Lost Companies House authentication code: how to get a new one

In short: Request it again through Companies House WebFiling, which you sign in to with GOV.UK One Login. Companies House posts the 6-character code to the registered office, or to an officer's home address if you can't reach the office, and it can take up to 10 working days (GOV.UK). It never comes by email or phone. Taxley prepares and files the CT600 for £44.50 (promotion price until 31 Dec 2026; £89.00 from 1 Jan 2027) with micro-entity accounts, then files the accounts at Companies House with that code once the return is paid and finished.

Take the 30-second check to see whether Taxley fits your company, or read how to file company accounts at Companies House online for the whole filing process.

Key facts (checked on 1 October 2026)

How do you get a new Companies House authentication code if you've lost it?

Sign in to Companies House WebFiling and request the code. Companies House posts it to the company's registered office, which can take up to 10 working days, and if the company already has a code the letter is a reminder of that same code (GOV.UK: Company authentication codes). It isn't sent by email.

Signing in to WebFiling has needed GOV.UK One Login since 13 October 2025. If you don't have a One Login yet, the service prompts you to create one, ideally with the email address your WebFiling account already uses (GOV.UK: WebFiling moves to GOV.UK One Login). Before you request a reminder, check who might already hold the code. One code covers every online filing for the company, in WebFiling, in the Find and update company information service and in commercial software, so a co-director or a former accountant may have it on file. If the registered office is a service address run by an accountant or formation agent, the reminder letter goes there, so ask them to look out for it and pass it on. Companies House also warns not to wait until the accounts are due, because delivery can take longer than usual in busy periods (GOV.UK: Company authentication codes for online filing). The step-by-step guide to filing accounts online covers what happens once the code arrives.

What can you do if you can't get post at the registered office?

Ask Companies House to post the code to an officer's home address instead. GOV.UK says that if you can't access the company's registered office, it can send the authentication code to your home address (GOV.UK: Company authentication codes). You request this through a separate Companies House service, not through WebFiling.

The service is called "Request an authentication code to be sent to a home address", on Companies House's Find and update company information site. It posts the code to an active officer's home address, takes around 10 working days, and needs the company number and Companies House sign-in details, which are different from WebFiling's (Companies House: Request an authentication code to be sent to a home address). You can't use it if the company has filed a document online in the last 30 days, isn't based in the UK, isn't a limited company or LLP, or is dissolved. Use it only if the officer has given Companies House their most recent home address, because for security you can't see or update that address in the service. Moving the registered office doesn't get round a lost code either: changing the address online needs the authentication code too, and GOV.UK points anyone who can't reach the office to the home-address request (GOV.UK: Change a company's registered office address (AD01)).

What should you do if the accounts deadline is too close to wait for the code?

Count the working days left before the deadline. With fewer than 10, the posted code may not arrive in time, so a director can sign paper accounts instead: online filing needs the code as the equivalent of an officer's signature, while paper accounts carry a director's signature and printed name (GOV.UK: Preparing and filing Companies House accounts).

Taxley's troubleshooting table: a lost or missing authentication code

Paper is slower: GOV.UK says it usually takes longer to process paper accounts sent by post, and accounts rejected close to the deadline get no extra time (GOV.UK: Preparing and filing Companies House accounts). Paper filing of accounts ends on 1 April 2028, when software becomes the only route. Accounts delivered up to 1 month late cost a private company a £150 penalty, rising to £1,500 after 6 months, as Companies House late filing penalties explains. An extension is a narrow option: you apply before the deadline, for an event outside your control such as unexpected illness or a fire that destroyed records, and Companies House says to file by the deadline if possible rather than wait for its decision (GOV.UK: Applying for more time to file your company's accounts). Waiting for a posted code isn't one of the examples it gives.

Is the authentication code the same as the Companies House personal code?

No. The company authentication code has 6 characters, belongs to the company and authorises its online filings. The personal code has 11 characters, belongs to one person and confirms that person has verified their identity with Companies House (GOV.UK: Companies House personal codes). Neither replaces the other.

The personal code comes from identity verification, done through GOV.UK One Login or an Authorised Corporate Service Provider (ACSP). An existing director gives it in the company's next confirmation statement filed from 18 November 2025, a new director gives it in the appointment filing, and a person with significant control has a 14-day period to provide it (GOV.UK: Companies House personal codes for identity verification). One code covers every company you're involved in, and GOV.UK says you may also need it in future to file for a company. A Government Gateway account can't be used to send information to Companies House at all (GOV.UK: Company authentication codes); it's the HMRC sign-in, explained with HMRC's own activation code in the guide to the Corporation Tax activation code. Taxley's page on verifying your identity for Companies House covers the personal code in more detail.

