IAP and account subscriptions

If I have an app available on IOS/Android/Web and offer subscriptions in each (Obviously using apple IAP / Google Play Billing when in those contexts) and a user creates an account on Android / Web and pays for that subscription and then logs in with the same account on the App Store, do I need to charge them again for a new subscription, or can I use their account subscription?

IAP and account subscriptions
 
 
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