The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States; but all Duties, Imposts and Excises shall be uniform throughout the United States; .
By the terms of the Constitution, the power of Congress to levy taxes is subject to but one exception and two qualifications. Articles exported from any State may not be taxed at all. Direct taxes must be levied by the rule of apportionment and indirect taxes by the rule of uniformity. The Court has emphasized the sweeping character of this power by saying from time to time that it reaches every subject,1 that it is exhaustive2 or that it embraces every conceivable power of taxation.3 Despite these generalizations, the power has been at times substantially curtailed by judicial decision with respect to the subject matter of taxation, the manner in which taxes are imposed, and the objects for which they may be levied.