There is much a book keeper needs to think about.  Let Custodian do the thinking for them on their insurance needs.

Here is a simple summary.

All of them will need professional indemnity. It is, after all, their professional service that they are offering.

Some may wish to consider buying public liability to protect them against causing damage or injury to a third party.

If they employ staff then they will have to buy employers liability.

If they hold data they may want to consider cyber cover.