The Principles of Legality, Equality and Prohibition of Double Taxation in Switzerland
The Swiss tax system rests on three fundamental pillars that guarantee its coherence and fairness: the principle of legality, the principle of equality and the prohibition of double taxation. These structuring principles strictly frame tax practices at all levels of the Swiss Confederation. In a federal structure where federal, cantonal and municipal taxes coexist, these principles constitute the foundation on which the tax administration relies to levy taxes in a fair and predictable manner.
Overview of the Three Fundamental Constitutional Principles
| Principle | Constitutional Basis | Content | Practical Consequence |
|---|---|---|---|
| Tax legality | Art. 127 para. 1 FC | Every tax must rest on a formal law defining taxpayers, subject-matter and calculation | Invalidity of taxation without clear legal basis |
| Equality before tax | Art. 8 + 127 para. 2 FC | Taxation according to ability to pay (horizontal + vertical) | Progressive tax scales; social deductions |
| Prohibition of inter-cantonal double taxation | Art. 127 para. 3 FC | Prohibition of taxing the same subject-matter twice by two different cantons | Nexus criteria + distribution rules |
Inter-Cantonal Tax Nexus Criteria
| Type of Taxpayer / Asset | Nexus Criterion | Competent Canton |
|---|---|---|
| Natural person (main residence) | Tax domicile (centre of vital interests) | Canton of main domicile |
| Natural person (tax sojourn) | >30 days with gainful activity, or >90 days without | Canton of sojourn (secondary nexus) |
| Properties | Geographic location of the asset (economic nexus) | Canton where the property is located |
| Sole proprietorship | Location of the main activity | Canton of the registered office / permanent establishment |
| Legal entity (AG, GmbH) | Statutory registered office or place of effective management | Canton of registered office (+ cantons of permanent establishments) |
| Movable assets (succession) | Last domicile of the deceased | Canton of the last domicile of the deceased |
Methods of Elimination of International Double Taxation
| Method | Principle | Application by Switzerland |
|---|---|---|
| Exemption with progression | Foreign income exempt from Swiss tax but included to determine the rate | Main method in Swiss DTAs |
| Credit method (tax credit) | Foreign tax deducted from Swiss tax due on the same income | Applicable notably for dividends, interest, royalties |
The Principle of Legality in Swiss Tax Matters
The principle of legality constitutes the cornerstone of Swiss tax law. Enshrined in article 127 paragraph 1 of the Federal Constitution, this principle stipulates that no tax may be levied without a legal basis. This fundamental rule guarantees that only the legislator, and not the administration, may create or modify a tax.
In practice, the principle of legality is broken down into two distinct but complementary requirements:
- The formal legal basis: every tax must be provided for by a law adopted according to ordinary legislative procedure
- The precision of the legal basis: the law must clearly define the circle of taxpayers, the subject-matter of the tax and its method of calculation
The Principle of Equality Before Tax
The principle of equality before tax derives directly from article 8 of the Federal Constitution which guarantees equal treatment. In tax matters, this principle translates into two major requirements:
- Horizontal equality: taxpayers placed in identical situations must be taxed identically
- Vertical equality: taxpayers with different ability to pay must be taxed differently
Compliance with these two dimensions leads to the principle of taxation according to ability to pay, explicitly mentioned in article 127 paragraph 2 of the Federal Constitution.
The Prohibition of Inter-Cantonal Double Taxation
The prohibition of inter-cantonal double taxation is a fundamental constitutional principle in Switzerland, enshrined in article 127 paragraph 3 of the Federal Constitution. This principle aims to prevent the same taxpayer from being taxed twice for the same tax subject-matter by different cantons. In a country where each canton has broad tax autonomy, this principle is of paramount importance in guaranteeing the economic unity of the territory and the mobility of persons and businesses.
Frequently Asked Questions on the Fundamental Principles of Swiss Tax Law
How to invoke a violation of the principle of equality before tax in Switzerland?
A violation of the principle of equality (art. 8 FC + art. 127 para. 2 FC) may be invoked in an objection to the tax authority, then in a cantonal appeal, and finally before the Federal Supreme Court. It must be demonstrated that two taxpayers in identical situations are treated differently without objective justification, or that the taxation does not correspond to their ability to pay.
What is the tax nexus for a property in an inter-cantonal succession?
By virtue of the principle of territoriality (economic nexus), properties are taxed in the canton where the asset is located, even if the deceased was domiciled in another canton. Thus, if a deceased domiciled in Geneva owns a property in Zurich, the succession tax on that property falls under Zurich, while movable assets fall under Geneva (canton of last domicile).
Does the 30/90 day rule automatically determine Swiss tax residence?
These thresholds are nexus criteria: a stay of more than 30 days with gainful activity, or more than 90 days without gainful activity, creates a personal nexus in Switzerland. But tax residence depends on the centre of vital interests (family, social relationships, main activity). In the event of dual domicile, the tie-breaker rules of DTAs (permanent home, centre of vital interests, habitual abode, nationality) apply.
How do companies distribute their profits between several Swiss cantons?
For companies with a registered office in canton A and a permanent establishment in canton B, profits are distributed according to objective criteria: turnover, payroll, or asset value, depending on the nature of the activity. The Federal Supreme Court has developed extensive case law (BGE) specifying these inter-cantonal distribution rules to avoid double taxation or under-taxation.