The Mobile Workforce State Income Tax Simplification Act of 2025 aims to streamline state income tax regulations for employees who perform duties in multiple states. Under this bill, an employee's wages or other remuneration would only be subject to income tax in their state of residence or in a non-resident state where they are present and perform employment duties for more than 30 days during the calendar year. Furthermore, state income tax withholding and reporting requirements would only apply if the employee is subject to income tax in that state under the 30-day rule, with withholding commencing from the start date of duties if the threshold is met. To protect employers, the bill allows them to rely on an employee's annual determination of time spent in various states, unless there is actual knowledge of fraud or collusion. This reliance holds even if the employer maintains records of employee location, unless the employer uses a specific daily time and attendance system . The bill defines a "day" for tax purposes based on where the majority of duties are performed, excluding transit time. Notably, the provisions of this Act do not apply to certain categories of workers, specifically professional athletes, professional entertainers, qualified production employees, and certain public figures . The Act is set to take effect on January 1 of the second calendar year following its enactment, and it will not apply to any tax obligations accrued before this effective date.