BR-11
A rule of the European standard EN 16931 – applies to every invoice following the standard, including Peppol BIS Billing 3.0.
What this error means
BR-11
The buyer's postal address has no country code (BT-55).
How to fix it
In the buyer address add cac:Country → cbc:IdentificationCode with a two-letter code, e.g. LT or PL.