Dual-Platform Tax Filing App

I need a fully-functioning tax-filing mobile application built for both iOS and Android, delivered as soon as realistically possible. The core flow should guide users from account creation through document capture, data validation, and final e-filing, with secure storage and end-to-end encryption at every step.

Please walk me through your proposed architecture and timeline in a detailed project proposal. I am especially interested in how you will:

• Handle cross-platform development (React Native, Flutter, or native)
• Integrate OCR for receipt and form scanning
• Calculate federal and state taxes with up-to-date rules
• Manage encryption, authentication, and cloud back-ups
• Prepare the app for App Store and Google Play submission
• must have Hmrc apis
•must have robust security

Acceptance criteria will include a test build on both platforms, passing unit and integration tests, and clear deployment documentation so I can maintain future updates.