The KampData TaxEngine was designed to return the same tax schedule ID for taxable and tax exempt line items. Exempt lines on a transaction are flagged by the LineExempt property
The DocDefaultUseExemptSchedules property and the LineUseExemptSchedules property were added in version 2.1.4289(September 29, 2011) to allow the KampData TaxEngine to return Zip Code Exempt Schedules for tax exempt line items.