Hello,
something to confirm on your end. Can someone perform product save as admin with checked "Auto Recalculate on Save" and see if price in "Recurring Amount" field will be saved with or without tax. Until now always this price has been saved without tax which is only added on invoices during invoice creation.
This might be related to:
CORE-13545 - Correct calculation for "Auto recalculate on save" option on service in system with inclusive tax for tax exempt client
but account owners which I've checked has tax exempt set to "no".
Thanks