Bigcapital is an open-source financial accounting and inventory management platform designed for small and medium businesses seeking full control over their financial data. Built as a self-hosted alternative to proprietary tools like QuickBooks and Xero, it provides double-entry accounting, automated reporting, invoicing, bill tracking, and inventory management—all in a single unified system. With AGPL licensing and Docker-based deployment, it empowers businesses to maintain data privacy while benefiting from real-time financial insights. The platform is ideal for finance teams, bookkeepers, and SMB owners who need transparency, customization, and compliance without recurring SaaS fees.
What You Get
- Double-entry accounting system - Fully implements double-entry bookkeeping with ledgers, journals, and trial balances to ensure accurate financial records and audit readiness.
- Automated financial reporting - Generates intelligent reports such as profit & loss statements, balance sheets, and cash flow statements with customizable date ranges and export options.
- Invoicing & bill management - Create, send, and track customer invoices and vendor bills with automated reminders and payment status updates.
- Inventory tracking - Monitor stock levels, track cost of goods sold (COGS), and link inventory items directly to transactions for accurate financial reporting.
- Headless API integration - Exposes a comprehensive RESTful API to integrate accounting data with existing ERP, e-commerce, or CRM systems without using the web UI.
- Docker-based self-hosting - Deploy securely on your own infrastructure using Docker Compose with preconfigured services for web, database, and background jobs.
Common Use Cases
- Building a small business accounting system - A local retail store uses Bigcapital to track daily sales, manage vendor payments, and generate monthly tax-ready financial statements without paying SaaS subscription fees.
- Creating a multi-location inventory and finance system - A small chain of 5 stores uses Bigcapital to centralize inventory tracking and financial reporting across locations, syncing data via the API into a corporate dashboard.
- Problem → Solution flow: Avoiding vendor lock-in with proprietary accounting software - A business tired of rising subscription costs and data export restrictions migrates from QuickBooks to Bigcapital, gaining full access to their financial database and the ability to customize reports.
- Team/workflow scenario: Bookkeeping firms serving multiple clients - A CPA firm hosts separate Bigcapital instances for each client, using the API to pull financial data into their internal reporting tool while maintaining strict data isolation.
Under The Hood
BigCapital is a multi-tenant SaaS platform built on a monorepo architecture, combining NestJS for backend services and React with Vite for frontend rendering. It emphasizes extensibility, modular design, and enterprise-grade integrations to support scalable business applications.
Architecture
This project adopts a layered architecture within NestJS, ensuring clear separation between modules, services, and repositories. The design promotes modularity and maintainability through consistent use of decorators, interceptors, and filters.
- Implementation of layered architecture with well-defined modules and services
- Use of decorators, interceptors, and filters to handle cross-cutting concerns like validation and error management
- Strong emphasis on separation of concerns and scalable structure for multi-tenant environments
Tech Stack
Built with TypeScript, the project leverages modern web and backend frameworks to deliver a robust, extensible platform.
- TypeScript with NestJS for scalable backend and React with Vite for modern frontend
- Rich ecosystem including Redux, React Router, Ramda, Lodash, and third-party services like Stripe and Plaid
- Development tools such as Lerna for monorepo management, Husky for Git hooks, and ESLint/Prettier for code quality
- Comprehensive testing suite using Jest, Playwright, and structured test configurations for both frontend and backend
Code Quality
Code quality is moderate, with a focus on structured error handling and testing practices, although some technical debt exists.
- Strong emphasis on end-to-end and unit testing with extensive test configurations
- Consistent use of TypeScript for type safety and improved code reliability
- Evidence of technical debt and inconsistent patterns that affect long-term maintainability
- Code linting and formatting tools are in place to support consistency
What Makes It Unique
BigCapital stands out through its implementation of tenant-aware systems and modular extensibility for enterprise use cases.
- Modular configuration system enabling per-tenant customization without monolithic changes
- Sophisticated repository pattern with caching and multi-tenant data handling for scalability
- Extensive use of decorators and interceptors to reduce boilerplate and enforce consistency
- Built-in integrations with cloud storage, email, payment processing, and analytics tools