The staff member who left took the working knowledge with them

A bookkeeper who has handled a client for two years knows things that are not written down: which recurring payment is really a director's loan, how the till export needs adjusting, which supplier invoices arrive late.

The efficiency is the risk

That knowledge is why the account takes three hours rather than five. It is also why it takes eight when someone else covers it, and why an unplanned departure is a genuine crisis.

Documenting the treatment, not the process

Generic procedure notes are of limited use. What matters is the client-specific decisions — the mappings, the recurring adjustments, the known oddities — recorded against the client where the next person will look.

Leave is the honest test

If a fortnight's absence causes a visible drop in quality on an account, the knowledge is not in the record. That is a better test than any documentation audit, and it happens naturally every year.