Developer Documentation

APIs and AI integrations for automating UK company filings. Choose your integration path below.

Corporation Tax & Accounts API

Submit corporation tax returns to HMRC and iXBRL accounts to Companies House — all via a single REST API. Supports dormant, micro (FRS 105), and small (FRS 102) companies, including LLPs and extended accounting periods. We handle the tax calculations, XML generation, and Government Gateway submission. You just send the financials.

Quickstart

Submit your first filing in 5 minutes.

API Reference

Complete endpoint documentation.

Authentication

API keys, rate limits, and security.

Sandbox

Test with magic company numbers.

Partner API

Private integration for white-label partners. Generate secure activation URLs and push trial balance data so the submission form is pre-populated when your customers arrive.

Partner Guide

Activation endpoints and trial balance imports.

OpenAPI Spec

Machine-readable spec for code generation.

MCP Server

Connect AI assistants like Claude Desktop and Cursor directly to TinyTax. Look up companies, check filing obligations, validate submissions, and track filing status — all through natural language.

Setup Guide

Add the TinyTax MCP server to your AI tool.

Pricing: API filings cost £20 each, charged only on acceptance. Get your API key and top up your balance to get started.