S.J.R. No. 18 is a proposed constitutional amendment in Texas that seeks to prohibit the imposition of taxes on the realized or unrealized capital gains of individuals, families, estates, or trusts. This includes any taxes related to the sale or transfer of capital assets that would be payable by the seller. The amendment aims to protect taxpayers from capital gains taxes, ensuring that such taxes cannot be levied by the legislature.

However, the resolution clarifies that this prohibition does not affect the existing applicability of certain taxes, such as ad valorem taxes on property, sales taxes on goods and services, or use taxes on the consumption of goods or services within the state. The proposed amendment is set to be submitted to voters during the election on November 4, 2025, allowing the public to decide whether to support or oppose the measure.