The Three-Column Cash Book With Discounts Well Explained - SS1 Accounting Past Questions and Answers - page 1

 The four rules are: 

1) all cash received is entered in the cash received column, and all cash payments are entered in the cash payments column, 

2) entries should be dated and have a brief description of the transaction, 

3) all transactions must be entered in the correct columns and with the correct amounts, and 

4) the cash book must be balanced regularly to ensure that the total of the cash received column equals the total of the cash payments column, and the net balance is the cash in hand or the bank balance.

The purpose of recording discounts in a cash book is to keep track of discounts given or received and maintain accurate records of cash transactions. This helps businesses to monitor their cash flows and make informed decisions about managing their finances.