19 CFR 182.112: Goods re-entered after repair or alteration in Canada or Mexico.

(a) General. This section sets forth the rules that apply for purposes of obtaining duty-free treatment on goods returned after repair or alteration in Canada or Mexico as provided for in subheadings 9802.00.40 and 9802.00.50, HTSUS. Goods returned after having been repaired or altered in Canada or Mexico, regardless of whether the repair or alteration could be performed in the United States or has increased the value of the good and regardless of their origin, are eligible for duty-free treatment, provided that the requirements of this section are met. For purposes of this section, “repairs or alterations” means restoration, addition, renovation, re-dyeing, cleaning, re-sterilizing, or other treatment that does not destroy the essential characteristics of, or create a new or commercially different good from, the good exported from the United States.

(b) Goods not eligible for duty-free treatment after repair or alteration. The duty-free treatment referred to in paragraph (a) of this section will not apply to goods that:

(1) In their condition, as exported from the United States to Canada or Mexico, are incomplete for their intended use and for which the processing operation performed in Canada or Mexico constitutes an operation that is performed as a matter of course in the preparation or manufacture of finished goods; or

(2) Are imported under a duty-deferral program that are exported for repair or alteration and are not re-imported under a duty-deferral program.

(c) Documentation. The provisions of § 10.8(a), (b), and (c) of this chapter, relating to the documentary requirements for goods entered under subheading 9802.00.40 or 9802.00.50, HTSUS, will apply in connection with the entry of goods which are returned from Canada or Mexico after having been exported for repairs or alterations and which are claimed to be duty-free.