Cross-Platform Bill Payment App

I need a full-featured bill payment application that runs smoothly on both iOS and Android. The core flow is straightforward: users select a service provider, enter their account details, review the amount due, and complete payment.

Three capabilities are non-negotiable. First, the app must send timely payment reminders—push notifications and, where permitted, email—so users never miss a due date. Second, every transaction has to be stored in an easily browsable history screen with filters by date, provider, and status. Third, the checkout screen must accept multiple payment methods (card, bank transfer, and popular mobile wallets) with PCI-DSS-compliant encryption from end to end.

A single codebase in Flutter or React Native is ideal, but I’m open to native builds if you feel that’s the better route. Whichever approach you take, please include:

• Source code with clear comments
• API documentation for any third-party integrations
• Test builds for both platforms and guidance on App Store / Play Store submission

Let me know your preferred tech stack, any relevant past work, and the timeline you can confidently hit for a first functional build and final release.