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            cbc:ID
            
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                Purchase order reference 
                An identifier of a referenced purchase order, issued by the Buyer. An invoice must have buyer reference (BT-10) or purchase order reference. In cases where sales order reference is provided, but there's no purchase order reference, then use value "NA" as this element is mandatory in UBL.
             
            
            
                Example value: 98776
             
            
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            0..1
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            cbc:SalesOrderID
            
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                Sales order reference 
                An identifier of a referenced sales order, issued by the Seller. In cases where sales order reference is provided, but there's no purchase order reference, then set cac:OrderReference/cbc:ID to value "NA" as this element is mandatory in UBL.
             
            
            
                Example value: 112233
             
            
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