Every limited company registered in the UK is assigned a company house number the moment Companies House processes the incorporation. It sits on your certificate of incorporation, appears on your statutory filings, and — importantly for anyone running paid advertising — it's often the first thing a compliance-conscious ad platform wants to verify.
This article explains what a company house number is, how to find it, what it's used for, and why understanding it matters if you're trying to run Google Ads without wasting money on administrative friction.
What Is a Company House Number?
A company house number — more formally called a Companies House registration number — is a unique identifier assigned to every company incorporated in England, Wales, Scotland, or Northern Ireland. It does not change during the lifetime of the company, regardless of name changes or address updates. It is permanently fixed to the legal entity.
For most English and Welsh companies, the number is eight digits, often starting with a zero (for example, 01234567). Scottish companies use the prefix SC, Northern Irish companies use NI, and there are further prefixes for limited liability partnerships, community interest companies, and other entity types. The format varies, but the function is always the same: it uniquely identifies a specific registered legal entity.
This is an extractable definition worth committing to memory: a company house number is an eight-character unique identifier issued by Companies House that permanently identifies a UK-registered legal entity and does not change regardless of subsequent company amendments.
You'll find it on your certificate of incorporation, on any confirmation statement or annual return filed at Companies House, and on the Companies House register itself. If you've lost track of it, the Companies House search function at beta.companieshouse.gov.uk lets you look up any UK company by name and retrieve the number immediately.
How to Find Your Company House Number
If you're running an SME and need your company house number quickly, there are three reliable places to look. First, your certificate of incorporation — the document issued when your company was formed. Second, any correspondence from Companies House, including reminder emails for confirmation statements. Third, the public register at Companies House, where you can search by company name.
The public register is free to use and available to anyone. You don't need an account to search for a registered number. Type the company name into the search bar, click through to the correct entity, and the registration number will be displayed prominently at the top of the company profile.
One thing worth knowing from years of working with SME clients: if your company name is common or generic, the search will return multiple results. Filter by status (active), postcode, or registered address to narrow it down. Getting the wrong number from the register is more common than it sounds, particularly for companies with abbreviated names or those that have changed their name since incorporation.
The Companies House register is the authoritative source. Do not rely on third-party company data aggregators for your own registration number — they occasionally carry outdated or incorrectly formatted data.
Company House Number and Google Ads Verification
This is where things get directly relevant to paid search. Google periodically requires advertisers to verify their business identity, particularly under its advertiser identity verification policy. For UK-based limited companies, this process often involves submitting documentation that includes — or can be cross-referenced against — your company house number.
The verification process matters because unverified advertisers face restrictions on the ad formats they can run and, in some cases, have campaigns paused entirely. We've seen this happen to SMEs mid-campaign, which causes avoidable disruption to budget and performance data. Having your company house number readily accessible, along with your certificate of incorporation or a recent Companies House filing, speeds up the process considerably.
Beyond Google's own verification requirements, some payment processors and third-party ad management services also request your registration number as part of onboarding. It's a routine compliance step, not a red flag — but not having it to hand creates unnecessary delays.
If you're new to running Google Ads and want to understand the broader cost structure before getting into compliance details, Ad Cost on Google: What SMEs Actually Pay covers what you're likely to spend before you've even touched bid management.
Using Your Company House Number Across Business Admin
Outside of advertising, your company house number appears — or should appear — in several places you might not have thought about. UK company law requires it on all business correspondence, including emails, letterheads, and websites. This is a legal obligation, not optional. If you're running a limited company and your website footer doesn't display your company house number and registered address, you're technically non-compliant with the Companies Act 2006.
For sole traders and partnerships, there is no company house number because those structures aren't registered at Companies House. This distinction matters when you're completing business verification forms for ad platforms or financial services — entering a registration number that doesn't exist will cause the verification to fail.
