purchaseOrderReference Field
Add a purchase order reference to the invoice.
Default Value: series/number/date
Example: Α/12345/27/06/2024
To send empty string, use Nothing
Example: purchaseOrderReference = Nothing
Otherwise, if purchaseOrderReference = "", then the default value will be used.
Example: purchaseOrderReference = Nothing
Otherwise, if purchaseOrderReference = "", then the default value will be used.