ApprovalMax enables Requesters and Approvers to manually match Bills submitted for approval to the approved Purchase Orders before making their decision. This allows for much more control and accuracy at this stage of the approval process.
Auto-matching is supported for QuickBooks Online Bills that were copied from Purchase Orders.
Restrictions for approvals can be set to apply even more control.
Bill-to-Purchase Order Matching is available in the Advanced and Premium plans. You'll find more information on the subject here.