How do I set maximum value of purchase orders?

This section will only appear if the user has permission to raise purchase orders. Here you can set a maximum value of purchase orders and/or purchase invoices that they can authorise for. For example, if the limit was set to £1000 and a purchase order was raised for £700, they have the ability to authorise it. However, if the purchase order was for £1500 they would not be able to authorise it.