@MarkLL I am probably not copying the right things.
what I tried is this: https://mywebsite.com/api/business identifier/sales-invoices.json?Customer= and I put in the first customer id and the number next to it. I assume that the number next to the customer id is the fileID?
I just get a Sql Server error message. I am running Server version 20.7.31 if that helps as maybe there was an update after this date that fixed the issue.
It was Lubos himself that said that I would need custom reports to do what I wanted to do. Should I be using Rest API to sync certain data