Helen, we already had this conversation a few weeks ago.  you can change it per PO.

Yes, but the PO and receiving are done. But, my question is more on the Vendor set up level. We would like two or more tax group set up in the Vendor code so users can only pick and choose from the one we have set up in the Vendor code. Not the same question :)

then the answer is no.  you can only have 1 default tax group per vendor and you can't limit which ones are available to use to users.  You can't change it once the PO is done.  if it's critical, then do a PO RETURN and make a new receipt with the corrected taxes.  And if it's going to be a big deal and you need buyer to know, then possibly look into popup notes such as the system from Orchid.  We use that one.  But we also use separate vendor codes for vendors that have a high chance of using wrong taxes.

Noted. Thaks!