Hi @CassieC ,
I just had a try. The discounts available in the customize section of the invoice are those which are define in the items section of the dashboard:
https://squareup.com/help/au/en/article/3955-create-and-manage-discounts
I noticed that my variable discounts (one without a $ or % defined) are excluded so it looks like only pre-defined discounts will work.
Regards,
Bruce
Square Community
Square Products