The ITL verifies transactions proposed by registries to ensure they are consistent with rules agreed under the Kyoto Protocol. Each registry sends transaction proposals to the ITL, which checks each proposal and returns to the registry its approval or rejection. Once approved, registries complete the transaction. In the event that a transaction is rejected, the ITL sends a code indicating which ITL check has been failed and the registry terminates the transaction.

Data Exchange Standards (1393 kB) coordinate the functions of systems when processing transactions. They define technical requirements for the communication between the ITL and registries. They also define the checks performed by the ITL, embodying the policy rules agreed by Parties for the accounting of their assigned amounts and their use of the Kyoto mechanisms.

Each registry is to be connected to the ITL through secure communication channels established across the Internet. These connections will allow a registry to receive an immediate response from the ITL, typically within a matter seconds after sending the transaction information.

The administrator of the ITL is the UNFCCC secretariat, which has awarded a contract for the development and operation of the ITL to leading companies in the field of IT services. The ITL is hosted at two commercially-operated data centres, one for primary operations and the other as a backup site, both located in the United Kingdom. A service desk, also based in the United Kingdom, has been put in place to support the administrators of the ITL, registries and the CITL.

Since live operations began on November 14, 2007, several national registries have connected to the ITL.  Japan, Switzerland, New Zealand, Russia and Hungary have each commenced live operations with the ITL.

As of beginning of June 2008, thirty eight parties, (37 Annex B parties and the CDM registry) have successfully completed initialization.  Through the initialization process, the ITL operator verifies and confirms that each national registry operates according to the technical and procedural requirements prior to authorizing connection to the ITL

The ITL administrator has convened the Registry System Administrator Forum in order to ensure that technical and management issues across registry systems are effectively coordinated. The Forum met for the first time in April 2006 and typically meets as a full group three times a year. In addition, groups are established under the Forum to conduct more detailed work in preparing and implementing procedures of joint concern to administrators of all registry systems.