Mapping the PEPPOL Payment Methods Code to the PEPPOL Payment Means Code is essential.

PEPPOL Payment means code is how the "How to pay you" code.

Different from Payment methods Payment means can be, the same code even the P. methods is different.

In Business Central, you can link/map these codes under Payments Methods.

You add the PEPPOL Payment means code for your BC on the right, see sample in print screen

Make sure each customer has a Payment Method Code, it's mandatory

Peppol Document setup allows you to add a default payment method, so that if it's not setup anywhere, it'll use it by default

The Sales Invoice will not be sent if this is not set up, because it fails our validations if it is not set up