warningEN 16931syntax binding ruleCIIBT-125
Only one AdditionalReferencedDocument AttachmentBinaryObject BT-125 is allowed with TypeCode 916.
More than one attached document (BT-125) is present in an AdditionalReferencedDocument with TypeCode 916. EN 16931 gives this a single value, so a receiver has no rule for choosing between the copies. This one is reported as a warning, not an error: the invoice still passes EN 16931, but which copy a receiving system picks is undefined and some will refuse it. To attach two files, repeat the whole AdditionalReferencedDocument group, once per file.
Keep the one attached document (BT-125) that is correct and delete the others. Repeated singular elements almost always come from a serialiser emitting every value it holds instead of choosing one — fix it at the source, not by trimming the output file.
CII — context /rsm:CrossIndustryInvoice/rsm:SupplyChainTradeTransaction/ram:ApplicableHeaderTradeAgreement
count(ram:AdditionalReferencedDocument[normalize-space(ram:TypeCode) = '916']/ram:AttachmentBinaryObject) <= 1
Nothing is stored, and the whole invoice is checked, not just this rule. A PDF only works if it is Factur-X / ZUGFeRD — a PDF with the invoice XML inside it.