Title IV of the Clean Air Act (the Act), as amended by the Clean Air Act Amendments of 1990, authorized the Environmental Protection Agency (EPA or Agency) to establish the Acid Rain Program. The program sets emissions limitations to reduce acidic particles and deposition and their serious, adverse effects on natural resources, ecosystems, materials, visibility, and public health. The allowance trading component of the Acid Rain Program allows utilities to achieve sulfur dioxide emissions reductions in the most cost-effective way. Utilities trade allowances and EPA records ownership and trades of allowances in the Allowance Tracking System for use in determining compliance at the end of each year. On January 11, 1993, EPA initially promulgated the regulations governing Acid Rain Program permitting and allowance trading. Today's action revises certain provisions in the regulations concerning the deduction of allowances for determining compliance. The revisions will improve the operation of the Allowance Tracking System and the allowance market generally, while still preserving the Act's environmental goals.