Tax not calculated based on party fiscal classification

Hi,

I want tax to be calculated based on the customer resgistation. If the tax is just based on registration status (y/n), That is straight forward. But the problem here is to have different tax if the customer is registered in UK . So I thought to have party fiscal classification to get this.  Created party fiscal classification and assigned to customer . Setup rule based on this and created AR transaction. But tax is not getting calculated as expected. Can you help where it went wrong or is there any other way to achieve this?

Thanks

Venkatesh kata