As part of your system of internal controls, you may require that all purchases be approved by someone authorized to do so before being filled. All Orders enables purchase order approval so that if a purchase order is not approved, it cannot be received. To use purchase order approval CHECK 'Require order approval' in Purchase Order Preferences. This preferences works in conjunction with the All Orders User Manager so that only certain users can approve sales order. To prevent a user from approving purchase orders, simply UNCHECK 'This user can purchase sales orders'.
When you open a purchase order you will notice an 'Approved' check box. Authorized user can check or uncheck the box at any time. If the purchase order is approved it become 'read only' so that users without approval authorization cannot change the sales order after it has been approved.