Finding companies in the UK: Companies House and B2B prospecting

Propler and the United Kingdom

Propler's company search covers Norway only today. The UK is not available in the product, and we make no promise about when or whether it will be. This page is a guide to finding and checking UK companies using official sources.

Companies House: the starting point

Companies House is the UK government's registrar of companies. Its Find and update company information service lets anyone look up a company without registering, free of charge. For each company you can see the registered office, status, incorporation date, company type, nature of business (SIC codes), officers (directors and secretaries), people with significant control, and the filing history with the documents themselves.

For developers, the Companies House Public Data API gives free access to the same public data. You register an application to get an API key. It is built for lookups, not for downloading the whole register, so Companies House also publishes free bulk products, including a monthly snapshot of basic data on live companies and a bulk file of electronically filed accounts.

The company number

Every company has a company registration number of eight characters. Shorter numbers are padded with leading zeros, and some numbers start with a letter prefix, such as SC for Scottish companies or NI for Northern Ireland. Always store the full number with its prefix and leading zeros; it is the reliable key when you match records, because names can change and many companies have similar names.

Companies House records the nature of business with SIC codes from a condensed list. Like industry codes everywhere, they are chosen by the company and describe the intended main activity, not everything the company does.

Filed accounts: what you actually get

Every UK company must file accounts with Companies House each year. A private company normally has nine months from the end of its financial year, and late filing triggers automatic penalties.

How much financial detail you see depends on the company's size:

• Companies that do not qualify as small generally file fuller accounts, so you are more likely to see turnover and profit.
• Small companies and micro-entities can leave the profit and loss account out of the copy they file at Companies House. Micro-entities file a balance sheet and notes. For many small companies you therefore see the balance sheet but not turnover.
• Format matters. Accounts filed electronically are available as structured data (iXBRL) that software can read. Paper filings are only scanned images.

The government has paused a planned requirement for small and micro companies to file profit and loss accounts, so do not expect this gap to close soon. From April 2028, accounts will have to be filed using commercial software.

How reliable is the register?

Historically, Companies House accepted most filings with limited checks. The Economic Crime and Corporate Transparency Act 2023 changed that: Companies House can now query, reject or remove information that appears incorrect, and identity verification became mandatory for new directors and people with significant control from 18 November 2025, with a transition period for existing ones. That improves trust in who is behind a company, but it does not mean every filed fact has been checked. Cross-check important facts such as addresses and activity with the company's own website.

Prospecting in the UK

1. Use SIC codes, company status and location to define a first list.
2. Drop dissolved companies and those with overdue accounts or confirmation statements.
3. Use filed accounts where they exist to judge size, remembering that small companies may not show turnover.
4. Check officers and filing history to see if the company is active and stable.
5. Read the company's website before contacting anyone.

Our guide to building a qualified B2B prospect list covers the general method.

Finding suppliers and public contracts

For supplier checks, the filing history is valuable: regular filings, stable officers and recent accounts are good signs, while repeated changes of registered office or overdue filings deserve questions. On the public-sector side, procurements started under the Procurement Act 2023 from 24 February 2025 are published on Find a Tender, the UK's central digital platform for procurement notices.

Data protection and e-mail marketing

The UK has its own rules after Brexit: the UK GDPR and the Privacy and Electronic Communications Regulations (PECR), enforced by the Information Commissioner's Office (ICO).

• PECR's consent rule for marketing e-mails does not apply to corporate subscribers such as limited companies and LLPs. You must still identify yourself and offer a valid way to opt out, and the ICO advises respecting opt-outs.
• Sole traders and some partnerships are treated as individuals. You need consent or the "soft opt-in" (an existing customer relationship, your own similar products, and an opt-out offered every time).
• You cannot tell from an e-mail address whether it belongs to a company or a sole trader. If unsure, the ICO says to treat it as an individual.
• The UK GDPR still applies to B2B marketing whenever you use a named person's details.

Where to go next

If your main market is Norway, the data and tools there are live in Propler: see the Norway market page. For the EU-level tools that do not cover the UK, see Europe.