The correct option is 3Vouching is a procedure followed in the process of the audit to authorize the credibility of the entries entered in the books of accounts. Important PointsSince the vouching of Cash at the bank has to be done, we have to take into consideration only the transactions which affect the bank balance. Bank Statement “ This is the statement of the bank account that shows all the transactions related to the amount withdrawn or deposited in the bank account. Since the vouching of cash at the bank has to do, this statement will prove to be useful in the process. Salary Register “ This register keeps the record of the salaries paid to the employees, whether in cash or through a bank account. Since these entries are already recorded in Cashbook and the Bank statement itself will contain all the entries related to the salary paid, this statement will not be required for vouching. Bank reconciliation statement- This Statement is prepared to tally the Bank Balance as per the Cashbook and the Balance as per the passbook. Variation in Passbook and Cashbook arise due to several reasons like the difference in the dates of transaction and Debit/credit made by the bank, Omission of any transaction to be recorded, customer directly depositing the amount in our bank account, etc. Since this statement is prepared to match the balance of the cash book with the banks passbook, this statement will be required for vouching. Stock register- This register keeps all the records of stock or inventory which is owned/ purchased/ sold in the business. Since the stock must have been purchased or sold via bank or cash, the entry must have already been recorded in the cash book. Moreover, if the transaction has been made on a credit basis, this will not affect Cash a bank. So, this will not be required for vouching.