do not turn over to the client are maintained in my office for three years, then tossed out. However, the Record of Training does indicate the incorrect responses along with the correct answers for the supervisor to review.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.