I am developing a hosted shopping cart service, much like Shopify.com. I would like to charge my clients a fee on top of their payment processor.
Shopify charges 0.5% to 2% (depending upon your plan) on top of Authorize.net fees.
How can I do this?
Stripe and Paypal offer this kind of payment handling [0] and [1].
[0] https://stripe.com/docs/connect/payments-fees
[1] https://developer.paypal.com/docs/classic/adaptive-payments/gs_AdaptivePayments/