Incorrect Companies House Authentication Code
You will need to double-check your Companies House authentication code. This is a 6-digit alphanumeric code issued by Companies House to each company and it is used to submit any company information changes to Companies House as well as to submit the company’s annual returns.
If you have misplaced your code, you can request a reminder by signing into Companies House WebFiling - the code will be sent by post to your company's registered office and can take up to 10 working days to arrive.