Form 1120-F for a Canadian Corporation: When to File

A Canadian corporation files Form 1120-F for any year it’s engaged in a trade or business in the United States, even when the Canada-US treaty means it owes no US tax because it has no permanent establishment there. It also files when it has US-source income that withholding didn’t fully cover, or when it wants a refund. Filing on time is what keeps the company’s deductions. For how this fits with your other structure choices, start with the cross-border business structures comparison.

When does a Canadian corporation have to file Form 1120-F?

The Form 1120-F instructions say a foreign corporation must file if, during the year, it was engaged in a trade or business in the United States “whether or not income from such trade or business is exempt from U.S. tax under a tax treaty,” had income treated as effectively connected with a US business, or had US-source income whose tax wasn’t fully satisfied by withholding at source.

The same instructions add three more triggers that catch Canadian companies: claiming a refund, claiming any deduction or credit, and taking a treaty position that has to be disclosed on Form 8833. A corporation with no gross income because of a treaty exemption still files to show the income was exempt.

When a Canadian company does have income effectively connected with a US business, IRC 882(a) taxes that net income at the regular corporate rates in section 11, which IRC 11(b) sets at 21 percent. The treaty then narrows what the US may tax. Under Article VII, a Canadian resident’s business profits are taxable only in Canada unless it carries on business in the US through a permanent establishment, and then only the profits attributable to it.

Article V of the treaty defines a permanent establishment, and these are the parts that usually decide a Canadian company’s case:

• A fixed place of business such as an office, branch, factory or workshop is a permanent establishment.
• A dependent agent counts if they have, and habitually exercise, authority to conclude contracts in the company’s name.
• Storage, display or delivery facilities, and a stock of goods kept for those purposes, are excluded from the definition.
• Independent agents (a broker or commission agent acting in the ordinary course of their business) don’t create one.
• Services create a deemed permanent establishment if an individual is in the US 183 days or more in a 12-month period and more than 50 percent of the company’s gross active business revenue comes from their US services, or if services on the same or connected projects run 183 days or more in a 12-month period.

“Trade or business within the United States” has no complete statutory definition, but IRC 864(b) says it includes performing personal services in the US. Whether shipping goods to US buyers from Canada amounts to a US business turns on the facts, which is exactly why the protective return exists.

What is a protective 1120-F, and why file one?

A protective return is a Form 1120-F filed on time by a company that has decided it has no effectively connected income, or no US tax because of the treaty. Under Treas. Reg. 1.882-4(a)(3)(vi), it protects the right to deductions and credits if the IRS later decides the original call was wrong. You report no income, just attach a statement.

The stakes come from IRC 882(c)(2): a foreign corporation gets the benefit of its deductions and credits “only by filing or causing to be filed” a true and accurate return. The regulation sets what “on time” means for this purpose:

• Prior year filed, or first required year: the return must be filed within 18 months of its due date.
• Prior year not filed: the earlier of 18 months after the due date or the date the IRS mails a notice saying the return hasn’t been filed and no deductions or credits may be claimed.
• Waiver: the IRS can waive the deadline if the company acted reasonably and in good faith, but not if it knew it had to file and chose not to.

The instructions list the few items allowed even on a late return: the charitable contributions deduction, the credit from Form 2439, the credit for federal tax on fuels, and US tax paid or withheld at source. Everything else, such as the wages, rent and other expenses you’d deduct against effectively connected income, rides on filing within that window.

To file one, check the “Protective return” box, complete the identifying items, and if the position rests on a treaty exemption, attach a completed Form 8833.

Do I need Form 8833 with a treaty-exempt 1120-F?

Yes, in the usual case. IRC 6114 requires disclosure of any position that a treaty overrules or modifies the Code, and Treas. Reg. 301.6114-1 names the exact Canadian-company position: that effectively connected income “is not attributable to a permanent establishment” in the US.

The 1120-F instructions build this into the form. If you answer “Yes” to item K(1) (you had effectively connected income) and “No” to item L (no permanent establishment), you complete item W(1) and attach Form 8833 with a statement of the nature and amount, or a reasonable estimate, of the gross receipts exempt because you have no permanent establishment. The Form 8833 itself lists a treaty reduction of the branch profits tax as another position that’s specifically reportable.

Skipping it is expensive. IRC 6712 imposes a penalty of $1,000 for each failure, or $10,000 in the case of a C corporation. IRC 1361(a)(2) defines a C corporation as any corporation that isn’t an S corporation, and only a domestic corporation can be an S corporation, so a Canadian company faces the $10,000 figure for each position left undisclosed. Our Form 8833 guide covers how the form is filled out.

When is Form 1120-F due, and can I extend it?

