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HMRC internal manual

COTAX Manual

Case records: new company records: company registration numbers

It is very important to maintain accurate Company Registration Numbers (CRNs) on COTAX records for several reasons.

  • CRNs are unique and cannot change even if a company changes its name or Registered Office address.
  • They are used for data matching and risk assessment.
  • The link between Companies House and COTAX relies on CRNs to identify the correct record to which to apply amendments.

New COTAX records are set up automatically through the Companies House link and so should always show the correct CRN. You only need to set up a record manually for a registered company where COTAX has been unable to do so automatically using the Companies House data or a company was registered with Companies House before the automatic data feed to COTAX, but for some reason was not set up on COTAX.

It may take two working days for a company registering at Companies House to be set automatically on COTAX. To avoid duplicate records, you must be certain that a case has not been set up automatically before you set it up yourself.

When maintaining records, you must only enter a CRN that is assigned by:

  • Companies House in England and Wales, Scotland or Northern Ireland
  • the Financial Services Authority in the UK or
  • Companies House in Southern Ireland (Eire IE prefix CRNs).

COTAX validation makes sure that you must enter a Company Registration Number (CRN) for a company with the following status codes.

  • ‘C’ (Limited Company or PLC).
  • ‘S’ (Society registered under the Industrial Provident Societies Act).
  • ‘E’ (Close Investment Holding company).
  • ‘P’ (Public Corporation).

Only use an ‘FC’ prefix for foreign companies registered with Companies House in England and Wales and never add it to a numeric CRN issued by another country, such as the British Virgin Islands. Those companies should be set up as company status ‘F’ and show no CRN.

Use type ’O’ to set up other cases where there is no valid CRN but which require a COTAX record.

The CRN is made up of up to eight numerals or normally two alphabetical characters referred to as the prefix followed by up to six alphanumeric characters, the suffix.


  • the glossary entry for Company Registration Number Formats for further information on the CRN
  • COM40020 for a list of functions to use in particular situations
  • COM40021 for a list of forms relevant to this subject
  • COM40022 for legislation applying to this subject.