Invoice Ninja is a free, open-source platform for invoicing, payments, expenses, and time tracking. It is built for freelancers, contractors, and small businesses that bill clients and want full control over their data. You can run it on your own server at no license cost, or pay for a hosted plan if you prefer not to manage infrastructure. Hundreds of thousands of businesses use it to send invoices, accept online payments, and track billable work. If your current process is spreadsheets and hand-built PDF templates, this article explains what Invoice Ninja does and whether it fits your workflow.

What is Invoice Ninja?

Invoice Ninja is an invoicing application, not a full accounting suite. The current version is a modern web app with a PHP and Laravel backend and a Flutter-based interface that works in any browser. The self-hosted edition is free and includes the core product: quotes, invoices, payments, expenses, tasks, projects, and a client portal where your customers can view and pay what they owe. A paid hosted service and a small white-label license, which removes Invoice Ninja branding from client-facing pages, fund the project. Because it is open source, you can inspect the code, extend it through the REST API, and move your data whenever you like.

What is Invoice Ninja used for?

• Client invoicing and quotes. Build branded invoices, send quotes for approval, and convert an accepted quote into an invoice with one click.
• Accepting payments. Connect gateways such as Stripe and PayPal so clients pay directly from the invoice email or the client portal, and record bank or cash payments manually.
• Recurring billing. Set up recurring invoices for retainers and subscriptions, with optional auto-billing that charges a saved card on schedule.
• Expense and vendor tracking. Log expenses, attach receipt photos, mark them billable, and pull them onto an invoice later.
• Time tracking. Track hours against tasks and projects, view work on kanban boards, and convert logged time into invoice line items.
• E-invoicing and client documents. Where clients or regulations require it, generate EN 16931 e-invoices such as Factur-X or ZUGFeRD, and let clients upload documents through the portal.

Key features

• Custom invoice designs. Templates plus a drag-and-drop editor let you match fonts, colors, and layouts to your brand.
• Multi-currency and tax handling. Invoice each client in their own currency and language, with tax rates set per client or per item.
• Payment reminders and late fees. Automated reminder emails and configurable late fees reduce manual chasing.
• Client portal. Clients approve quotes, pay invoices, and review their history in one branded place.
• Integrations. A REST API, webhooks, and Zapier and Make connectors link Invoice Ninja to the rest of your stack.
• Mobile apps. Companion apps for iOS and Android let you create invoices and log expenses from your phone.

Invoice Ninja on OpenSysLab

Every OpenSysLab server is a private virtual machine in the region you chose at purchase. The app installs automatically in about ten minutes, and the Vibe-code agent inside Open WebUI can read, configure, and manage it for you — you just connect your own AI API key. Servers start at $6/month. See the Invoice Ninja product page for plans and regions.

The bottom line

Invoice Ninja covers the money-in side of a small business well: quotes, invoices, payments, expenses, and time, at no license cost. It will not replace a general ledger or run your payroll, and self-hosting means updates and backups are yours unless you pick a hosted option. For freelancers and small teams, it is one of the strongest open-source invoicing tools available.