You don't get to decide the format of the documents
Yes, a supplier can change the template of its invoice from one month to the next without telling anyone. That isn't a mishap that wrecks an automation, it's one of the ordinary things an automation built properly has to take in its stride
The supplier owes you nothing on the format of its own documents. It moves a total, adds a line, renames a column, or switches to another invoicing program and the PDF comes out looking different. All of that stays its own business
Only one part of it concerns you, what your system does the day that new document arrives
The system stops, and that is the right behavior
When a Muffin Suite automation finds a document that no longer matches the template it knows, it stops and flags it, instead of pressing on and recording numbers taken from the wrong place
The difference between the two is a big one. An automation that stops costs you a wait and an alert to look at, while an automation that tries to guess puts a taxable amount read from the box next door into your accounts, and you find that out much later, once it has already dragged other documents along with it
Checks are the most important part of the work on a document that comes from outside, not a garnish, reading PDFs and Excel files always compares what it finds with what it expects to find, and makes sure the figures add up
Meanwhile the rest doesn't come to a halt. The invoices from your other suppliers keep going through as always, and all that is held up is that handful of documents in the new format, which at worst you enter by hand as you did before automating
Putting it right falls under maintenance
Adapting an automation to a changed invoice template is a small job. You look at the new document, you see where the fields have ended up, you update the reading and you try it again on real documents before putting everything back to work
Small adjustments of this kind fall under the maintenance included in the monthly fee, under the plan set out in the project contract, so they don't turn up as a surprise to be settled separately every time a supplier changes its mind
It's also one of the reasons Muffin Suite works on a fee rather than on a closed project. A program that reads documents produced by other companies isn't something you deliver and forget, the documents out there change on their own, and somebody has to keep up with them
The story is the same when what changes is a program instead of a document, and for that case there's the guide on what happens when your business software changes