Send the receipt the way you already send photos
You should not have to log into a portal to drop a lunch receipt. Forward it. It is matched to the payment, or you get a question back in the same thread.
Each client gets an inbound address. Forward supplier PDFs or phone photos. The file is stored and attached to the matching Xero transaction when the match is clear.
The same matching runs on WhatsApp, on Standard and Plus. Reply in the thread if it cannot tell Tesco groceries from Tesco fuel.
When it cannot match
The item lands on a short list. You are told what was read and what is still needed. A low-confidence receipt is not posted as a guess.