GST Billing System
Introduction
This project is developed to automate the billing and service workflow of a GST-registered service business. Managing invoices, tracking service orders, and maintaining customer records manually is time-consuming and error-prone.
The GST Billing System replaces paper-based processes with a centralized web platform. It handles the complete service lifecycle — from customer onboarding and work order creation to step-by-step task tracking, automated GST invoice generation, and payment management — all accessible through a secure admin login from any browser.
🧾 Designed for a single-admin service business operating on Hostinger shared hosting with phpMyAdmin (MySQL) as the database backend.
Key Features
Secure Admin Login
Session-based auth with hashed passwords. Single admin access for full control.
Customer Management
Add, edit, delete customers with GST number, address, state, and contact details.
Work Order / Task System
Create service orders, define steps/milestones, update status as work progresses.
Invoice Linking
Work orders link directly to invoices — create a bill from an existing task in one click.
GST Invoice Generation
Auto-calculates CGST/SGST or IGST with sequential invoice numbers and all mandatory GST fields.
Payment Tracking
Track payment status per invoice — Paid, Pending, Partial, or Cancelled.
Print-Ready Invoices
One-click print view generates a clean, professional GST invoice formatted for A4 paper.
Admin Dashboard
Revenue summary, pending payments, active orders, and invoice count at a glance.
Tools & Technologies
- Frontend: HTML5, CSS3, JavaScript (Vanilla)
- Backend: PHP (Server-side logic & sessions)
- Database: MySQL — managed via phpMyAdmin
- Hosting: Hostinger Shared Hosting
- Local Testing: XAMPP
- Editor: Visual Studio Code
- Documentation: ERD, DFD, Use Case Diagrams, MS Word
System Design
The system follows a 3-tier architecture: Presentation Layer (HTML/CSS/JS), Business Logic Layer (PHP), and Data Layer (MySQL). ERD, DFD, and Use Case diagrams define the data structure and workflows.
Service Billing Flow:
↓
Task Progresses → Status Updated Step-by-Step → Work Completed
↓
GST Invoice Generated → Sent to Customer → Payment Tracked
Implementation Modules
| # | Module | Key Functions |
|---|---|---|
| 1 | Auth Module | Admin login, session management, logout, bcrypt password hashing. |
| 2 | Customer Module | Add/Edit/Delete customers. Store GST number, address, state, contact. |
| 3 | Work Order Module | Create service orders, define steps/milestones, assign to customer, set deadlines. |
| 4 | Task Tracker | Update step-by-step status (Pending → In Progress → Done), add notes per step. |
| 5 | Invoice Module | Create invoices manually or directly from a completed work order. |
| 6 | GST Calculator | Intra-state: CGST + SGST split. Inter-state: IGST. Multiple tax slabs supported. |
| 7 | Payment Module | Mark invoices Paid / Pending / Partial / Cancelled. Log payment date and mode. |
| 8 | Print / Export | Print-ready A4 invoice view with all mandatory GST fields and business details. |
| 9 | Dashboard | Revenue summary, pending payments, active orders, invoice count — at a glance. |
| 10 | Company Profile | Set business name, GST number, address, bank details — auto-used on invoices. |
Results & Discussion
The system successfully automates the complete billing and service workflow for a single-admin service business. Invoice creation time reduced significantly — from manual calculation to auto-generated in seconds. GST computation errors eliminated with automatic CGST/SGST/IGST calculation based on customer state.
Work orders provide clear service accountability with step-by-step status tracking, ensuring no service goes unbilled. The admin dashboard provides instant revenue visibility, and all data is permanently stored in MySQL on Hostinger.
Testing & Results
| Test Case | Result | Remarks |
|---|---|---|
| Admin Login & Session Management | ✓ Pass | bcrypt verified, session active correctly |
| Customer Add / Edit / Delete | ✓ Pass | All CRUD operations working correctly |
| Work Order Creation with Steps | ✓ Pass | Steps saved and linked to order correctly |
| Step Status Update (In Progress / Done) | ✓ Pass | Status updated in real-time |
| Invoice Generation from Work Order | ✓ Pass | Customer and service details auto-filled |
| CGST / SGST Calculation (Intra-state) | ✓ Pass | Tax split correctly as 50/50 |
| IGST Calculation (Inter-state) | ✓ Pass | Full GST applied as IGST correctly |
| Sequential Invoice Numbering | ✓ Pass | Auto-incremented with FY prefix |
| Payment Status Update | ✓ Pass | All 4 statuses working correctly |
| Print Invoice (A4 Format) | ✓ Pass | Clean print view, nav hidden on print |
| Dashboard Revenue Summary | ✓ Pass | Aggregates from invoices table correctly |
| Data Persistence (phpMyAdmin / MySQL) | ✓ Pass | All records saved and retrievable correctly |
Future Scope
- WhatsApp API integration to share invoices directly with customers.
- Direct PDF export with one click using a server-side PDF library.
- GSTR-1 compatible export (JSON/Excel) for easy GST return filing.
- Multi-user system with role-based access — Owner, Staff, Accountant.
- SMS/Email notifications for new invoices and payment reminders.
- Recurring invoice feature for subscription-based or retainer clients.
- Expense tracking and profit/loss reports for better business insights.
- Mobile-friendly Progressive Web App (PWA) version.
Conclusion & Next Steps
The GST Billing System successfully automates the complete billing and service workflow for a single-admin service business. It eliminates manual GST calculations, ensures accurate sequential invoicing, and provides clear service accountability through the work order tracking module.
The system is user-friendly, accessible from any browser, and stores all data permanently on Hostinger via MySQL. It provides a strong foundation for future enhancements — particularly PDF export, WhatsApp sharing, and GSTR-1 filing support.