Companies House Authentication Code: What Is It and Why Is It Important?

What is a Companies House Authentication Code?

A Companies House authentication code is a unique 6-character alphanumeric code assigned to every UK limited company. It acts as a digital signature or password that authorises online filings made through the Companies House WebFiling service.

Without this code, you cannot file documents online on behalf of your company — including your Confirmation Statement, annual accounts, or changes to company details.

Why is the Authentication Code Important?

The authentication code is your company's key to the Companies House online filing system. It is used to:

• File your annual Confirmation Statement (CS01)
• Submit your company's annual accounts
• Update director details or registered office address
• Make changes to your share structure or PSC register
• File any other statutory documents online

It is essentially proof that you are authorised to act on behalf of the company. Anyone with this code can make filings, so it should be kept secure and only shared with trusted individuals such as your accountant or company secretary.

When Do You Receive Your Authentication Code?

Companies House sends your authentication code by post to your company's registered office address shortly after your company is incorporated. This is one of the key reasons why having a reliable, monitored registered office address is so important — if the letter goes to the wrong address or is missed, you won't be able to file online.

Spectre Offices provides registered office addresses with mail scanning and mail forwarding, ensuring you receive important correspondence like your authentication code promptly.

Where to Find Your Authentication Code

If you've already received your authentication code, you can find it:

• In the original letter sent by Companies House to your registered office address after incorporation
• In your Companies House WebFiling account (if you've previously logged in)
• With your accountant or company formation agent, if they set up the company on your behalf

What to Do if You've Lost Your Authentication Code

If you've lost your authentication code, don't panic — you can request a new one from Companies House. Here's how:

1. Go to the Companies House WebFiling service at find-and-update.company-information.service.gov.uk
2. Search for your company and select it
3. Click "Request an authentication code"
4. Companies House will post a new code to your company's registered office address
5. Allow up to 5 working days for delivery

Note: the new code is always sent by post to your registered office address — it cannot be emailed or sent to a personal address. This is another reason why keeping your registered office address up to date and monitored is essential.

Can You Change Your Authentication Code?

Yes — once you're logged into the WebFiling service, you can change your authentication code to something more memorable. It must be exactly 6 characters and can contain letters and numbers.

Keep Your Authentication Code Secure

Your authentication code should be treated like a password. If it falls into the wrong hands, someone could make unauthorised filings on behalf of your company. Best practice is to:

• Store it securely (e.g. in a password manager)
• Only share it with your accountant or authorised agents
• Change it if you suspect it has been compromised

Need Help with Companies House Filings?

If you need support with Companies House administration — including Confirmation Statements, address changes, or director updates — Spectre Offices offers Companies House admin support to keep your company compliant and up to date.