Answer: The 16th Amendment to the U.S. Constitution was ratified in 1913 and allows Congress to levy a tax on income from any source without apportioning it among the states and without regard to the census.
Amendment means:A minor change or addition designed to improve a text, piece of legislation, etc.
"an amendment to existing bail laws"
an article added to the US Constitution.
noun: Amendment; plural noun: Amendments
"the First Amendment"
something which is added to soil in order to improve its texture or fertility.
16th means: Constituting number sixteen in a sequence; 16th.
"the late sixteenth century"