Hi simbai_ pen 

Please have a look at the following link below showing how to setup reminder campaign.
https://communityhub.sage.com/za/sage-x3/b/sage-x3-support-insights-ame/posts/how-to-setup-reminder-campaign

Test and advise, hope this is helpful.

Kind regards
Bonolo

Cana you expand on that?  There is a customer statement in Sage X3 that shows all transaction at the top level.  The invoice header level.