PEPPOL defines different formats which can be extended to accommodate local/country restrictions.
The two main formats are PEPPOL BIS 2.0 and PEPPOL BIS 3.0.
The main changes between BIS 2.0 and 3.0 formats are:
Negative amounts and/or grand totals are allowed in invoices.
For parties the use of identifiers ISO 6523 changes: use of numbered ids instead of names (example: BE:VAT becomes 9925).