Companies House Authentication Code Explained

Under One Login, do I still get a company authentication code after company formation?

Yes, you still get a company authentication code after company formation under GOV.UK One Login.

Companies House issues the code automatically when your limited company is incorporated. The six alphanumeric character code arrives by post at your office address within a few working days. Companies House will not send the code via email or provide it over the phone for security reasons.

GOV.UK One Login verifies your personal identity and secures access to government services. The Company Authentication Code serves a different purpose: it proves you have authority to file on behalf of the company.

Think of it this way: One Login confirms who you are. The authentication code confirms you’re authorised to act for that specific company.

How do I find my Companies House authentication code?

The authentication code is a unique six-character alphanumeric code required to authorise filings for your company. Finding your code depends on whether you need the original or a replacement.

1. Initial Receipt for Newly Formed Companies

   Companies House automatically issues the authentication code when a limited company is incorporated. The code arrives by post at your company’s registered address, typically within 5 working days from the date of incorporation or making the request. Companies House will never send the code by email or provide it over the phone.

2. Requesting a Reminder via WebFiling

   If you’ve misplaced your code, request a reminder through the official online service:

   1. Sign in to the Companies House WebFiling service (or create an account if needed).
   2. Select ‘Your companies’ or ‘File for a company’.
   3. Enter your company registration number and country of registration.
   4. Select ‘Help with authentication code’, then choose ‘I do not have an authentication code’ (or select the ‘Request code’ link).

   Companies House will post a new code to your company’s registered office address.

   If you cannot access your company’s registered office, you can request that the code be sent to a home address of an active director. However, the director’s home address on the Companies House register must be current and accurate.

   If you requested the code to the registered address and haven’t received it after the expected timeframe, check the address listed on the Companies House register. If the address is incorrect, you must update your address first (using a paper form if enrolled in the PROOF scheme) before requesting the code again.

3. Retrieving the Code from Your Company Formation Agent

   If you formed your company through a formation agent and haven’t changed the code since incorporation, you can likely retrieve it from the agent’s platform. Log in to your customer account or online portal and find the 6-character code under your company details.

   Without the correct code, you cannot make online filings and must use slower paper submissions. Error codes like “502: authorisation failure” or “9999” in filing software typically indicate an incorrect or missing authentication code.

As a company secretary or accountant, how do I get an authentication code for the limited company I manage?

As a company secretary or accountant acting as an authorised agent, you obtain the company through specific procedures that prioritise physical mail verification. It is a unique six-character alphanumeric code that acts as the electronic equivalent of a company officer’s signature and is mandatory for submitting electronic filings.

1. Requesting a Reminder via WebFiling

   If you don’t have the code, request a reminder through the online system. Since WebFiling requires GOV.UK One Login credentials (effective October 13, 2025), you must use your personal credentials.

2. Alternative Delivery Options

   If you cannot access the company’s office address, you can request that the code be sent to an active director’s home address instead. The director’s most recent home address details must be accurately recorded with Companies House, as the address cannot be viewed or updated during the request process. This specialised delivery may take around 10 working days.

   For security and fraud prevention, Companies House will not provide the authentication code by email or over the phone.

3. Retrieval from a Company Formation Agent

   If the company was incorporated through a formation agent and the code hasn’t been changed since incorporation, you can often retrieve it by logging in to the agent’s customer portal, where the 6-character code may be displayed alongside the company details.

4. Using the Code for Filing via Software

   If you use commercial software (rather than Companies House WebFiling) to submit documents for your clients, you’ll need the Company Authentication Code along with your own Presenter ID and Presenter Authentication Code (obtained when setting up your software filing account). If the company’s directors change the authentication code directly with Companies House, they must inform you immediately, as the old code will be invalid and filing attempts will be rejected (e.g., Error 502 or 9999).

How do I change my Companies House webfiling authentication code under One Login System?

Change your code within the WebFiling interface, which you now access through GOV.UK One Login. The steps for changing the code remain the same, but sign-in now relies on your GOV.UK One Login credentials.

1. Procedure for Changing the Authentication Code

   1. Sign in to Companies House WebFiling using your GOV.UK One Login credentials (email and password with two-factor authentication).
   2. Select ‘Manage account’.
   3. Select ‘Company authentication’.
   4. Choose a new 6-character alphanumeric code. Make it memorable but not easy to guess.
   5. Re-enter the new code to confirm and select ‘Change code’.

   The old authentication code stops working immediately once the change is confirmed.

How do you use your code to change your company details on one login?

The Companies House system requires two distinct codes to validate your authority to change company details via WebFiling, which now uses GOV.UK One Login for access. You use your GOV.UK One Login credentials to access the system and the Company Authentication Code to authorise filings on behalf of the company.

Once logged in and authorised for the company, use the WebFiling interface to access and submit the necessary forms. The company code replaces a handwritten signature on the document. You can make various changes to company details:

• Corporate details: Change registered office address, company name by resolution, or accounting reference date.
• Officer details: Appoint or resign directors or secretaries, or change their details (service address or home address).
• Share capital and control: Submit return of allotment of shares (SH01), update shareholder information, or report changes to Persons with Significant Control (PSCs).

The WebFiling system automatically validates the information and uses the code as the corporate authorisation for that change.

FAQs Companies House Authentication Code