Airbase
The all-in-one spend management platform for mid-market and enterprise finance teams.

The premier open-source, self-hosted platform for professional quote and invoice management.
InvoicePlane is a robust, self-hosted open-source application designed for managing quotes, invoices, clients, and payments. Built on the CodeIgniter PHP framework, its architecture is optimized for data sovereignty, making it a preferred choice for privacy-conscious freelancers and small-to-medium enterprises in 2026. Unlike SaaS-based competitors, InvoicePlane allows users to maintain full control over their financial data by hosting the application on their own servers. The system features a modular design that supports high-level customization via CSS/HTML templates and a flexible API. Its technical 2026 market position is defined by its stability and the community-driven development of its v1.6+ and v2.x branches, which focus on modernizing the UI and enhancing security protocols. It effectively bridges the gap between simple spreadsheets and complex enterprise ERP systems, offering a streamlined workflow for converting quotes into invoices and tracking receivables through integrated payment gateways like Stripe and PayPal via the Omnipay library.
Utilizes the Omnipay PHP library to support 25+ payment gateways including Stripe, PayPal, and Authorize.net.
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Uses a PHP/HTML-based templating system that allows for granular control over PDF generation via mPDF.
Logic-based recurring billing system that triggers via server-side cron jobs to generate and email invoices.
Distinct module for draft proposals that includes a one-click 'Approve and Convert' workflow to Invoice status.
A dedicated, authenticated front-end for customers to view, download, and pay invoices online.
Direct database access and built-in export tools for SQL and CSV formats.
Configurable tax levels (item-level vs. invoice-level) with support for compound tax calculations.
A small software agency needs to bill 50 clients monthly without paying a percentage of revenue to a billing platform.
Registry Updated:2/7/2026
Moving from a 'verbal agreement' to a 'paid invoice' is friction-heavy.
Legal firms cannot store sensitive client financial data on third-party US-based cloud servers.