A carbon unit registry is an electronic accounting system in which climate projects are registered, units with unique serial numbers are issued, and their transfers between accounts and their retirement are recorded. It is the registry entry that makes a unit exist: without it there is no ownership and no way to make a claim. Registries are run by independent programs, by governments and by the UN mechanism under Article 6.4.
What a registry holds
A typical registry holds three layers of data:
- Projects: description, methodology, country, owner, status (under validation, registered, suspended), and documents such as the PDD and validation and verification reports.
- Units: serial number, project, reduction period (vintage), quantity, quality labels, and details of authorization and any corresponding adjustment.
- Transactions: issuance, transfer, retirement, cancellation, and transfer to the buffer.
The serial number links each tonne to a project and a period. This puts the tracking principle of the ICVCM CCP into practice and protects against double issuance.
Types of registries
| Type | Run by | Example |
|---|---|---|
| Program registry | Independent standard | Verra and Gold Standard registries |
| National registry | Government | Uzbekistan's carbon unit registry |
| Mechanism registry | UN body | Article 6.4 mechanism registry |
The Article 6.4 mechanism registry operates under registry procedure version v03.0 of July 30, 2026; until the final infrastructure is launched, an interim registry is used (see Article 6).
National registries are needed by countries that take part in international trading: they show which units have been authorized, transferred abroad and accounted for in adjustments. In Uzbekistan, a national carbon unit registry is being set up under the Ministry of Economy and Finance pursuant to Resolution PP-110, and Law ZRU-1073 enshrines the registry in law (see Uzbekistan's regulation).
Registry of climate claims
A separate task is keeping track of who used a unit and for what purpose. When a unit is retired, the registry records the beneficiary, the purpose and the period of the claim. A public retirement record lets anyone check that the company actually took the units out of circulation rather than merely announcing it. For details, see Retiring carbon units.
How one project can end up in two registries
The risk of double issuance arises when a project is registered at the same time with a voluntary market program and in a national or international registry. The safeguards are:
- Registries exchange information or require a declaration that the project is not registered elsewhere.
- When a project moves from one program to another, its units in the original registry are canceled or blocked.
- The national registry covers all projects in the country so that the government can see the full volume.
How it works in the platform
- The platform is not a carbon unit registry and does not issue units. The Market and MRV contours are marked “Soon”: they are under development.
- Today, the platform helps you collect the data a future project will rely on: monthly energy and fuel accounting by facility, with supporting documents (Data entry).
- The change history for a facility's year shows who changed what and when, which comes in handy when a verifier asks where the data came from.
Frequently asked questions
Can a unit be sold without a registry?
No. Transferring title to a unit is a registry transaction. A contract with no registry entry does not give the buyer the ability to retire the unit.
What is a unit's vintage?
It is the year or period in which the emission reduction took place. Buyers take it into account because methodology requirements change over time.
Does a buyer need a registry account?
Not necessarily: units can be retired through the seller's or an intermediary's account on the buyer's behalf, with the buyer named as the beneficiary. The procedure depends on the registry's rules.