If you set a Tax Rate to be for PO and SO a single
description is used in the Acctg Fact Details
regardless of PO or SO context.
If you create an Invoice Tax report you can group using
the "is sales" flag.
If you need to create an equivalent report using Acctg
Fact details (because you need to see all trx in the
accounting currency) then there is no "is sales" flag
This could be improved if the Tax Rate provided an
option to store a 'label' to be used for a sales trx
and a separate label to be used if that Tax Rate was
used in a purchase context. The Acctg Fact could be
created with with the appropriate Tax Rate 'label'