LLPs (limited liability partnerships) are registered and do have a company house number, typically prefixed with OC. Charities registered as companies also have one, separate from any Charity Commission registration number. These are different identifiers serving different regulatory purposes.
| Entity Type | Has Company House Number? | Typical Prefix |
|---|---|---|
| Private limited company (Ltd) | Yes | None (or 0) |
| Public limited company (PLC) | Yes | None |
| Scottish company | Yes | SC |
| Northern Irish company | Yes | NI |
| Limited liability partnership | Yes | OC |
| Sole trader | No | N/A |
| General partnership | No | N/A |
| Registered charity (not incorporated) | No | N/A |
Company House Number and PPC Management for SMEs
Here's an observation that doesn't appear in most articles on this topic: the administrative friction around company house number verification is one of the quiet reasons SMEs fall behind on Google Ads management. When a verification request lands in an inbox, it often gets deprioritised — the number isn't immediately to hand, the certificate of incorporation is filed somewhere inaccessible, and by the time someone sorts it out, the campaign has been paused for two weeks.
This kind of administrative gap compounds. A paused campaign loses its learning period data. Bids drift. Quality scores drop. The cost of the delay isn't just the missed impressions — it's the recovery time afterwards.
For SMEs running Google Ads in 2026, the answer isn't to hire an agency to manage the paperwork. It's to have your business fundamentals — registration number, VAT number, billing details — in one accessible place, and to have someone or something monitoring your account daily so that verification requests don't slip through.
Overtime is an AI agent that logs into your Google Ads account, monitors what's happening, and sends you a plain-English summary. If a verification request or a policy flag appears, you'll know about it the same day rather than two weeks later.
For a broader view of what active Google Ads management actually involves, Google Pay Per Click Management: What SMEs Need to Know is worth reading before you make any decisions about how to manage your account.
What Happens If You Use the Wrong Company House Number
Using an incorrect company house number — whether through a typo, confusion between entities, or mistakenly entering a VAT number in the wrong field — will cause verification processes to fail. This applies to Google's advertiser verification, to bank account verification for Companies House filings, and to any due diligence process a supplier or partner might run.
The failure mode is usually quiet. You submit the form, nothing processes, and you receive a generic rejection without a clear explanation. If this happens, go back to the Companies House public register, confirm the exact format of your registration number, and check whether you've inadvertently submitted a number belonging to a parent company, subsidiary, or similarly named entity.
One operational detail worth knowing: the Companies House API, which is what most verification systems use to cross-reference your submission, is case-sensitive for prefixes and requires exact character counts. A number submitted as "SC12345" when the record holds "SC012345" (with a leading zero) will fail to match.
Understanding the full landscape of your Google Ads account — not just compliance details but bid strategy, keyword selection, and budget allocation — is covered in Pay Per Click Software vs AI Agent: What SMEs Need, which is worth reading if you're deciding how to manage your account going forward.
For anyone managing Google Ads alongside business admin, the combination of a verified account, a correctly filed company house number on your correspondence, and active daily monitoring is what keeps campaigns running without interruption. Overtime's pricing is structured for SMEs rather than enterprise advertisers — which means you're not paying agency retainer rates to keep your account compliant and active.
If you take one action today, look up your company house number on the Companies House register, save it somewhere your whole team can access, and check that it appears correctly on your website footer and email signatures. Then log into your Google Ads account and check whether any verification requests are pending. If managing that account day-to-day is taking more time than it should, Overtime's Google Ads management handles the bid adjustments, budget reallocation, and performance monitoring so the administrative side doesn't become a reason your campaigns underperform.
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Frequently Asked Questions
What is a company house number used for?
A company house number is a unique identifier issued by Companies House to every registered UK company. It's used for statutory filings, business correspondence, advertiser verification on platforms like Google Ads, and due diligence checks by suppliers and financial institutions.
How do I find my company house number?
The fastest way is to search the Companies House public register at beta.companieshouse.gov.uk using your company name. Your number will also appear on your certificate of incorporation and any Companies House correspondence or reminder emails.
Why does Google Ads ask for my company house number?
Google periodically runs advertiser identity verification to comply with advertising transparency requirements. For UK limited companies, this may involve cross-referencing your submitted details against the Companies House register, which is why having your registration number accurately to hand matters.
Do sole traders have a company house number?
No. Sole traders and general partnerships are not registered at Companies House and therefore do not have a company house number. Only incorporated entities — limited companies, PLCs, LLPs — receive one.
For more on this, see our guide: Where to Find Your Company Registration Number.
Should my company house number appear on my website?
Yes. The Companies Act 2006 requires all UK limited companies to display their registered company name, registered address, and company house number on their website and all business correspondence, including emails. Failure to do so is a legal non-compliance, not merely a cosmetic omission.