19 C.F.R. § 143.24
Customs Form 7501, or its electronic equivalent, may be prepared by importers or their agents or by Customs officers when it can be presented to a Customs cashier for payment of duties and taxes and for numbering of the entry before the merchandise is examined by a Customs officer. Where there is no Customs cashier, Customs Form 368 or 368A (serially numbered) or Customs Form 7501 must be used, and it shall be prepared by a Customs officer unless the form can be prepared under his control by the importer or agent for immediate use in clearing merchandise under the informal entry procedure. The conditions for the preparation of Customs Form 7501 by importers or their agents, as described in the first sentence of this section, do not apply to the acceptance of these entries for shipments not exceeding $250 in value released under a special permit for immediate delivery in accordance with part 142 of this chapter.
19 C.F.R. §143.24