Every limited company in the UK is issued a unique identifier the moment it is incorporated at Companies House. That number stays with the business for its entire life — and knowing what it is, where to find it, and when you are legally required to use it is more important than most business owners realise.
Your company registration number is a permanent, legally required identifier that appears on official documents, verifies your business to third parties, and is increasingly checked by advertising networks, financial institutions, and government bodies.
What Is Company Registration Number, Exactly?
A company registration number (CRN) is a unique eight-character code assigned to every company incorporated in England, Wales, Scotland, or Northern Ireland. It is issued by Companies House at the point of registration and never changes, even if the company changes its name, address, or business activity.
For companies incorporated in England and Wales, the CRN is typically eight digits — for example, 12345678. Scottish companies are prefixed with "SC" (e.g. SC123456), Northern Irish companies with "NI", and limited liability partnerships with "OC" or "SO". The format signals where the company was registered, which matters when verifying a supplier or partner.
The CRN is not the same as a VAT number, a UTR (Unique Taxpayer Reference), or a PAYE reference. Each of those serves a different function across different regulatory bodies. Confusing them is a common mistake, particularly among newly incorporated businesses.
Understanding what is company registration number means understanding that it is primarily a public record identifier. Anyone can look up a CRN on the Companies House register and see basic company information — registered address, filing history, director names, and confirmation statement status.
Where to Find Your CRN
The most reliable place to find your company registration number is your certificate of incorporation, which Companies House issues automatically when your company is formed. If you registered online, this arrives as a PDF to the email address used during registration. If you used a formation agent, they will have received it on your behalf.
Beyond the certificate of incorporation, your CRN appears in several other places. It is printed on every official letter Companies House sends you. It appears in your online Companies House account. It should also appear on your company's website, business letters, and order forms — this is a legal requirement under the Companies Act 2006, not a suggestion.
If you cannot locate your certificate, you can search for your company on the Companies House register using your company name. The CRN appears prominently on the company's public record page. There is no fee to look this up, and the search takes under a minute.
Many business owners only go looking for their CRN when they urgently need it — usually when opening a business bank account, applying for credit, or being asked to verify their identity by a payment processor or advertising network. Having it saved somewhere accessible saves a surprising amount of friction.
What Is Company Registration Number Used For?
The CRN is required in more situations than most people expect. Knowing where it applies helps you avoid delays and demonstrates that your business is properly constituted.
| Situation | Why CRN Is Required |
|---|---|
| Opening a business bank account | Banks must verify the company exists and is active at Companies House |
| Filing annual accounts and confirmation statements | Companies House uses the CRN to match submissions to the correct company |
| Applying for business credit or finance | Lenders check CRN against public records to assess legitimacy |
| Business-to-business contracts | Counterparties use it to verify they are contracting with a legal entity |
| VAT registration | HMRC cross-references CRN with Companies House during the application process |
| Advertising account verification | Networks including Google may request CRN to verify business identity |
| Displaying on business stationery | Legally required under the Companies Act 2006 for all limited companies |
The advertising network use case is one that catches SMEs off guard. Google Ads and other advertising platforms periodically request business verification documents, particularly when accounts hit certain spend thresholds or operate in restricted categories. Your CRN is one of the documents they may request. If your Google Ads account gets flagged for verification and you cannot supply it quickly, campaigns can be paused — which is a real operational problem if paid search is driving your revenue. For context on how Google Ads accounts work in practice, Google Pay Per Click Management: What SMEs Need to Know covers the account structure and compliance requirements in detail.
CRN vs VAT Number vs UTR: What Is the Difference?
These three identifiers are frequently confused, and each comes from a different government body for a different purpose.
Your company registration number comes from Companies House and identifies your company as a legal entity. It is public, permanent, and applies the moment your company is incorporated — even before you trade, have a bank account, or employ anyone.
Your VAT number comes from HMRC and only applies if your business is VAT registered. Registration is mandatory once your taxable turnover exceeds the current threshold (£90,000 as of 2024), and optional below that. A VAT number typically starts with "GB" followed by nine digits.
Your Unique Taxpayer Reference (UTR) also comes from HMRC but is used for corporation tax purposes. It is ten digits long and appears on correspondence from HMRC after your company is registered. Unlike the CRN, it is not publicly available.
For completeness, sole traders do not have a CRN. The CRN system exists exclusively for companies registered under the Companies Act — limited companies and limited liability partnerships. If you are a sole trader, you will have a UTR but no CRN.
Legal Requirements Around Displaying Your CRN
Under the Companies Act 2006 and the Company, Limited Liability Partnership and Business (Names and Trading Disclosures) Regulations 2015, every limited company in the UK must display its company registration number in specific places.
The CRN must appear on all business letters, order forms, invoices, receipts, and websites. On a website, it is typically placed in the footer alongside the registered company name and registered office address. Failing to display it is technically a criminal offence, though enforcement tends to focus on more serious non-compliance in practice.
This is worth knowing if you run Google Ads. As part of business advertising online best practice, your landing pages should reflect a properly constituted business — registered address, CRN in the footer, and a privacy policy. Google's quality rater guidelines and business verification processes look for these signals. A landing page that omits basic company information can affect both ad approval and Quality Score.
From nine years running a marketing agency, we saw a recurring pattern: SMEs with perfectly good products and reasonable budgets underperforming on paid search because their landing pages signalled distrust. Missing company information was one of the simplest fixes, and almost nobody implemented it unprompted.
