This bill, titled the "Maritime Fuel Tax Parity Act," proposes to expand an existing exemption from federal excise taxes. It specifically targets the excise tax levied on alternative motorboat fuels when sold as supplies for vessels or aircraft. The legislation seeks to extend this exemption to include certain vessels that operate exclusively between Atlantic or Pacific ports of the United States, encompassing its territories and possessions. This provision aims to offer tax relief for qualifying vessels engaged in coastal trade, ensuring parity with other exempted vessels. The amendment would be effective for sales occurring after December 31, 2023.