CORSIA and Article 6
The present section describes eligibility requirements and procedures for Project Developers that seek to issue credits that are eligible as:
emissions units for the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) and/or
Internationally Transferred Mitigation Outcomes (ITMOs) for trading and use towards the Nationally Determined Contribution (NDC) target of the country buying the RCCs, through the use of Article 6.2 of the Paris Agreement under the The United Nations Framework Convention on Climate Change (UNFCCC).
For clarity, these cases shall be referred to as issuing CORSIA credits and issuing Article 6 credits.
Project Developers seeking to issue credits that not CORSIA or Article 6 eligible do not need to meet the following requirements.
CORSIA eligibility procedure
Project Developers seeking eligibility for CORSIA Phase 1 shall comply with the following:
Projects shall have their first crediting period start on or post January 1, 2016
RCCs are issued for vintages 2021 and beyond
RCCs have been authorized by the host country, following the Host Country authorization procedure outlined below.
Projects must be under a Rainbow methodology that has been approved by the CORSIA TAB for issuing CORSIA Eligible Emissions Units
Projects must report their sustainable development contributions or co-benefits, following the co-benefit reporting requirements outlined in the Rainbow Standard Rules
Projects must follow all other ICAO requirements.
Rainbow shall act as the final guarantor for CORSIA-eligible emissions units in cases where other safeguards, such as mechanisms outlined in Buffer Pool or insurance policies, are insufficient to fully compensate for any reversal of issued CORSIA-eligible emissions units.
Project Developers seeking to issue CORSIA credits shall:
ensure that CORSIA-eligible emissions units are not claimed both by airline operators for CORSIA compliance, and by Host Countries for the fulfillment of their Nationally Determined Contributions (NDCs).
monitor Host Country reporting and submit accurate, timely information on corresponding adjustments to Rainbow.
The specific procedures to meet the above requirements are outlined in the sections below.
Request
To have credits labeled as CORSIA-eligible, Project Developers must submit a formal request to Rainbow, specifying the relevant vintage year of the GHG avoidance and/or removal. This may be submitted after credits are already issued.
Following receipt of the request, the concerned credits will be labeled in the registry as “Pending CORSIA-eligibility”.
Letter of Authorization
To ensure that credits are not counted toward both a Host Country’s NDCs and CORSIA compliance, Project Developers shall obtain explicit authorization from the Host Country, in the form of a Letter of Authorization (LoA). This shall be issued by an authorized representative of the Host Country’s national focal point, and completed using the UNFCCC template or country's own template or Rainbow’s template Letter of Authorization for CORSIA.
The LoA must follow all requirements outlined in the detailed LoA section below.
Reconciliation mechanism
Project Developers shall comply with the Procedure for updates to Host Country authorization and the CORSIA double claiming reconciliation procedures.
In addition, Project Developers shall establish a reconciliation mechanism to resolve any disputes between them and the host country concerning the revocation of a Corresponding Adjustment (CA). This mechanism shall ensure that all parties have a clear, transparent and mutually agreed-upon process for addressing and resolving disagreements.
Insurance
Project Developers shall secure double-claiming insurance coverage from a provider approved by Rainbow. The insurance policy must ensure that, in the event of double claiming:
The insurer replaces an equivalent volume of the affected units authorized with CORSIA-eligible units; or
The insurer provides financial compensation sufficient to procure an equivalent volume of eligible units, such as CORSIA-eligible RCCs or other recognized units.
CORSIA approval
The Letter of Authorization, reconciliation mechanism, and insurance policy shall be evaluated by the Rainbow to assess completeness and compliance with the present requirements.
Once Rainbow has reviewed the requirements and approved, and the Letter of Approval (LoA) is publicly made available on the Rainbow Registry, the units shall be labeled as CORSIA-eligible.
Registry management
In addition to the standard-level requirements for managing Rainbow Carbon Credits on the registry, CORSIA-Eligible Units shall include:
Public Documentation: The Letter of Authorization will be made publicly available alongside other project documentation on the Rainbow Registry.
Public Record: The status of authorized use and Corresponding Adjustments will be recorded and made publicly available through the Rainbow Registry.
Retirement Transparency: Retirement records will clearly specify the airline operator for which the carbon credits were canceled, as well as the date of retirement.
Ongoing monitoring of Corresponding Adjustments
Following the first transfer or retirement of eligible credits, Rainbow will monitor the annual Host Country’s submissions to the Article 6 database in the Agreed Electronic Format, biennial transparency reports, and any relevant listings or reporting required by future CMA decisions. This monitoring ensures evidence of the appropriate Corresponding Adjustment against the Host Country’s NDCs.
