Every limited company registered in England, Wales, Scotland, or Northern Ireland is assigned a unique eight-digit company registration number the moment incorporation is approved. If you need it and cannot find it, you are almost certainly looking in the wrong place — not because it is hidden, but because it appears in several locations that are easy to overlook.
This article explains exactly where to find company registration number details, which documents carry it, and why getting this right matters more than most business owners realise — particularly when setting up verified advertising accounts.
Where to Find Company Registration Number on Official Documents
The most reliable place to find your company registration number is your Certificate of Incorporation. Companies House issues this document at the point of registration, and the number sits prominently on the front page. If you registered digitally, the certificate was emailed as a PDF — worth searching your inbox for "Companies House" if you cannot locate the physical copy.
Beyond the certificate, your company registration number appears on the statutory register held at your registered office address. It also appears on every piece of correspondence sent by Companies House, including reminders to file annual accounts and confirmation statements. If you have ever received a letter from Companies House, the number is on it.
For a quick lookup without digging through paperwork, the Companies House public register allows anyone to search by company name and retrieve the registration number instantly. This is free, requires no login, and is the fastest option when you are mid-task and need the number now.
How to Find Company Registration Number in Your Own Records
Outside of official Companies House documents, your company registration number is required to appear on certain business stationery and digital assets by law. This makes your own materials a useful secondary source.
Under the Companies Act 2006, limited companies must display their registration number on all business letters, order forms, and websites. Check your email footer, your website's footer or legal page, and any invoice templates you use. If your accountant set up your systems correctly, the number is already embedded in several places you use daily.
Your accountant or company formation agent will also have the number on file. If you used a formation agent — Companies Made Simple, 1st Formations, or similar services that handle UK company registration — they store your details in your account dashboard. Log in and the number is typically displayed on your company summary page.
| Document or Source | Where the Number Appears | Access Required |
|---|---|---|
| Certificate of Incorporation | Front page, prominently displayed | Your own records |
| Companies House register | Company profile page | Public, no login |
| Business letterhead / invoices | Footer or header section | Your own templates |
| Website legal / footer | Usually footer or "About" page | Public |
| Accountant records | Company summary or filing history | Contact your accountant |
| Formation agent dashboard | Company overview page | Login required |
| Companies House correspondence | Top of each letter | Your own records |
Once you know where to find company registration number details from multiple sources, you are protected against the scenario where one document is unavailable — which matters more than it sounds.
What the Company Registration Number Actually Is
The company registration number (CRN) is a unique identifier assigned by Companies House at the point of incorporation. In England and Wales it is eight digits, typically starting with a zero or a number between 1 and 9. Scottish companies begin with SC, Northern Irish companies with NI, and limited liability partnerships use OC as a prefix. The format varies slightly, but the function is the same: it identifies your legal entity precisely and permanently.
The number never changes, even if your company name changes. This is an important operational detail — if you rebrand, your CRN remains the same, which is why relying on the number rather than the name is standard practice in legal and financial contexts.
This permanence is also why Google Ads account verification processes ask for it. When verifying a business advertiser, Google cross-references your CRN against public records to confirm the entity is real and registered. Getting the number wrong at that stage stalls campaigns. For SMEs managing their own advertising, this is often the first moment they go looking for where to find company registration number details and realise they do not know offhand.
Why Your CRN Matters for Google Ads and Business Advertising
Google has tightened its advertiser identity verification requirements significantly over recent years. If you are running Search campaigns, Shopping ads, or any paid activity on Google, you will at some point be asked to confirm your business identity. Your company registration number is central to that process for UK-registered businesses.
The verification process cross-checks your submitted details against the Companies House register. If your business name on your Google Ads account does not match the registered name exactly — even minor formatting differences can cause issues — verification is delayed. Knowing where to find your company registration number, and submitting it accurately alongside your registered business name, avoids this friction entirely.
For businesses spending meaningful budget on paid search, delays caused by failed verification can pause campaigns at critical times. If you are preparing to run Google Ads or reviewing your account setup, it is worth confirming your CRN now and ensuring it is recorded consistently across your advertising accounts, your website, and your billing details. Inconsistency across those three points is where most problems originate.
