Who must file Form 1042 or 1042-S, and what triggers withholding?

Form 1042 and Form 1042-S are how the US collects tax on income that flows out of the country to foreign hands. When a US payer sends a dividend, interest, a royalty, or a fee to a foreign person, the foreign recipient usually files no US return — so the law collects the tax at the source, by making the payer withhold it and report it. Form 1042 is the payer's annual return of that withholding; Form 1042-S is the per-recipient statement that itemizes it. Like the other international information returns they compute no tax of their own — but unlike them, real money rides on top: under §1461 the withholding agent is personally liable for any tax it should have withheld and did not. A missed Form 5471 costs a flat penalty; a missed Form 1042 obligation can cost the tax itself.

This guide works the threshold question that precedes the forms' boxes and income codes: did someone pay US-source income to a foreign person in a way that required withholding — and who is the "withholding agent" on the hook to report it? Form 1042 has no filer-category system. The structure is a withholding agent, a payment of US-source FDAP income (under Chapter 3, §§1441–1442, with a Chapter 4 / FATCA overlay), and the liability that makes the report matter. We work who is an agent, then what is subject to withholding, then the FATCA layer on top.

In plain terms if your client pays a foreign person or company US-source money that isn't wages — a dividend, interest, rent, a royalty, a service fee — they almost certainly have to withhold US tax (usually 30%, less if a treaty applies) and report it. Form 1042 is the once-a-year summary they file; Form 1042-S is the slip they send each foreign payee (and the IRS), one per payee per kind of income. And it is not just paperwork: the payer — the "withholding agent" — is personally liable for tax it failed to withhold. PILOT determines whether that filing obligation exists; it never computes the rate or the tax.

Two forms, one regime

The two forms are a matched pair — an annual return and the statements that feed it — filed by the same withholding agent.

Form 1042 — the withholding agent's annual return

Form 1042 is the agent's single annual return. It reconciles, for the calendar year, the total US-source amounts paid to foreign persons, the tax withheld under Chapter 3 (the ordinary nonresident-alien and foreign-corporation withholding), and the tax withheld under Chapter 4 (FATCA) — one consolidated return covers both. It reports the agent's own withholding liability, which is why it is filed even by an agent that uses third parties to make payments.

Form 1042-S — the per-recipient statement

Form 1042-S is the income-specific statement. The agent files a separate Form 1042-S for each recipient, each type of income, and each withholding rate — and furnishes a copy to the payee. The volume can be large: a fund with 100 foreign investors paying four kinds of US-source income can generate 400-plus Forms 1042-S. The 1042-S is the foreign-payee counterpart of the domestic Form 1099 — it tells the IRS (and the payee) what was paid and what was withheld, payee by payee.

In plain terms think of Form 1042 as the cover return (one a year, the totals) and Form 1042-S as the individual slips behind it (one per foreign payee per income type, like a 1099 for foreign recipients). The agent files both — the totals with the IRS, and a slip to each payee.

Who is a withholding agent?

Everything turns on this, and the net is deliberately wide. A withholding agent is not just "the US company that owes the money." The regulation defines it broadly:

For purposes of chapter 3 of the Internal Revenue Code and the regulations under such chapter, the term withholding agent means any person, U.S. or foreign, that has the control, receipt, custody, disposal, or payment of an item of income of a foreign person subject to withholding …

— Treas. Reg. §1.1441-7(a)(1)

So a US or foreign bank, broker, custodian, intermediary, partnership, fund, employer, fiduciary, or US branch that controls or pays out US-source income to a foreign person is a withholding agent — the obligor's identity does not control. More than one person in a payment chain can qualify; when that happens, "only one tax is required to be withheld and deposited" (Reg §1.1441-7(a)(1)). The reason this breadth matters is the liability rule — see Penalties — which falls on the agent, not the foreign payee.

Example 1 — the agent is whoever controls the payment. USP A, a US brokerage, holds an investment account for FC B, a foreign corporation, and pays US-source dividends and interest into it. USP A is a withholding agent under Reg §1.1441-7(a)(1) — it controls and makes the payment — even though it is not the company that issued the stock. It withholds and files Form 1042 plus a Form 1042-S for FC B. (If a foreign intermediary bank also stands in the chain, it too can be a withholding agent, but only one tax is withheld on the payment.)

