The existence and completeness assertions are complementary but require different audit approaches. Required a. Why is it

Question:

The existence and completeness assertions are complementary but require different audit approaches.

Required
a. Why is it more difficult to test for the completeness than the existence/ occurrence of an account balance or a class of transactions?
b. What procedures can an auditor use to test the completeness of and sales?

Accounts Receivable
Accounts receivables are debts owed to your company, usually from sales on credit. Accounts receivable is business asset, the sum of the money owed to you by customers who haven’t paid.The standard procedure in business-to-business sales is that...