📇 SaaS-Based Invoicing System

A robust, multi-tenant SaaS invoicing platform built with Express.js and React.js, designed for business scalability, real-time operations, and secure invoice management. Features include Stripe payments, role-based access, real-time dashboards, and an AI assistant to boost productivity.

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🚀 Tech Stack

Layer	Tech
Backend	Node.js, Express.js, Sequelize/SQLite
Frontend	React.js, Tailwind CSS
Auth	JWT (JSON Web Tokens)
Payments	Stripe API
Analytics	Socket.IO (Real-time), Chart.js
PDF	PDFKit or Puppeteer
AI Service	Python (scikit-learn, FastAPI) or TensorFlow.js
Database	SQLite (with Sequelize ORM)

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📦 Key Features

• ✅ Invoice creation, management, and delivery
• ✅ Multi-tenant architecture with scoped access
• ✅ Role-based access control (Admin, Editor, Subscriber)
• ✅ Stripe for payments (one-time + subscriptions)
• ✅ Real-time financial dashboard (Socket.IO)
• ✅ PDF generation with branding
• ✅ Email verification & password reset
• ✅ Admin panel for employee management
• ✅ Smart AI assistant for workflows

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🤖 AI-Powered Smart Features

📌 Overview

AI assistant learns from invoice data to provide:

• 📄 Layout suggestions from templates
• ⏱️ Recommended payment terms
• 🔮 Late payment predictions
• 🧠 Auto-filled items & pricing
• 🌍 Region-based tax calculation

🧠 Workflow

1. Data Collection – invoice data + user interaction
2. Training – ML model learns patterns
3. Prediction APIs – exposed via REST endpoints
4. Feedback Loop – improves suggestions over time

📡 API Endpoints

Endpoint	Description
POST /api/ai/suggest-layout	Suggest invoice layout
POST /api/ai/suggest-terms	Recommend payment terms
POST /api/ai/auto-fill-items	Auto-fill descriptions & pricing
POST /api/ai/predict-late	Predict likelihood of delayed payment
GET /api/tax/lookup?region=ZA	Get tax rate based on location

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👤 User & Role Model

🧑‍💼 Platform Admin

• Full control of the platform
• Manages employees, clients, and invoices

👥 Employees

Role	Permissions
Admin	Full access to all client & invoice data
Editor	Can manage invoices, but limited settings access
Subscriber	Read-only access

🔐 Passwords are auto-generated upon employee creation and can be reset by the employee.

🧾 Customers

• Individuals or companies
• Tied to an admin account
• Recipients of invoices

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🗝️ Permission Matrix

Feature	User (Admin)	Admin Employee	Editor	Subscriber
Manage Invoices	✅	✅	✅	❌
View Invoices/Analytics	✅	✅	✅	✅
Manage Clients	✅	✅	❌	❌
Employee Management	✅	❌	❌	❌
Subscription Settings	✅	❌	❌	❌
Stripe Configuration	✅	❌	❌	❌

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💳 Stripe Integration

• Supports credit card payments
• One-time and recurring billing
• Stripe webhook events:
  • invoice.paid
  • invoice.payment_failed
  • customer.subscription.deleted

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🔐 Security Features

• Email confirmation + password reset
• JWT authentication
• Role-based API/UI access
• Two-Factor Authentication (optional)
• Helmet.js for security headers

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📊 Real-Time Dashboard

Powered by Socket.IO and Chart.js:

• 📈 Revenue charts
• 🧾 Invoice status breakdown
• ⏰ Overdue alerts
• 👥 Client activity logs

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🖨️ PDF Invoice Generation

• Built with PDFKit or Puppeteer
• Printable/downloadable invoices
• Branding with logo & footers

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🗃️ Database Design (Sequelize)

SQLite Implementation

• Lightweight file-based database
• Sequelize ORM for model management
• Migrations and seeders supported

Models

• User
• Employee (w/ roles)
• Customer
• Invoice / InvoiceItem
• Payment
• Subscription
• AITrainingData (optional)

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📁 Folder Structure

SaaS-Invoicing/
├── backend/
│   ├── controllers/
│   ├── models/
│   ├── routes/
│   ├── middlewares/
│   ├── services/
│   ├── config/
│   │   └── database.js
│   ├── app.js
│   └── package.json
├── frontend/
│   ├── src/
│   │   ├── components/
│   │   ├── pages/
│   │   ├── services/
│   │   ├── auth/
│   │   └── App.jsx
│   └── public/
├── docs/
│   └── api-spec.md
├── README.md
└── .env.example