A three-column cash book is one that has three columns on both the debit and credit side of the journal. The first column corresponds to cash transactions, the second to bank transactions and the third to discounts issued and received.
In addition to the three entry columns, a three-column cash book will also customarily contain columns to record the date, folio and particulars of each transaction. When contra entries are registered in the cash book, these are denoted with a letter "C" in the folio column and are reflected on both the debit and credit sides of the cash book. Since contra entries are self-canceling, they are not transferred to the general ledger.