Frequently Asked Questions
This FAQ list is offered by the secretariat of the UNFCCC as a convenience to members of the public wishing to learn more about the clean development mechanism. The answers cannot replace or affect the official modalities and procedures and related official documents/decisions pertaining to the CDM. If you do not find your question in the list below, please do not hesitate to contact us.
+ What is the CDM?
The clean development mechanism (CDM) allows emission-reduction (or emission removal) projects in developing countries to earn certified emission reduction (CER) credits, each equivalent to one tonne of CO2. These CERs can be traded and sold, and used by industrialized countries to meet a part of their emission reduction targets under the Kyoto Protocol.
The mechanism stimulates sustainable development and emission reductions, while giving industrialized countries some flexibility in how they meet their emission reduction targets.
The projects must qualify through a rigorous and public registration and issuance process designed to ensure real, measurable and verifiable emission reductions that are additional to what would have occurred without the project. The mechanism is overseen by the CDM Executive Board (EB), answerable ultimately to the countries that have ratified the Kyoto Protocol.
In order to be considered for registration, a project must first be approved by the Designated National Authorities (DNA).
The mechanism is seen by many as a trailblazer. It is the first global, environmental investment and credit scheme of its kind, providing a standardized emissions offset instrument, CERs.
+ What is a programme of activities (PoA)?
A programme of activities (PoA) under the CDM is the coordinated implementation of a policy, measure or goal that reduces emissions.
Under a PoA, emission reductions achieved by many individual activities (known as component project activities or CPAs) can be considered in aggregate, without requiring each CPA to undergo individualized registration and issuance processes. This reduces transaction costs and makes the CDM more attractive and accessible, particularly to least developed countries that have not historically benefited from the CDM. For further information, please see our PoA page
+ Does the UNFCCC offer training on the CDM?
The UNFCCC secretariat is charged with the responsibility of supporting the Conference of the Parties and the Conference of the Parties serving as the meeting of the Parties to the Kyoto Protocol and their associated bodies. In the case of the clean development mechanism (CDM), the secretariat solely supports the CDM Executive Board.
In light of the above and as an impartial organization, the UNFCCC secretariat is not in a position to provide any training or any specific advice on where to get one. It is therefore recommended to turn to the relevant DNA to enquire about their initiatives. You will find their contact details here
You may also want to seek more information by visiting the CDM Bazaar website. This free web portal enables CDM players to interact and exchange tips, contact details, etc.
+ I have an idea for a project, where do I begin?
If you are interested in starting a CDM project, first become familiar with the objectives of the Kyoto Protocol, the background of the CDM, the modalities and procedures of the CDM , as well as the project activity cycle.
Information on small-scale projects more >>
Information on afforestation/reforestation projects more >>
+ Is there a CDM representative in my country?
In order to take part in the CDM, a country must have a designated national authority (DNA). Contact details of DNAs are available here.
+ What is the role of the UNFCCC secretariat in implementing CDM projects?
The UNFCCC secretariat is mandated to support the Conference of the Parties and the Conference of the Parties serving as the meeting of the Parties to the Kyoto Protocol and their associated bodies. In the case of the clean development mechanism (CDM), the secretariat is responsible for supporting the work of the CDM Executive Board, the decision-making authority on all CDM project activities.
The UNFCCC secretariat does not provide individual project developers assistance in:
(a) pre-appraising project ideas/proposals;
(b) sourcing financing or expert help;
(c) preparing required documents.
More information, and even advice, is available through the CDM Bazaar website, a free web portal where CDM stakeholders, buyers, sellers and service providers share information and contact details.
+ Does the UNFCCC provide project-specific technical assistance?
In an effort to help under-represented regions benefit from the CDM, the UNFCCC secretariat has set up a help desk for projects located in Africa, least developed countries (LDCs), small island developing states (SIDS) and countries with 10 or fewer registered CDM projects as of 31 December 2010. The help desk is open to any query regarding CDM projects or programmes of activities (PoA) from targeted countries, so long as the project is in the process of validation or verification. Further information is available here
An overview of all initiatives to support the CDM in under-represented regions can be found here
+ What is the difference between small-scale and large-scale project activities?
