Each process under Annex IX shall be assigned a transaction identification code. Transaction identification codes shall be generated by registries and shall be unique throughout the registries system. Transaction identification codes shall not be re-used. The re-submission of a process concerning a transaction that was previously terminated or cancelled shall be assigned a new, unique transaction identification code.

The elements of the transaction identification codes are set out in the functional and technical specifications for data exchange standards for registry systems under the Kyoto Protocol, elaborated pursuant to Decision 24/CP.8 of the Conference of the Parties to the UNFCCC.