Washington state constitution
Article VII
Section 10

Notwithstanding the provisions of Article 7, section 1 (Amendment 14) and Article 7, section 2 (Amendment 17), the following tax exemption shall be allowed as to real property:
The legislature shall have the power, by appropriate legislation, to grant to retired property owners relief from the property tax on the real property occupied as a residence by those owners. The legislature may place such restrictions and conditions upon the granting of such relief as it shall deem proper. Such restrictions and conditions may include, but are not limited to, the limiting of the relief to those property owners below a specific level of income and those fulfilling certain minimum residential requirements.