There are three types of small-scale project activities. Decision 1/CMP.2 revised the definitions for small-scale project activities referred to in paragraph 6 (c) of decision 17/CP.7, and Annex II of Decision 4/CMP.1 as follows:
(a) Type I: renewable energy project activities with a maximum output capacity of 15 megawatts (or an appropriate equivalent);
(b) Type II: project activities relating to improvements in energy efficiency which reduce energy consumption, on the supply and/or demand side, by up to 60 gigawatt hours per year (or an appropriate equivalent);
(c) Type III: other project activities that result in emission reductions of less than or equal to 60 kilotonnes of carbon dioxide equivalent annually.
Any CDM project activity not possessing the abovementioned characteristics is considered a large-scale CDM project activity.
+ Where can I find CDM forms, such as the blank project design document (PDD) form?
All CDM forms, including the blank PDD form, can be found in the reference/documentation section.
+ How do I communicate with the CDM Executive Board?
For communications which are not in response to a call for input, please check the modalities and procedures for direct communication with stakeholdersbefore sending them.
Communications on policy issues initiated by AEs/DOEs have to be sent using the F-CDM-RtB-DOEform through the 'New DOE-EB Interface' under Operational Entities Extranet.
Communications on policy issues initiated by DNAs should be sent using the F-CDM-RtB-DNAform via email to the Moderator DNA account, until a dedicated interface is put in place on the DNA extranet.
Communications on policy issues initiated by project participants and other stakeholders should be sent using the F-CDM-RtBform via e-mail to firstname.lastname@example.org or by fax at +49 228 815 1999, until a dedicated interface is put in place on the UNFCCC CDM website.
Letters submitted from stakeholders are available here.
Stakeholders who would like to send a query on an approved methodology, request for revision of an approved methodology, and proposal for a new methodology, should refer to the Procedures available hereor to the methodologies section of this FAQs page.
+ How can I request observer status to attend a CDM Executive Board meeting?
Observers at the CDM Executive Board meeting are either representatives of Parties to the Convention or representatives of admitted NGO observer organizations ( Rule 27 of the Rules of Procedure of the CDM EB.) Pursuant to this rule, nominations of representatives must be communicated through the designated contact point for climate change of the Party or the admitted observer organizations.
In general, the deadline for registration is three weeks before the date of the meeting. In order to avoid late requests, we would recommend that you check the up-coming date in the report of previous meeting of the CDM Executive Board.
Project participants and DOEs interested in the review process of specific project activities shall be given the opportunity to attend the Executive Board meeting at which the request for review shall be considered.
If a request for review for a proposed CDM project activity is considered for the first time by the Executive Board, stakeholders may register as observers until two weeks before the meeting. For any meeting thereafter, when this proposed CDM project activity is on the agenda, the normal three week deadline has to be observed.
Stakeholders meeting the above requirements and deadlines are registered as observers subject to availability of space on a first come first serve basis.
+ Where could I get information about projects being implemented in my country?
A project search facility is available on the UNFCCC CDM website. For additional filters, you may want to chose the 'advanced search' option. All information contained in the result table is publicly available.
+ Is there any available CDM Terms collection of definitions?
The Glossary of CDM Terms can be found here.
The secretariat of the UNFCCC has launched a new RSS feed service for CDM News and CDM project related information. Through RSS, users can receive updates on the specific information they need, as it becomes available. To learn more, and to subscribe, go to the CDM RSS page.
The RSS feed service now replaces CDM News email distributions. Switching to RSS (1) allows CDM stakeholders to receive information tailored to their specific needs or interests, (2) quickens the delivery of information, (3) reduces the volume of email traffic, and thus the number of possible unwanted emails.
If you experience technical problems using this RSS service, please contact email@example.com.
+ What is an RSS feed?
RSS (also known as web feed, XML feed, syndicated content) stands for really simple syndication. When you subscribe to a feed, you receive notices of updated content on the website/webpage to which you have subscribed.
RSS feeds can be used to deliver all types of digital content, such as text, pictures, video or audio. Feeds that deliver audio content (usually in MP3 format) are called podcasts.
More CDM website RSS feeds are planned in the coming months, such as:
- CDM Audio File service
- CDM Governance (meetings of the CDM Executive Board, its panels and working groups)
- CDM Methodologies
If you experience technical problems using this RSS service, please contact us at firstname.lastname@example.org
+ I have forgotten my password, what do i do?
If you have forgotten your username and/or password, use the login/password recovery function.
+ What is a methodology and where can I learn about them?
