Error 3001: Document has failed due to departmental specific logic in the body tag
IRIS KashFlow Payroll
This is a generic message generated by HMRC indicating ONLY that the submission has been rejected.
These types of errors usually occur when a field in your submission has an invalid data entry, ie. text in a number field, the wrong number of decimal places, an incorrect date format. They can also be caused by account issues with HMRC gateway service.
Usually, when a submission is rejected by HMRC with a 3001 error it is accompanied with further information about which data field their system has a problem with. This should tell you why the submission has been rejected, however, some of these messages can be difficult to interpret.