What is subject to withholding — US-source FDAP

Chapter 3 withholding reaches US-source "FDAP" income — fixed or determinable annual or periodical income — and the default rate is 30%:

… all persons, in whatever capacity acting … having the control, receipt, custody, disposal, or payment of any of the items of income specified in subsection (b) (to the extent that any of such items constitutes gross income from sources within the United States), of any nonresident alien individual or of any foreign partnership shall … deduct and withhold from such items a tax equal to 30 percent thereof …

— IRC §1441(a)

The "items of income" are the broad list of passive, recurring US-source payments:

The items of income referred to in subsection (a) are interest …, dividends, rent, salaries, wages, premiums, annuities, compensations, remunerations, emoluments, or other fixed or determinable annual or periodical gains, profits, and income …

— IRC §1441(b)

That last catch-all — "fixed or determinable annual or periodical" (FDAP) — is the concept that defines the regime: dividends, interest, rents, royalties, and service fees are the everyday examples. For payments to foreign corporations, §1442 applies the very same machinery:

In the case of foreign corporations subject to taxation under this subtitle, there shall be deducted and withheld at the source in the same manner and on the same items of income as is provided in section 1441 a tax equal to 30 percent thereof.

— IRC §1442(a)

Two points a generalist must hold onto. First, the 30% is a default, not a floor — an income-tax treaty often reduces it (commonly to 15%, 10%, or 0%), and statutory exemptions remove it entirely, most importantly the portfolio-interest exemption (§1441(c)(9), cross-referring to §871(h)) and bank-deposit interest. Second — and this trips people up — a reduced or zero treaty rate does not remove the filing. The agent still files Form 1042-S reporting the income and the reduced rate, with the payee's Form W-8BEN / W-8BEN-E on file as the basis for the lower rate.

Example 2 — a royalty, and the treaty rate that still gets reported. USP A pays a $100,000 royalty to FC B for the US use of a patent. That is US-source FDAP, so A withholds 30% and files Form 1042 plus a Form 1042-S for FC B. Now suppose FC B furnishes a valid W-8BEN-E claiming a treaty that drops the royalty rate to 0%. A withholds nothing — but still files the Form 1042-S, reporting the income at the 0% treaty rate. A reduced rate changes the number, not the filing.

The boundary: effectively connected income is not FDAP

The most important boundary is between FDAP (passive, gross-basis income that Chapter 3 withholds) and effectively connected income (ECI) — income from a US trade or business, taxed on a net basis. ECI is carved out of §1441 withholding:

No deduction or withholding under subsection (a) shall be required in the case of any item of income (other than compensation for personal services) which is effectively connected with the conduct of a trade or business within the United States …

— IRC §1441(c)(1)

A foreign person with ECI reports and pays on its own US return; the payer does not withhold under §1441. And where that ECI is earned through a partnership with foreign partners, a different withholding regime applies — §1446, reported on Form 8804/8805, not Form 1042. FDAP runs through Form 1042; effectively connected income does not.

Example 3 — the same payment, on the ECI side of the line. USP A pays FC B for services, but the income is effectively connected with FC B's own US trade or business, and FC B furnishes a Form W-8ECI. Now §1441(c)(1) applies: no Form 1042 withholding — FC B reports the income on its own US return. Had FC B instead earned that effectively connected income as a partner in a US partnership, the partnership would withhold under §1446 and report on Form 8804/8805. Same dollars, a different regime, because the income is effectively connected rather than FDAP.

The Chapter 4 (FATCA) overlay

Layered on top of the ordinary Chapter 3 rules is Chapter 4 — FATCA (§§1471–1474), which imposes its own 30% withholding on a "withholdable payment" made to a foreign financial institution that is not FATCA-compliant:

In the case of any withholdable payment to a foreign financial institution which does not meet the requirements of subsection (b), the withholding agent with respect to such payment shall deduct and withhold from such payment a tax equal to 30 percent of the amount of such payment.