A methodology is a standard procedure to calculate emission reductions of a typical CDM project, and also to monitor the emissions of that project. The methodology used depends on the type of project. For example for an energy efficiency project, a renewable energy project or a transportation project, the methodology to apply will be different. There are different categories of projects for which different categories of methodologies are available.
Project participants may use an existing methodology. Lists of existing methodologies approved by the CDM Executive Board are available here under "Standards". If no methodology is available, the project participant can submit to the UNFCCC a proposal for a new methodology. The proposed methodology will be evaluated by the Methodologies Panel of the CDM Executive Board, and finally approved or rejected by the Board. If the methodology is rejected, the project participant can submit it again, after taking into account the comments made by the Methodologies Panel.
+ What is baseline?
The baseline is the scenario that represents the GHG emissions that would occur in the absence of the proposed CDM project activity. The project participants can either use the approved methodologies or propose a new methodology for determining the baseline scenario. For more details on baseline, please see the Glossary of CDM Terms.
+ What is additionality?
Emission reductions under the Clean Development Mechanism must be real, measurable, verifiable and additional to what would have taken place without the project. For a proposed CDM project activity, it must be established that the project would not occur under the baseline scenario. Consequently, the amount of GHG emissions from the proposed CDM project activity should be lower than that from the baseline scenario. The additionality of the CDM projects may be demonstrated by the Tool for the demonstration and assessment of additionality.
+ What is the project boundary?
The project boundary defines the area within which emissions reductions occur. Emissions reductions must occur on the project site or result from the project. The project boundary shall encompass all GHG emissions under the control of the project participants that are significant and reasonably attributable to the CDM project activity. Please refer to paragraph 52 and appendix C, paragraphs (a) (iii) and (b) (vi) of the CDM modalities and procedures, in accordance with provisions of Appendix B for the relevant project category.
+ What is leakage?
Leakage refers to any GHG emissions that occur outside the project boundary, as a result of the project. For more details on leakage, please see the Glossary of CDM Terms.
+ How do I submit a new methodology?
To submit a new large scale methodology, please read this information as well as the procedurefor the development, revision and clarification of baseline and monitoring methodologies and methodological tools.
The proposed methodology will be evaluated by the Methodologies Panel of the CDM Executive Board, and finally approved or rejected by the Board. If the methodology is rejected, the project participant can submit it again, after taking into account the comments made by the Methodologies Panel
+ How can I ask for clarification on a methodology or tool?
In accordance with the procedure for the development, revision and clarification of baseline and monitoring methodologies and methodological tools, please fill the CDM-AMC-Form and email to email@example.com.
Further information is available here
All submitted queries and related clarifications can be accessed through our methodologies page.
+ How can I ask for the revision of a methodology or tool?
To request the revision of an approved CDM methodology or tool, please read this information and the procedurefor development, revision and clarification of baseline and monitoring methodologies and methodological tools.
All revision requests may be accessed through the Methodologies page.
+ Which Global Warming Potentials (GWPs) do I have to use starting from 1 January 2013?
In accordance with the Standard for the application of the global warming potentials to clean development mechanism project activities and programme of activities for the second commitment period of the Kyoto Protocol and the underlying CMP Decision, for all emission reductions achieved starting 1 January 2013, the following global warming potentials (expressed in tCO2e/t) should be used:
+ What is a Designated Operational Entity (DOE)?
A Designated Operational Entity under the CDM is either a domestic legal entity or an international organization accredited and designated, on a provisional basis until confirmed by the CMP, by the Executive Board (EB).
It has two key functions:
+ Is there a list of Designated Operational Entities?
The accredited and provisionally designated operational entities can be found here
+ Who can apply for accreditation/designation as a DOE?
Any legal entity (either a domestic legal entity or an international organization) may apply for accreditation/designation as a Designated Operational Entity (DOE). A DOE shall be a legal entity under applicable national and/or international law so that it can function legally, enter into contracts, make decisions independently and may be sued.
For further information please check section III of the CDM Accreditation Standard for Operational Entities.
To become a DOE an organization has to:
+ How much do CERs cost?
The price of CERs is negotiated between buyers and sellers. The secretariat has no role in the negotiation of price, and as such has no information on price.
However, if your question relates to the CDM Registry administered by the secretariat, please see https://cdm.unfccc.int/Registry/index.html.
+ What is validation?
