An auditor compares remittance advices or lists of cash receipts with entries in the cash receipts journal and entries in the cash receipts journal with the remittance advices or lists of cash receipts because: 

(a) the first provides evidence about the completeness of entries in the cash receipts ledger and the second provides evidence about the existence of cash receipts ledger entries. 

(b) you can’t test for existence unless you compare in both directions. 

(c) it gives junior staff training in comparing records. 

(d) there are usually many thousands of cash receipts in a year.