Additionally, Project Developers are responsble for continuous monitoring and reporting any updates to Host Country authorization.
Any cases of double claiming will be managed following the CORSIA double claiming reconciliation procedures.
Article 6 eligibility procedure
Project Developers seeking to issue Article 6 credits must comply with following requirements.
Request
To have credits labeled as Article 6 eligible, Project Developers must submit a formal request to Rainbow, specifying the relevant vintage year of the GHG avoidance and/or removal. This may be submitted after credits are already issued.
Following receipt of the request, the concerned credits will be labeled in the registry as “pending CORSIA-eligibility”.
Letter of Authorization
Project Developers shall obtain explicit authorization from the Host Country, in the form of a Letter of Authorization (LoA). This shall be issued by an authorized representative of the Host Country’s national focal point, and completed using the UNFCCC template or country's own template or Rainbow’s template Letter of Authorization for CORSIA.
The LoA must follow all requirements outlined in the detailed LoA section below.
Reconciliation mechanism
Project Developers shall comply with the Procedure for updates to Host Country authorization.
In addition, Project Developers shall establish a reconciliation mechanism to resolve any disputes between them and the host country concerning the revocation of a Corresponding Adjustment (CA). This mechanism shall ensure that all parties have a clear, transparent, and mutually agreed-upon process for addressing and resolving disagreements.
Registry management
In addition to the standard-level requirements for managing Rainbow Carbon Credits on the registry, Article 6-Eligible Units shall include:
Public Documentation: The Letter of Authorization will be made publicly available alongside other project documentation on the Rainbow Registry.
Public Record: The status of authorized use and Corresponding Adjustments will be recorded and made publicly available through the Rainbow Registry.
Retirement Transparency: Retirement records will clearly specify the country for which the carbon credits were canceled, as well as the date of retirement.
Ongoing monitoring of Corresponding Adjustments
Following the first transfer or retirement of eligible credits, Rainbow will monitor the annual Host Country’s submissions to the Article 6 database in the Agreed Electronic Format, biennial transparency reports, and any relevant listings or reporting required by future CMA decisions. This monitoring ensures evidence of the appropriate Corresponding Adjustment against the Host Country’s NDCs.
Additionally, Project Developers are responsble for continuous monitoring and reporting any updates to Host Country authorization.
Any cases of double claiming will be managed following the Article 6 double claiming reconciliation procedures.
Host Country authorization
Letter of Authorization
Project Developers shall obtain a Host Country Attestation in the form of a Letter of Authorization (LoA) completed by an authorized representative of the relevant national authority of the Host Country.
Project Developers shall use the LoA template provided by their Host Country. If one is not provided by the Host Country, Project Developers shall use the applicable Rainbow template:
The letter of Authorization shall meet the following general requirements, and include all information listed below in the Information to include in the LoAsection:
Be issued by the relevant government authority (such as designated national authority or UNFCCC focal point), and their include contact details such as email address and/or phone number and/or physical address of the office.
Explicitly authorize the use of RCCs for the purpose of CORSIA or Article 6. This shall reflected in the LoA as “CORSIA” or “International Mitigation Purposes” or “Other International Mitigation Purposes”.
Explicitly confirm that a Corresponding Adjustment will be made.
Include information on the project, including at least the complete project name on the Rainbow registry and Rainbow reference number.
Specify the amount of RCCs authorized, which may cover all credits issued during the project's crediting period, a defined portion of credits, or credits from a specific monitoring period.
Include the established reconciliation mechanism set up by the Project Developer.
If the project’s credits are generated in more than one country, each country involved must issue its own Letter of Authorization.
Information to include in the LoA
The Letter of Authorization must include the following information:
The official name of the Host Country and the name and title of its authorized representative.
The date the authorization is issued.
The name, details, and project code of the project covered by the authorization.
The sector, activity type, and crediting period for which the authorization applies (or vintage).
Explicit confirmation that the host country authorizes the use of the specified credits for CORSIA or Article 6.
Any limits on the number of credits permitted for CORSIA (e.g. CORSIA compliance period) or Article 6 use and any applicable time restrictions.
A formal declaration that the host country will not count the mitigation outcome toward its Nationally Determined Contribution (NDC).
A definition of “first transfer,” specifying when a Corresponding Adjustment will be applied, this may be at the time of authorization, issuance, or use/cancellation of the mitigation outcome.
