IRS – International Notices 3.38.147 Page 1 & 9
Article XXV refers to a tax treaty between the United States and Canada based on a Non-Discrimination provision which allows citizens/residents of Canada to figure their
1040NR tax based upon a hypothetical 1040 tax computed on married filing joint tax rates. The taxpayers must include worldwide income in their 1040 tax computation. Article
XXV returns can be recognized by any of the following on Form 1040NR:
Two names are present in the entity section of the return; or
Form 1040 or statement is attached with a hypothetical married filing joint tax rate computation; or
Statement attached indicating that a special computation permitted by the U.S./Canada Tax Treaty has been used; or
A notation of XXV is found on the return or attachments
Note:
Single taxpayers are not eligible to claim the benefits of Article XXV or to use the Tax rates for Head of Household. When the Article is claimed and the necessary
information is not included, the Form 1040NR is to be processed using Filing Status Code 1 for single.
Use the following formula to figure the computation for Article XXV:
(Form 1040NR Taxable income/Form 1040 Taxable Income) X 1040 Tentative Tax = Tax
Note:
Alternative Minimum Tax may still apply.
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US-Canada equal treatment is narrated in the following paragraph of US-Canada Income Tax Convention.

This consolidated version of the Canada-United States Convention with Respect to Taxes on Income and on Capital signed at Washington on September 26, 1980, as amended by the Protocols signed on June 14, 1983, March 28, 1984, March 17, 1995 and July 29, 1997, is provided for convenience of reference only and has no official sanction.

Article XXV

Non-Discrimination

1.  Citizens of a Contracting State, who are residents of the other Contracting State, shall not be subjected in that other State to any taxation or any requirement connected therewith which is other or more burdensome than the taxation and connected requirements to which citizens of that other State in the same circumstances are or may be subjected.

2.  Citizens of a Contracting State, who are not residents of the other Contracting State, shall not be subjected in that other State to any taxation or any requirement connected therewith which is other or more burdensome than the taxation and connected requirements to which citizens of any third State in the same circumstances (including State of residence) are or may be subjected.

3.  In determining the taxable income or tax payable of an individual who is a resident of a Contracting State, there shall be allowed as a deduction in respect of any other person who is a resident of the other Contracting State and who is dependent on the individual for support the amount that would be so allowed if that other person were a resident of the first-mentioned State.

4.  Where a married individual who is a resident of Canada and not a citizen of the United States has income that is taxable in the United States pursuant to Article XV (Dependent Personal Services), the United States tax with respect to such income shall not exceed such proportion of the total United States tax that would be payable for the taxable year if both the individual and his spouse were United States citizens as the individual’s taxable income determined without regard to this paragraph bears to the amount that would be the total taxable income of the individual and his spouse. For the purposes of this paragraph,

(a) the “total United States tax” shall be determined as if all the income of the individual and his spouse arose in the United States; and

(b) a deficit of the spouse shall not be taken into account in determining taxable income.

5.  Any company which is a resident of a Contracting State, the capital of which is wholly or partly owned or controlled, directly or indirectly, by one or more residents of the other Contracting State, shall not be subjected in the first-mentioned State to any taxation or any requirement connected therewith which is other or more burdensome than the taxation and connected requirements to which other similar companies of the first-mentioned State, the capital of which is wholly or partly owned or controlled, directly or indirectly, by one or more residents of a third State, are or may be subjected.

6.  Notwithstanding the provisions of Article XXIV (Elimination of Double Taxation), the taxation on a permanent establishment which a resident of a Contracting State has in the other Contracting State shall not be less favourably levied in the other State than the taxation levied on residents of the other State carrying on the same activities. This paragraph shall not be construed as obliging a Contracting State:

(a) to grant to a resident of the other Contracting State any personal allowances, reliefs and reductions for taxation purposes on account of civil status or family responsibilities which it grants to its own residents; or

(b) to grant to a company which is a resident of the other Contracting State the same tax relief that it provides to a company which is a resident of the first-mentioned State with respect to dividends received by it from a company.

7.  Except where the provisions of paragraph 1 of Article IX (Related Persons), paragraph 7 of Article XI (Interest) or paragraph 7 of Article XII (Royalties) apply, interest, royalties and other disbursements paid by a resident of a Contracting State to a resident of the other Contracting State shall, for the purposes of determining the taxable profits of the first-mentioned resident, be deductible under the same conditions as if they had been paid to a resident of the first-mentioned State. Similarly, any debts of a resident of a Contracting State to a resident of the other Contracting State shall, for the purposes of determining the taxable capital of the first-mentioned resident, be deductible under the same conditions as if they had been contracted to a resident of the first-mentioned State.

8.  The provisions of paragraph 7 shall not affect the operation of any provision of the taxation laws of a Contracting State:

(a) relating to the deductibility of interest and which is in force on the date of signature of this Convention (including any subsequent modification of such provisions that does not change the general nature thereof); or

(b) adopted after such date by a Contracting State and which is designed to ensure that a person who is not a resident of that State does not enjoy, under the laws of that State, a tax treatment that is more favorable than that enjoyed by residents of that State.

9.  Expenses incurred by a citizen or resident of a Contracting State with respect to any convention (including any seminar, meeting, congress or other function of a similar nature) held in the other Contracting State shall, for the purposes of taxation in the first-mentioned State, be deductible to the same extent that such expenses would be deductible if the convention were held in the first-mentioned State.

10.  Notwithstanding the provisions of Article II (Taxes Covered), this Article shall apply to all taxes imposed by a Contracting State.