What is my company authentication code?

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.

What is your Companies House authentication code, and why does it matter?

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:

• File a confirmation statement
• Update directors or people with significant control (PSCs)
• Change your registered office or other company details
• Submit certain documents through third-party filing software

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.

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• How to update shareholder information at Companies House
• Company filing and reporting requirements

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.

How can you find your company authentication code?

Exactly where your code is stored depends on how the company was formed and who handles your filings.

If you used a company formation agent

If you formed your company through an agent, the authentication code is normally:

• Included in your welcome email or incorporation pack
• Visible in your online client portal (if your agent provides one)
• Stored by your accountant or company secretarial provider if they manage filings for you

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.

If you registered directly with Companies House

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.

How do you request a new authentication code if you’ve lost it?

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.

Requesting a reminder through Companies House online services

1. Go to the Companies House online filing service and sign in (or create an account if you don’t already have one).
2. Enter your company registration number to link the company to your login.
3. Choose the option to request an authentication code.
4. Confirm the delivery address – by default, this will be your registered office.

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.

How long does it take to receive a new code?

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.

How can you change your company authentication code securely?

You can change your code at any time, and it’s good practice to do so if:

• Someone outside your business has left a role where they used the code
• You’ve changed accountants or formation agents
• You think the code might have been seen or shared more widely than intended

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:

• The old code stops working immediately, and
• You’ll need to give the new code to any accountant, agent or software provider who files on your behalf.

What should you do if someone else has your authentication code?

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:

1. Change the code immediately using Companies House online services.
2. Check your recent filings on the public register for any changes you don’t recognise (for example, to directors, registered office or share structure).
3. If you see anything suspicious, contact Companies House and, where appropriate, seek advice from your accountant or a legal adviser.
4. Review who has access to the new code and keep a clear record of where it’s stored.

What does a UK company authentication code look like?

An authentication code is always:

• six characters long
• a mix of letters and numbers
• unique to your company

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.

Final tips for managing your authentication code

A little organisation goes a long way. To avoid last-minute problems:

• Store the code securely – Keep the code in your formation agent’s portal, a password manager, or with your accountant, rather than in open emails or shared documents.
• Keep it up to date – Change the code when staff, directors or service providers who knew it move on.
• Plan for deadlines – If you can’t find the code, request a new one well before your confirmation statement or accounts are due.
• Know who’s responsible – Decide whether the director, company secretary, accountant or formations provider is in charge of using and updating the code.

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.

Staying organised with your Companies House credentials

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.