The one document most small businesses don't have: an IT asset list
A simple list of every device, account and subscription your business depends on — who has access, and who to call if it breaks.
Ask most small businesses to list every device, software subscription and system they depend on, along with who has access to each one, and there's usually a long pause. Not because the information doesn't exist — it's just scattered across memory, old emails, and whoever happened to set each thing up.
An IT asset list fixes that with almost no effort: a single spreadsheet with a row per device or system, who owns it, who else has access, and roughly what it costs. It sounds basic because it is basic — that's exactly why it works.
The value shows up at the worst possible moment, which is precisely when you need it. A laptop gets stolen, an employee leaves unexpectedly, or something breaks at 9pm — and instead of a scramble to remember what exists and who to call, there's a document that already has the answer.
It also tends to surface forgotten subscriptions nobody's using any more, which is a pleasant side effect rather than the main point.