The test of a record is not how complete it looks. It is whether it answers a question months later: what did that day actually bring, and where did the difference go.
Four columns
- Opening float, written before the first customer.
- Closing cash, counted twice, by the same person.
- Transactions taken, from the device, not from memory.
- Anything unusual, in one line of plain words.
That last column does the most work and gets skipped first. «Power out 2—4pm», «helper left early», «two reversals» — three months later those lines are the only thing that explains a bad week.
Keep the book at the counter, not at home. A record you have to fetch is a record that stops being written by the second week.
What not to keep
Customer names and numbers beyond what the system already stores. It adds risk, it adds work, and it answers no question you will actually ask.