Hi Wesley,
If you are wanting to charge additional amounts to a customer you would need to contact Stripe to discuss something like this. We cannot alter an invoice in KashFlow at point of payment and our integration would not support such a request i'm afraid.
My sentiments and idea also
Thanks for responding on this. From what I understand from the stripe api, the ability to charge the handling fee has to be done from the client application not from their side unfortunately.
What I would like is the ability to email them a link to pay online directly from Kashflow, rather than including a pay online button on each invoice. Then if they request to pay online, I can add the fee's as required.