The BR3015 error is the result of a declaration being submitted by a party not authorised to do so. We most commonly see this error when a new user of Declaron submits a declaration without having completed the necessary authorisation for Revenue.
When you register with Declaron, we will ask you to complete a Customs and Excise Clearance Agent Form (previously known as AEP5). This form provides for "Authority allowing Customs Clearance Agents to use a Trader's EORI or TAN Account to pay Customs Taxes or Excise Duties." Declaron needs you have to completed this form, have submitted it to Revenue, and have received an acknowledgement that we have been appointed as your direct representative.
If you have not compeletd any of these steps, you will will get this error. You can find our everything you need to know about appointing Declaron as your customs agent by clicking here.