If it's just a case of the correct amount has been deposited, but allocated to the wrong invoices, then even if the amount has been bank reconciled you should just be able to delete the receipt and re-enter it against the correct invoices. You will then have to go back into the bank reconcile function and re-reconcile the amount. If, as Trueman has asked, the client is on cash accounting for VAT you will have to be a bit more careful.