Authentication code

The company authentication code is a 6-character code of letters and numbers that Companies House issues to each company. It authorises information filed online and is the equivalent of a company officer’s signature¹.

Why it matters

You need it to file online, whether through Companies House’s own services or commercial software. Companies House posts it to the registered office, which can take up to 10 working days, so request it well before a deadline. It can’t be sent by email or given over the phone, though it can be sent to a director’s home address if you can’t get to the registered office¹.

Treat it like a bank card PIN: anyone who has it can change the company’s details online. Change it if someone who no longer files for you, such as a former accountant, knows it¹.

It is not the same as a director’s personal code, which proves a person has verified their identity: see your Companies House personal code. You need both to file a confirmation statement.