Use Withholding Tax field is not selected - need to exclude WHT Tax Calculation for few Suppliers

Summary

Use Withholding Tax field is not selected - need to exclude WHT Tax Calculation for few Suppliers

Content

Business would like to ignore WHT tax calculation for few suppliers or Supplier/Site combination (Profile level enabled, Site level disabled).

I have done required setups in Supplier Master.  

If I give WHT Tax code and WHT tax getting calculated for particular supplier even though above setup is done correctly.

Please suggest the root cause for the issue.