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.

If you're a U.S. person receiving income from abroad, or a foreign person earning income connected to the U.S., withholding rules can catch you off guard. Getting the basics right now can prevent notices, penalties, and cash-flow surprises later.

Putting your spouse, child, or parent on the payroll is one of the most common — and most misunderstood — small business tax moves. Done correctly, family employment can shift income to lower tax brackets, unlock retirement plan contributions for a minor, and even eliminate certain payroll taxes entirely. Done carelessly, it's one of the fastest ways to draw an IRS examination, because the family relationship itself is a built-in audit flag.