I have added a coupon code to my website which applies to subscriptions. Is there a workaround to apply the discount to only the first subscription payment?
Hello. This is not currently supported. I do not know of a workaround for the default WiX app which is what I am assuming you mean. If you are building a custom site you can create the coupon logic but this is of course more work.
You could modify the coupon so that the total amount you want discounted is spread over the course of the subscription. For example if you wanted to give $15 off a 3 month sub, modify the coupon to take $5 off a month.
Here is the wishlist request for that feature if you would like to vote for it.