UK B2B Lead Generation with Companies House: A Practical Guide

The Companies House API gives every UK company filing history, registered address, SIC codes, and director information for free. Most B2B teams pay thousands a month to ZoomInfo or Cognism for what is essentially the same dataset wrapped in a UI. Here is how to use the raw source instead — and what to layer on top so it actually books meetings.

Why Companies House is underused

Three reasons most teams skip it:

  • The API is rate-limited and the docs are dry.
  • You only get the company; you don't get emails or LinkedIn profiles.
  • The advanced-search endpoint requires basic auth with an awkward trailing colon.

All three are solvable. We built a UK lead-sourcing module on top of Companies House that handles the rate limits, the auth quirks, and the SIC-code selection — and pipes the result into Hunter.io for email enrichment.

Picking the right SIC codes is 80% of the work

SIC codes are the UK equivalent of NAICS — five-digit industry classifiers attached to every UK company at incorporation. The trick is that most companies pick a generic code, so a naive search for "62012 Business and domestic software development" returns thousands of irrelevant results.

The pattern that works:

  • Start with a curated short-list of 20–40 SIC codes for your ICP.
  • Filter by company size band (incorporation date as a proxy if you don't have headcount).
  • Filter out dissolved and dormant companies.
  • Deduplicate against your CRM before enrichment (don't pay to enrich what you already own).

Adding emails and decision-makers

Companies House gives you the company. Hunter.io gives you the people. Map the directors from Companies House to LinkedIn profiles, then use a domain search on Hunter to surface the decision-maker pattern (e.g. firstname@company.co.uk).

Compliance tip: for cold outreach in the UK, B2B email is permissible under PECR if the recipient is a corporate role and you offer a clear opt-out. Don't email sole traders the same way.

A weekly prospecting workflow

Monday: pull 200 net-new UK companies matching your ICP from Companies House. Tuesday: enrich the top 100 via Hunter, deduplicate against CRM. Wednesday–Thursday: outbound. Friday: measure connect-to-meeting rate, refine SIC code list.

We run this whole loop as a managed service — list build, enrichment, sequence drafting and weekly reporting — for UK B2B SaaS teams. Get pricing.