The Acid Rain Program under title IV of the Clean Air Act provides for automatic excess emissions penalties in dollars per ton of excess emissions for sources that do not meet their annual Acid Rain emissions limitations. The Acid Rain Program under title IV of the Clean Air Act limits annual sulfur dioxide and nitrogen oxide emissions of fossil fuelfired utility units. Under the Acid Rain Program, affected sources must hold enough allowances to cover their sulfur dioxide emissions, and certain coalfired sources must meet an emission limit for nitrogen oxides. Under 40 CFR 77.6, sources that do not meet these requirements must pay a penalty. This results in an automatic penalty of $3,504 per excess ton of sulfur dioxide or nitrogen oxides emitted for 2011 and $3,636 per excess ton of sulfur dioxide or nitrogen oxides emitted for 2012.