# Business documents
On the 'What is Peppol?' page, we explained how the Peppol network is used by senders, receivers and Access Points. In this section we dive into the different document types that are used on the Peppol network. We display some of the most used examples and provide links to useful documentation and validation websites.
When sending documents there is a chance the receiver does not support your document type. For example, when you're sending invoices in the SI-UBL-2.0/NLCIUS format, but the receiver is only registered for the Peppol BIS V3 invoice. As a sender you do not have to worry about this, because as an Access Point eConnect is transforming the invoice to the best document type for the receiver.
The same goes for receiving invoices. There is a chance you're receiving Peppol BIS V3 invoices, but your software can only handle NLCIUS invoices. As a receiver you do not have to worry about this either. In the download call you can add a targetDocumentTypeId to specify which document you want to receive. We will then transform the document to a format your software supports.
# Useful websites
The website Semantic Treehouse (opens new window) let you see the syntax binding of different invoices.
The website NPa Peppol Test Tool (opens new window) has the opportunity for you to validate the UBL to see errors and warnings based on the most recent XSL validation file of the used DocumentType.