What is a reader?
Edited
A reader is a piece of custom software we build just for you. It reads your files, pulls out the data, and puts it into Xero exactly the way you need it.
Every reader is built around your exact setup — your file format, your rules, your workflow. It can do things like add markup, deduct commission fees, split amounts into multiple line items, or apply any other business rules you need.
You may see the term "document parser" in some older references — that's the old name for the same thing. We now call them readers.