| 2020 | This service is temporarily unavailable. Please try again later. | The filing service is unavailable due to communication failure or other reasons. |
| 5012 | This field contains an invalid character. Please try again and if the problem recurs contact your software supplier. | The data used isn't within the set standards of the schema. |
| 5018 | Tax Office Number and Tax Office Reference in message header do not match values in message body. | All TaxOfficeNumber and TaxOfficeReference values within the submission must be the same. |
| 5020 | This message contains a form that is not currently supported for online submission. | You're trying to submit a form that HMRC has prohibited now. |
| 5020 | This submission must contain at least one form. | No forms in submission. |
| 5030 | Invalid value in Class tag. | Invalid Class value. |