— IRC §1471(a)

A "withholdable payment" is, in essence, the same US-source FDAP income (plus certain gross proceeds) (§1473(1)). The practical points for a generalist: Chapter 4 withholding is reported on the same Form 1042 / 1042-S as Chapter 3 — one consolidated return covers both — and the two regimes do not stack: when Chapter 4 withholding has been applied to a payment, the Chapter 3 obligation on that payment is treated as satisfied. The FATCA classification work — diligencing a payee's FATCA status, and the separate Form 8966 FATCA report — is a specialist exercise beyond determining whether a Form 1042/1042-S is required.

Example 4 — a dividend to a non-compliant institution. USP A pays a US-source dividend to a foreign bank that has not met its FATCA requirements (a nonparticipating foreign financial institution). Under §1471(a), A withholds 30% as Chapter 4 withholding and reports it on the same Form 1042 / 1042-S — it does not also withhold a second 30% under Chapter 3 on the same dollars.

Other payments that land on Form 1042

FDAP withholding is the core, but the Form 1042 "Who Must File" list is a little broader, and a complete answer names the rest. Form 1042 is also the return for: an eligible deferred compensation item paid to a covered expatriate (or a distribution from a nongrantor trust to one) under §877A; certain specified federal procurement payments to foreign persons under §5000C; gross investment income paid to a foreign private foundation under §4948(a); and certain amounts that are reported on Form 1042-S even though they ride other regimes — a publicly traded partnership's distribution of effectively connected income under §1446, and §1445 (FIRPTA) amounts. These are narrower fact patterns; the everyday Form 1042 question is the FDAP one above.

Due dates and how it is filed

• Form 1042 is due March 15 for the prior calendar year — filed separately to the IRS service center in Ogden, UT, or electronically; it is not attached to the agent's income-tax return. An extension of time to file is requested on Form 7004, but it does not extend the time to deposit the tax.
• Form 1042-S is due March 15 as well — both filed with the IRS and furnished to each recipient.
• Electronic filing is now the norm, not the exception. The aggregate 10-information-return threshold (Reg §301.6011-2, as amended by T.D. 9972, effective for returns required to be filed on or after January 1, 2024) sweeps most filers into mandatory e-filing; in addition, a financial institution must e-file Form 1042 regardless of volume, and so must a partnership with more than 100 partners. (Forms 1042-S are transitioning from the legacy FIRE system to the IRS's IRIS platform.)

The March 15 deadline is earlier than the Form 1040 / 1120 / 1065 deadlines — a calendar trap for agents who treat 1042 as just another return.

Penalties — the agent bears the risk

This is where Form 1042 departs from the §6038 information returns. The information-return penalties are real, but the defining exposure is the withholding agent's personal liability for the tax itself:

Every person required to deduct and withhold any tax under this chapter is hereby made liable for such tax and is hereby indemnified against the claims and demands of any person for the amount of any payments made in accordance with the provisions of this chapter.

— IRC §1461

So an agent that fails to withhold does not merely face a filing penalty — it is liable for the under-withheld tax, plus interest, and must chase the foreign payee for reimbursement if it can. (One offset: under §1463, if the foreign payee itself later pays the US tax on the income, the agent is no longer liable for the tax — but it remains on the hook for interest and penalties.) On top of that:

• §6651(a)(1) — late filing of Form 1042 (the return): 5% of the unpaid tax per month, up to 25%.
• §6721 / §6722 — the Form 1042-S information-return and payee-statement penalties: a per-form penalty (a few hundred dollars each, indexed annually, with annual caps), rising to a much larger per-form amount with no cap for intentional disregard. Reasonable-cause relief is available (§6724).

The contrast with the other international forms is worth stating plainly: Form 1042 is not a §6038-family return, so its exposure is not a flat $10,000 (Forms 5471 / 8858 / 8865), $25,000 (Form 5472), 10%-of-value (Form 926), or percentage-of-the-amount (Form 3520) penalty. Here the agent can owe the tax it should have collected — frequently the largest number in the analysis.

