Tax Deducting from G/L instead of Vendor

Gurus,

I'm in the middle of testing a scenario.

Tax Code - KK - 12% is configured with all account determination and calculation procedure

PROBLEM --

Testing was done on FB60 + F-02 -- in both scenarios the Tax is being calculated on G/L instead of Vendor. It should deduct from Vendor but its not.

Can you help..?

Suggestions welcome.