26 C.F.R. § 49.4291-1
Except as otherwise provided in section 4263(a), every person receiving any payment for facilities or services on which a tax is imposed upon the payor thereof under chapter 33 shall collect the amount of the tax from the person making that payment. Under section 7501, all taxes collected in this manner are held by the collecting agent in trust for the United States. If the person from whom the tax is required to be collected refuses to pay it or if for any reason it is impossible for the collecting agent to collect the tax from that person, the collecting agent is required to report to the Commissioner the name and address of that person, the nature of the facility provided or service rendered, the amount paid therefore, and the date on which paid. Applicable October 1, 2004, this report must be made on or before the report due date. Upon receipt of this report the Commissioner will proceed against the person to whom the facilities were provided or the services rendered to assert the amount of tax due, affording that person the same conference, protest, and appellate rights as are available to other excise taxpayers. In addition, when a field or office audit of a collecting agent's records, or of a taxpayer's records, discloses that the collecting agent failed during prior reporting periods to collect taxes due, the Commissioner may assert those taxes directly against the person to whom the facilities were provided or the services rendered, whether or not the collecting agent had attempted collection or the person liable for the tax had refused payment thereof. For purposes of this section, the report due date is-
26 C.F.R. §49.4291-1