tax exempt number must be specified in AX?

Hi, i am using US localization Ax 2012 featurepack, and in the AR parameters I specified “none” as tax exempt number requirement. However, when I try to create an invoice from the Sales Order, the system generate an error message “Tax exempt number for the SO is not specified”

What is the reason for this error message? Appreciate your help.

I found the reason. one of the AR tax requirement parameter was set to “Domestic+EU” that was causing it.