Audience research
Companies House, ONS and SIC code lists for UK B2B demand generation targeting
How Companies House records, ONS business statistics and SIC code lists differ, and which one to use when building a UK B2B target account list.
What to take away
- Companies House gives you a list of individual companies. The ONS gives you counts of businesses by industry, size and area. They answer different questions.
- A SIC code on the register is chosen by the company itself, and a company can list up to four. Treat it as a hint about activity, not as a verified industry label.
- The free Companies House data snapshot holds company-level fields such as address, status and SIC codes. It does not hold contacts, so it is a starting list and not a lead list.
- ONS figures size a market and set targets. They do not name businesses, so you cannot upload them to a CRM.
Three sources, three jobs
Teams building a target list for UK B2B demand generation tend to mix up three things that sound alike: the Companies House register, the ONS business statistics and the SIC code lists. Each has a different owner, a different purpose and a different blind spot.
Companies House keeps the public register of companies. Its job is legal: who is incorporated, where the registered office is, when accounts are due. It lists named entities, so it is the only one of the three that can seed an account list.
The ONS publishes statistics. Its annual release, UK business: activity, size and location, counts enterprises and local units from an extract of the Inter-Departmental Business Register (IDBR) taken each March. The ONS describes the IDBR as a list of businesses registered for VAT and/or PAYE, holding over 2.8 million enterprises, and the main sampling frame for ONS business surveys. The statistics come with disclosure controls, so information attributable to a single organisation is not released.
SIC codes are not a database. They are a classification, UK SIC 2007, maintained by the ONS. Both of the sources above use it to say what a business does, but they get the code in different ways.
What the Companies House data gives you
The free Company Data Product is a downloadable snapshot of basic data on live companies on the register. It arrives as ZIP files holding CSV files, either as one large file of about 471 MB or as seven smaller parts. The snapshot is updated within five working days of the previous month end, so a record can be several weeks old when you read it.
The published field list covers company name and number, registered office address, company category, company status, incorporation date, accounts category and filing dates, previous names, mortgage charge counts and up to four SIC code columns. It also carries a URI for each company, which links to the current record.
Two limits matter for demand generation:
- No people.The product holds no contact names or email addresses. Turning a company record into a named contact is a separate step with its own legal duties.
- No size data.The record carries an accounts category and filing dates, but no headcount or turnover figure. Companies House states that the snapshot is provided free of charge and will not be supported, so build your process knowing that nobody will fix a broken file for you.
Use it for what it does well: filtering by status, incorporation date and registered location, and spotting recently incorporated or recently renamed companies.
How SIC codes get onto the register
A company chooses its own SIC codes. Companies House explains that you must give at least one code and can choose up to four, and that the list has more than 600 codes grouped into 21 main industry categories. Filings must use only codes from the Companies House condensed list, which is a shortened version of the full ONS list, or the filing may be rejected.
Codes are changed through a confirmation statement, either at the next one or by filing one early. Companies House has also said that the Economic Crime and Corporate Transparency Act now allows it to challenge information that looks incorrect or misleading, and that a dormant (99999) or non-trading (74990) code on an active company is a common discrepancy.
For list building this has three consequences:
- Filtering on one SIC code will miss companies that picked a different code for the same work.
- A company with four codes can appear under four industries. Deduplicate before you count.
- Old codes linger. Treat the code as a prompt to check the company website, not as proof.
What the ONS data gives you
The ONS tables break down enterprises and local units by geography, industry, legal status, and employment and turnover size bands. That makes them the right tool for questions such as how many businesses of a given size exist in a given region and sector, before you commit budget to reaching them.
The ONS methodology note is plain about the limits. Businesses below the VAT threshold appear only if they are also PAYE registered or hold a VAT registration. Turnover data come mainly from administrative sources the ONS cannot validate, so it advises caution. Multiple registrations at one address can distort small-area analysis. The IDBR allocates SIC codes as part of its own quality control, a different route from a company choosing its own codes on the register, so do not expect the two to agree.
The practical rule: do not try to reconcile the two at company level. Use the ONS to estimate the size of a segment and the Companies House data to find candidates inside it.
A workable sequence for a target list
- Size the segment first.Use the ONS tables to estimate how many enterprises fit your size band and sector in the area you serve. This sets a realistic ceiling for the list.
- Pull candidates from Companies House.Filter the monthly snapshot by status, location and the SIC codes that plausibly match, including neighbouring codes.
- Check against the ceiling.If the candidate list is far larger or smaller than the ONS estimate, your SIC filter or size assumption is wrong. Fix it before enrichment.
- Verify by hand on a sample.Open the websites of a few dozen companies and note how many do what their code says.
- Enrich with contacts separately.Contact data from a supplier or your own research is a separate decision with its own legal duties.
- Hand the list to sales as tiers.The audience research guide covers how to score and tier accounts once you have them, and account-based marketing work starts from a short, agreed list.
Compliance once you have a list
A company-level list from public sources is the easy part. Once you add a named person, the UK GDPR applies as well as the Privacy and Electronic Communications Regulations (PECR). The Information Commissioner's Office (ICO) explains that corporate subscribers, such as companies and limited liability partnerships, are not covered by the PECR consent rule for email, but you must not disguise your identity and must give a valid opt-out address. Sole traders and some partnerships are treated as individual subscribers and need consent or must meet the soft opt-in conditions. If you are unsure which a recipient is, the ICO advises treating them as an individual subscriber.
For live calls, the ICO says to screen against both the Corporate TPS and the TPS. The wider rules on lawful basis and records are in our data protection guide for demand generation.
Common mistakes
- Treating the register as a customer list.A live company on the register is not necessarily trading. Check status and activity before you count it.
- Counting one business many times.A company with up to four SIC codes can appear under several industries, and one group can hold several registered companies.
- Mixing time periods.The Companies House snapshot is monthly while the ONS release reflects a March extract, so the two will never match exactly.
- Relying on a single code.Use a shortlist of codes, then validate.
Official sources
- Standard Industrial Classification of economic activities (SIC), GOV.UK
- Keeping your standard industrial classification (SIC) code accurate, Companies House blog
- Choosing a standard industrial classification (SIC) code for your company, Companies House blog
- Free Company Data Product, Companies House
- UK business: activity, size and location, quality and methodology information, ONS
- UK Standard Industrial Classification of Economic Activities 2007, ONS
- Business to business marketing, ICO
