# BT-13 — Purchase order reference

> https://billhorse.com/en/terms/bt-13/

The buyer's purchase order number. Many buyers auto-match incoming invoices against their orders — without this reference the matching fails.

## Where does it live in the XML?

- UBL: `cac:OrderReference/cbc:ID`
- CII: `rsm:SupplyChainTradeTransaction/ram:ApplicableHeaderTradeAgreement/ram:BuyerOrderReferencedDocument/ram:IssuerAssignedID`