GST Invoice Checker

A comprehensive Next.js application for validating GST invoices with 11 compliance checks.

Features

✅ AI-Powered OCR Capability - Instantly auto-fill invoice data from PDF/Image uploads. ✅ Quick Check & Comprehensive Invoice Form - Validate without logic barriers, featuring distinct sections for Supplier, Buyer, Invoice info, and detailed Line Items. ✅ Real-time Compliance Engine - Identifies format errors, arithmetic mismatches, and missing mandatory fields. ✅ Detailed Compliance Reports - Get instant feedback, generated reports with fix instructions. ✅ 11 Comprehensive Validation Rules:

1. GSTIN Format Validation
2. Tax Type Logic (CGST/SGST vs IGST)
3. GST Calculation Accuracy
4. CGST/SGST Equal Split Verification
5. HSN Code Validation
6. Tax Rate Validation
7. Invoice Number & Date Validation
8. Taxable Amount Sum & Invoice Total Validation ✅ Risk Level Assessment - Low, Medium, or High risk classification ✅ User Authentication - Login and Sign-up to track validation history. ✅ Modern, Professional UI - Designed with Tailwind CSS for responsiveness and clarity.

Getting Started

Installation

1. Install dependencies:

   npm install
   

2. Configure environment variables:

   Update .env.local with your API keys (optional for basic testing):

   NEXT_PUBLIC_SUPABASE_URL=your_supabase_url
   NEXT_PUBLIC_SUPABASE_ANON_KEY=your_anon_key
   

3. Run the development server:

   npm run dev
   

4. Open your browser: Navigate to http://localhost:3000

Usage

Click the "Validate Sample Invoice" button to see the validation system in action with a pre-configured test invoice.

Project Structure

gst-invoice-checker/
├── app/
│   ├── api/validate/route.ts    # Validation API endpoint
│   └── page.tsx                 # Main application page
├── components/ui/               # UI components
├── lib/services/
│   ├── validationRules.ts      # 11 validation rules
│   └── validationService.ts    # Validation orchestrator
├── types/index.ts              # TypeScript definitions
└── .env.local                  # Environment variables

Validation Rules

• GSTIN Format: 15-char pattern validation
• Tax Type Logic: CGST/SGST for same state, IGST for interstate
• Calculations: Verifies all GST calculations
• HSN Codes: 4-8 digit validation
• Tax Rates: Valid GST rates (0%, 0.25%, 3%, 5%, 12%, 18%, 28%)
• Totals: Sum verification for line items and invoice total

Tech Stack

• Next.js 15 with App Router
• TypeScript
• Tailwind CSS
• Custom UI Components

Built with ❤️ using Next.js and TypeScript