Complex if statement returns incorrect results

Thanks. What I have tried to do is isolate the sample and provide the full detail of taxass. See attached.

The first sheet gives the AA2 value (a calculated parameter), the context for GQ2 (etc, this will be different for each row), and shows how the statement is applied (the links are broken). To demonstrate the issue, I have included the manual calc based on the legislation.

Hope this helps.
amk