Carbon Credit Registries Explained: How Credits Are Issued, Tracked and Retired

A carbon credit is only useful if it can be found, checked and cancelled. That job belongs to a carbon credit registry, an electronic system that keeps an account for each credit, records when it was issued, shows who holds it and marks it as retired once it has been used to support a claim. Registries are the record-keeping layer of the carbon market, and they are the first place a buyer should look when checking that a credit exists.

Issuance. After a project has been validated, and its emission reductions or removals have been verified by an independent auditor, the standard body instructs the registry to issue credits. Each credit receives a unique serial number that identifies the project, the vintage (the period in which the reduction or removal took place) and the registry that issued it. The serial number is what allows a buyer to trace a unit back to its source.

Holding and transferring. Credits sit in accounts, and each transfer from one account to another is recorded. A credit can change hands several times before it is used, through brokers, traders and corporate buyers. The registry record shows the current holder, which helps buyers check for double sales and confirm that the seller really owns the units it is offering.

Retirement. Retirement is the final step in a credit's life. The holder instructs the registry to cancel the unit so that it can never be sold or used again. The registry then records the retirement together with the beneficiary, meaning the company, organisation or claim the retirement is meant to support. Retirement is what stops the same tonne of reduction from being used twice, once by the buyer as an offset and again by the project or country that generated it.

Registry types. Some registries are run by standards bodies and hold credits issued under their own methodologies. Others are national systems set up by governments that want to track credits generated within their borders, and several countries have launched or are building such systems. Because credits can appear in more than one place, a buyer should be clear about which registry holds the unit it intends to buy.

Article 6 and corresponding adjustments. Under Article 6 of the Paris Agreement, a host country that authorises a credit for use toward another country's climate target has to adjust its own emissions accounting so the same reduction is not claimed twice. Registries are increasingly expected to show whether a unit carries such an authorisation and whether the corresponding adjustment has been applied. The rules are still developing, so the status of a credit should be checked rather than assumed.

What a registry check should cover. Before buying, ask for the serial numbers and look them up on the registry that issued them. Confirm that the credits are shown as active and unretired, that the project identifier matches the project documents, and that the vintage is the one quoted in the contract. Check whether the registry has flagged the project, suspended issuance or delisted the credits. After purchase, make sure the retirement is recorded in the name of the entity that will make the claim.

Registries and marketplaces. Many buyers find credits on a broker platform or trading exchange rather than on a registry directly. A listing shows what a seller says it holds, but the ownership and retirement status sit in the registry. A platform listing is a useful starting point, and the serial numbers should be checked against the registry before any payment is made.

Retirement statements and timing. When credits are retired, the registry can record a beneficiary name and a short retirement statement describing the purpose, such as the reporting year or the product the credits support. Buyers who retire credits on behalf of a client or a customer should make sure that name is entered correctly at the time, because the record is hard to change afterwards. It also helps to retire close to the time the claim is made, and to keep the registry confirmation with the sustainability report it supports, so that anyone reading the claim can find the matching record.

What a registry does not prove. A registry records what it has been told. It confirms that a unit exists, where it sits and who holds it, but it does not confirm that the underlying reduction was real. Additionality, baseline setting, permanence and leakage are separate questions, assessed by standards and verifiers before issuance. A clean registry record is a necessary condition for a credit to be trusted, not a sufficient one.

Frequently asked questions.

Is a registry the same as a standard? No. A standard sets the rules a project must follow. A registry records the credits that result, and some standards operate their own registries while others use third-party systems.

Can a credit be cancelled after it has been retired? In general, no. Retirement is designed to be permanent, which is why buyers should retire credits only once they are sure about the claim they are supporting.

Why do registry records matter for buyers? They are the only independent way to see whether a credit has already been used, sold or cancelled, and they give a clear audit trail when a claim is challenged.

Can credits be retired on behalf of another company? Yes, in most registries the retiring account holder can name a different beneficiary. The named beneficiary is the party the retirement is recorded for, so it should match the entity that will make the claim.