Market Entry Assurance is the process applicants must take to provide assurance that their business capability can uphold market obligations.

The MEA process consists of a series of documents applicants must complete to establish their interest in entering the market, their plan for operation, how they gained assurance and evidence on how they are able uphold their obligations, and if necessary, how they will carry out market entry assurance testing. For further information on this process please refer to CSD 0001 (Market Entry Assurance and Market Re-assurance).


This is the first step in the MEA process. The Trading Application is a simple form designed to signal an applicant’s intent to start the process. It provides MOSL with information on the applicant and their intentions within the market.

The Applicant Information Return (AIR) asks applicants to set out their plans for operating in the market. It includes questions around business structure, operating model, training, policies, procedures and systems that will be used. Not all capability needs to be in place at this stage of the process, but if it’s not, applicants need to provide dates of when it will be available to MOSL. The AIR is also where applicants decide how they will progress through the MEA process and whether they plan to go through enhanced certification or self-certification.

The decision whether to go through enhanced or self-certification MEA should be made by applicants based on the following criteria:

  • Small scale of operations
  • Use of only the LVI
  • Mainly manual processes

 If applicants meet all the above criteria, they can progress through self-certification MEA. If they are using the HVI, have a large scale of operations, or mostly automatic processes, they will need to go through the enhanced route.

Here, applicants will set out their planned Market Entry Assurance Plan (MEAP) showing when they expect to proceed through the rest of MEA. Using this draft template, applicants should enter the dates in which they would prefer to attend training, and when they plan to submit the rest of the documentation required. The MEAP helps applicants to plan when they are estimated to complete the process, and helps MOSL plan resourcing for activities such as training and testing accordingly.

Market and Interface Training is made up of two stages. The first, Market Training, is designed to provide applicants with an overview of the market, including codes and subsidiary documents, the market framework, market entry assurance, and settlement. The second, Interface training, is ‘classroom-style’ and provides applicants with direct training on how to use the CMOS Portal (or LVI). All applicants must attend both stages of training, but it is particularly beneficiary for applicants who plan to only or mostly use the LVI.

Market Training
Market training is made up of these training slides. Applicants must review the slides before attending Interface Training.

Interface Training
Dates for interface training are confirmed on agreement of an applicant’s MEAP. For the subjects covered in Interface Training, please see the attachment below. MOSL runs two types of Interface training, aimed at both wholesalers and retailers. While a lot of the content is transferable, the sessions are targeted specifically to either wholesalers or retailers to provide the best view of the transactions applicants are likely to use in the market. As such, it is important that applicants who are entering as both a wholesaler and a retailer attend both sets of training.

Interface training will take up to two days, and will be based either in London or Reading, depending on the availability of trainers. MOSL will confirm the location when confirming the dates.

Click to view the Interface training content outline for wholesalers or the Interface training content outline for retailers.

Applicants who meet the criteria to complete the self-certification route need to complete a Self-Certification Declaration. This is a way for applicants to self-certify their own readiness to operate in the market. Applicants must provide assurance on a set of 36 assurance statements, confirming they have the capability in place to uphold market obligations. Applicants also need to include a third-party report, covering the applicant’s approach to assurance and the outcomes of this assurance. Any capability that was not in place when the AIR was submitted should now be ready, as applicants are providing assurance that they can operate and uphold all their market obligations.

The Security Return should be submitted at the same time as the Self-Certification Declaration, for applicants going through self-certification MEA. It provides additional assurances on the applicant’s interaction with CMOS, and provides evidence that they have sufficient security policies and procedures in place.

The Business Solution Assessment (BSA) should be completed by all applicants going through enhanced MEA. It asks applicants to provide details of the approach they took to completing the assessment (which should be risk-based) and requests assurance on a set of 36 assurance statements, the assurance activities undertaken, and a view of company-specific risks considered. Similar to self-certification, the enhanced MEA process also asks companies to provide a third-party report. The third-party report should provide assurance on the approach the applicant has taken and on as many assurance statements as the applicant deems appropriate. Any capability that was planned but not in place for the AIR should now be implemented, as applicants are providing assurance on their ability to operate and uphold their market obligations.

