(a) General. All merchandise imported into the United States is required to be entered, unless specifically excepted.

(b) Exceptions. The following are the exceptions to the general rule:

(1) The exemptions listed in General Note 19 to the Harmonized Tariff Schedule of the United States (HTSUS).

(2) Vessels (not including vessels classified in headings 8903 and 8907 and subheadings 8905.90.10 and 8906.00.10 or in Chapter 98, HTSUS, such as under subheadings 9804.00.35 or 9813.00.35). See also Chapter 89, Additional U.S. Note 1, HTSUS.

(3) Instruments of international traffic described in § 10.41a and § 10.41b(b) of this chapter, under the conditions provided for in those sections. See also Chapter 98, Subpart III, U.S. Notes 3 and 4, HTSUS.

(4) Railway locomotives classified in heading 8601 or 8602, HTSUS, and freight cars classified in heading 8606, HTSUS, on which no duty is owed (see paragraph (d) of this section). See Chapter 86, Additional U.S. Note 1, HTSUS; Chapter 99, Subchapter V, U.S. Note 9, HTSUS; see also 19 CFR part 123 for reporting requirements for railway equipment brought into the United States from Canada or Mexico.

(c) Undeliverable articles. The exemption from entry for undeliverable articles under General Note 19(e), HTSUS, is subject to the following conditions:

(1) The person claiming the exemption must submit a certification (documentary or electronic) that:

(i) The merchandise was intended to be exported to a foreign country;

(ii) The merchandise is being returned within 45 days of departure from the United States;

(iii) The merchandise did not leave the custody of the carrier or foreign customs;

(iv) The merchandise is being returned to the United States because it was undeliverable to the foreign consignee; and

(v) The merchandise was not sent abroad to receive benefit from, or fulfill obligations to, the United States as a result of exportation.

(2) Upon request by Customs, the person claiming the exemption shall provide evidence required to support the claim for exemption.

(d) Railway locomotives and freight cars. To be excepted from entry, railway locomotives and freight cars described in Additional U.S. Note 1 of Chapter 86, HTSUS, and railway freight cars from Canada described in subheading 9905.86.05 or 9905.86.10, HTSUS, are subject to the following requirements, as applicable:

(1) For a railway freight car described in subheading 9905.86.05, HTSUS, the importer shall certify, subject to Customs verification, that the freight car was produced before July 1, 1991, or if admitted after July 1, 1994, that the freight car was produced not less than 3 years before the date of importation;

(2) For a railway freight car described in subheading 9905.86.10, HTSUS, the importer shall certify, subject to Customs verification, that the freight car will be exported within 1 year from the date of importation. (Any railway freight car admitted into the United States under this provision which is not exported within the 1-year period becomes subject to entry and the payment of any applicable duties.);

(3) For railway locomotives and freight cars described in Additional U.S. Note 1 of Chapter 86, HTSUS, and railway freight cars described in subheading 9905.86.05 or 9905.86.10, HTSUS, to be released in accordance with paragraph (b)(4) of this section, the importer shall first file a bond on Customs Form 301, containing the bond conditions set forth in either § 113.62 or 113.64 of this chapter.

(e) Informal entry. Merchandise qualifying for informal entry by regulation, pursuant to 19 U.S.C. 1498, is exempt from formal entry under 19 U.S.C. 1484 and this part, but must be entered as required under applicable regulations (see part 143, subpart C, and §§ 10.151 through 10.153, 128.24, 145.31, 145.32, 148.12, 148.13, 148.51, and 148.62 of this chapter).