What is the Companies House authentication code?
The authentication code is a 6-character code, mixing letters and numbers, that Companies House issues to each company. According to Companies House’s guidance on authentication codes (updated 25 September 2026), it is “the equivalent of a company officer’s signature” for anything filed online.
That makes it one of the few pieces of company information worth guarding. Anyone holding the code and the company number can file documents in the company’s name, which is why Companies House only ever posts it.
The code is needed in three places:
- WebFiling, the Companies House website, for confirmation statements and other filings;
- Find and update company information, for some online changes;
- Commercial software, including accounts software, which sends the code with each filing.
Where can you find your code?
The code is on the letter Companies House posted to the company’s registered office when it was issued. It is not on the public register, and Companies House will not read it out on the phone or send it by email.
Places worth checking before asking for a new one:
- the incorporation pack, if the company was set up through a formation agent;
- old correspondence from an accountant who filed for the company;
- a password manager or the notes kept when the company was formed.
How do you get a new authentication code?
Request it by signing in to Companies House WebFiling with the company number. Two things can happen:
| Situation | What Companies House sends |
|---|---|
| The company already has a code | A reminder of the existing code |
| The company has no code, or it has been cancelled | A new code |
Either way it goes by post to the registered office and can take up to 10 working days to arrive. If the registered office can’t be reached, for example because it is an agent’s address the company no longer uses, Companies House can send the code to a director’s home address instead.
Overseas companies follow a different route through Find and update company information, and their code can only be used for package accounts.
When should you change it?
Change the code if someone who shouldn’t have it might: a former director, a former accountant or an agent the company has stopped using. Changing or cancelling it is done in WebFiling.
The change takes effect immediately. The old code stops working for everyone, including an accountant mid-way through a filing. Tell anyone who files for the company before changing it, so nothing is rejected close to a deadline.
Is the code being replaced by identity verification?
Not as far as any published guidance says. Since 18 November 2025 directors have had to verify their identity and receive an 11-character personal code, which belongs to the person rather than the company. The personal codes guidance (updated 13 July 2026) says only that “in the future” the personal code may also be needed to file for a company.
Identity verification for people who file at Companies House is planned for no earlier than November 2027, with at least six months’ notice. Until something changes, filings still need the company authentication code. The identity verification guide covers the personal code in detail.
What else does software filing need?
From 1 April 2028 accounts can only be filed with software, as explained on the WebFiling closure page. Software filing needs the authentication code plus a presenter account: a presenter ID and presenter authentication code that identify who is sending the filing. A director filing their own accounts can hold their own presenter account.
A Government Gateway login, used for HMRC, does not work at Companies House. The two systems are separate.
Why the code causes so many late filings
Searches for “companies house authentication code” run at about 2,400 a month in the UK, with a further 260 for “companies house auth code” and 110 for “lost companies house authentication code” (DataForSEO, November 2026). That steady volume reflects how often directors reach a filing deadline and find the code has gone missing.
The 10-working-day post time is what turns a lost code into a penalty. Accounts are late from the day after the deadline, and a code requested in the final week will usually arrive after it. Directors who file once a year tend to find the code is the part of the process they remember least.
Sources
- Company authentication codes for online filing (GOV.UK), updated 25 September 2026. Checked 6 November 2026.
- Companies House personal codes for identity verification (GOV.UK), updated 13 July 2026. Checked 6 November 2026.
- Using software to file your company's information (GOV.UK), updated 25 September 2026. Checked 6 November 2026.
Search figures are 12-month UK averages from DataForSEO (Google Ads data), pulled 6 November 2026. Spotted something out of date? Tell us and it will be corrected.