Validation is the process of independent evaluation of a CDM project activity (or programme of activities) by a Designated Operational Entity (DOE) against the CDM rules and requirements. It is a prerequisite for submitting a request for registration. Proposed CDM projects are validated in line with CDM rules and regulations based on the information contained in a project design document (PDD) which, at the beginning of the validation process, has to be published on the UNFCCC CDM website inviting comments from the general public. All PDDs open for public comments are available here.
+ How long does the validation process take?
The length of the validation process differs from project to project depending on the individual circumstances of the project. It starts with the publication of a project design document (PDD) which has to be open for public comment for 30 calendar days (or 45 days in the case of large scale afforestation and reforestation projects). The received comments as well as all project-related details have to be thoroughly assessed by the validating designated operational entity (DOE) and reported in a detailed validation report (VR). This process, which is essential for safeguarding the high quality and environmental integrity of the CDM, can take from 9 months to 2 years and sometimes longer (in exceptional cases). During the validation process, corrective actions by the project participant may be required by the validating designated operational entity (DOE), in order to meet the high standards of the CDM.
+ How long does the registration process take and what does it entail?
Once the validation process is completed, a designated national entity (DOE) can submit an official registration request. The shortest possible time for going through the registration process would be 58 days. However, due to the high number of submissions it usually takes longer, especially in cases where a review is being requested.
After a registration request is submitted and the registration fee is paid, the secretariat endeavours to begin the registration process as soon as possible. The first step is the completeness check, scheduled for 7 days, followed by the information and reporting check, scheduled for 23 days. The relevant checklists may be viewed here
If a registration request does not meet the checking-requirements, it is considered incomplete and the responsible DOE and project participants are notified accordingly. In this case, the registration request may be re-submitted with revised documentation, and will then be treated as a new submission.
Only after the successful completion of both checks is the registration request published on the CDM website and presented to the CDM Executive Board. Parties involved in the project or members of the CDM Executive Board may request a review of any project within the first 28 days of publication. If a Party involved or at least three members of the CDM Executive Board do so, the registration request will go under review. Otherwise, the secretariat will take action to register the project. (please see also 'What is the registration date of my project')
If the secretariat and the RIT differ in their assessment decision, or if a member of the CDM Executive Board objects to the decision, the process will take longer, depending on the schedule of the secretariat and the Executive Board meetings. Further information is available in the CDM Project Cycle Procedure
+ What is the registration date of my project?
For all registration requests submitted on or after 11 December 2010 (including PoA), it is the date on which a complete request for registration has been submitted. This is considered to be the day by which both the registration request and the registration fee have been received by the secretariat. In cases when no fee is required, it is the day on which the registration request was submitted. However, the registration request will only be considered complete when it successfully passes the completeness check and the information and reporting check described in the CDM Project Cycle Procedure
In cases where a registration request is considered incomplete at one of the checks, it has to be re-submitted with revised documentation. The date on which a registration request is re-submitted and successfully passes the checking stages will then be considered the effective date of registration. For all registration requests submitted before 11 December 2010, it is the day following the period during which a review may be requested.
For all registration requests which were under review, and for which the review resulted in the conclusion to register, it is the day on which the latest revisions to the validation report and/or supporting documentation were submitted."
+ What is the start date of my project?
In the context of a CDM project activity or programme of activities (PoA), it is the earliest date at which either the implementation or construction or real action of a CDM project activity or PoA begins. Further clarification is given in paragraph 67 of the forty-first meeting report of the CDM Executive Board
+ What is CDM prior consideration?
The submission of the "prior consideration of the CDM" form is an initial notification of the intention to seek CDM status.
If a project has already started before
a notification of CDM prior consideration is required to demonstrate that the benefits of the CDM were a decisive factor for taking up the project. This notification has to be sent to the host country's DNA and the UNFCCC secretariat within 6 months of the project start date, as specified in the CDM Project Cycle Procedure
The relevant form is available here.
Notifications are publishedon the UNFCCC CDM website.
Please see also 'What is the start date of my project'?
+ How can I check the status of my project?
To check the status of your project once it has been submitted for registration by the DOE, please see this page.
For projects which have successfully passed the completeness check and the information and reporting check or which are already registered, please click here
+ How does the end of the Kyoto Protocol's first commitment period on 31 December 2012 impact my monitoring reports?
