How to derive invoice tax from InvoiceDetailSummary in OBN cXML

Summary:

How to derive invoice tax from InvoiceDetailSummary in OBN cXML

Currently because of the Suppliers Local laws they have to input tax details at the Invoice Line level in the cXML, but due to them charging tax on the Freight Line as well we are unable to derive the tax calculation for the Freight line when they send the invoice.

To get around this we would like to only derive the tax from the InvoiceDetailSummary Tag where the tax is entered as whole for all the lines including the Freight line.

Could you help us map this to ignore the line level tax and directly look at the tax in InvoiceDetailSummary?