If you work for an employer, then your employer withholds income taxes from each of your paychecks. That’s because both federal and most state governments collect income tax year-round, not just on April 15. Every January or early February, you should receive a form W-2 from your employer that lists exactly how much money you made the previous year and how much of it went to taxes. Form W-2 is one of those forms that you, the taxpayer, don’t have to fill out; your employer provides all of the information on the form. In fact, your employer has to mail you, the IRS and your state the W-2 by January 31 or face a penalty.