An assigned amount unit was a tradable "Kyoto unit" or "carbon credit" representing an allowance to emit greenhouse gases comprising "one metric tonne of carbon dioxide equivalent, calculated using global warming potentials".^[1][2] Assigned amount units were issued up to the level of initial "assigned amount" of an Annex 1 Party to the Kyoto Protocol.^[3][4]

The "assigned amounts" were the Kyoto Protocol Annex B emission targets (or "quantified emission limitation and reduction objectives") expressed as levels of allowed emissions over the 2008–2012 commitment period.^[5]

Article 17 of the Kyoto Protocol allowed emissions trading between Annex B Parties (countries). Parties that had "assigned amount units" to spare because of reductions in emissions below their Kyoto commitment set out in Article 3 and Annex B could sell those units to countries that had emissions exceeding their targets.^[6] Article 17 also required that any such emissions trading must be supplemental to domestic action for the purpose of meeting quantified emission limitation and reduction commitments.

• Certified Emission Reduction
• Emission Reduction Unit
• Removal Units
• Voluntary Emissions Reduction
• Flexible mechanisms
• List of Kyoto Protocol signatories