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:
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.
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.