Grocery back office clerks match every supplier invoice to its delivery note by hand, and a proof of concept did it straight off the paperwork.

Somebody at the group has to confirm that what a supplier invoiced is what the supplier actually delivered. That means putting each invoice next to its delivery note, and it is done by hand.

The shape of it is a person holding paper. They take a bundle of invoices for one store and one range of dates, open the finalisation screen, filter it down to that store and those dates, and then work through the stack in their hands looking for each document in the list on the screen. When they find it, they compare the figure on the screen to the figure on the paper and confirm it.

The dates are the part that does not survive contact with reality. A document carries the date it was issued, printed on it, and the date the goods were received, which is written on by hand with a pen onto a rubber stamp. The client's own estimate is that the receipt date has to be corrected manually around ninety percent of the time.

There is a harder problem underneath. Not every document arrives. Roughly a third do not come down the electronic channel at all, and the client was unambiguous that a system covering half the documents is not worth starting: without a way to check that everything is actually there, there is no project.

A proof of concept, and the word is doing real work in that sentence. It was built to answer whether this is possible on their actual paperwork, demonstrated in April, and it is where the engagement still sits.

It reads the documents, extracts the fields, and matches in two passes. The first looks for an explicit cross-reference, where the invoice names the delivery note. The second falls back to comparing several things at once when no such reference exists.

Product descriptions are compared by overlap rather than by exact string, because a supplier's product codes and the group's product codes are two different systems that were never going to line up. It also compares quantities line by line, so a short delivery shows up as a short delivery rather than as a failed match.

The design agreed afterwards adds the check the client made a condition: a stage that confirms every document exists in at least one channel before any matching begins.

On the demonstration set, seven of ten delivery notes were matched correctly to their invoices with no tuning of any kind, across six real documents and thirty seven pages. That is a demonstration on ten documents. It is not an accuracy rate, and it is stated here with its denominator attached because it is the only measured number this project has.

What it settled was feasibility, which was the question actually being asked. The architecture that followed was agreed in May and the commercial terms were negotiated close to final.

It is not running. The contract is unsigned, the data protection agreement and the confidentiality agreement are both still with the lawyers, no code repository has been opened, and no pilot has been run. This page is a record of a proof, not of a delivery.