For correction in invoices, you can notify to your supplier and they will send back the vouchers by removing ‘***’ (Three stars) in narration, which AccXchange marks in narration every time as an evidence of transmitted voucher.
After the revised Invoices is received by you, the posting process is same as new invoice.
If the wrong Invoice is already posted, then you can still post the revised Invoice. When you click on Post now AccXchange will correct the previous posted Invoice.