What is the tax bracket percentage for a person making 20K a year?

Your taxable income (the amount you made to apply a tax rate to) is, because of deductions, exemptions, dependents and other considerations, is normally very different (lower) than what you "make". A person who made 20K will have a tax rate of about 15%, however, again EITC and other credits may make this much less. Many, if not most people, especially with any family who make 20K will pay little or no tax and many actually get money back because of the credit features available for low earners.