The correct answer is to Examine payment in CashbookVouching: Vouching is one of the activities of an auditor in process of auditing, in which an auditor checks each and every entry in the books of accounts and verifies it with the evidence available in the form of vouchers. Vouchers are nothing but the cash memo, bills other documents that were issued or received at the time of the transaction for future references. The process of Vouching is performed to check the authenticity of the transactions. Important PointsExamine Debtor Ledger: The debtor ledger contains all the transactions related to persons to whom goods are sold on credit. Since it records all the credit transactions, It is not required in vouching for Cash Purchases. Examine Cash Sales: Cash sales represent the number of goods sold on a cash basis. These are not required in vouching Cash Purchases. Examine credit sales: Credit sales represent the number of goods sold on a credit basis. These are not required in vouching Cash Purchases. Examine payment in Cashbook: Cashbook records all the transactions relating to cash payments and cash receipts. Since purchases made on cash are recorded in Cashbook, these must be verified in vouching of Cash purchases.