Bigcapital

Bigcapital is an open‑source, self‑hosted accounting and inventory platform designed for small to medium businesses. At its core it implements a double‑entry bookkeeping engine that automatically reconciles sales, purchases, inventory movements, and expenses into a unified chart of accounts. The system exposes a RESTful API that mirrors the UI data model, enabling developers to integrate Bigcapital as a headless accounting layer in custom workflows or third‑party ERP stacks. The application is licensed under AGPL, giving full access to the source code while ensuring that any derivative works remain open.

Architecture & Technical Stack

Bigcapital follows a micro‑service style split between a web application and a background job worker, both written in Node.js (TypeScript). The front‑end is a single‑page application built with React and Redux Toolkit, consuming the same API that powers the headless mode. Data persistence relies on a PostgreSQL database, with schema migrations managed by Knex.js. The worker layer runs on the same Node process but can be scaled independently via Docker Compose or Kubernetes deployments. All services communicate over HTTP/JSON, and the API is versioned with semantic tags (v1, v2). Container images are published to Docker Hub (bigcapitalhq/webapp), making deployment straightforward on any host that supports Docker or Podman.

Core Capabilities & API

• Financial Objects – invoices, credit notes, purchase orders, expense reports, journals, bank feeds. Each object exposes CRUD endpoints with validation rules that enforce double‑entry integrity.
• Reporting Engine – pre‑built financial statements (P&L, Balance Sheet, Cash Flow) are generated on demand via SQL views and can be extended with custom report definitions using a JSON‑based template language.
• Inventory Management – real‑time stock levels are updated automatically on sales or purchase events. The API supports batch inventory adjustments and multi‑warehouse configurations.
• Multi‑currency Support – foreign‑exchange rates are fetched from an external service (e.g., Open Exchange Rates) and cached in PostgreSQL; the API accepts amounts in any supported currency.
• Webhook System – developers can subscribe to events (invoice created, payment received, inventory low) and trigger downstream processes in real time.
• Role‑Based Access Control – fine‑grained permissions are enforced at the API level, allowing granular sharing with accountants or external auditors.

Deployment & Infrastructure

The application ships as a set of Docker Compose files that expose the web, worker, and database services. For production environments, developers can deploy Bigcapital on any cloud provider or bare‑metal server using Kubernetes manifests provided in the k8s/ directory. The database can be moved to a managed PostgreSQL service, while the web and worker pods are horizontally scalable. High‑availability is achieved by running multiple replicas of each service behind a load balancer, and persistent storage for PostgreSQL is backed by cloud block volumes or NFS.

Integration & Extensibility

Bigcapital’s extensibility is twofold: first, the API allows full programmatic control over all financial entities; second, a lightweight plugin architecture lets developers inject custom business logic into the event pipeline. Plugins are simply Node modules that register HTTP endpoints or hook into lifecycle events (onInvoiceCreated, onPaymentReceived). The platform also offers an SDK (available on npm) that wraps the REST API with typed clients, simplifying authentication and error handling for TypeScript projects.

Developer Experience

The project follows strict semantic versioning and provides comprehensive documentation on docs.bigcapital.app, including a detailed API reference with example payloads. The repository includes a GitHub Actions CI pipeline that runs linting, unit tests, and integration tests against a temporary PostgreSQL instance. Community support is active on Discord, GitHub Discussions, and the issue tracker, with a clear contribution guide that enforces code style and documentation standards. The AGPL license ensures that any enhancements remain open, fostering a collaborative ecosystem.

Use Cases

• Custom ERP Integration – Companies can embed Bigcapital’s accounting engine behind their own front‑end, exposing only the data they need while keeping financial integrity intact.
• Financial Reporting as a Service – SaaS providers can host Bigcapital instances per tenant, delivering ready‑made P&L and balance sheets via the API.
• Audit Automation – By hooking into webhooks, auditors can receive real‑time notifications of ledger changes and automatically generate audit trails.
• Multi‑currency POS Systems – Retailers can integrate inventory updates and sales transactions directly into Bigcapital, ensuring consistent stock levels across currencies.

Advantages for Developers

• Open‑Source Flexibility – Full source code access allows deep customization of business logic, UI components, or database schema.
• Modern Tech Stack – TypeScript, React, and PostgreSQL provide a familiar environment for full‑stack developers.
• Container‑Ready Out of the Box – Docker images and Kubernetes manifests reduce deployment friction, enabling rapid CI/CD pipelines.
• Rich API & Webhooks – Developers can treat Bigcapital as a backend service, integrating it into micro‑service architectures with minimal friction.
• AGPL Licensing – Guarantees that any derivative work remains open, encouraging community contributions and avoiding vendor lock‑in.

In summary, Bigcapital offers a robust, developer‑friendly accounting platform that balances ease of deployment with the extensibility required for modern business workflows. Its open‑source nature, coupled with