Are you self-employed? Then Tax Day comes with an extra task for you. If you gain income from your business, even if it is a side gig, freelancing or contract work, then you need to estimate your taxes for the following quarter. In the U.S. Tax system, there is a pay-as-you-earn deal. If you do not have an employer that is withholding taxes from your paycheck, then you have to own up to the IRS as you make money throughout the year!