DE-R-018
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-018
When both seller and buyer are located in Germany, prompt-payment discounts (Skonto) in payment terms (BT-20) must follow the strict format #SKONTO#TAGE=n#PROZENT=n.nn#, in capitals, without extra whitespace, each row ending with # and a line break.
How to fix it
In cbc:PaymentTerms/cbc:Note write e.g. "#SKONTO#TAGE=14#PROZENT=2.00#"; percentage with a dot and two decimals.