I'll inform the ABAP developer to add the new requirement to ZDATATAX report.
Could you elaborate on your expectation related to adding the Tax code in the Selection screen?
In the current logic of the report, Tax code information is in Purchase orders, so if the Tax code be added in the Selection screen, my understanding is that only Purchase orders that have the corresponding Tax code which was used in the selection parameters will be extracted in the file. Example of this is, Tax code VX is used in the selection parameters, only Purchase orders with VX and line items will be extracted in the file. Let me know if my understanding is correct.