Amendment 24

SECTION. 1. The right of citizens of the United States to vote in any primary or other election for President or Vice President, for electors for President or Vice President, or for Senator or Representative in Congress, shall not be denied or abridged by the United States or any State by reason of failure to pay poll tax or other tax.

SECTION. 2. The Congress shall have power to enforce this article by appropriate legislation.

This is from  http://constitutioncenter.org/constitution/the-amendments/amendment-24-poll-tax-barred

This amendment made it where a person did not have to pay to vote, they did this so everyone had a fair chance at getting to vote.