Article Numbers in ZUGFeRD: SellerAssignedID (BT-155) and BuyerAssignedID (BT-156)

Trade invoices often contain two article numbers per line item: your own number and the number under which your customer lists the same article. Both belong in separate, purpose-built fields of EN 16931 – otherwise important information for automated invoice processing is lost.

> Quick answer: Your own article number goes into the ZUGFeRD XML as the SellerAssignedID (BT-155) and the customer's article number as the BuyerAssignedID (BT-156) – each per line item in the SpecifiedTradeProduct element. The line number (LineID, BT-126) stays separate from both. TaxLayer maps both automatically.

Two article numbers, two fields

A typical example from a trade invoice:

A common mistake: the seller's own article number is used as the line number (LineID), and the customer's article number never appears in the XML at all. Neither is necessary – the standard has a dedicated field for each item.

Why the buyer's article number is decisive

Large retail customers process incoming invoices automatically. Their system matches each line item against the order and the goods receipt using their own article number (that is, your customer's number). If this number is not present as the BuyerAssignedID in the e-invoice, the matching comes up empty – the invoice then has to be reworked manually or is rejected. With retail groups and DIY chains in particular, the BuyerAssignedID is therefore often decisive for whether your invoice goes through smoothly.

What it looks like in the XML

In ZUGFeRD/CII, both numbers appear per line item in the product block, in this order:

• ram:SpecifiedTradeProduct → ram:SellerAssignedID – your article number (BT-155)
• ram:SpecifiedTradeProduct → ram:BuyerAssignedID – the customer's article number (BT-156)
• ram:SpecifiedTradeProduct → ram:Name – the article name (BT-153)

The line number stays separate, in ram:AssociatedDocumentLineDocument → ram:LineID.

How TaxLayer handles it

TaxLayer detects both article numbers per line item and maps them correctly into the ZUGFeRD XML as SellerAssignedID and BuyerAssignedID. The line number remains a plain, sequential LineID. In the review step you see the detected article numbers for each line before the file is generated.

Conclusion

Keep the line number, your own article number, and the customer's article number cleanly separated: BT-126, BT-155, and BT-156. The BuyerAssignedID in particular is decisive for automated processing at larger retail customers.

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Try TaxLayer for free now – maps article numbers, the delivery date, and references automatically into ZUGFeRD and XRechnung. Questions to info@landauer.de.