Stripe Web Checkout in a Mobile App: The Post-Epic External Payments Pattern (.NET Implementation)

Part of a short series on shipping subscriptions in .NET MAUI — see also the full RevenueCat setup guide and the AMM0000 build-error fix.

Since the Epic v. Apple injunction took effect, US App Store apps can link out to external purchase flows — and keep the store's 15–30% cut. Google has its own external-offers programs. Every subscription-app developer is now asking the same question: how do I actually build the web-payment path without getting rejected or double-charging users?

Here's the architecture that works, with a concrete ASP.NET Core + .NET MAUI implementation. The pattern is identical in any stack.

The architecture in one diagram

┌─ App ─────────────┐ ┌─ Your API ────────────┐ ┌─ Stripe ─────────┐