How do you find a lost Companies House personal code?

If you verified with GOV.UK One Login, sign in to Companies House with the email address you verified with and open "Manage account" to see the code. Anyone who verified after 8 July 2026 was also sent it by email (GOV.UK: Companies House personal codes). An ACSP's customers got it at the email address that provider gave.

If you verified at a Post Office through GOV.UK One Login, GOV.UK emailed the result of the identity check, usually within one day, and the code is then in "Manage account" too. If an ACSP verified you and no code arrived, ask the ACSP which email address it gave, and ask it to contact Companies House if that address was wrong (GOV.UK: Companies House personal codes for identity verification). GOV.UK recommends saving an ACSP-issued code to a Companies House account, so you can sign in and see it whenever you need it. If you think someone else has your personal code, contact Companies House: it can cancel the old code and email you a new one. When the code won't connect to your appointments, GOV.UK says your details may not match, for example because of a mistyped code or a wrong date of birth on Companies House's records, which you check and correct through WebFiling.

How do you keep the authentication code safe once it arrives?

Treat it like a bank card PIN, because anyone who knows it can change the company's details online. GOV.UK advises mixing letters and numbers, sharing it only with someone you trust to file for the company, and changing it when a former accountant or member of staff still knows it (GOV.UK: Company authentication codes).

You change or cancel the code by signing in to WebFiling, and you can pick something more memorable as long as it isn't easy to guess. Once it changes, tell everyone else who files online for the company, such as an accountant, because the old code stops working for them (GOV.UK: Company authentication codes for online filing). That includes filing software where the code is saved: in Taxley, type the new code into the company's details. Companies House says it will never ask you for the code over the phone, and anyone who calls claiming to be from Companies House and asks for it should be reported to Companies House as fraud.

How does Taxley use your company's authentication code?

Taxley uses the code to file the company's annual accounts at Companies House, which it has done live since 28 September 2026 for the micro-entity, small, abridged and dormant accounts it prepares. You save the code once in the company's details and file once the Company Tax Return (CT600) is paid and the accounts are finished.

Taxley (taxley.co.uk), UK online software that prepares and files the Company Tax Return (CT600) with HMRC and the annual accounts with Companies House, stores the code encrypted and never displays it again. On the company details page, leave the box blank to keep the saved code, type a new one to replace it, or tick "Remove the saved code". Only the company's owner can change the code; someone the company is shared with can't. Until a code is saved, the filing page shows the "File accounts at Companies House" button greyed out, with a link to add the code. Pressing the button asks you to confirm, because accepted accounts go on the public register and can't be withdrawn. If Companies House rejects the filing because of the code, update the code and file again from the filing page; refiling is included in the fee. Companies House's own fee list has no fee for filing a UK company's annual accounts (GOV.UK: Companies House fees).

Taxley files accounts at Companies House for every return it supports once the return is paid and finished, with a few exceptions. It doesn't file the confirmation statement, accounts you uploaded yourself, accounts for a period Companies House already has, or first accounts whose period doesn't start on the date of incorporation. File those yourself on Companies House's online service, signing in with GOV.UK One Login and entering the authentication code (GOV.UK: File your company's annual accounts). Take the 30-second check to see whether Taxley fits your company, or start your return.

Frequently asked questions

Can Companies House email or phone me the authentication code?

No. GOV.UK says Companies House cannot send the company authentication code by email or tell you the code over the phone, and it will never ask you for the code by phone. The code comes only by post (GOV.UK: Company authentication codes).

Does asking for the code again change the old one?

No. If the company already has a code, Companies House posts a reminder of that code. To replace it, sign in to WebFiling and change it, then tell anyone else who files for the company, because the old code stops working for them (GOV.UK: Company authentication codes).

Can I file company accounts without the authentication code?

Not online or through software, where the code authorises every filing. Until 1 April 2028 you can send paper accounts by post instead, with the balance sheet signed by a director and that director's name printed, though paper takes longer to process (GOV.UK: Preparing and filing Companies House accounts).

Do I need the Companies House code to file a CT600 with HMRC?

No. The CT600 goes to HMRC, which you reach by signing in to HMRC online services with the company's Government Gateway user ID (GOV.UK: Add Corporation Tax services). The authentication code only authorises filings with Companies House.

What if my former accountant still has the code?

Ask them for it, or change it in WebFiling so that only people you trust know it. GOV.UK advises changing the code when someone no longer authorised to file, such as a previous accountant, still knows it (GOV.UK: Company authentication codes).

General information, not personalised tax or accounting advice.