A Companies House authentication code is required to file accounts and a confirmation statement, and make changes to the Company. This is a code made up of letters and numbers and is unique to a company. The code is similar to a PIN that provides Companies House with confirmation that you have the authority to file on behalf of a company. You should not share your authentication code with anyone other than your accountant or other directors in the business.
When you register a company, an authentication code is automatically sent to your registered office. Keep it safe and stored securely for future use.
If you have lost your authentication code, you can apply to Companies House for a new one. You will need to visit this page on Companies House WebFiling where you can sign in and request a new one. If you incorporated the business yourself through Companies House, you will already have a login, if not, you may need to register for a new account. You will receive your authentication code at your registered office address within 5 days.