This error code is a HMRC error. The message reads:

The UKCompaniesHouseRegisteredNumber in the accounts must match the RegistrationNumber in the CT600.

The following element content values must match:

• CT600 - Registration number
• UK GAAP - UKCompaniesHouseRegisteredNumber

The Company Registration Number in the accounts must match the one in the CT600 return.

This is caused by the CRN in the accounts not being identical to the CRN in your CT600

We recommend checking your accounts production software and Sage Corporation Tax.

1. Make sure your Company Registration Number match exactly in each program
2. Regenerate the tagging file in your accounts production program and in Sage CT
   

   NOTE: Sage Accounts Production and Sage Accounts Production Advanced you should give the new HTML tagging file a distinct name to distinguish the correct file from the previously submitted incorrect file.

3. In Sage Corporation Tax, re-tag the Corporation Tax submission
4. Click Online Filing, then click Start Again
5. Select the new accounts tagging file