The correct answer is: A cross reference on a despatch note which accompanies all goods despatched to an authorised purchase order; A check by the warehouse supervisor to ensure that the goods leaving the warehouse are those that are noted on the despatch note; The locking of doors in the despatch bay on those days when deliveries are not made.

A cross reference on a despatch note which accompanies all goods despatched to an authorised purchase order and a check by the warehouse supervisor to ensure that the goods leaving the warehouse are those that are noted on the despatch note both help to ensure that unauthorised goods do not leave the warehouse. The locking of doors in the despatch bay on those days when deliveries are not made also prevents unauthorised despatches.

A delivery note signed by the customer confirming that the goods have been received shows that the delivery has been made, but not that it has been authorised. A check by the staff in the ordering department to ensure that the price charged on the invoice for inventory is correctly calculated helps ensure that the correct amounts are posted, but not that they have been authorised.