I'm not seeing any reference in the docs to coupon codes or discounts on subscriptions. Is this possible? More specifically, our project scope includes applying coupon codes to either the first month's subscription charge or all subsequent months in a given subscription.
At present there are no coupon/discounts that have been created that do either/or.
The built in settings govern whether or not discounts should be applied on subsequent payments (based on a discount set in the cart on purchase), but there's nothing created at this point that does specifically what you're asking.
I suggest you schedule a Phone/Skype appointment with the CartThrob/Mightybigrobot support team at http://support.mightybigrobot.com. A member of our support team can speak with your personally and discuss possible solution to this issue.