Tax not Automatically Calculating on AP invoices matched to POs

 Hello,

I'm in the process of setting up new tax regimes based on the EBtax seed data.  It is working for me and calculating taxes fine when I enter a manual invoice against the supplier in AP and assign the tax code.  It is not calculating the tax automatically, however, when the standard invoice is matched to a purchase order.  Any ideas on where to look?

Thanks,

Julia