When you form a new Company, Companies House will send the Web Authentication Code by post to the Registered Office. 

Inform Direct will advise you of the postal address to which the code will be sent.

If you no longer have access to this address you will need to write to Companies House on your company notepaper explaining your situation. The letter will also need to be accompanied by a properly completed Form AD01 (change of Registered Office address).

If Companies House conclude that you have the authority to change the Registered Office they will update their records with the new Registered Office and then send the Authentication Code to this new address.

Note: This is not a quick process. It is always easier seeing if the occupants of the old address will pass on the letter with your authentication code. Also checking all previous correspondence you have had from Companies House. You may find the original letter with the code has been safely filed with the other incorporation documents.

You may be able to request a reminder of the Authentication Code to be sent to an active Officer's home address