Using Companies House data for sales prospecting: what you can and can't know

What's on the register, and how to get it

All the main Companies House sources are free. They differ in how up to date they are and how much work they take to use.

There are two gaps to be aware of. First, director (officer) records aren't in the free monthly download. To get them in bulk, you either call the API one company at a time or contact Companies House about its bulk officer products, which aren't a self-service download. Second, the accounts data only covers accounts filed electronically. Companies House's own pages put that at between 60% and 75% of the 2.2 million sets of accounts filed each year. The rest sit on the register as documents you have to read one by one.

What it can tell a salesperson

The register is a record of events. Each one is a dated fact, and some are worth a closer look. The right-hand column matters as much as the middle one.

One event is rarely enough on its own. Look for several recent events pointing the same way, then check them against fresher evidence.

What it can't tell you

Most poor prospecting from Companies House data comes from forgetting one of these limits.

The financial figures are old. A private company normally has nine months after its year end to file its accounts, and its first accounts usually get longer, typically 21 months from incorporation. A company with a year end of 31 December 2025 can file as late as 30 September 2026, so a balance sheet can easily be a year or more old by the time you read it.

Most small companies don't publish their turnover. The law lets small companies file "filleted" accounts: the balance sheet and notes, without the profit and loss account. Most small and micro companies do this, so for many prospects you won't see sales or profit at all. Companies House confirmed in June 2026 that from April 2028 small companies and micro-entities must file a profit and loss account, but they can choose not to have it published (ACCA). Turnover may therefore stay out of public view for many of them.

Not every set of accounts is in the data files. The free accounts data covers electronic filings only. Everything else has to be read as a document.

SIC codes are only a rough guide. Companies choose up to four codes themselves and can update them in their yearly confirmation statement. A code picked at incorporation may no longer fit what the company does today, and the broad codes say very little. A company's own website is usually a better guide.

The registered office often isn't where they work. Many companies use their accountant's or a formation agent's address.

The register says who is a director, not what they do. It won't tell you who the finance director is or who looks after IT. The occupation field is whatever the person typed in. Confirm job titles from the company's own website or news coverage before you rely on them.

There are no sales contacts. The register gives addresses, not email addresses, phone numbers or the name of the buyer. Companies must give Companies House an email address, but it isn't published.

Nobody checks the figures. Companies prepare their own filings, and Companies House doesn't verify that what's filed is true. In our own work reading filed accounts, we've seen staff numbers tagged as sums of money and staff numbers recorded at the wrong scale. If a figure looks surprising, check it against the filed document itself.

What we found when we counted

We hold the whole register and read the electronically filed accounts ourselves, so we measured how much of this data is actually there. Turnover is the biggest gap: it appeared in only about 1 in 50 companies' latest accounts.

How we counted: these figures come from Squarely's copy of the Companies House register and accounts data, counted on 12 October 2026. For accounts, we used each company's most recent period in the files. A figure counts as present only if our reader found it in the filing, so anything filed in a form we don't yet read counts as missing. We tested this for turnover on 15 October 2026 against a random sample of 7,650 filings. The one real gap was group accounts, which tag their turnover in a way our reader currently skips. Allowing for those lifts the figure from 1.8% to about 2%. The low number itself is genuine: most companies simply don't file a turnover figure.

Staff numbers need care too. In an earlier check of 904,140 staff figures we had read, 129 were impossible: negative numbers, numbers over a million, or a micro-entity reporting more than 100 staff. That's about 1 in 7,000. Our reader also rejected a further 112,934 staff figures because the way they were tagged would have put them at the wrong scale.

Good and bad conclusions

The skill isn't finding signals. It's knowing how far each one lets you go.

A worked example. Take an illustrative manufacturer. Its accounts show average staff up from 22 to 31 and fixed assets up sharply. Two months later it registers a charge in favour of an asset-finance company, and the local council approves its planning application for a unit extension. Each signal is weak on its own. Together, recent and pointing the same way, they make it worth asking whether the business is adding capacity. They don't prove it: planning approval doesn't mean building has started, and a charge doesn't mean money has been spent. So the first call should ask, not assume.

Staying within the rules

Public doesn't mean you can use it however you like. The ICO's B2B marketing guidance is clear that publicly available data, including Companies House data, is still covered by the marketing rules. What follows is a summary, not legal advice.

• Emails to limited companies and LLPs. The electronic marketing rules (PECR) don't require consent, but you must say who you are and give a working way to opt out. If the address names a person, the data protection rules below apply as well.
• Emails to sole traders and most partnerships. PECR treats these as individuals, so you need their consent or the "soft opt-in". The soft opt-in only applies if you got their details while selling to them or negotiating a sale, you're marketing your own similar products, and you offered an opt-out at the time and in every message since. A bought list never qualifies.
• Live sales calls. Screen numbers against the Corporate Telephone Preference Service, the Telephone Preference Service and your own do-not-call list. Say who's calling, show your number, and give your contact details if asked. Calls with a recorded message need consent.
• Named people. As soon as you hold a person's name, or an email address such as jane.smith@company.co.uk, UK GDPR applies, even at work. You need a lawful basis. Legitimate interests is often the right one for B2B marketing, but only once you've weighed your interest against theirs, and you should write that assessment down.
• Telling people. If you collect someone's details from public sources, you must give them privacy information within a month, or at your first contact if that comes sooner. It must say where you got their details.
• Objections. A person can object to direct marketing at any time, including to being profiled for it, and you must then stop. Keep the minimum details on a suppression list so they don't reappear on your next list.
• Bought data. If you buy contacts from a data provider, you're still responsible for them. Check where the data came from and what people were told.

Companies House itself points out that businesses which reuse register data become controllers of that personal data, with duties of their own. The ICO says its B2B guidance is under review following the Data (Use and Access) Act, so check it for updates. See also its guidance on using data brokers.

A simple way to work

1. Write down who you sell to. Sector, region, company age and size, and the events that tend to come before someone buys from you.
2. Build your first list from the register. Filter active companies by SIC code, region and incorporation date. Use the free monthly file for volume, or the advanced search for a few hundred.
3. Flag the ones to check first. Dormant companies, overdue filings, strike-off notices and holding companies each mean something different. Some are still worth a call: a holding company may be the one that signs the contracts.
4. Look for recent events. New charges, changes in control, director changes and new accounts from the last 6 to 12 months. Note the date of each one.
5. Check the evidence is current. Look at the company's website, job adverts, the planning portal and local news. The register tells you where to look; these tell you what's happening now.
6. Find the right person, lawfully. Use the company's own website, or a data provider you've checked, and follow the rules in the section above.
7. Open with the evidence, honestly. "I saw you registered new finance in March and have put in a planning application for an extension" works far better than pretending you know their plans.

How Squarely uses this

Squarely is built around the rules in this guide. It reads the Companies House register and other public sources, checks each company against the kind of customer you sell to, and shows the evidence behind every verdict with its source and date. Anything inferred rather than filed is labelled as inferred.

Book a demo to see a real report.