UBL-CR-667: The buyer's item number must be written without a scheme

What it means

The buyer's item identifier (BT-156) is the number the buyer uses for the product, for example their own article number. In UBL it is cbc:ID inside cac:BuyersItemIdentification on the line. EN 16931 treats it as a plain identifier with no scheme. This rule checks that this cbc:ID has no schemeID attribute.

Why it matters

This is a warning. The scheme has no place in the EN 16931 data. It is worth fixing if your export always adds it.

How to fix it

Look at how the buyer's article number is set on your lines in the invoicing software. It should be a plain number or code, with no scheme or type chosen next to it. If the number is a standard code such as a GTIN, enter it as the standard item identifier (BT-157) instead, which is the field where a scheme is allowed. If you build the XML yourself, delete the schemeID attribute from cbc:ID in cac:BuyersItemIdentification.

The rule as published

A UBL invoice should not include a Buyer Item Identification schemeID

Where this rule applies