Check one: when did it last run?
Open the backup software and find the last successful run. Not the last attempt — the last success. The most common failure we find isn't a missing backup; it's one that has been quietly erroring since a Windows update several months ago, with the alert emails going to a staff member who left.
Check two: what's actually in it?
List what the backup covers and compare it to where your business data really lives. People are consistently surprised by what isn't included.
The 365 misunderstanding
Microsoft keeps the service running and holds deleted items for a limited window. It does not keep a long-term backup of your mail and files. If something is deleted or encrypted and you notice two months later, it is gone unless you backed it up separately.
Check three: is there a copy off-site?
A backup drive sitting next to the server is destroyed by the same fire, taken in the same burglary and encrypted by the same ransomware. You need a copy somewhere else — cloud, or a rotated drive that genuinely leaves the building. Keep the local copy too; it makes restores faster.
Check four: restore something
Pick a file from a month ago. Restore it to a new folder. Open it. If that takes more than ten minutes or nobody knows how, you have found a problem worth fixing before you need it at speed. Do this quarterly and write down the result — an insurer may ask.
Check five: how long would a full recovery take?
Not how long the copy takes to download — how long until people are working again. That includes rebuilding a machine, reinstalling software, restoring data and checking it. For most small offices the honest answer is most of a day, and knowing that number in advance is the difference between a bad day and a crisis.