Field help (FREINV) 

Flag used to specify if freight must be charged to the customer or if the latter does not have to bear these charges. This exemption can be linked to no conditions at all or to a tax excl. or tax incl. threshold.
The freight calculated from the carrier price and integrated when delivering via a dedicated invoicing element.
SEEREFERTTO For more details, see the general setupFRENUM.
The thresholds are defined in the carrier record.