Diagnosis
In Customizing under Define Check Parameters
, bill lines with the ID &V1& are defined as tax-free. This is doneusing check type 30. The IDs of the tax-free lines can then beentered under Permitted Checks.
However, the bill line with ID &V1& and net amount &V2&, contains thetax amount &V3&.

Procedure
Make sure that the bill and the Customizing settings are correct.