A statement confirming that a Corresponding Adjustment will be made in accordance with the Paris Agreement to account for the use under CORSIA or Article 6.
A commitment to demonstrate that Corresponding Adjustments have been completed and reported in the country’s biennial transparency reports, as required by the Annex to decision 18/CMA.1 and consistent with decisions in 2/CMA.3, as well as any relevant future decisions by the CMA.
An assurance that the host country will transparently report on granted authorizations and the use of carbon dioxide avoidance/removals for CORSIA or Article 6 in its biennial transparency reports under Article 13 of the Paris Agreement or in subsequent reports as required by future CMA decisions.
Rainbow shall make publicly available all LoAs that have been approved on the Rainbow Registry.
Rainbow shall support the Project Developer in identifying the designated national point of contact responsible for the authorization and oversight of the attestation process.
Project Developers shall ensure the project adheres to all host country regulations and guidance regarding the voluntary use of carbon credits that are also accounted for in a country’s NDC.
Corresponding Adjustments
A Corresponding Adjustment is an accounting entry made by a Host Country to its national greenhouse gas inventory, ensuring that GHG avoidance and removals are not counted toward both the host country’s Nationally Determined Contribution (NDC) and the acquiring country’s or entity’s climate targets.
Project Developers shall follow the steps outlined in the Letter of Authorization section to obtain written confirmation from the host country that the carbon credits will receive a corresponding adjustment.
Procedure for updates to Host Country authorization
Project Developers must inform Rainbow of any changes they become aware of to the Host Country authorization. This may result in:
Increase in Authorized Credits: If a change results in an increased number of authorized credits, the Project Developer must submit a formal request and provide a revised LoA that covers the concerned RCCs. The LoA shall be evaluated for compliance by the Rainbow Certification team, and if all requirements are met, the credits shall be labeled as CORSIA-eligible or Article 6-eligible on the registry.
Reduction or Revocation of Authorization: If a Letter of Authorization reduces the number of CORSIA-eligible or Article 6-eligible credits, or is revoked entirely, Rainbow will review the affected credits and work with the host country to resolve any discrepancies. If the issue remains unresolved after three months, Rainbow will take the following steps:
Untransacted or Developer-Held Credits: The CORSIA-eligible or Article 6-eligible designation will be removed.
Transacted but Unretired Credits: The CORSIA-eligible or Article 6-eligible designation will be removed with the agreement of the credit holder. If no agreement is reached, the credits will be treated as double claimed, and compensation must be provided in accordance with Rainbow’s Double claiming reconciliation procedures.
Retired Credits: The Double claiming reconciliation procedures must be followed.
If Rainbow identifies changes in a host country authorization, through ongoing reporting, reconciliation processes, or direct notifications from the host country or Project Developer, it will promptly notify all relevant stakeholders, including the Project Developer, credit holders, the Host Country, UNFCCC, and ICAO.
Double claiming reconciliation procedures
Despite the present requirements, double claiming may occur due to, for example, reduction or revocation of the LoA or CA, or failure of the Host Country to carry out the CA as planned. The following sections outline fallback procedures for handling cases where double claiming occurs, violating the Host Country authorizationrequirements.
CORSIA double claiming reconciliation procedures
For RCCs to be labeled as CORSIA-eligible, Project Developers must establish a reconciliation mechanism for any double claims of their CORSIA-eligible emissions units between airline operators and Host Countries.
Any double-claimed units that have not received a CA must be compensated with an equivalent volume of eligible units, following the project's established a reconciliation mechanism.
The reconciliation mechanism must include an insurance policy guaranteeing that any double-claimed units will be replaced with an equivalent volume of CORSIA-eligible credits for the same compliance cycle. The guarantee shall commit to one of the following:
Replace the units directly, or
Provide full financial compensation for Rainbow to procure replacement units.
Insurance must be provided by Rainbow-approved insurance providers, which must be highly reputable, regulated, and hold a Very Strong rating from recognized agencies (e.g., Fitch’s, Standard & Poor’s).
In the event of double-claiming, the following steps must be taken:
Notification: Rainbow will notify the Project Developer within 48 hours of confirming a double-claiming event.
Compensation: Upon notification, the Project Developer shall deploy the defined compensation mechanism.
Revoke CORSIA eligibility: Rainbow shall revoke the CORSIA-eligible label for the affected credits until the double-claimed event is investigated and resolved. The project should re-obtain eligibility under CORSIA following CORSIA eligibility procedure.
