Every limited company in the UK is required to file accounts, annual returns, and director information with Companies House. All of it is publicly available. Free to search. Free to download. And almost nobody in B2B marketing uses it properly.
This is genuinely baffling. Businesses spend thousands on data subscriptions and broker lists while sitting next to the most comprehensive database of UK companies in existence. It's not hidden. It's not behind a paywall. It's sitting at companieshouse.gov.uk waiting for someone to do something useful with it.
The basic company record is just the beginning. For every limited company in the UK, you can access:
Company name, registered address, incorporation date, and current status. SIC codes (Standard Industrial Classification), which tell you what industry the company operates in. Director names, appointment dates, and in many cases their other directorships. Filing history, including confirmation statements and accounts.
For companies that file full or abbreviated accounts, you can often identify turnover bands, employee numbers, and asset values. Smaller companies file less detail, but even the minimal filing tells you something useful: that the company is still active, still filing, and still trading.
The real power is in the combination. SIC codes tell you the industry. Incorporation date tells you the company age. Director information tells you who's in charge. Filing history tells you whether the company is healthy and current. Cross-reference these data points and you have a prospect qualification tool that most data brokers would charge handsomely for.
We put this to work for an accountancy practice broker earlier this year. Their target market is accounting firms looking to sell, merge, or acquire. Traditional prospecting meant attending industry events, advertising in trade publications, and relying on word of mouth.
We took a different approach. We pulled every company registered with accountancy-related SIC codes from Companies House. That gave us a starting pool of over 127,000 companies. A large number, but raw. The filtering is where it gets interesting.
We filtered by incorporation date, looking for practices established more than 15 years ago. The logic: partners who started a practice in 2005 or earlier are now in their late 50s or 60s and statistically more likely to be thinking about succession or sale.
We filtered by company status, removing dissolved, dormant, and liquidated companies. We filtered by filing history, removing companies that hadn't filed in over a year (likely no longer actively trading).
We cross-referenced director ages where available, looking for practices where the founding director was approaching retirement age. We checked for recent director changes, which can indicate succession planning already in progress.
After filtering, we had just under 10,000 companies that matched the ideal prospect profile. Ten thousand accountancy practices with ageing principals, active filing, and no apparent succession plan. Not contacts from a broker's database that might be two years stale. Real, current, verified companies identified from public data.
Most people who've heard of SIC codes think of them as a bureaucratic filing requirement. They are. But they're also a remarkably precise way to identify companies in specific industries.
SIC code 69201 is "Accounting, bookkeeping and auditing activities; tax consultancy." SIC code 25990 is "Manufacture of other fabricated metal products not elsewhere classified." SIC code 62012 is "Business and domestic software development." Each code maps to a specific activity, and companies self-select their code at registration.
The codes aren't perfect. Some companies pick the wrong code, or pick a generic one when a specific one would be more accurate. But for bulk prospecting, they're a remarkably efficient way to identify companies in your target market.
Combine SIC codes with geography (registered address by postcode or region) and company size indicators (filing category, estimated turnover) and you have a segmented prospect list built entirely from free, public data.
Companies House data becomes significantly more powerful when you combine it with other public sources.
Director names from Companies House can be cross-referenced with LinkedIn to find current contact details and verify they're still at the company. Company websites (often findable from the registered address or a simple Google search) reveal email patterns, phone numbers, and current service offerings.
Charge data (loans and mortgages registered against the company) can indicate financial health or expansion activity. A company that recently took on significant debt might be investing in growth, making them a different kind of prospect than one that's been debt-free for years.
Filing patterns tell their own story. A company that's always filed on time and suddenly misses a deadline may be experiencing operational difficulties. A company that upgraded from abbreviated to full accounts may be growing rapidly.
None of this information is secret. It's all public record. The competitive advantage isn't in accessing it. It's in knowing what to do with it.
Turning Companies House data into a usable prospect database is a process, not a quick download. Here's roughly how it works.
Extract. Pull all companies matching your target SIC codes using the Companies House API or bulk data products. The API is free and well-documented. For large extracts, the monthly bulk data snapshot is more efficient.
Filter. Apply your qualification criteria: company age, active status, filing history, geography, and any other relevant factors. This typically reduces the initial pool by 80% to 90%.
Enrich. Cross-reference the filtered list with other sources to add contact details, email addresses, phone numbers, and LinkedIn profiles. This is the most time-consuming step and the one that determines the quality of the final list.
Verify. Run every email address through a verification service. Check phone numbers. Confirm the company is still trading and the contact is still in role. This step is non-negotiable. Unverified data is worse than no data, because it creates the illusion of a usable list while damaging your sender reputation and wasting your sales team's time.
Segment. Divide the final list into actionable segments based on whatever criteria matter for your campaigns: industry sub-sector, geography, company size, estimated likelihood to buy.
The result is a proprietary prospect database that you own outright. No subscription fees. No annual price increases. No dependency on a third-party platform. Just a list of verified, qualified prospects built from public data.
The honest answer is that it takes effort. Buying a list from a broker takes a phone call and a credit card. Building a list from Companies House takes research, filtering, enrichment, and verification. The output is better, but the process is slower and requires skill.
For businesses that need data quickly and have the budget, a broker list makes sense as a starting point. For businesses that want to build a lasting, proprietary prospect asset, Companies House is the foundation.
Most businesses would benefit from both: broker data for speed, Companies House data for depth and ownership. The worst option, and the most common one, is doing neither properly.
Martin Dugan, AA2
