Yes. From the subscription's admin page you can apply a coupon code to the subscription's renewal rate. The code must belong to a coupon that is Is Active, has Apply Discount to Recurring Subscription Rate on, and is a Fixed Dollar or Percentage type — otherwise you get "Coupon not found", "Coupon is not active", "This coupon is not configured for recurring subscription rate discounts" or "Only Fixed Dollar or Percentage coupons can be applied to subscription rates". The subscription keeps its original price on record and renews at the discounted price. Removing the coupon restores the original price ("No recurring coupon applied to this subscription" appears if there is none).