Trainees or interns who earn income from a U.S. host company are responsible for paying U.S. federal, state, and local (if applicable) income tax. You are not required to pay Social Security or Medicare taxes. This tax return form is due on April 15 following the year of your training opportunity. If you did not earn income during your training/internship, you must still file a tax return due June 15, but you will not owe any tax money.