Company Authentication Code: How to Find or Request Yours

The company authentication code is a 6-character code, made of letters and numbers, that Companies House issues to every UK company. It works like a signature: you need it to file accounts, a confirmation statement or changes to directors online. If you have lost it, you can request a new one through Companies House WebFiling, and it arrives by post at your registered office within about 10 working days.

Official Companies House links

• Request a code or change it: sign in to Companies House WebFiling.
• Cannot get post at the registered office? Ask for the code to go to your home address.
• Read the official guidance: Company authentication codes for online filing on GOV.UK.
• Look up your company: Find and update company information shows your registered office and filing dates.

What the authentication code is

Companies House treats the code as the equivalent of a company officer's signature on anything filed online. One code covers the whole company, not an individual director, and the same code works in WebFiling, in the Find and update company information service, and in accounting software that files with Companies House.

That is why it matters who holds it. Anyone with your company number and authentication code can file changes, including changing the registered office or appointing a director. Companies House recommends treating it with the same care as a bank card PIN.

Where to find your code

Before requesting a new code, check:

• The letter from Companies House sent when the company was incorporated, or when a code was last requested. It goes to the registered office address.
• Your formation agent or accountant. If someone set the company up for you, or files your accounts, they may already hold the code.
• Your own records. Some owners change the code to something memorable in WebFiling; if you did, it will be the one you chose.

If none of those work, request a reminder or a new code. If the company already has a code, Companies House posts a reminder of the existing one.

How to request a new code

1. Go to Companies House WebFiling and create an account or sign in. Since the 2025 changes, signing in uses a GOV.UK One Login.
2. Enter your company number. You can find it on the Companies House register if you do not have it to hand.
3. Choose to request an authentication code. Companies House posts it to the registered office address.
4. If you no longer have access to post at the registered office, use the home address request service instead.

Companies House will not email the code or read it out over the phone, so there is no faster route than the post.

How long it takes

Companies House says to allow up to 10 working days for the letter to arrive, and longer at busy times such as the weeks before common accounts deadlines. Request it well before your accounts or confirmation statement are due. Late filing penalties for a private company start at 150 pounds and rise to 1,500 pounds, and they double if accounts are late two years running.

Codes it is often confused with

Code	Who issues it	What it is for
Company authentication code	Companies House	Filing accounts, confirmation statements and changes for the company
Companies House personal code	Companies House	Proves an individual director or person with significant control has verified their identity
HMRC activation code	HMRC	Adding Corporation Tax, PAYE or VAT to your business tax account
Corporation Tax UTR	HMRC	The company's 10-digit tax reference; see how to find your UTR

Your HMRC Government Gateway login cannot be used to file at Companies House, and your Companies House code cannot be used with HMRC.

Keeping your code safe

• Mix letters and numbers if you change it, so it is not easy to guess.
• Share it only with someone you trust to file for the company, such as your accountant.
• Change it when an accountant, director or member of staff who knew it leaves.
• Report anyone who contacts you claiming to be from Companies House and asking for the code.

What Cloudkeepers can do

If we file your annual accounts and Corporation Tax return, we keep track of your filing dates and request your authentication code well ahead of time if you do not have it. Our company secretarial service also files your confirmation statement and director changes for you. When you switch to us, we also make sure your previous accountant's access is closed off by changing the code with you.