default tax code for material group

Hi All,

I would like to determine a tax code as default in the PO.For this I have created an info record for a material group XYZ with tax code maintained as P1 in the info record.

Now when I create a text PO with the same material group and vendor combination the system does not determine the info record in the PO so as to determine the tax code P1 as default in the PO.