UBL-SR-56

Explanation

An invoice may contain at most one originator document reference (BT-17, e.g. the tender or lot the invoice relates to). The requirement comes from the European standard EN 16931, not from VAT law.

How to fix

Give only one originator document reference. List further references as an additional supporting document or in the invoice note. (Typically a software-side issue, not user input — raise this with your invoicing software vendor; if you're receiving the invoice, ask the sender to address it with theirs.)