Introduction

International taxation is the study or determination of tax on a person or business subject to the tax laws of different countries or the international aspects of an individual country's tax laws as the case may be. Governments usually limit the scope of their income taxation in some manner territorially or provide for offsets to taxation relating to extraterritorial income.

The manner of limitation generally takes the form of a territorial, residence-based, or exclusionary system. Some governments have attempted to mitigate the differing limitations of each of these three broad systems by enacting a hybrid system with characteristics of two or more.

Many governments tax individuals and/or enterprises on income. Such systems of taxation vary widely, and there are no broad general rules. These variations create the potential for double taxation (where the same income is taxed by different countries) and no taxation (where income is not taxed by any country). Income tax systems may impose tax on local income only or on worldwide income. Generally, where worldwide income is taxed, reductions of tax or foreign credits are provided for taxes paid to other jurisdictions. Limits are almost universally imposed on such credits. Multinational corporations usually employ international tax specialists, a specialty among both lawyers and accountants, to decrease their worldwide tax liabilities.

With any system of taxation, it is possible to shift or recharacterize income in a manner that reduces taxation. Jurisdictions often impose rules relating to shifting income among commonly controlled parties, often referred to as transfer pricing rules. Residency-based systems are subject to taxpayer attempts to defer recognition of income through use of related parties. A few jurisdictions impose rules limiting such deferral ("anti-deferral" regimes). Deferral is also specifically authorized by some governments for particular social purposes or other grounds. Agreements among governments (treaties) often attempt to determine who should be entitled to tax what. Most tax treaties provide for at least a skeleton mechanism for resolution of disputes between the parties.

Systems of taxation vary among governments, making generalization difficult. Specifics are intended as examples, and relate to particular governments and not broadly recognized multinational rules. Taxes may be levied on varying measures of income, including but not limited to net income under local accounting concepts (in many countries this is referred to as 'profit'), gross receipts, gross margins (sales less costs of sale), or specific categories of receipts less specific categories of reductions. Unless otherwise specified, the term "income" should be read broadly.

Jurisdictions often impose different income-based levies on enterprises than on individuals. Entities are often taxed in a unified manner on all types of income while individuals are taxed in differing manners depending on the nature or source of the income. Many jurisdictions impose tax at both an entity level and at the owner level on one or more types of enterprises. These jurisdictions often rely on the company law of that jurisdiction or other jurisdictions in determining whether an entity's owners are to be taxed directly on the entity income. However, there are notable exceptions, including U.S. rules characterizing entities independently of legal form.

In order to simplify administration or for other agendas, some governments have imposed "deemed" income regimes. These regimes tax some class of taxpayers according to tax system applicable to other taxpayers but based on a deemed level of income, as if received by the taxpayer. Disputes can arise regarding what levy is proper. Procedures for dispute resolution vary widely and enforcement issues are far more complicated in the international arena. The ultimate dispute resolution for a taxpayer is to leave the jurisdiction, taking all property that could be seized. For governments, the ultimate resolution may be confiscation of property, incarceration or dissolution of the entity.

Other major conceptual differences can exist between tax systems. These include, but are not limited to, assessment vs. self-assessment means of determining and collecting tax; methods of imposing sanctions for violation; sanctions unique to international aspects of the system; mechanisms for enforcement and collection of tax; and reporting mechanisms.

Taxation systems
Countries that tax income generally use one of two systems: territorial or residence-based. In the territorial system, only local income – income from a source inside the country – is taxed. In the residence-based system, residents of the country are taxed on their worldwide (local and foreign) income, while nonresidents are taxed only on their local income. In addition, a small number of countries also tax the worldwide income of their nonresident citizens in some cases.

Countries with a residence-based system of taxation usually allow deductions or credits for the tax that residents already pay to other countries on their foreign income. Many countries also sign tax treaties with each other to eliminate or reduce double taxation. In the case of corporate income tax, some countries allow an exclusion or deferment of specific items of foreign income from the base of taxation