Project Developers are responsible for continuously monitoring Host Country reporting and submitting accurate, timely information to Rainbow. Rainbow will verify submissions from Project Developers, and conduct independent annual checks of Host Country GHG reporting and completed CAs.
If, three months after the expected declaration and execution of the CA, the Host Country has not provided evidence of the required CA, Rainbow will oversee the carrying out of the compensation for any double-claimed units using the established reconciliation mechanism.
Article 6 double claiming reconciliation procedures
Any double-claimed units that have not received a CA must be compensated with an equivalent volume of eligible units. This includes specifically:
Revocation of a CA: The CA is not applied as previously agreed with the Project Developer, or if reliable evidence of the CA is not provided within one year from the date the host country was expected to report it to the UNFCCC.
Non-Use of Authorization: The host country is unable to apply CAs in the same calendar year in which the net GHG removal occurred.
In the event of double-claiming, the following steps must be taken:
Notification: Rainbow will notify the Project Developer within 48 hours of confirming a double-claiming event.
Remedy: Upon notification, the Project Developer shall:
Sign a new Letter of Authorization (LoA) with the host country, ensuring that any subsequent units issued will not be double claimed.
Develop and implement a compensation plan
Revoke CORSIA eligibility: Rainbow shall revoke the Article 6-eligible label for the affected credits until the double-claimed event is investigated and resolved. The project should re-obtain eligibility under Article 6 following Article 6 eligibility procedure.
Gap in supply: If the Project Developer has signed a new LoA but cannot supply the required units due to a shortage of eligible units, Rainbow may grant a three-year grace period to replace the double-claimed units. During this period, the project may regain its eligibility for Article 6 and issue units with the corresponding tag. If, after three years, the Project Developer has not supplied the required units, the project’s eligibility for Article 6 will be permanently revoked.
Reporting
Review of Host Country Adjustments
Rainbow will review each Host Country’s biennial transparency report under Article 13 of the Paris Agreement to verify that required Corresponding Adjustments have been applied.
If the Host Country has applied the CA, Rainbow will identify the affected credits (e.g., by unique batch identifiers) and publish evidence of the Adjustment on the Rainbow Registry.
If the Host Country has not applied the CA this will also be documented and published with the credits. Rainbow will continue monitoring for any future claims, according to the timeframe committed in the LoA. If after the end of the timeframe CA hasn't been applied, then reconciliation procedures for CORSIA or Article 6 apply.
The monitoring of the national emissions reports shall ensure consistency with the provided LoA with the specified information in the LoA, including notably the relevant accounting (in accordance with Section IV of Annex I to Decision 2/CMA.3 and expected timing of the CAs.
Notification of relevant bodies
Rainbow will notify relevant Host Countries, and ICAO, and other pertinent bodies on an annual basis regarding all issuances and retirements that may impact claims under Nationally Determined Contributions (NDCs) or ICAO guidelines.
Rainbow will publish every year a CORSIA Annual Oversight Report including detailed information on CORSIA-eligible emissions units, covering:
Quantity and serial numbers of credits authorized by Host Countries for CORSIA, broken down by country, vintage, and calendar year.
Quantity of CORSIA-eligible credits retired by airline operators for each CORSIA compliance period.
Corresponding Adjustments confirmed for Rainbow-authorized credits.
Quantity of CORSIA-eligible credits that are active, retired, or canceled, including their serial numbers.
Quantity of CORSIA-eligible credits identified as double-claimed and subsequently compensated by Rainbow, including both quantity and serial numbers.
Rainbow will publish an Article 6 Annual Oversight Report including detailed information on Article 6-eligible emissions units, covering:
Quantity and serial numbers of Internationally Transferred Mitigation Outcomes (ITMOs) authorized by Host Countries, broken down by country, vintage, and calendar year.
Quantity of Article 6-eligible credits transferred or retired for international mitigation purposes, including the receiving entities or compliance periods.
Corresponding Adjustments confirmed for Rainbow-authorized Article 6 credits.
Quantity of Article 6-eligible credits that are active, transferred, retired, or canceled, including their serial numbers.
Quantity of Article 6-eligible credits identified as double-claimed and subsequently compensated by Rainbow, including both quantity and serial numbers.
The reports must be publicly shared on the Rainbow's Administrative Oversight Record and submitted to UNFCCC Focal Points linked with the authorization of RCCs and relevant organisations (e.g., ICAO) within six months following the close of the calendar year.
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