If you want to file anything online with Companies House – from a confirmation statement to a change of director – you’ll need your company authentication code. It’s a small piece of information, but it acts like a digital signature for your company.
Never seen your company authentication code? Can’t remember it? Not sure where it was sent? This guide walks you through what the code is, where to find it, how to request a new one, and what to do if you think someone else has access.
Your company authentication code is a six-character mix of letters and numbers issued by Companies House. It links specifically to your company and is used to prove you’re authorised to submit filings online.
You’ll use it when you:
A company authentication code isn’t the same as your company registration number . The registration number is public and appears on the Companies House register; the authentication code is private and should be treated like a password or PIN.
With the rollout of identity verification under new Companies House reforms, directors and PSCs will also have their own personal credentials – but the company authentication code remains the key credential for online filings made on behalf of the company.
Exactly where your code is stored depends on how the company was formed and who handles your filings.
If you formed your company through an agent, the authentication code is normally:
If you’re a 1st Formations customer, you’ll usually find the code in your online dashboard and in the documentation supplied when the company was set up. If you can’t locate it there, get in touch with our support team, and we’ll help you locate it.
When you form a company yourself via Companies House, they send the authentication code in a letter to the registered office address shortly after incorporation. If you still have that letter, the code printed on it is your active company authentication code (unless you’ve since changed it).
If the letter has been mislaid, or you’ve never seen it – for example, because the registered office is a previous address or a former agent – you’ll need to request a new code rather than trying to guess the old one.
If you can’t find the original letter or don’t have access to your agent’s records, you can ask Companies House to send you a fresh code.
For most companies, the new code is sent by post to the registered office. Companies House does not issue authentication codes by email or over the phone.
If you no longer have access to the registered office address – for example, if you’ve moved or changed providers – you’ll usually need to update the registered office first, or in some cases use the newer service that allows the code to be posted to a director’s home address .
Companies House advises allowing up to 10 working days for the letter to arrive, and this timeframe may be longer during busy periods of the year. You won’t be able to file online until you receive the new code, so it’s sensible to request it well before any filing deadline.
Once the letter arrives, use the code shown there for all future online submissions, unless you deliberately change it.
You can change your code at any time, and it’s good practice to do so if:
To change it, log in to Companies House online services, select your company and navigate to the section for company authentication. You’ll be asked to enter the existing code and then choose a new one.
Pick something that isn’t easy to guess and avoid reusing other passwords. Once the change is confirmed:
Because the authentication code acts like a digital signature, anyone who has it can submit changes to your company’s record. If you suspect an unauthorised person knows your code, treat it as a security issue.
Here are the steps to take:
An authentication code is always:
The format doesn’t follow your company registration number and isn’t derived from your name. If you’ve changed the code in the past, only the most recent version will work.
If you see something longer than six characters, or information that looks like a director’s personal verification code, that’s not your company authentication code – and it won’t be accepted for online filing.
A little organisation goes a long way. To avoid last-minute problems:
Once you know where your company authentication code is and how to manage it, online filing with Companies House becomes much more straightforward – and you can focus on running the business rather than chasing paperwork.
Your company authentication code is a small detail that carries a lot of importance. Keeping track of it – and knowing how to recover or update it when necessary – means you can handle filings smoothly, avoid delays, and maintain full control over the information held on the public register . Once you have a clear process for managing the code, everything, from filing a confirmation statement to updating directors, becomes far easier.
And remember, if you’d rather use our registered office or service address , then your Companies House correspondence (including replacement authentication codes) comes straight to us – so nothing goes missing and you’re never stuck waiting for a code.
No, Companies House only sends authentication codes by post for security reasons. By default, they’re sent to the registered office address listed on the public register. If you’ve changed providers or no longer have access to the registered office address, you may need to update your registered office first, or, in some cases, request that the code be sent to a director’s home address instead.
If you still have access to the current authentication code, you can update your registered office online using the Companies House WebFiling service. If you don’t have the code, you may need to submit a paper AD01 form and include supporting evidence. The new address must meet legal requirements: it must be in the same UK jurisdiction and capable of receiving official post.
If an unauthorised person files changes using your code, act quickly. Change the code immediately through Companies House online services, review all recent filings, and report anything suspicious. You may also need to file corrective forms and notify Companies House in writing. In serious cases, speak to a solicitor and consider reporting the incident to Action Fraud.
Yes, many UK businesses delegate filings to an accountant, company secretary, or formation agent. If you choose to do this, ensure they store the code securely and inform you if any staff changes affect access. It’s good practice to update the code if you change providers and to keep a backup record in a password manager or a secure system that you control.