- # This one links a tax-exempted line item (billpkgnum) to a tax rate (taxnum),
- # and gives the amount of the tax exemption. EXEMPT_WHERE should be replaced
- # with a real WHERE clause to further limit the tax exemptions that will be
- # included.
+ # This one links a tax-exempted line item (billpkgnum) to a tax rate
+ # (taxnum), and gives the amount of the tax exemption. EXEMPT_WHERE must
+ # be replaced with an expression to further limit the tax exemptions
+ # that will be included, or "TRUE" to not limit them.
+ #
+ # Note that tax exemptions with non-null creditbillpkgnum are always
+ # excluded. Those are "negative exemptions" created by crediting a sale
+ # that had received an exemption.