how do i calculate the 183 day rule 
for most countries that apply a 183 day rule you are a tax resident of that country if you spend 183 or more there the united states however has a different criteria for applying a tax residency test you are a tax resident if you were physically present in the u s for 31 days of the current year and 183 days in the last three years including all days present in the current year 1 3 of the days from the previous year and 1 6 of the days from the year before that the bottom linethe 183 day rule refers to a common test used to determine tax residency in most countries individuals who are physically present for 183 days or more are considered residents for tax purposes in the u s a substantial presence test is used to determine tax residency and it s slightly more tricky than the common 183 day rule it considers time spent in the u s in a given year in addition to fractions of time spent in the u s in the two years prior lastly many states use a 183 day rule to determine residency for local tax purposes consulting local and federal tax regulations and international tax treaties can help an individual determine their total tax obligations 