tax rule not being considered.

Hi,

I have created a tax rule(with condition sets etc) and based on a tax classification code etc,but when i create an AR transaction and provided that code ,apparently that rule is not being considered. Although when i tested another tax rule with identical setup(with a different tax classification code) is working fine.  I am not able to figure out what is the issue here. After defining a tax rule is there any additional step that needs to be done, for it to be considered. I ensured it is enabled(enabled flag is checked).

Please let me know,