PHP + MySQL: Build a Complete SaaS Invoicing System

This is a complete SaaS invoicing system built with PHP and MySQL. One install runs many businesses. Each company signs up, gets its own separate data, and works on a subscription plan that you control as the platform owner. Inside each company, staff create invoices, track stock, take payments and read reports from one central dashboard.

Built as a real multi-tenant SaaS

• Platform owner panel: manage companies, plans, trials, subscription periods and payment references. Each plan decides which modules a company can open.
• Company roles: business Admin, Manager and Employee, plus custom roles with a View / Add / Edit / Delete permission matrix.
• Multi-branch: staff can be limited to their own branch, managers can switch between branches, and stock moves between branches through transfers.

Invoicing and documents

Invoices, quotations, credit and debit notes, purchase orders, supplier bills, delivery challans and recurring invoices all use one posting engine that keeps totals, the stock and the customer ledger in step. Every invoice prints in five designs (modern, classic, corporate, elegant and bold), with an optional QR code for verification. Payment receipts print on A4 or on an 80mm thermal roll.

Stock, money and reports

• Stock ledger with barcode, batch (FEFO) and serial / IMEI tracking, price lists and alternate units
• Multi-currency invoicing, with every report kept in your base currency
• Expenses, bank reconciliation, cheques, late fees, collections and loyalty points
• A reports pack covering sales, purchases, tax, profit and loss, and customer balances
• Edit lock and year close, so finished periods cannot be changed by mistake

Who it is for

This is for developers and freelancers who want a ready base for their own billing SaaS, and for businesses that want a self-hosted invoicing and inventory system. The full build is shown in the video walkthrough.