The 183-day rule is part of the "substantial presence test" used by the Internal Revenue Service to determine if a person, who is a dual taxpayer, will have to pay taxes in the United States. It is commonly used by aliens to establish residency in the United States. The determining factor is whether the number of days on which the person was present in the United States exceeds 183 days.

The United States has tax treaties with other countries that contain a provision for resolution of conflicting claims of residence. The Internal Revenue Code section that contains the definition of the "substantial presence test" and the relevant multiplier is 26 IRC 7701(b)(3)(A)(ii).