To limit the authority of States to tax certain income of employees for employment duties performed in other States.

Mobile Workforce State Income Tax Simplification Act of 2013 - Prohibits the wages or other remuneration earned by an employee who performs employment duties in more than one state from being subject to income tax in any state other than: (1) the state of the employee's residence, and (2) the state within which the employee is present and performing employment duties for more than 30 days...