As circumstances in the United States change, federal tax structures change as well. According to the United States Treasury Department, changes in the federal tax system often can be traced to significant historical events such as war or constitutional events like the addition of the 16th Amendment giving Congress the ability to tax personal income. As of 2012, the United States has six different tax brackets that determine how much tax an individual or a couple pays on their income.
Lowest Tax Brackets
Income tax brackets are divided into six categories based on income. As of 2012, married couples filing jointly earning less than $17,400, or individuals making less than $8,700 annually, fall into the 10 percent tax bracket. This means these taxpayers will pay 10 percent of their earnings into the federal tax system.
Married couples filing jointly making more than $17,400 but less than $70,700 annually, or single individuals who make more than $8,700 but less than $35,350, are in the 15 percent tax bracket.
Middle Tax Brackets
The middle of the tax bracket scales cover the majority of taxpayers, also known as the "middle class" Americans. These working individuals are not nearing the poverty line but also are not wealthy; therefore, they can be considered "in the middle." As of 2012, married couples filing jointly who earn between $70,700 and $142,700, or individuals who earn between $35,350 and $85,650 annually, are in the 25 percent tax bracket.
Jumping to the 28 percent tax bracket are married couples filing jointly who earn between $142,700 and $217,450 and individuals who earn between $85,650 and $178,650 each year.
Highest Tax Brackets
The two highest tax brackets are 33 and 35 percent. As of 2012, married couples filing jointly who earn between $217,450 and $388,350 and individuals who earn between $178,650 and $388,350 annually are in the 33-percent tax bracket.
The highest tax bracket possible is the 35 percent bracket, which includes married couples filing jointly who earn more than $388,350 and individuals who earn more than $388,350.
Percentage of Brackets
As of 2012, approximately 26 percent of all taxpayers were included in the 15-percent tax bracket, while fewer than 1 percent were included in the highest tax bracket. In fact, fewer than 3 percent of all United States taxpayers were included in the top three tax brackets ranging from 28 to 35 percent that year.
According to CBS News, the number of people who claimed no income tax liability between 1950 and 1990 averaged at approximately 21 percent, with a low of 18 percent in 1986. In the 1990s, that number grew to about 25 percent and in 2009, 43.4 percent -- or 65.6 million -- of Americans paid no federal income taxes.