# CosBooks

> Open-source, double-entry accounting for solo operators, freelancers, and small teams — run through Claude with MCP.

CosBooks is an MCP (Model Context Protocol) server that gives Claude a complete
double-entry accounting system: chart of accounts, invoices and receivables, bills and
payables, payments, bank import and reconciliation, financial statements, budgets,
recurring transactions, tax codes and a full audit trail. Users describe transactions in
plain English; the server validates the arguments and writes balanced journal entries to
a Postgres database scoped to their organization. The AI selects tools — it never writes
to the ledger directly, and cannot produce an unbalanced entry.

## Key facts

- Category: accounting and bookkeeping software; a QuickBooks alternative
- Interface: conversational, through Claude on web, desktop and mobile
- Protocol: MCP over Streamable HTTP with OAuth 2.1 (PKCE, dynamic client registration),
  or local stdio with an API key
- Accounting model: strict double-entry; debits must equal credits or the write is rejected
- Storage: Postgres on Supabase, one isolated organization per tenant
- Access control: role-scoped — viewer (read-only), bookkeeper (full accounting), admin (plus settings)
- Best suited to: freelancers, agencies, e-commerce sellers, early-stage startups,
  bookkeepers and small non-profits
- Out of scope: payroll, multi-currency consolidation, regulated-industry workflows

## Documentation

- [How CosBooks works: double-entry accounting that lives inside Claude](https://cosbooks-web.onrender.com/blog/how-cosbooks-works): What actually happens between “invoice Widget Co for 10 hours at $150” and a balanced set of books.
- [How to set up CosBooks: your books in Claude in about ten minutes](https://cosbooks-web.onrender.com/blog/set-up-cosbooks-with-claude): From signup to your first reconciled month — connector setup, opening balances, and the habits that keep the books clean.
- [Who CosBooks is for — and who should keep using QuickBooks](https://cosbooks-web.onrender.com/blog/who-cosbooks-is-for): Five kinds of business where conversational books genuinely win — and three where they do not.

## Pages

- [Home](https://cosbooks-web.onrender.com/): product overview, capabilities, and FAQ
- [Blog](https://cosbooks-web.onrender.com/blog): guides on how the system works and who it suits
- [Sign up](https://cosbooks-web.onrender.com/signup): create an organization
- [Sign in](https://cosbooks-web.onrender.com/login): existing accounts

## Optional

- [Full text of every page](https://cosbooks-web.onrender.com/llms-full.txt): all guides as plain Markdown
- [Source](https://github.com/naga-deepledger/cosbooks): implementation, schema and tool definitions