How to calculate tax on interface invoices

Hi,

For calculating tax on an invoice,we enter a value in tax classification code and then press the calculate tax button, and this adds the tax lines .(This is a manual process ).

We have a system which sends us AP invoices through interface table.

How do we calculate tax for all these invoices?

Do we have a batch process which does this or uses have to manually go to individual invoice and press the calculate tax button?