Creditors, including the ibet, can file detailed claims against the estate of a deceased person in probate court. An estate administrator is responsible for contacting creditors who may have a proof of claim.
Filing a proof of claim is a time sensitive matter and different courts administer probate proceedings with different deadlines.
Send your request for a proof of claim to the ibet Collection Advisory group in the area of the last address of the deceased. See Publication 4235, Collection Advisory Offices Contact Information PDF.