How to Turn off EB Tax for PO Module in 12.1.3 after upgrade from 11.5.10.2

Hello,
After upgrade, we automatically have tax calculation enabled for PO module. How do we turn it off for PO module? (We still want to use it for AP, as we do in 11.5.10.2).

I checked note 811272.1 (thanks to Carol and other contributors) and tried to create one new record with Allow Tax Applicability unchecked. However we do not have any value in "Regime Determination Set" after upgrade and therefore I could not save it. How can we define Regime Determination Set" in upgraded instance so that I can save the record and retest.

Also, we have 53 Party Names all with Party Type of "Operating Unit owning Tax Content". Since PO has 3 event Class, do we have to create 159 (53 X 3 ) new records just to disable PO module from tax calculations?