In the TCS payload for tax calculations on the sales order and purchase order, we believe the order numbers should be sent in the TCS payload. Most users do not know where to search for the record id that is sent in the TCS payload, it is much easier to look up the sales or purchase order number when troubleshooting and comparing the TCS payload to the order. Ideally, there would be an additional field with the order number sent or the Transaction Header ID field would contain the sales/purchase order number.