To complete a petty cash book, keep a running tally of cash in the account, deposits, withdrawals and dates. The petty cash book is a summary of trivial expenses. It can take the form of a ledger sheet or a spreadsheet, such as a Microsoft Excel file. Typically a business maintains a petty cash account for minor expenses, such as meals, flowers, stamps and office supplies, according to Accounting Tools.

Petty cash bookkeeping starts with a beginning sum and a date. Then each transaction is noted, along with a brief description of how the money was spent, if the transaction is a withdrawal. The balance is calculated after each transaction. When the account reaches a pre-determined minimum balance, it is replenished and new cash is added to the existing balance. Some businesses choose to close out the petty cash account on a monthly or quarterly basis so the sums can be added to an accountant's reports. The petty cash book can be kept in one of two ways: with debits in a separate column from credits, or with withdrawals and credits in the same column. In either case, the balance should be tallied after each deduction so the manager or bookkeeper knows when the petty cash account needs to be replenished, according to Accounting Tools, which notes that petty cash accounts are being eliminated in today's business environment in favor of employee credit cards.