(MM-SRV) Tax code determination in an external Service PO

Hello there,

Question: How to automaticaly determine the tax code for a service PO generated externally?

We don't want to edit the document.

Even if we try to edit the service PO the system shows this error message:

BBP purchase order cannot be changed (Display only)

You wish to change a purchase order that was created in the BBP system.

The purchase order was transmitted to the standard system so that the goods receipt and invoice could be posted.

A purchase order created in the BBP system has the value K - Purchase Order from BBP in field EKKO-STATU.

Addtitional Info:

• It has to be automatically determined.

• This is a one time service: no service master data.

• We need tax code at PO item level (not service item level).

Thanks in advanced.