How Tax code is automatically picked in PO for GCC VAT

Hi Friends ,

If anyone worked on GCC VAT or any thought . Please help me on this

For GCC VAT - fields like tax indicator for materials TAXIM , TAX catg. etc are not available in field catalog . Even though we extend MM fields

(ref- SPRO- FA-Tax on sales purchase - Access seq fields . The Fields catalog does not have the fields . Only useful field available is tax code, rest are mat code, material group etc )

So how tax code is auto picked in PO with condition records ?

regards

manu