Engaged in a US trade or business: what triggers it and what you have to file

If you are a foreign company or individual with some activity touching the United States, the question of whether you are engaged in a US trade or business decides how your US income gets taxed, and often whether you have to file at all.

There is no statutory definition. It is a facts and circumstances test, and the standard courts apply is whether the activity is considerable, continuous, and regular rather than sporadic. If you are engaged, your US-connected income is taxed on a net basis at ordinary rates and you file a US return. If you are not, your US income is generally limited to passive categories taxed at a flat rate withheld at source, and there may be nothing to file.

A treaty can change the answer again, but only if you file to claim it. Here is how the test works, what commonly triggers it by accident, and what the filing position needs to look like.

There is no definition, only a test

The Internal Revenue Code never defines what it means to be engaged in a trade or business within the United States. It tells you the consequences and leaves the trigger to case law.

The standard that courts apply asks whether the activity is considerable, continuous, and regular, undertaken for profit rather than as a hobby or an isolated transaction. A single sale does not create it. Sustained selling, servicing, or producing inside the United States does.

Two points follow that people misread. First, the test applies to foreign persons and foreign corporations. A US company is not evaluated against it, because it is already taxable on its worldwide income. Second, the amount of income is not the trigger. Activity is. A foreign company can be engaged in a US trade or business and lose money, and it still has the filing obligation.

Being engaged changes how you are taxed, not just whether

This is the practical consequence and it runs in both directions.

If you are engaged, income effectively connected with that trade or business is taxed on a net basis at ordinary graduated rates. You deduct your expenses against it and file a return. Foreign corporations also face a branch profits tax on earnings treated as repatriated, on top of the income tax, though treaties commonly reduce it.

If you are not engaged, your US-source income falls into the fixed or determinable annual or periodical category. Dividends, interest, rents, and royalties are taxed at a flat 30% on the gross amount, withheld at source by the payer, with no deductions. A treaty may reduce the rate.

The counterintuitive result is that being engaged is often better. Net taxation with deductions at graduated rates can produce a smaller bill than 30% of gross. The problem is rarely the tax rate. It is discovering the obligation years late.

Agents, employees, and partnerships can create it for you

You do not have to open an office to become engaged. Three routes create it through other people.

Dependent agents. Someone in the United States who acts on your behalf, works substantially for you, and habitually concludes contracts or takes orders can create a US trade or business for you. An independent agent acting in the ordinary course of their own business generally does not.

Employees. People on your payroll performing services inside the United States are the most direct route. This catches companies that hire a US-based salesperson or engineer without considering the entity-level consequence.

Partnerships. If a partnership is engaged in a US trade or business, each partner is treated as engaged, including foreign partners who have never set foot in the country. This runs from the partnership down to the partners, not from a partner up to the partnership, which is the opposite of what a lot of guidance says. The partnership also has to withhold on effectively connected income allocable to its foreign partners.

A subsidiary is different. A US subsidiary is a separate taxpayer, and its activities do not by themselves make its foreign parent engaged in a US trade or business. That separation is the reason many foreign companies incorporate a US entity rather than operating directly.

Trading securities for your own account is protected

A specific safe harbor says that trading in stocks, securities, or commodities for your own account does not make you engaged in a US trade or business, even if you do it through a US broker or a US-based agent with discretionary authority.

The exception is dealers. Someone trading as a dealer, holding inventory and transacting with customers, falls outside the safe harbor. The line between a trader and a dealer has been litigated, and a fund whose manager carried on lending and origination activity in the United States has been found to be engaged in a US trade or business on that basis rather than protected by the safe harbor.

Passive holding is clearly outside. Buying shares in a US company and doing nothing else is an investment, not a trade or business, regardless of the size of the position.

US real estate is the common exception

Rental income from US property is the case that most often surprises people, because the default treatment is unhelpful.

Passive rental income is generally treated as fixed or determinable income, taxed at 30% of the gross rent with no deduction for mortgage interest, property tax, depreciation, or management costs. On a leveraged property that can exceed the actual profit.

There is an election that fixes this. A nonresident individual or foreign corporation can elect to treat income from US real property as effectively connected, which switches the treatment to net taxation with deductions at ordinary rates. It has to be made affirmatively, and property owners who never made it are frequently paying tax on gross rent they never kept.

Disposing of the property is a separate regime. Gain on the sale of a US real property interest is treated as effectively connected income by statute, and the buyer is generally required to withhold a percentage of the gross purchase price and remit it, with the seller reclaiming any excess by filing.

Filing is what preserves your position

A tax treaty may mean you are not taxable on business profits unless you have a permanent establishment in the United States, which is a higher threshold than being engaged in a trade or business. A dependent agent or a fixed place of business can create a permanent establishment. A preparatory or auxiliary presence usually does not.

The mistake is treating treaty protection as a reason not to file. It is the opposite. To claim a treaty position you disclose it on a return, with the treaty-based position statement attached. Filing a protective return when you believe you owe nothing is what preserves the position if the IRS later disagrees.

There is a harder consequence for foreign corporations. The right to claim deductions against effectively connected income depends on filing a true and accurate return, and filing late enough can forfeit deductions entirely. A foreign corporation that stays quiet for years and is then assessed can find itself taxed on gross receipts rather than on profit.

The forms differ from the domestic ones. A foreign corporation files Form 1120-F. A nonresident individual files Form 1040-NR. A US entity in the structure files the ordinary domestic returns alongside its own foreign-ownership reporting, and that is the route most companies end up taking. Inkle files Form 1120 and the Form 5472 reporting that goes with a foreign-owned US entity, and obtains Form 8802 residency certificates where a treaty claim needs one.

The bottom line

Work out whether you are engaged before you work out what you owe, because the answer changes the entire mechanism rather than the rate. Activity inside the United States is what creates it, not revenue, and people you hire or partnerships you join can create it without any decision on your part. If you hold US real estate and have never made the net election, check that first, because it is the most commonly missed item on this list. And if you are relying on a treaty, file the return that claims it, since treaty protection asserted only in your own records protects nothing.

Frequently asked questions

What does engaged in a US trade or business mean?

It means carrying on activity in the United States that is considerable, continuous, and regular rather than isolated. There is no statutory definition, so it is decided on facts and circumstances. The consequence is that your US-connected income is taxed on a net basis at ordinary rates and you have a US filing obligation.

Does having US customers make me engaged in a US trade or business?

Not by itself. Selling to US customers from abroad, with no people, office, or dependent agent in the United States, generally does not create it. What tends to create it is performing activity inside the country, through employees, a fixed place of business, or an agent acting habitually on your behalf.

Am I engaged if I trade US stocks through a US broker?

Generally no. A safe harbor covers trading in stocks, securities, and commodities for your own account, even through a US broker or a US agent with discretion. The exception is acting as a dealer, and the boundary between trading and dealing has been litigated more than once.

Does a tax treaty mean I do not have to file?

No. A treaty may mean you owe no US tax without a permanent establishment, but claiming that position requires filing a return with a treaty-based position disclosure. Not filing does not assert the treaty, and for foreign corporations it can also forfeit the right to deduct expenses.

Is rental income from US property effectively connected income?

Not by default. Passive rent is generally taxed at 30% of the gross amount with no deductions. An election is available to treat the income as effectively connected, which allows deductions and ordinary rates, and it has to be made affirmatively rather than assumed.

What does a foreign corporation file?

Form 1120-F, with a treaty-based position statement attached where a treaty is being claimed. A nonresident individual files Form 1040-NR. Filing on time matters beyond the usual penalties, because the ability to claim deductions against effectively connected income depends on having filed.