The 16th Amendment to the Constitution of the United States was never ratified by the required number of States.
This Amendment allegedly entitled the Federal Government and their private collection company, the IRS, to collect "income tax" as falsely declared to be ratified in February 1913.
Since 36 of 48 states were required to ratify, the failure of 13 to directly ratify was fatal to the amendment and arguably the most serious. Even if we were to ignore defects of spelling, capitalization, and punctuation, we would still have only two states which successfully ratified.
More information on the unconstitutionality of the 16th Amendment can be found at http://www.thelawthatneverwas.com/defects.aspx