Line 12c
If you were a dual-status alien, check the box on line 12c. If you were a dual-status alien and you file a joint return with your spouse who was a U.S. citizen or resident alien at the end of 2025 and you and your spouse agree to be taxed on your combined worldwide income, don’t check the box. See Nonresident aliens and dual-status aliens , earlier, for more information on making the election for you and your spouse to be taxed on your combined worldwide income.