AP invoice from Third party - tax calculation

Hi,

We are using a third party system for creating AP invoices. The 3rd party system collects the PO/receipt details and processes supplier AP invoices. Through a custom inbound program, the AP invoices are created. if we need to get the AP invoice tax handled through 3rd party integration, how can this be done?

Can we invoke the tax calculations when the invoice data is available in open AP interface tables?

Rgds,

pavan