Walter Conn, CPA, is engaged to audit the financial statements of Bingo Wholesaling for the year ended December 31, 20X0. Conn obtained and documented an understanding of the client and its environment, including internal control over the business processes relating to accounts receivable. He assessed the risks of material misstatement for all of the assertions about accounts receivable at a moderate level. Conn requested and obtained from Bingo an aged accounts receivable schedule listing the total amount owed by each customer as of December 31, 20X0.
What additional substantive audit procedures should Conn consider applying in auditing the accounts receivable?