🧾 Invoice OS – Invoice & Email Billing System with Accounting (GPL-Ready Source Description)

Invoice OS is a modern, full-featured invoicing and accounting web application designed to help freelancers, agencies, and small businesses manage invoices, track payments, and send professional email invoices effortlessly. Built with PHP + MySQL and an elegant Bootstrap UI, it includes automated email notifications, tax calculation, and a lightweight accounting dashboard.
This HTML description is optimized for GPL/resource repositories and follows E-E-A-T (Experience, Expertise, Authoritativeness, Trustworthiness) standards.

🚀 Overview

Invoice OS simplifies billing and bookkeeping by combining an intuitive invoicing interface with built-in accounting tools. Users can generate invoices, record expenses, and view income reports — all from one centralized system.
Whether you’re managing a startup, digital agency, or consulting firm, Invoice OS provides the right foundation to automate your financial workflow.

• 🧾 Create and send invoices instantly via email.
• 💰 Manage clients, taxes, and payments from a simple dashboard.
• 📊 Track income and expenses for basic accounting.
• 📧 Send automated payment reminders and thank-you emails.

Experience (E): built from real-world accounting and invoicing needs of freelancers and SMBs, designed to minimize administrative overhead and ensure fast billing cycles.

✨ Key Features

• 🧮 Invoice Management: create unlimited invoices with custom logo, due date, and notes.
• 👥 Client Database: manage clients, contact info, and payment history.
• 📬 Email Invoices: send PDF invoices automatically with one click via SMTP.
• 📊 Accounting Overview: view total sales, outstanding payments, and net profit summaries.
• 💳 Multi-Currency Support: choose currencies and apply tax rates per invoice.
• 📆 Expense Tracking: log daily expenses and categorize by type for reporting.
• 📈 Reports Module: generate sales, profit, and expense summaries for any period.
• ⚙️ Tax Management: set default VAT/GST rates with automatic calculation per invoice.
• 🧾 PDF Export: download professional invoices in PDF format for offline sharing.
• 🔒 Secure Login: admin authentication and session-based access.

⚙️ Technical Stack

• Language: PHP 8.x
• Framework: Laravel / CodeIgniter / Core PHP (depending on build)
• Database: MySQL / MariaDB
• Frontend: HTML5, Bootstrap 5, jQuery, AJAX
• Email Engine: SMTP / PHPMailer integration
• Reports: Chart.js for analytics and graphical summaries

Server Requirements: PHP 8.0+, MySQL 5.7+, mod_rewrite enabled, SSL recommended for email and API connections.

Expertise (E): demonstrates best practices in CRUD data management, secure SMTP integration, and lightweight financial reporting.

🧩 Installation Guide

1. 1. Upload files to your hosting directory.
2. 2. Create a MySQL database and import the provided invoice_os.sql file.
3. 3. Configure your .env or config.php file with database and SMTP credentials.
4. 4. Access yourdomain.com/install to complete setup.
5. 5. Log in to the admin dashboard with the default credentials provided.
6. 6. Add clients, create sample invoices, and test email delivery.

Tip: enable 2FA or reCAPTCHA for login security if handling sensitive financial data.

📦 Deliverables

• ✅ Full PHP source code for Invoice OS
• ✅ MySQL database schema with demo data
• ✅ Admin and client management dashboards
• ✅ Email notification templates (HTML-based)
• ✅ PDF invoice generation and accounting reports
• ✅ GPL redistribution statement (for educational/archive use)

📱 Supported Platforms

• Web: compatible with Chrome, Firefox, Edge, Safari
• Server OS: Linux (Ubuntu/CentOS), Windows Server compatible
• Devices: desktop, tablet, and mobile browsers supported
• Email Servers: works with Gmail SMTP, Outlook, SendGrid, or custom mail servers

🧠 Notes

• License: distributed under GPL for transparency and educational use; the original software may be commercially licensed.
• Customization: extend with recurring invoices, payment gateway APIs, or multi-user accounting.
• Security: protect invoice links with authentication and secure SMTP encryption (TLS/SSL).
• Performance: optimized query structure and caching for large invoice databases.
• SEO Assurance: keywords → “invoice management PHP script”, “email invoice system”, “accounting and billing software”.

👨‍💻 Original Developer Credit

This software was originally developed and distributed by its author on CodeCanyon and similar script marketplaces.
All rights and trademarks remain with the original creator. This entry serves as a GPL-compliant educational restatement for documentation and transparency purposes.

Authoritativeness (A): attribution ensures ethical credit and directs users to the official listing for updates or premium support.

🔒 Disclaimer

Important:

• This is a source-code documentation entry, not an official product listing.
• No official support or license keys are included unless purchased directly from the original author.
• GPL redistribution must preserve author credit and cannot be used for proprietary resale.
• Always comply with regional tax and invoice regulations (e.g., VAT, GST laws).

Trustworthiness (T): transparent disclosure of licensing, authorship, and compliance ensures ethical educational distribution.