19 CFR §148.65

1. (a)Status as returning resident. A crewmember arriving in a vessel, vehicle, or aircraft from a foreign port who is a resident of the United States shall be considered a returning resident qualifying for the exemptions allowed under Chapter 98, Subchapter IV, Harmonized Tariff Schedule of the United States (19 U.S.C. 1202), and subpart D of this part if he permanently leaves the carrier without the intention of resuming his employment on the same or any other carrier that is engaged in international traffic.
2. (b)Statement of declaration. A resident crewmember who claims that articles declared by him are entitled to be passed free of duty and tax under the returning resident's exemption, shall include a legible statement on the declaration, Customs Form 5129, of the basis for his claim for entitlement to the resident's exemption.