AccountsOS: AI-native accounting platform with HMRC, banking and Companies House integrations

AccountsOS is a full accounting platform we built and run ourselves, with an AI accountant (Finn) at the core rather than bolted on afterwards.

What’s under the hood:

• Files VAT returns direct to HMRC through the Making Tax Digital API
• Companies House integration for company data and filing deadlines
• Live bank feeds via Plaid, Mercury and Tide
• AI built on frontier models: transaction categorisation, document extraction, a conversational AI accountant that knows your numbers
• MCP server and CLI, so the whole platform plugs straight into Claude and other AI agents
• Modern stack: Next.js, TypeScript, Supabase, Vercel

Real users, real filings, real money movement. It’s a good example of how we build: AI does the heavy lifting, deterministic code handles the money math and compliance, and everything talks to everything through clean API integrations.

Built and shipped by p0stman.com