UK prospecting
Building a B2B prospect list in the UK
The UK has something most markets do not: a complete, public, machine-readable register of every incorporated business in the country, searchable by industry code, location and age. Almost every guide to UK list building skips it and sends you to a data vendor. Start with the register instead, then buy only the layer it genuinely cannot give you.
Checked against the Companies House developer specification on 22 September 2026. For the rules on contacting the list, see the PECR rules.
Layer one, the companies
Companies House is the best B2B source in the UK
It is the statutory register of every incorporated business, it is public, and its advanced search takes the filters an ideal customer profile is actually made of.
| Filter | What it gives you |
|---|---|
| SIC code | Industry, at the granularity the classification allows. The closest thing to a vertical filter. |
| Location | Geographic targeting, which is how you build a territory rather than a country. |
| Incorporation date | Company age. A five-year-old firm and a five-month-old one are different buyers. |
| Company status | Active, dissolved, in liquidation. Filtering the dead out before you write to them. |
| Company type | Limited company, LLP, and the rest, which turns out to matter legally as well as commercially. |
The same filters are on the public search and in the Public Data API, whose advanced company search endpoint returns up to 5,000 results in a call. The key is self-service. The documented rate limit is 600 requests in any five-minute window, and you get a 429 for the rest of the window once you cross it. That is generous enough to build a serious list and tight enough that you should cache what you pull rather than re-querying it.
Be clear about the gap
It gives you companies, not contacts
This is the honest limitation and the reason the data vendors exist at all. The register holds no email addresses and no phone numbers for selling to.
What you get is the company: name, number, registered address, SIC codes, incorporation date, status, type, officers and filing history. What you do not get is a person to write to, their role, their address or their direct dial. So Companies House builds the account list and something else has to build the contact list.
Worth knowing when you are being sold to: if a provider offers you Companies House data with emails attached, those emails were appended from another source. Ask which one. The accuracy and the lawful basis both travel with that answer, and neither is something the register can vouch for.
The part nobody else writes
Absence from the register is a legal signal
This is where the UK is genuinely different, and it is the reason to start here rather than with a vendor.
Only incorporated bodies register at Companies House. Sole traders do not appear on it at all. So a business you cannot find on the register is very likely a sole trader or an unincorporated partnership, and under PECR that makes them an individual subscriber rather than a corporate one.
The consequence is large. You may email a limited company without consent. You may not email a sole trader without consent or a genuine soft opt-in, and nothing about their email address tells you which you are looking at. The register does. So the same lookup that builds your list also classifies it legally, which is a thing you get for free in the UK and cannot get in most markets.
Practically: run the list against the register, mark every account you could not match, and treat that segment as individual subscribers. The ICO's own instruction where you cannot establish which a contact is, is to apply the stricter rule. The email rules go through this properly.
Layer two, the people
Turning companies into contacts
Four routes, and they are not alternatives so much as a sequence. Most teams need two of them.
- The company's own site. Slower than it sounds and better than it sounds. A named person on a team page, with a role you can verify, beats a database record of unknown age.
- LinkedIn Sales Navigator. Strong for roles and for movement. Note the ICO's point that someone on a professional network may be acting in a personal, albeit professional, capacity, so finding them there does not settle their status under PECR.
- A paid database. What you are buying is the contact layer, since the company layer came from the same public register. Ask about UK coverage specifically rather than global record counts.
- Verification, always. Whatever the source, verify before you send. Bounces cost more than bad copy does, and a hard bounce rate above a few per cent damages the domain you send everything else from.
On the paid layer, the honest framing is that UK and European coverage varies more between providers than any of them advertise, and that global record counts tell you almost nothing about how many usable UK contacts you will get in your particular vertical. Run a sample against your actual target list before signing anything. We have written up Cognism and ZoomInfo in more detail.
The unfashionable answer
Below about two hundred accounts, do it by hand
No guide says this because no guide is selling manual work, but it is usually true and it is worth saying.
For a first list of a couple of hundred accounts, reading each company is faster than configuring anything, and the list is better, because you are qualifying while you build rather than filtering and hoping. You also learn your own market, which is the part that cannot be bought and which makes every later automated list sharper.
The case for tooling is not the first list. It is the second, the third, and the maintenance of the first, since UK company data decays as companies move, change status, dissolve and re-register.
