DE-R-009
A Peppol Germany national rule (DE-R-*) – applies when the invoice is sent over the Peppol network to a receiver in Germany.
What this error means
DE-R-009
When both seller and buyer are located in Germany, the buyer post code (BT-53) must be provided.
How to fix it
Fill in cbc:PostalZone in the buyer cac:PostalAddress block.