Record and manage petty cash
In order to correctly record petty cash transactions, you need to create a bank account specifically for your petty cash.
Create a petty cash bank account
Whenever you top up the petty cash float, you transfer money from your main bank account to the petty cash bank account.
Transfer cash to petty cash account
Record purchases made with petty cash in the usual way (by recording a purchase invoice). When marking the invoice as paid, make sure that the petty cash bank account is selected.