In plain terms the danger in this corner is not a fixed fine — it is that the IRS can come after the payer for the 30% it should have taken out but didn't, plus interest, even though the money has already left for the foreign recipient. That is why getting the withholding right (and collecting a valid W-8 before paying) matters as much as filing the forms.

Currency notes

The live currency story here is administrative, not OBBBA:

• The 30% rate is unchanged. §1441(a), §1442(a), and the §1471(a) FATCA rate are all longstanding; none was amended recently. Treaties and the portfolio-interest exemption still do the rate-reduction work.
• Electronic filing expanded sharply. The drop to a 10-return aggregate e-file threshold (T.D. 9972, effective for 2024 returns), the financial-institution and large-partnership mandates, and the FIRE-to-IRIS transition are the real recent changes — they affect how you file, not whether you must.
• Form revisions: the current Form 1042 is the 2025 revision and Form 1042-S the 2026 revision; IRS Publication 515 (2026) remains the canonical reference.
• OBBBA did not change these triggers. The 2025 reconciliation act (OBBBA, Pub. L. 119-21) §70353 restored §958(b)(4), which governs the downward attribution that decides controlled-foreign-corporation and PFIC status (the subject of the Form 5471 and Form 8621 guides). It did not amend §1441, §1442, §1461, or the Chapter 4 rules — so who must withhold and file Form 1042/1042-S is unchanged. That is why this guide carries the "No OBBBA Change" tag.

Relationships to other regimes and forms

Form 1042 sits at the center of the "paying foreign persons" map, and the boundaries with its neighbors are where mistakes happen.

• Form 8804 / 8805 — the effectively connected sibling. This is the single most important distinction: FDAP (passive US-source income) is withheld under §1441/§1442 and reported on Form 1042/1042-S; income effectively connected with a US trade or business that is allocable to a foreign partner is withheld by the partnership under §1446 and reported on Form 8804/8805. One regime for passive income, the other for business income earned through a partnership. (A foreign partner's sale of its partnership interest is yet another rule — §1446(f), reported on Form 8288.)
• Forms 1099 and W-2 — the domestic analog. Form 1042-S is to foreign payees what Form 1099 is to US payees. The line between them is the payee's status, established by the W-8 series (W-8BEN / W-8BEN-E / W-8ECI / W-8IMY) for foreign persons versus Form W-9 for US persons. Note the wage boundary: an NRA employee's wages for services performed in the US go on Form W-2 with graduated payroll withholding (Form 941) — not on Form 1042-S; a US-source dividend or royalty paid to that same person does go on Form 1042-S.
• Treaty documentation, not this return. The payee's own treaty-position disclosure (Form 8833) is filed with the recipient's return; the W-8 the agent collects (W-8BEN / W-8BEN-E) is the agent's basis for applying a reduced rate. The Form 1042-S is the agent's information return — it reports the rate used; it is not the payee's treaty claim.
• FIRPTA and FATCA reporting are their own regimes. US-real-property withholding under §1445 (FIRPTA) and the FATCA account report on Form 8966 are separate from the Form 1042 determination, even though some of their amounts are reported on Form 1042-S.

In plain terms the key fork is passive income versus business income: a dividend, interest, rent, or royalty to a foreign person is a Form 1042 question; a foreign partner's share of a US business's profits is a Form 8804 question; and US wages — even to a foreign worker — are a W-2 question. Sort the kind of payment first, and the right form follows. PILOT runs that determination across a structure — which of these each payer must file, and why.

What Form 1042 is not

Form 1042 and 1042-S report and collect — they do not compute your client's net US tax, and PILOT does not compute the withholding. The correct treaty rate, the FDAP-versus-ECI characterization at the margin, the FATCA status of a payee, the §1461 liability for an under-withholding, and the foreign person's ultimate US tax are all separate, downstream work that builds on the facts these forms capture. The first question — and the one this guide answers — is simply whether a Form 1042 / 1042-S obligation exists: for which withholding agent, on which payments, and how the treaty and ECI boundaries cut.