Importing Bills from a csv file - Line VAT rate Problems!

Hi I need to import purchase invoices into Clearbooks from csv files. But I cannot work out how to define that a purchase needs to be excluded from the VAT return or is exempt. The only options available on the Line VAT rate column when importing I think is 20, 5 or 0. If I leave it blank it defers to zero rate. I was told on the phone last week to Clearbooks to use 0:00 OUT for exempt purchases but this does not work at all. As a result, everything I am importing is getting included in the VAT return (including Salaries that according to the Account codes set up are automatically excluded from the vat return). Please can someone help?! I need to know what to use in the Line Vat rate for Outside Scope and Exempt purchases when importing as a csv. Thanks!