All CERs issued under the CDM have to indicate the corresponding commitment period for which the related emission reductions are verified. In order to clearly differentiate emission reductions monitored for the period up to 31 December 2012 from those monitored for the period starting thereafter, project participants may adjust monitoring periods to end on 31 December 2012 and start on 1 January 2013 respectively. However, this approach is only possible if exact measurements can be carried out on those dates.
Alternatively, it is possible to cover this transitional period in one monitoring period. In this case, all monitored emission reductions for this period have to be allocated proportionally to the duration of the period up to 31 December 2012 and from 1 January 2013 onwards. If annual caps are being applied in the calculation of emission reductions, these annual caps have to be pro-rated to the period before and after 31 December 2012.
For detailed information, please refer to paragraph 71 of the EB 62 report.
On this basis, the relevant form has been amended to accommodate new fields for indicating emissions reductions or removals achieved in separate periods: up to 31 December 2012 and from 1 January 2013 onwards.
The monitoring report form is available here:
The guideline for completing the monitoring report form is available here:
The CER issuance forms are available here:
Please see also the "Post 2012" section of this page
+How do I provide a status update of my registered project activity or programme of activities?
According to the "Clean development mechanism project cycle procedure" , the project participants of a registered CDM project activity or the coordinating/managing entity (CME) of a registered CDM programme of activities (PoA) shall provide an update of the status of its implementation at the indicated timing and frequency unless a DOE has published a monitoring report for the project activity or PoA.
Also, according to the same procedure, the designated operational entity (DOE) shall provide an update of the status of verification at the indicated timing and frequency after publication of the corresponding monitoring report unless the DOE has submitted a request for issuance.
The dedicated interface referred to in the above mentioned paragraphs is currently under development. Until further notice, project participants, CMEs and DOEs are requested to provide an update of the status by sending an e-mail to firstname.lastname@example.org with the subject "Update of status of implementation of registered PA/PoA" or "Update of status of verification", clearly indicating the project activity/PoA number, title and the status in accordance with the relevant paragraph of the above-mentioned procedure.
+How do I notify the secretariat about postponing the start date of the crediting period by up to 1 year (or up to 2 years for projects in least developed countries)?
According to the "Clean development mechanism project standard , the project participants of a registered CDM project activity or the coordinating/managing entity of a registered CDM programme of activities (PoA), shall notify the secretariat of a change to the start date of the crediting period of the CDM project activity or PoA, if the change meets the condition set out in the same paragraph. In this case, the notification shall be submitted by email to email@example.com, including the following information:
+Is there an opportunity to discuss case-specific issues with the secretariat?
As of 1 February 2013, designated operational entities (DOEs) shall submit registration and issuance requests, requests for deviation from an approved methodology and requests for approval of changes to registered CDM projects under the CDM Project Cycle Procedure.
At certain stages of the assessment processes as described in this document, DOEs, project participants and/or coordinating/managing entities (CMEs) for programmes of activities (PoAs) may request, through email, a telephone call appointment from the secretariat in order to clarify issues identified during the relevant assessment stage.
Within three days of receipt of the request, the secretariat will acknowledge receipt and propose a date and time for a telephone appointment that can take place at a later stage. Only one call is permitted for each submission as these consultations are meant to clarify rather than provide solutions.
Requests for telephone calls under the Project Cycle Procedure have to originate either from the contracted DOE or the registered focal point for scope (c) as stated in the modalities of communication (MoC). All such requests MUST be sent to firstname.lastname@example.org the following subject line:Request for Telephone call - Direct Communication - Project No....
+How do I request post-registration changes for my project?
Detailed information on the permitted changes and the approval process is available in the respective section of the CDM Project Cycle Procedure the CDM project standard
The below provides practical guidance:Process / Format
+ What is the registration fee?
Project participants pay a registration fee to cover the administrative costs of registering their projects and an issuance fee to cover the cost of the issuing certified emission reductions (CERs) generated by the project activity. The calculation of the registration fee is based on the validated figure submitted by a DOE (i.e. the estimation of the annual emission reductions - on the basis of a PDD). The registration fee is usually paid by the project participants, through the DOE, at the time of the request for registration (once only). Further details are available in appendix 1 of the project cycle procedure
+ What is the Share of Proceeds (SOP-Admin)?
The share of proceeds paid by project participants is calculated in a similar way as the registration fee (see response above), but is calculated on the verified figure (i.e the actual amount of emission reductions that have been monitored over a period).
