In almost all businesses, it is found necessary to keep small sums of ready money with the cashier or petty cashier for the purpose of meeting small expenses such as postage, telegrams, stationary and office sundries etc. The sum of money so kept in hand generally termed as petty cash and book in which the petty cash expenditures are recorded is termed as petty cash book.

A petty cash book is generally maintained on a columnar basis - a separate column being allotted for each type of expenditure. The is only one money column on the debit side and all sum received from time to time by the petty cashier from the chief cashier are entered in it.