19 CFR § 24.5 - Filing identification number.
(a) Generally. Each person, business firm, Government agency, or other organization shall file Customs Form 5106, Notification of Importer's Number or Application for Importer's Number, or Notice of Change of Name or Address, with the first formal entry which is submitted or the first request for services that will result in the issuance of a bill or a refund check upon adjustment of a cash collection. A Customs Form 5106 shall also be filed for the ultimate consignee for which such entry is being made. Customs Form 5106 may be obtained from any Customs Office.
(b) Preparation of Customs Form 5106.
(1) The identification number to be used when filing Customs Form 5106 shall be:
(i) The Internal Revenue Service employer identification number, or
(ii) If no Internal Revenue Service employer identification number has been assigned, the Social Security number.
(2) If neither an Internal Revenue Service employer identification number nor a Social Security number has been assigned, the word “None” shall be written on the line provided for each of these numbers on Customs Form 5106 and the form shall be filed in duplicate.
(c) Assignment of importer identification number. Upon receipt of a Customs Form 5106 without an Internal Revenue Service employer identification number or a Social Security number, an importer identification number shall be assigned and entered on the Customs Form 5106 by the Customs office where the entry or request for services is received. The duplicate copy of the form shall be returned to the filing party. This identification number shall be used in all future Customs transactions when an importer number is required. If an Internal Revenue Service employer identification number, a Social Security number, or both, are obtained after an importer number has been assigned by Customs, a new Customs Form 5106 shall not be filed unless requested by Customs.
(d) Optional additional identification. Customs Form 5106 contains blocks for a two-digit suffix code which may be written in as an addition to the Internal Revenue Service employer identification number to provide optional additional identification. The two-digit suffix code may be used by a business firm having branch office operations to permit the firm to identify transactions originating in its branch offices, or by vessel owners to permit them to identify transactions associated with particular vessels. A separate Customs Form 5106 shall be required to report the specific suffix code and the name and address for each branch office or vessel to be identified. Transactions may be associated with a specific branch office or vessel by reporting the appropriate identification number, including the two-digit suffix code, on Customs Form 7501, or its electronic equivalent, or the request for services. Suffix codes may be either numeric, alphabetic, or a combination of both numeric and alphabetic, except that the letters O, Z, and I may not be used. The blocks may be left blank if the firm or vessel owner has no use for them and a “00” suffix will be automatically assigned.
(e) Retention of importer identification number. An importer identification number shall remain on file until 1 year from the date on which it is last used on Customs Form 7501, or its electronic equivalent, or a request for services. If not used for 1 year and there is no outstanding transaction to which it must be associated, the importer identification number will be removed from Customs files. To engage in future transactions described in paragraph (a) of this section, the person, business firm, Government agency, or other organization, previously covered by an importer identificatign number, must file another Customs Form 5106.
(f) “Freezing” importer identification information. Those importers identifying Customs transactions through the procedure specified in paragraph (d) of this section and desiring to ensure that they receive such Customs transaction notifications as may be issued may request Customs to “freeze” the name and address information, regardless of what is shown on the Customs Form 5106 or request for services, by designating the name and title/position of the individual in their company authorized to effect name/address changes to the Importer's Record Number (IRN) identification information, and specifying the IRNs and suffixes to be frozen and the mailing address and/or physical location address of the company where Customs notifications are to be directed. The request must be made in a separate writing on letterhead paper signed by the importer of record or his agent, whose name and title are clearly indicated. Participation in the “Freeze” Program is voluntary. Requests to participate should be sent to: the National Finance Center, U.S. Customs and Border Protection, Office of Administration, Revenue Division, 6650 Telecom Drive, Suite 100, Indianapolis, IN 46278, Attn: Freeze Program.