GST Billing Pro

A professional Android application for small businesses to manage invoices, track payments, and generate GST-compliant PDFs — all offline-first.

🎥 Demo Video: Watch on YouTube

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Screenshots

Login	Register	Dashboard	Dashboard 2

Create Invoice	Invoice History	Invoice Details	PDF Preview

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Problem Statement

Small businesses in India struggle with manual invoice creation, GST calculations, and payment tracking. GST Billing Pro digitizes the entire workflow — from customer onboarding to GST-compliant PDF generation — with offline-first support.

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Key Features

Feature	Description
Secure Auth	Google Sign-In via Firebase with per-user data isolation
Business Dashboard	Real-time revenue, pending payments & monthly sales charts
PDF Generation	GST invoices with CGST/SGST, QR code & digital signature
Invoice Management	Full CRUD with Paid / Unpaid / Partial status filters
Payment Tracking	Record partial or full payments with history logs
Business Profile	Customizable logo, GSTIN, address per account

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Tech Stack

Kotlin  •  Jetpack Compose  •  MVVM  •  Room DB  •  Firebase Auth
Android PdfDocument  •  MPAndroidChart  •  Compose Navigation

Layer	Technology
Language	Kotlin
UI	Jetpack Compose
Architecture	MVVM + Repository Pattern
Local DB	Room (with Migrations)
Auth	Firebase Auth + Google Sign-In
PDF Engine	Android Graphics PdfDocument
Charts	MPAndroidChart
Navigation	Compose Navigation + ModalNavigationDrawer

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Architecture

Jetpack Compose UI
        │
        ▼
   ViewModels (State Management)
        │
        ▼
  Repository Layer (Business Logic)
       / \
      /   \
Room DB   Firebase Auth
      \
   Analytics Engine → PDF Generator

Flow: User → Compose UI → ViewModel → Repository → Room / Firebase

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Setup & Installation

Prerequisites

• Android Studio Hedgehog or later
• JDK 17+
• A Firebase project with Google Sign-In enabled

Steps

# 1. Clone the repo
git clone https://github.com/sanket1035/GSTbillingApp.git

# 2. Open in Android Studio

# 3. Add your Firebase config
# Place google-services.json inside the /app directory

# 4. Build & Run
# Target: API 24+ (Android 7.0 and above)

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Key Challenges Solved

• Multi-user data isolation via Firebase UID scoped Room queries
• Offline-first storage with Room + reactive Flows
• Automated GST calculations (CGST/SGST split)
• Dynamic PDF generation with QR codes on-device
• Revenue analytics without a backend

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Roadmap

• Cloud sync (Firebase Firestore)
• Customer analytics & ranking
• AI-based expense prediction
• GST filing integration (GSTN API)
• Multi-language support (Hindi, Marathi)

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📄 License

This project is licensed under the MIT License.

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Built with ❤️ by Sanket Chaudhari for Small Businesses