MEA Testing (MEAT) is made up of two phases; Interface and Data Transaction Testing (IDTT), which tests whether the applicant’s systems can communicate with CMOS and; Market Scenario Testing (MSR), which is a series of business scenarios likely to be used in the market. Applicants need to complete both phases, but only need to carry out scenarios which involve capability to be used in the High-Volume Interface (HVI). If a scenario is intended to be carried out only using the Low Volume Interface (LVI), an applicant would not have to complete it.

The MEAT plan details how a company plans to run Interface and Data Transaction testing (through CMOS) and market scenario testing (the steps involved in switching a customer. i.e. registering a new supply point, submission of meter reads and settlement). It asks applicants to specify scenarios they will complete, the steps they will undertake in each scenario, and the exit criteria. The MEAT plan should be submitted at least 10 business days before applicants are due to begin testing. This allows MOSL sufficient time to review the plan and make amendments as required.

As part of the MEAT Plan, companies should fill in the MEA Test Script Pro-forma, where they specify scenarios they will complete, the steps they will undertake in each scenario, and the exit criteria. 

Once applicants have completed MEAT, they should submit a Systems Declaration to confirm the systems which were tested are those that will be used in the market. This is the last document enhanced applicants complete in the process. On acceptance of the Systems Declaration, MOSL will grant applicants with MEA Certification.


MEA test workflow

Once an applicant has successfully completed the MEA process, MOSL will grant MEA Certification, confirming the applicant’s capability is certified for use in the market MOSL will also inform Ofwat that MEA certification has been granted, so they can issue the applicant with a licence to operate. 


Most applicants take between 40-60 business days to complete the Market Entry Assurance process, depending on whether they go through self-certification or enhanced certification.

There are two routes applicants can take to complete MEA; self-certification and enhanced. Applicants with small scale operations, mostly manual processes, and who intend to only use the Low Volume Interface (LVI) in CMOS can go through self-certification. This is considered the ‘light-touch’ route. All other applicants must go through the enhanced certification route, which involves providing more in-depth assurance to MOSL and undergoing testing of the company’s systems. 

MEA provides MOSL and other Trading Parties with assurance that you can uphold your market obligations and ultimately participate in the market. It also fulfils two Trading Conditions.

MOSL does not charge applicants to undergo MEA. 

Each MEA document will ask for different types of information, and will clearly explain what you are expected to provide. While supporting documents such as process maps or policies are not required, you can submit these if you feel they will help MOSL to better understand your company’s capability. 

It is up to you who signs the documents, but it should be someone with authority to sign on behalf of your company. 

MOSL has not specified the level of detail required, as it differs between applicants and depends on individual circumstances. We are happy to review drafts and answer questions before you submit final versions. Please contact for more information. 

Market Entry Assurance Testing (MEAT) involves two stages; Interface and Data Transaction Testing (IDTT) and Market Scenario Testing (MST). IDTT is designed to ensure your company’s systems can interact with the CMOS, whereas MST provides a series of business scenarios to ensure your systems can complete common system transactions. For more information on MEAT, see the MEAT plan. 

Only applicants going through enhanced MEA need to do MEA Testing. 

Yes, MOSL provides test data for new entrants who need to complete MEA Testing.

No. You only need to complete all scenarios if you plan to use all transactions in the High-Volume Interface (HVI). If you only plan to use the HVI for select transactions, you only need to complete scenarios in which these transactions feature. 

We strongly encourage applicants to complete their MEA Testing within a 10-day window. However, if you are unable to complete testing within this timeframe, it can be extended. 

If one of the BSA assurance statements is not applicable to your business, for example you are not offering accredited entity schemes, you do not need to complete the statement.

The third party report should cover your company’s approach to completing the Business Solution Assessment, and should assure the outcomes of the assurance undertaken. If you consider some statements to carry a higher level of risk, you may consider it appropriate for the third party report to provide assurance on these statements as well.

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