A backup you have never restored is a guess

Most offices that lose files had a backup. It was just old, incomplete or impossible to open when it was needed (sample note).

Once a month, pick something real and bring it back: a folder from last week, a deleted email, a whole laptop. Time how long it takes and write it down.

If your IT company runs the test for you, the result should be in your monthly report, with the date and what was restored.