A commission charged on postal order is called "poundage." Poundage is a small fee that is charged by the postal service for processing and handling a postal order. This fee is a percentage of the total amount of the postal order and is designed to cover the costs of processing, handling, and delivering the order. Poundage is usually a small amount, but it can add up over time, especially if you use postal orders frequently. It is important to take poundage into consideration when calculating the total cost of a postal order, to make sure you have enough funds to cover both the cost of the order and the poundage fee.