Cross-border questions are layered by construction: the Code's international provisions, the regulations interpreting them, and, for the taxpayer's country pair, a treaty that can change the answer entirely. No practitioner holds all of it in memory, and the cost of a half-remembered rule is high, because the penalties in this area attach to information returns as much as to tax. The recurring territory looks like this.
Treaty positions
Treaties can reduce withholding rates, resolve dual residency through tie-breaker rules, and shield business profits that don't rise to a permanent establishment. But a treaty position must actually be established: the taxpayer must be a resident entitled to benefits, including under the limitation-on-benefits article, and disclosure on Form 8833 is required for many return-based positions. The treaty text and its technical explanation are the authority; summaries are not.
Outbound: §367, GILTI, and Subpart F
Moving assets or ownership outbound triggers its own regime. Section 367 can turn otherwise tax-free corporate transfers to a foreign corporation into recognition events. Once a foreign corporation is controlled by U.S. shareholders, the anti-deferral rules take over: Subpart F includes certain categories of the CFC's income currently, and GILTI sweeps in much of the rest of a CFC's active earnings as a current inclusion, with the deduction and foreign tax credit mechanics deciding the actual cost. The perennial questions: is the entity a CFC, who is a U.S. shareholder, which income is caught, and what elections change the result.
Inbound: FIRPTA and U.S. real estate
For foreign investors in U.S. real estate, FIRPTA treats gain on the disposition of a U.S. real property interest as effectively connected income, taxable in the U.S., and backs it up with withholding at the source under §1445, collected from the buyer. Whether an entity is a U.S. real property holding corporation, whether an exception or a withholding certificate applies, and how FIRPTA interacts with a treaty are the standard questions on any inbound real estate structure.
PFICs: the trap for portfolio investments
A U.S. person holding shares in a passive foreign investment company, a status many foreign mutual funds meet mechanically, faces the §1291 default regime: deferred-tax-plus-interest treatment on distributions and gains, unless a QEF or mark-to-market election changes the picture. PFIC status is tested annually on income and asset tests, the elections have their own timing rules, and Form 8621 reporting attaches. It's the classic case of a small investment generating outsized complexity.
Read from the sources, not from memory
Every question above shares one trait: the answer has to be read from the Code, the regulations, and the treaty: current text, exact words. That's how the AI Tax Assistant answers them: from the primary authorities themselves, with a clickable citation on every claim, so the treaty article or regulation behind an answer is one click from your screen. Ask the question in one line; verify the source before you rely on it.
Shashank Sharma is the founder of Partnertax.ai, an AI tax assistant for tax professionals, built on cited IRS and Treasury sources.