It is the allowance paid to an employee who is working on a special assignment. This amount is completely exclusive of his Compensation plan. These are given in scenerio's like, when the employee went for On Job Training or an Employee sent for short term Deputation to survive his expenses in the new location.
For material/Goods Purchases, the Po is required. In the Po, QTY, Product Name, Where is delivery price, Terms and Conditions. In the po there is no matter of final amount. It is just the approximate amount.