How CRN Relates to Your Google Ads Account Setup
When you set up a Google Ads account as a business, Google asks whether you are advertising as an individual or a business. If you select business, you will be asked for your business name and country of registration. At certain spend levels or in certain categories, Google may also trigger a business verification process that asks for documentary proof.
In that verification flow, your CRN is one of the acceptable forms of proof. Google will cross-reference the company name on your account against public records. If the name does not match — because you trade under a different name than your registered company name, for example — this can cause delays.
This is an operational detail that most generic Google Ads guides do not cover. But if you are spending meaningfully on Google Ads, knowing your CRN and having your account details aligned with your Companies House record removes a potential point of failure. For a deeper look at how ad costs on Google scale with account setup quality, that article covers the relationship between account hygiene and cost efficiency.
If managing these details alongside bid adjustments, budget allocation, and campaign performance feels like too much to track simultaneously, that is exactly the kind of operational overhead that Overtime's AI agent is designed to reduce. It handles the day-to-day management of your Google Ads account — adjusting bids, pausing underperformers, reallocating budget — so you are not context-switching between compliance administration and campaign decisions.
Searching for Another Company's CRN
Knowing what is company registration number is useful not just for your own business but for verifying others. Before entering a significant contract, taking on a new supplier, or extending credit to a customer, checking their CRN takes under two minutes.
The Companies House find and update company information service is free and publicly accessible. You can search by company name or CRN. The record shows the company's status (active, dissolved, or in liquidation), registered address, director names, and filing history.
A company that is dissolved or overdue on its confirmation statement is a risk worth knowing about before you sign anything. This is a habit worth building into any supplier onboarding process, particularly if you are placing significant advertising spend through agencies or vendors who will be acting on your behalf. For an objective look at what to expect from managed advertising services, what a paid search service actually does sets out the typical scope and responsibilities.
See also: how to fix high cost per acquisition in Google Ads — because the quality of whoever manages your account has a direct effect on what you pay per conversion.
What Is Company Registration Number in the Context of 2026 Compliance
As of 2026, Companies House has significantly increased its identity verification requirements following the Economic Crime and Corporate Transparency Act. Directors and persons with significant control (PSCs) must now verify their identity through Companies House — a process that requires, among other things, confirming the CRN of any company they are associated with.
This means the CRN is more operationally relevant than ever. If you have not verified your identity as a director, your company's ability to file documents may be restricted, which has downstream effects on your company's status — and a company with filing issues will not pass the verification checks that banks, advertisers, and business counterparties increasingly run.
Keeping your Companies House record accurate and your CRN filed correctly on all outward-facing business materials is not bureaucratic overhead. It is increasingly a prerequisite for doing business without unnecessary friction. The best way to advertise your business in any year starts with a business that is properly constituted on paper.
For businesses running Google Ads, consider checking your Overtime account setup to ensure the business details linked to your campaigns match your Companies House record. Mismatches between your trading name and registered name are a common and fixable source of verification friction.
The One Thing Most Guides Get Wrong About CRNs
Most articles about company registration numbers treat the CRN as a purely administrative detail — something you write down once and file away. In practice, it is a live operational asset. It surfaces in banking, credit, advertising, contracts, and now identity verification. The businesses that treat it casually are the ones that find themselves paused, delayed, or blocked at moments when speed matters.
The CRN is also the anchor of your company's public credibility. Because it is searchable by anyone, what appears against it — filing history, active status, registered address — is a form of public reputation. A company with overdue accounts or a dissolved status listed against its CRN will lose business to competitors who are clean on record, even if the underlying operation is fine.
Understanding what is company registration number properly means treating it as infrastructure, not paperwork. And if you are running paid search as part of your growth strategy, that infrastructure needs to be solid before you spend a pound on clicks. Overtime's AI agent can manage what happens inside your Google Ads account — from bid adjustments to budget reallocation — but the foundation of a verified, properly registered business is something you have to get right first.
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Frequently Asked Questions
What is a company registration number and where do I find mine?
A company registration number (CRN) is a unique eight-character code assigned to your company by Companies House at the point of incorporation. You can find it on your certificate of incorporation, on official Companies House correspondence, or by searching the free Companies House register using your company name.
What is the difference between a company registration number and a VAT number?
A company registration number is issued by Companies House and identifies your company as a legal entity — it exists from the moment of incorporation and is publicly searchable. A VAT number is issued by HMRC only if your business is VAT registered, and is separate from the CRN.
Do I have to display my company registration number on my website?
Yes. Under the Companies Act 2006, all limited companies must display their CRN on their website, business letters, invoices, and order forms. It is typically shown in the website footer alongside the registered company name and registered office address.
Can a sole trader have a company registration number?
No. Company registration numbers are only issued to companies incorporated under the Companies Act — primarily limited companies and limited liability partnerships. Sole traders are not incorporated and do not receive a CRN, though they do have a Unique Taxpayer Reference (UTR) from HMRC.
Why does Google Ads sometimes ask for a company registration number?
Google periodically runs business verification checks, particularly when accounts reach certain spend thresholds or operate in restricted advertising categories. Your CRN is one of the documents Google may request to confirm that your business is a legitimate, registered legal entity. Having it to hand prevents campaign disruption during the verification process.