A working order
The build, start to finish
Six steps. The first three cost nothing but time and they do most of the work.
- Define the profile in terms the register understands: SIC codes, locations, company age, status active.
- Pull the account list from Companies House advanced search, caching rather than re-querying.
- Mark every target you could not match on the register, and treat that segment as individual subscribers.
- Add the contact layer from the company site, LinkedIn or a database, and record where each contact came from.
- Verify every address before the first send, and watch the hard bounce rate.
- Screen the phone numbers against the CTPS and the TPS before anyone dials, which is a separate obligation from anything above.
Where software helps, and where it does not
What Empiraa Signal does about this
Signal includes a B2B prospect database and enrichment, so the contact layer and the CRM are the same system rather than two subscriptions that drift apart. Prospects arrive against your profile and land beside the account they belong to.
What it does not do: Signal does not tell you whether a UK contact is a corporate or an individual subscriber, and it does not screen numbers against the CTPS or the TPS. Both of those are yours, and both are specific to this market. Any vendor claiming their software makes you compliant is selling you something, because the obligation sits with the sender.
The prospecting side is at Prospect Spark. The rules on contacting a UK list are at is cold email legal in the UK and UK cold calling rules. The Australian equivalent of this page, which reaches the opposite conclusion, is building a B2B prospect list in Australia, and the American one, where there is no register at all, is building a B2B prospect list in the USA.
Questions people actually ask
UK list building, answered
What is the best source of UK B2B data?
For the company layer, Companies House. It is the statutory register of every incorporated business in the UK, it is public, and its advanced search filters on SIC code, location, incorporation date, company status and company type, which is most of what an ideal customer profile is made of. It holds no email addresses or phone numbers, so it gives you a company list rather than a contact list, and the contact layer has to come from somewhere else. Search the register.
Can I get UK company data through an API?
Yes. The Companies House Public Data API has an advanced company search endpoint that takes the same filters as the website and returns up to 5,000 results in a call. It needs a self-service API key, and it is rate limited to 600 requests in any five-minute window, after which you get a 429 until the window resets. That is generous enough to build a serious list and tight enough that you should cache rather than re-query. The rate limit, documented.
Does Companies House have email addresses or phone numbers?
No. It holds company names, numbers, registered addresses, SIC codes, incorporation dates, status, type, officers and filing history. No contact details for selling to. Anyone offering you Companies House data with emails attached has appended those from another source, and you should ask which one, because the accuracy and the lawful basis both travel with the answer.
How do I tell whether a UK prospect is a sole trader?
Check whether they are on Companies House. Only incorporated bodies register there, so a business you cannot find is very likely a sole trader or an unincorporated partnership. That matters beyond curiosity: sole traders are individual subscribers under PECR, so you need consent or the soft opt-in to email them, while a limited company does not require consent. The lookup that builds your list also classifies it legally. Why that distinction decides everything.
Should I buy a UK B2B list instead?
You can, and there are good providers, but understand what you are buying. You are paying for the contact layer, being names, roles, emails and direct dials, because the company layer underneath it came from the same public register you can query yourself. Ask any provider how recently the contacts were verified, what their UK coverage actually is rather than their global record count, and what happens to data you exported if you leave.
Is it legal to build a list from Companies House?
Building the list is not the regulated act. Contacting it is. The register is public and you may use it, but the moment your list holds personal data you are under UK GDPR, which means a lawful basis, privacy information within a month if the data came from elsewhere, and an absolute right to object. Then PECR governs the sending, differently for companies and sole traders. This page is general information rather than legal advice. The UK email rules.
How many contacts do I need before this is worth automating?
Below roughly two hundred accounts, building the list by hand is usually faster than any tooling and produces a better list, because you are reading each company rather than filtering it. The case for automation is not the first list, it is the second and every one after, and the maintenance of the first.
Question not answered here? Ask ANI and get a straight answer.
Show your working
Sources
Checked against these on 22 September 2026. This page is general information rather than legal advice.
- Companies House Public Data API, advanced company search for the available filters and the 5,000-result ceiling.
- Companies House, rate limiting for the 600 requests per five minutes and the 429 behaviour.
- Find and update company information for the public search itself.