A Less Previously Invoiced line will only be generated on an additional invoice in:

• groupBook if the additional invoice is raised for the Entire Booking or All Itineraries. If the additional invoice is raised for just one or a selection of Itineraries Tourplan cannot generate a Less Previously Invoiced line.
• fastBook and groupBook if the additional invoice is in the same currency as the previous invoice or invoices.  For example if the first invoice is in EUR and the additional invoice in GBP there will be no Less Previously Invoiced line on the GBP invoice.