The registration fee is deductible from the SOP-Admin, i.e. the registration fee could be considered as a sort of administrative advance payment. This means that, following the first monitoring period after the implementation of the project, should the paid registration fee be superior to the SOP-Admin, it would not only offset this first SOP-Admin payment, but the positive balance would be applied to the second monitoring period, and so on.
The SOP-Admin is usually paid at the time of each request for issuance of certified emission reductions.
For the exemption of fees and reimbursement rules, please refer to appendix 1 of the project cycle procedure
+ Is the UNFCCC secretariat a "Sovereign" or "Statutory" Body? What type/line of business does this fall under?
The UNFCCC secretariat is an international organization. Please note that it is not a company and does not have a company ID.
+ In which currency should the registration or share of proceeds (SOP) fees be paid?
Please always pay in US Dollars. All transfer charges are to be borne by the payee to ensure the full invoiced amount is received by UNFCCC secretariat. Please instruct your bank accordingly.
+ What are the terms of payment?
Payment is due upon receipt of the submission confirmation email which includes the amount to be paid. Any transfer charges incurred during the payment of the fee shall be borne by the project participants.
+ Where can we obtain the bank details of the UNFCCC?
Please contact your DOE for the UNFCCC bank details. If you are a DOE, please click on the following secure link and log in to see the bank details. https://cdm.unfccc.int/DOE/BankingInfo.html
+Is there a Tax ID number or German identification equivalent?
The UNFCCC secretariat is registered with the German tax office under the reference number S 7495 - 22010000.
+ Can Tax ID numbers be included on invoices?
No, this is not required, as the UNFCCC secretariat is tax exempt.
+ Can we have a Tax residence certificate?
No, the UNFCCC does not have a Tax residence certificate. If you require further information regarding the secretariat's tax exempt status, please contact us at email@example.com
+Summary of the rules agreed in Doha for the mechanisms during the second commitment period of the Kyoto Protocol
This section summarizes the rules agreed at the United Nations climate change conference in Doha in December 2012 for the operation of the mechanisms in relation to the second commitment period under the Kyoto Protocol, which runs from 1 January 2013 to 31 December 2020 inclusive. These rules do not affect the operation of the mechanisms in relation to the first commitment period (e.g. the issuance, transfer, acquisition, and use of units valid for the first commitment period, including in the true-up period), which remains unchanged.
+What CERs may be used in complying with emission targets for the first commitment period?
CERs may be used by Annex I Parties for compliance with their emission targets for the first commitment period as long as they are valid for the first commitment period. CERs are valid for the first commitment period if they are issued for emission reductions or removals taking place in the first commitment period, regardless of their actual date of issuance. The validity of a CER can be determined by looking at its serial number.
+Can CERs valid for the first commitment period be traded after 2012?
The Kyoto Protocol rules allow CERs valid for the first commitment period, as with other types of units, to be traded into or out of accounts in a Party's national registry until the end of the 'true-up period' associated with that commitment period. This applies to all Annex I Parties with emission targets for the first commitment period, whether or not they accept emission targets for the second commitment period. This true-up period is defined as extending to 100 days after the date agreed by the Parties for completing the reviews of Annex I Parties' emission inventories for the 2012 calendar year. On this basis, the true-up period associated with the first commitment period is expected to extend until mid-2015. CERs valid for the first commitment period may not be traded after this date unless they are first 'carried over' to the second commitment period, at which point they become valid for the second commitment period.
Most non-government buyers and sellers of CERs will, however, fall under the rules for domestic or regional emissions trading systems, such as the EU emissions trading system, which may impose other deadlines for using CERs valid for the first commitment period. These market participants are likely to need to confirm the deadlines for surrendering CERs against entity-level targets and/or exchanging CERs valid for the first commitment period for units issued by such trading systems, as applicable, under the rules of such systems.
+How can CERs valid for the first commitment period be carried over to the second commitment period?
Annex I Parties may decide to 'carry over' CERs valid for the first commitment period into the second commitment period. Such carry-over transactions, as initiated by national registries, result in the serial numbers of the CERs being updated. Each Annex I Party is limited in the number of CERs that it may carry over from the first commitment period. This limit is set at 2.5% of the Party's original allocation of assigned amount for the first commitment period. Each Party may determine which CERs in its national registry are to be carried over. It is not possible to carry over tCERs or lCERs. There are no provisions allowing the carry-over of CERs held in accounts in the CDM registry.