Companies House have suffered a data breach in the past few days (March 2026).
Here is their advisory email on the topic (reformatted for the purpose of this post):
This is an official email from Companies House, sent to all registered email addresses, and is relevant to all companies registered in the UK.
We are writing to let you know about an issue that affected our WebFiling service, and to explain what you should do next. This advice is relevant to all companies, whether or not you use the WebFiling service to file.
On Friday 13 March, we identified an issue with WebFiling. We took the service offline at 1:30pm that day while we investigated and fixed the problem. WebFiling has been independently tested and has been back online since 9am on Monday 16 March.
The issue arose from a system update in October 2025 and was not the result of a malicious attempt to attack our systems. It is not a cyber-attack. The issue could only have been exploited by a logged-in user performing a specific set of actions. Our investigation found that it was technically possible for a logged-in registered user to:
1. See certain data not normally published on the public register:
• the day of the date of birth for directors and PSCs
• residential address for directors and PSCs
• company registered email address2. File updates to any information without consent. For example, new accounts or changes of director.
We want to reassure you that:
• You do not need to reset your WebFiling password.
• No identity verification data, such as passport information or personal codes, was accessed.
• No existing filed documents could have been altered.
• If you have applied to protect your personal details under the Companies Act 2006, your information was not affected by this issue.What you should do now:
We are contacting you proactively on a precautionary basis to make you aware of this issue.
At this stage, we have no confirmed reports of any data having been accessed or changed without permission, and we believe the issue could not have been used to extract data in large volumes.
However, as a precaution, please check your registered details and filing history to make sure everything looks correct. You can do this in WebFiling and on the Find and update company information service.
If anything seems incorrect or unexpected, please contact us on [email protected] using ‘WebFiling issue’ in the subject heading. Please include as much detail as you can about your concern, including your company name and number. The more information you can give us to support our investigation – the easier it will be to resolve the issue for you.
Further recommendations:
We also recommend signing up to our free Follow service. Follow sends you an instant email alert whenever a document is filed with us for any company you choose to follow – including your own. It’s a simple way to stay informed and spot anything unexpected as soon as it happens. You can sign up through the Find and update company information service and then select ‘Follow this company’ on your company’s page.
Next steps:
We have reported this incident to the Information Commissioner’s Office (ICO). We are analysing our data, and if we find evidence that anyone has accessed or changed another company’s details without authorisation, we will take firm action.
We will keep you updated as our investigation progresses.
An apology
We recognise that this incident may have caused concern, and we are sorry for that. Companies House takes its responsibility to protect your data extremely seriously, and we are committed to doing everything we can to support those affected and to maintaining your trust in our services.
We suggest clients check their company details at Companies House, this link enables this to be done quickly and without login
Find and update company information