Saving clause

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Unpacking how tax treaties preserve a country's right to tax its own residents and citizens

Tax treaties are often misunderstood as instruments that reduce a country’s power to tax its own people. In fact, one of the core legal mechanics of Article 1 of the OECD Model Convention is that a treaty normally limits taxation of cross-border income, but does not generally strip a state of its right to tax its own residents under domestic law. The treaty allocates or restricts taxing rights only where the treaty language and the relevant distributive article actually apply.

This is the first legal checkpoint for students: before applying a treaty rule, identify who is claiming treaty relief, what income is involved, and which state is being asked to give up taxing power. Article 1 answers the personal scope question: the Convention applies to persons who are residents of one or both Contracting States. That means the treaty starts from residence, not from nationality, and its main function is to coordinate the interaction between two domestic tax systems.

Key idea

A tax treaty is not a general surrender of taxing power. It is a coordination rule that preserves the basic right of each state to tax residents under its own law unless the treaty specifically limits that right. In practice, the treaty mainly prevents both states from taxing the same income in incompatible ways.

Why this matters

This principle is important because many students assume that a treaty automatically protects all income from domestic taxation. That is not correct. A resident state may still tax worldwide income under its domestic law, subject to treaty limitations such as reduced withholding tax rates, business profits rules, or residence-based exemptions.

The treaty also preserves the distinction between residence-based taxation and source-based taxation. A state remains free to tax its residents, and the treaty usually only restricts source taxation where cross-border income is involved. In other words, the treaty is a filter on overlap, not a blanket immunity.

Core legal mechanics

The mechanics can be tested through three questions:

1. Is the taxpayer a resident under Article 4?

2. Does the income fall within a treaty article that allocates taxing rights?

3. Does the treaty actually limit the residence state’s or source state’s right to tax?

If the answer to the third question is no, the domestic taxing right remains intact. This is why Article 1 must be read together with the operative distributive articles and the relief articles on double taxation. The treaty only changes domestic tax consequences where its own text does so.

Citizens and residents

A useful point for learners is that the OECD Model Convention is built around residence, not citizenship. A country may tax its citizens under domestic law if its internal law allows that, but Article 1 itself does not create a special treaty category for citizens. The treaty question is whether a person is a resident of one of the Contracting States and whether the relevant income article applies.

This helps students see that treaty protection is not based on personal loyalty or nationality. It is based on legal residence and on the allocation rules in the Convention. That distinction is especially important when comparing treaty law with domestic anti-avoidance or citizenship-based tax rules.

Learning check

Use these questions to test understanding:

• Why does Article 1 begin with residence rather than citizenship?

• In what sense does a tax treaty preserve domestic taxing rights?

• How does the treaty prevent double taxation without eliminating residence-based taxation?

• Why must Article 1 be read together with Article 4 and the distributive articles?