I have enabled PVA Import 20% for invoices from EU suppliers for goods. When I try to save I get an error message "QB encountered an error while calculating tax"

Hi sales249, thanks for your post 

We're aware of an issue where customers are receiving this error when saving a bill/expense using the PVA 20% VAT code, and we're tracking this on INV-53549.

We've linked you to this investigation so that you'll be notified once the fix is in place, in the meantime, please use the workaround of selecting the 20% RC MPCC code, and note the transaction to change back to the correct code once resolved. Alternately, you can use No VAT, and note the transaction to change back to the correct code once resolved, and to create an exception. 

Get back to us below if you have any Q's in the meantime :)