26 CFR 1.1402(a)-9: (a)-9 Puerto Rico.

(a) Residents. A resident of Puerto Rico, whether or not a bona fide resident thereof during the entire taxable year, and whether or not an alien, a citizen of the United States, or a citizen of Puerto Rico, shall compute his net earnings from self-employment in the same manner as would a citizen of the United States residing in the United States. See paragraph (d) of § 1.1402(b)-1 for regulations relating to nonresident aliens. For the purpose of the tax on self-employment income, the gross income of such a resident of Puerto Rico also includes income from Puerto Rican sources. Thus, under this special rule, income from Puerto Rican sources will be included in determining net earnings from self-employment of a resident of Puerto Rico engaged in the active conduct of a trade or business in Puerto Rico despite the fact that, under section 933, such income may not be taken into account for purposes of the tax under section 1 or 3.

(b) Nonresidents. A citizen of Puerto Rico who is also a citizen of the United States and who is not a resident of Puerto Rico will compute his net earnings from self-employment in the same manner and subject to the same provisions of law and regulations as other citizens of the United States.