Taxpayers must pay more as their taxable income rises into higher tax brackets. This progressive system generally means that the more taxpayers earn, the more taxes they pay. However, deductions and exemptions can lower taxable income, resulting in a smaller tax bill, TurboTax explains.
Federal tax brackets are marginal, which means that each bracket applies only to a portion of a taxpayer's income, TurboTax notes. For instance, a single person whose 2015 taxable income is less than $9,225 owes a 10 percent tax, according to Forbes. A person whose taxable income is between $9,226 and $37,450 owes 10 percent on the first $9,225 of income and 15 percent on the rest of the income.