What is the 183-day rule for state residency and how do I count days?

Many high-tax states, including New York, treat you as a statutory resident if you keep a permanent home there and spend more than 183 days in the state during the year, even if your domicile is elsewhere. Under New York's long-standing rule, any part of a day physically present generally counts as a full day, with narrow exceptions for travel through the state or medical treatment. That means a layover or a single afternoon can count. If you split time between two states, keep meticulous records such as cell-phone location data, travel receipts, and a day-by-day calendar, because the burden of proof usually falls on you in an audit. Rules and thresholds vary by state, so verify your specific state's definition on its department of revenue website before assuming you're safe.