the employee shall make a return for the calendar year in respect of the employee tax not collected by the employer. Except as otherwise provided in this subparagraph, the return shall be made on Form 1040. The form to be used by residents of the Virgin Islands, Guam, or American Samoa is Form 1040SS. In the case of a resident of Puerto Rico who is not required to make a return of income under section 6012(a), the form to be used is Form 1040SS, except that Form 1040PR shall be used if it is furnished by the Internal Revenue Service to such resident for use in lieu of Form 1040SS.
26 C.F.R. §31.6011(a)-1