If you want to understand the full setup process for Google Ads as an SME, the guide on how to advertise your business with Google Ads covers the account structure and what details you need before you start spending.
For businesses that want their Google Ads managed without having to handle the ongoing operational complexity — adjusting bids, pausing underperforming keywords, reallocating budget between campaigns — Overtime handles all of that automatically, logging into your account and making changes the way an experienced manager would, without requiring your involvement in the day-to-day.
Where to Find Company Registration Number if You've Lost Your Certificate
Losing the Certificate of Incorporation is more common than people admit. It is a PDF sent to an email address that may no longer be active, or a physical document filed years ago. The good news is that the certificate is not the only source, and the Companies House register is always current.
To retrieve your number without the certificate, go to the Companies House public register and search your company name. Your company profile page shows the CRN, registered office address, filing history, and current status. This is a public record and has no restrictions on access.
If you need a replacement certificate, Companies House allows you to order one online for a small fee. The turnaround is typically a few working days for a digital copy. For most practical purposes — advertising verification, opening a business bank account, filling in supplier forms — the number displayed on the register is sufficient and does not require the physical certificate.
For related context on how registration details connect to your online business identity and advertising credibility, the article on company house number details for SMEs covers the adjacent questions that tend to come up alongside this one.
Managing Google Ads Once Your Account Is Verified
Finding your company registration number and getting your Google Ads account verified is the necessary groundwork. What comes after — managing campaigns, controlling spend, making decisions about which keywords to keep and which to pause — is where most SMEs lose time or money, often both.
Having spent nine years running a marketing agency, the pattern we saw repeatedly was that SMEs would get their account set up correctly, run campaigns for a few weeks, and then stop making adjustments because nobody had time. Campaigns drift. Bids become inefficient. Budget flows to keywords that stopped converting months ago. The account is technically active but performing well below where it could be.
This is the problem Overtime was built to address. It is an AI agent that logs into your Google Ads account, analyses performance, adjusts bids, pauses underperformers, and sends you a plain-English summary of what it did and why. There is no dashboard to learn and no decisions to make manually every week.
For SMEs who want to understand what good management looks like before committing to anything, the guide on Google Pay Per Click management for SMEs is a practical starting point. And if you are trying to understand the full cost picture before you begin, how much Google Ads actually costs for SMEs gives transparent figures without the sales-speak.
If you are at the stage of comparing what an AI agent offers versus hiring an agency or a consultant, the breakdown in best PPC agency versus AI agent for SMEs covers the trade-offs honestly — including where an agent is the wrong choice.
Knowing where to find company registration number details gets you past the first gate. Making sure your campaigns are managed properly after that is how you get a return on the spend.
---
Frequently Asked Questions
What is a company registration number and where does it come from?
A company registration number (CRN) is a unique identifier assigned by Companies House at the point of incorporation. It is permanent — it does not change if your company name changes — and identifies your legal entity in all official filings and public records.
How can I find my company registration number without my Certificate of Incorporation?
Search the Companies House public register at find-and-update.company-information.service.gov.uk using your company name. Your CRN is displayed on your company profile page, which is publicly accessible with no login or fee required.
Why does Google Ads ask for my company registration number?
Google uses advertiser identity verification to confirm that businesses running paid campaigns are legitimate registered entities. Submitting your CRN allows Google to cross-reference your details against the Companies House register. Errors or mismatches at this stage will delay verification and can pause your campaigns.
Should my company registration number appear on my website?
Yes. Under the Companies Act 2006, UK limited companies are legally required to display their company registration number on their website, business letters, and order forms. It typically appears in the website footer or on a legal information page, alongside the registered office address.
Do sole traders have a company registration number?
No. Company registration numbers are issued only to limited companies and limited liability partnerships registered with Companies House. Sole traders are not incorporated entities and do not have a CRN. If a sole trader needs to verify their identity for advertising or banking purposes, they would typically use their UTR (Unique Taxpayer Reference) from HMRC instead.