After several fixes in AX 2012 te design of this feature was decided to:

- Do not verify if both the sales tax group and item sales tax group are blank.

- Do not verify if either the sales tax group or item sales tax group is blank. This is to prevent verification warning/error for scenarios such as multi-line journals and payment journals.

But this is still highly required specially in some countries and the workaround does not fully cover the lack and it is complex to setup.

Please, consider to improve the design to include those scnearios without breaking any other scenario.