How do you reconcile your Mews invoices now they're supposedly taking them out of receipts?

Has anybody worked out how to tell whether a deduction from a receipt is the transaction charge for that particular transaction or a deduction due to the invoices Mews send?

I have two invoices outstanding on my system because I can’t work out which charges are those invoiced. I can’t not put the invoices on the system, because Mews will take payment if they can’t deduct from receipts.

Is there some way of telling when a charge should be allocated to the invoice?