The IRS dates back to 1862, when President Lincoln signed into law a revenue-raising measure to help pay for Civil War expenses. The law created a Commissioner of Internal Revenue and the nation's first income tax of 3 percent on incomes between $600 and $10,000 and 5 percent on incomes of more than $10,000. Ten years later, it was repealed.

However, Congress revived the income tax in 1894 but the Supreme Court ruled it unconstitutional shortly afterward. The reason: It was a direct tax and not allocated among the states on the basis of population.

The income tax as we know it was created in 1913, when the 16th Amendment to the Constitution was ratified, giving Congress the authority to enact an income tax. That same year, the first Form 1040 was introduced.