It depends on whether the company keeps an office or place of business in the US. With one, the return is due by the 15th day of the 4th month after year end (the 15th day of the 3rd month for a June 30 year end). With none, it’s due by the 15th day of the 6th month. A deadline on a weekend or legal holiday moves to the next business day.

Those rules come from the Form 1120-F instructions. For a calendar-year Canadian corporation, they work out as follows.

Tax year	US office or place of business	No US office or place of business	Extended with Form 7004
2025	April 15, 2026	June 15, 2026	October 15, 2026 or December 15, 2026
2026	April 15, 2027	June 15, 2027	October 15, 2027 or December 15, 2027

To extend, file Form 7004 by the original due date. The Form 7004 instructions say the automatic extension is generally 6 months and that “Form 7004 does not extend the time to pay any tax due.” An extension doesn’t buy extra time on the protective window, though: the regulation counts the 18 months from the due date under section 6072, which is the original due date.

Late returns cost money when tax is owed. The 1120-F instructions set the failure-to-file penalty at 5 percent of the unpaid tax per month or part month, up to 25 percent, and for a return required to be filed in 2026 that’s more than 60 days late, a minimum of the smaller of the tax due or $525.

What is the branch profits tax for a Canadian company?

It’s a second US tax on a foreign corporation that operates through a US branch instead of a US subsidiary. IRC 884 imposes 30 percent of the “dividend equivalent amount,” which the instructions describe as after-tax effectively connected earnings not reinvested in the US business by year end.

The treaty cuts it hard. Article X(6) caps the additional tax at 5 percent, and only on “earnings” left after subtracting, among other things, five hundred thousand Canadian dollars ($500,000), reduced by any amount the company has already deducted, or an associated company has deducted for the same or a similar business. That exemption is cumulative: once it’s used up, it’s gone.

Two conditions sit on top. The instructions say a corporation generally has to meet the treaty’s limitation on benefits article (or be a qualified resident) in the year it has a dividend equivalent amount to get treaty benefits on this tax. And Form 8833 lists a treaty reduction of the branch profits tax as a reportable position. The branch tax is computed in Section III of Form 1120-F. For the subsidiary-versus-branch trade-off, see US subsidiary vs US branch for a Canadian company, and for the wider rule set on effectively connected income, foreign-owned US business tax rules.

When is no Form 1120-F needed?

When the company has no US trade or business and its US-source investment income was fully taxed by withholding. The instructions exempt a foreign corporation that “did not engage directly or indirectly in a U.S. trade or business during the year, and its full U.S. tax was withheld at source,” or whose only US-source income is exempt under section 881(c) or (d).

That income is the passive kind. IRC 881(a) taxes a foreign corporation’s US-source dividends, interest, rents, royalties and similar income at 30 percent of the gross amount, collected by the payer. The treaty lowers the rate: for example, Article X caps dividends at 5 percent for a company owning at least 10 percent of the voting stock and 15 percent otherwise. The company claims the rate by giving the payer a Form W-8BEN-E; see W-8BEN-E for a Canadian corporation.

If the payer withheld too much, the company files Form 1120-F to get it back, using the simplified refund procedure in the instructions with proof of withholding such as Form 1042-S.

Decision table: your US activity and what to file

Use this as a starting map. Each row turns on facts, and the treaty test is the permanent establishment test in Article V.

Your US activity	File 1120-F?	Forms and schedules	Due date, calendar year
US dividends or interest only, correct treaty rate withheld	No (exception)	W-8BEN-E to the payer	n/a
Same, but over-withheld	Yes, to claim the refund	1120-F refund procedure, 1042-S as proof	15th day of 6th month
Selling to US customers from Canada, nobody and nothing in the US	Protective return recommended	Protective box, statement, 8833 if relying on the treaty	15th day of 6th month
US business activity but no permanent establishment (for example a storage and delivery facility)	Yes	1120-F, item W(1), Form 8833	15th day of 4th month if the company keeps a US office or place of business, otherwise 6th
Employee or dependent agent who habitually signs contracts in the company’s name, or a US office	Yes, with tax	Full 1120-F, Section III branch profits tax, 8833 for any treaty reduction, Form 5472 if there are reportable related-party transactions	15th day of 4th month with a US office or place of business, otherwise 6th

The instructions describe Form 5472 as filed by a foreign corporation engaged in a US trade or business that had reportable transactions with a related party. And the federal return isn’t the whole story: the treaty’s Article II covers only the “Federal income taxes imposed by the Internal Revenue Code,” so each state where the company has people, property or sales has to be checked on its own rules.

Moving south yourself?

If you own the Canadian corporation and you’re moving to the US as well, the company’s own US filings are only one piece. Your move changes how the corporation itself is taxed in your hands, which our guide on what happens to your Canadian corporation when you move to the US covers, and the full personal sequence is in tax planning before a move from Canada to the US.

This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.