How to get your Companies House authentication code
The 6-character code every online filing needs: how to request it, why it arrives by post, and what to do when your deadline is closer than ten working days.
By PromptFiling · Published · Reviewed
What the authentication code is
The company authentication code is a 6-character alphanumeric code Companies House issues to each company; it is the online equivalent of an officer's signature, and no online filing — accounts, confirmation statement, officer changes — can be made without it. It belongs to the COMPANY, not to a person: one code covers every director and any agent filing on the company's behalf. It is not the same thing as the personal code used for identity verification, and it is not your WebFiling password.
How to request one
You request it from Companies House WebFiling: sign in (or create an account), choose 'Your companies' or 'File for a company', enter the company details, then 'Help with authentication code' and 'I do not have an authentication code'. Companies House then posts the code to the company's REGISTERED OFFICE address. If the company already has a code and nobody can find it, the same route gets you a reminder — also by post. Companies House cannot e-mail the code or read it out over the phone, and no agent can request it through an API on your behalf: the postal step to the registered office IS the security check, so there is no faster official channel that anyone can sell you.
How long it takes — and why that matters more than it sounds
Companies House says the code can take up to 10 working days to arrive, and warns that busy periods take longer. Ten working days is two full weeks on the calendar, before anyone opens the envelope. Their own guidance puts it plainly: do not wait until your accounts are due to request the code. If your filing deadline is less than about three weeks away and no code exists, requesting one is the first thing to do today — before preparing anything, including with us.
If you cannot get post at the registered office
Companies House runs a separate service that posts the code to a director's HOME address instead, for exactly this case — a registered office at a former agent, a closed office, a service address nobody checks. It is at find-and-update.company-information.service.gov.uk/auth-code-requests/start and asks for details only a genuine officer can answer. Same postal timescale; the difference is only where the envelope lands.
What the code looks like
Six characters, letters and digits mixed, printed on a letter from Companies House addressed to the company at its registered office — the letter is headed as an authentication code notice and contains nothing else of substance. The code is not on your certificate of incorporation, not in any email (Companies House does not send it electronically), and not visible anywhere in WebFiling after issue. If you are staring at an 11-character code instead, that is your PERSONAL code from identity verification — a different thing for a different job.
Lost it, never received it, or it does not work
Lost: request a reminder through WebFiling — it goes by post to the registered office, same as a new code. Never arrived: first check the registered office address on the register is actually somewhere that receives post; if it is not, either fix the address or use the send-to-home-address service above. Rejected as wrong: the usual culprits are lookalike characters — 0 against O, 1 against I — and a code that a previous agent changed without telling anyone. If an old agent may still hold the working code, change it in WebFiling once you are in: whoever has the code can file for the company.
Keep it safe once it arrives
Anyone holding the code can file for the company — that is the point of it, and the risk of it. Store it the way you store a password, never in a shared inbox thread, and change it in WebFiling if a former agent or director still has it. If you file through us, we hold the code encrypted (AES-256-GCM), decrypt it only at the moment of submission, never log it and never show it back to anyone, including our own staff; you can also give it once per filing and let us forget it.
What we can and cannot do about it
We cannot request the code for you and nor can any other filing service — Companies House provides no API or XML route for requesting one, and says so directly. What we can do is make the wait a scheduled thing rather than a dead end: request the code today, tell us when you have it, and your filing sits ready in the meantime. If your deadline is inside the postal window, the honest answer is that the code is the critical path — not the accounts, which take minutes once it arrives.
Official sources
Sources checked .
Guidance, not advice. Reviewed against gov.uk and legislation.gov.uk sources.