Did you develop your subscriptions purchase process using Apple's "SubscriptionStoreView" or have you developed your own subscription purchase view? I am currently testing my subscriptions purchase process using TestFlight and sandbox accounts ... I have developed my subscriptions purchase process using the "SubscriptionStoreView" ... I have never seen this multiple subscription purchases when testing using Xcode & Simulator and Xcode & iPhone ... Conceptually, I believe it should not matter whether you developed your own view or not, Store Kit 2 should properly handle subscription purchases properly and prevent duplicated subscriptions because a new subscription should only become active when the previous subscription is expires or is upgraded.