During matching, the remaining balances of Purchase Orders and Bills are calculated and can be stated in reports.
The remaining balance of Purchase Orders is the difference between the Purchase Order amount and the allocated amounts for all matching entries related to this Purchase Order.
The remaining balance of the Bills is the difference between the Bill amount and the allocated amounts of all matchings related to this Bill.
The remaining balances of Purchase Orders and Bills are recalculated when:
A matching is created
A matching is removed
The matching amount is changed
The amount of a document is changed in Xero
A document is deleted/cancelled or the Supplier/Currency/date has changed