U.S. Constitution, Article I — The Legislative Branch, Section 9, Clause 4
No Capitation, or other direct, Tax shall be laid, unless in Proportion to the Census or enumeration herein before directed to be taken.
Notes
Bars any capitation or other direct tax unless it is laid in proportion to the census or enumeration directed earlier in the Constitution. A direct tax must be divided among the states according to population as counted in that census, rather than laid in any other manner.
Use as reference
Lexinter.net | U.S. Const. art. I, § 9, cl. 4 | https://laws.lexinter.net/constitution/us/article-1/section-9/clause-4