This can also be called the Company Registration Number (CRN) and is allocated by Companies House on registration of a company and is an 8 digit number or 2 alpha characters followed by a 6 digit number. You will find it on any documentation received from Companies House and a company would normally display it on letter headings or compliment slips. If you cannot locate this number please contact your HM Revenue & Customs (HMRC) Corporation Tax Office.
Please note: When entering the CRN upon registration for the HMRC Corporation Tax online service, please omit any preceding letters or leading zeros.
For example: CRN AC097609 should be entered as 97609 and CRN 07589628 should be entered as 7589628.