The SET service is being replaced by the Secure Data
Exchange Service (SDES). If you don’t already use SET then you must follow the new SDES guidance. If you already use SET, HM Revenue and Customs (HMRC) will contact you with details about how and when you can migrate over to SDES.
This service was designed to replace transfers of physical media like tapes, disks, CDs and paper.
HMRC’s services may be slow during busy times. Check if there are any current problems with this service, or times it won’t be available.