Every cross-border tax question eventually collapses into the same underlying issue: is this dollar of income U.S.-source or foreign-source? It sounds like a formality, but the answer drives some of the most consequential numbers on an international return — the foreign tax credit limitation under IRC §904, whether a nonresident alien owes U.S. tax at all under §871 or §882, which income falls into which FTC “basket,” and how a tax treaty's sourcing tie-breakers apply.

The green card test — not the card itself — determines U.S. tax residency. This week's Tax Talk Thursday walks through dual-status filing, the LTR 8-of-15-year test, Form 8854 mechanics, and the compliance risks of an expired-but-unterminated green card.