SAP Message CA_TTE699 - Duplicate item number &1 in item &2 and item &3

Diagnosis The item numbers of the items which were being sent via the COM_TAXinterface to the external tax system are the same. The COM_TAX interface expects item numbers of length 6 characters. So,if the item number supplied by the document is longer the 6 characters,TTE selects the last 6 characters before sending to the external taxsystem. Procedure If the item numbers of the items in the document are less than 6characters long, please ensure that the item numbers are unique. If theitem numbers are longer than 6 characters, please ensure that the last 6characters are unique.