Hi again @paul2009
Do u have any examples of an external invoicing package? I appreciate any insight or ideas you might have.
Alternatively I see that Squarespace Scheduling offers for an additional fee: "Do not accept payment online Clients can’t pay during booking, but you can charge them from the Scheduling panel. " https://support.squarespace.com/hc/en-us/articles/360039291732-Managing-payments-in-Scheduling
$14/month is a pretty expensive way to disengage from an otherwise mandatory checkout function.