An emission reduction unit (ERU) is a unit converted from either an assigned amount unit (AAU) or removal unit (RMU) and issued to project participants in Joint Implementation (JI) project activities. ERUs are defined in 9/CMP.1, Annex, paragraph 1(a) as follows:
An "emission reduction unit" or "ERU" is a unit issued pursuant to the relevant provisions in the annex to decision 13/CMP.1 and is equal to one metric tonne of carbon dioxide equivalent, calculated using global warming potentials defined by decision 2/CP.3 or as subsequently revised in accordance with Article 5 (9/CMP.1, Annex, paragraph 1(a)).
The limitations that apply to transfers of other credits under the international emissions trading rules under Article 17 do not apply to ERUs issued in respect of emission reductions that were verified under the Track 2 verification procedure:
Any provisions relating to the commitment period reserve or other limitations to transfers under Article 17 shall not apply to transfers by a Party of ERUs issued into its national registry that were verified in accordance with the verification procedure under the Article 6 Supervisory Committee (9/CMP.1, Annex, paragraph 41).
This means that Parties are eligible to transfer Track 2 ERUs from their national registry without breaching their commitment period reserve and to use as many Track 2 ERUs as they wish for compliance with their Kyoto targets.