When you globally add charges through an import , specific fields are required for each charge (BB330236).  In the import file, if the category for a charge is different than the billing fee type defined in Configuration, you will receive the exception Error: Invalid Billing Item specified for field Billing Item Id/Product Item.  For example the billing item, Course fee, is a flat rate billing item and in the import file the charge has the category Automatic Item: Vary amount by Grade. 

To import the charges without getting this exception; enter the correct Category in your import file for the Billing Items being imported.