Companies House Address Lookup: Why Every Practice Should Monitor

The Companies House register is public, searchable, and updated daily. Yet the vast majority of UK accountancy practices have no systematic process for monitoring which companies are registered at their own address. This gap — seemingly minor — can have significant practical and reputational consequences, and closing it is simpler than most firms realise.

How Companies End Up Registered at Your Address Without Your Knowledge

You might assume that a company could not register your address without your knowledge. In practice, however, Companies House does not verify that the person filing the registered office address has the consent of the occupier. When a new company is incorporated, the director or agent simply enters an address in the online form. Companies House will write to that address as part of its standard processes, but it does not proactively confirm that the address is authorised.

This means a company can — and sometimes does — appear on the register at your address without your firm ever having agreed to act as registered office. This can happen in several ways:

• A former client who has moved to another accountant fails to update their registered address, or deliberately delays doing so
• A client forms a new subsidiary or related company and uses your address without mentioning it, assuming that your existing arrangement covers all their entities
• A fraudulent actor uses your professional address to lend credibility to a company being set up for illegitimate purposes
• A client's company changes hands through a share sale, and the new directors do not update the registered address — leaving your address on record for a business you have no relationship with

Each of these scenarios creates a different problem, but all of them have one thing in common: you do not know about them until post arrives, a client mentions it in passing, or something goes wrong.

The Risks of Unknown Registrations

Why does it matter if a company you have never heard of is registered at your address? The risks fall into several categories:

Reputational Risk

If a company registered at your address is involved in fraudulent activity, money laundering, or other misconduct, Companies House records will show your firm's address as the registered office. Members of the public, HMRC investigators, or journalists searching the register will see your address associated with that company. Even if your firm has no connection whatsoever to the entity, explaining that can be time-consuming and difficult.

Compliance and AML Risk

Under the Money Laundering, Terrorist Financing and Transfer of Funds (Information on the Payer) Regulations 2017, accountancy firms are supervised entities — typically by HMRC, ICAEW, ACCA, or another professional body. Your supervisory body expects you to know who your clients are and to have conducted appropriate due diligence. A company registered at your address, receiving official correspondence through your firm, without your knowledge or a client engagement on file, creates an obvious gap in your AML procedures.

If your firm were ever subject to a supervisory visit or a routine inspection, unexplained companies on the register at your address would be difficult to account for.

Operational Risk

Correspondence from HMRC or Companies House addressed to an unknown company will arrive at your office. Someone will spend time trying to figure out who it belongs to. If no one can identify the company, the letter may sit unprocessed. If it is an important statutory notice — a penalty, a warning of strike-off, or a compliance demand — the failure to deal with it promptly could have consequences that, whilst not legally your firm's responsibility, will still consume your time to resolve.

How to Search Companies House for Your Address

Companies House provides a free, public search facility at find-and-update.company-information.service.gov.uk. You can search by company name, officer name, or registered address. Searching by your firm's address will return a list of all companies currently registered there.

To carry out this search, navigate to the advanced search functionality and enter your postcode or full address. The results will show every active company registered at that address, along with their incorporation date, status, and the names of the current directors.

Companies House also offers a Companies House API, which allows more sophisticated programmatic searches. For firms with technical resource, or using tools built on the API, this makes it possible to run automated daily or weekly checks against your address — rather than relying on a manual search that someone has to remember to perform.

What to Do When You Find an Unknown Company

If your address search returns a company you do not recognise, the immediate steps are:

• Check your client list. The company may be a recently formed entity for an existing client that has not yet been formally onboarded for the registered office service.
• Contact the directors. Companies House records the names and (where applicable) the service addresses of directors. Reaching out to the director is usually the most direct route to understanding how your address came to be used.
• Review your engagement letters. If you have an existing client with a similar name, check whether your engagement letter covers this entity.
• If the company is unknown and appears suspicious, you can apply to Companies House to have your address removed as the registered office. Companies House has a process for this — under section 1097A of the Companies Act 2006 — which allows an individual or firm to apply to have an address removed if it was used without authorisation.

Building a Monitoring Process Into Your Firm's Routine

A one-off address search is useful, but the real value comes from making it a recurring process. Address misuse can happen at any time, and a company that was legitimately registered at your address six months ago may have been sold, restructured, or — in the worst case — used for fraudulent purposes since then.

A practical monitoring schedule for most practices looks like this:

• Monthly: Run a Companies House address search and compare the results against your registered office client list. Any discrepancies should be investigated immediately.
• Quarterly: Cross-reference the Companies House results against your AML client records to confirm that every company at your address has a current engagement letter and appropriate due diligence on file.
• Annually: Review your registered office service agreement terms with each client, confirm their details are current, and ensure you have a signed mandate to act as their registered office.

Automating this process — or using software that does it for you — removes the dependency on someone remembering to run the search. The Companies House API makes automation straightforward for firms with development resource, and a growing number of practice management tools are beginning to include registered address monitoring as a feature.

The Broader Picture

Monitoring your registered address is not a complex or time-consuming task once you have a process in place. But it is one of those compliance activities that tends to be neglected precisely because it is invisible — you do not know what you are missing until something goes wrong. Practices that establish a regular monitoring routine protect themselves against reputational exposure, AML compliance gaps, and the operational headache of correspondence from unknown companies arriving at their door. Given that the Companies House register is public and the search tool is free, there is no good reason not to check.