Data Assurance Service

Accurate and reliable data is critical to the effective operation of the non-household (NHH) market and is key to operational efficiency, evidence-based improvement, and positive customer and environmental outcomes. However, data quality remains a principal market friction that is driving significant cost for trading parties and impacting the market’s ability to deliver better outcomes.

The logic and cost of trading parties working independently to fix core data fields has been questioned, with the current rate of improvement being too slow for benefits to be realised.

As part of the 2024-27 Business Plan, trading parties have approved the second year of the Data Assurance Service (previously name Data Cleanse Service), which is being funded by wholesalers under code change Data Cleanse Funding (CPW050).


On 5 October MOSL presented a webinar on the progress of the Market Eligibility Assurance (previously referred to as 'high-confidence non-eligible') phase of the programme.

Proposed solution

In partnership with a data services provider, MOSL will deliver a centrally supported data assessment and cleanse service to enable trading parties to improve and maintain the data held in CMOS.

This service will complement the work that is already underway within trading parties. Trading parties will remain the data owners and will be responsible for making the appropriate changes.

MOSL will be responsible for implementing, maintaining, and monitoring the service, incentivising data quality improvement, and ensuring data quality targets are being met.

We will work collaboratively with trading parties during the detailed design phase to agree the specific data items that are provided and the mechanism by which feedback is received and addressed. The data provided to trading parties will include:

  • Ineligible premises (residential, demolished, and duplicate)
  • Unmatched supply points (i.e., address data insufficient to identify a unique premises with confidence)
  • Missing Unique Property Reference Number (UPRN) and Valuation Office Agency (VOA) reference data
  • Full address data non-deliverable and non-addressable premises.

We will adopt a gated approach which will set out a number of ‘proof points’ to evidence the value in continuing the next phase of work. This approach mitigates the potential impact on retailers to implement changes and reduced the costs of the service in year one to the lower range proposed in our consultation at £550k (covering third party costs and MOSL resource).

In parallel, we will review the impact of key market processes on the enduring data quality, for example, the new connections process, and recommend improvements.

Programme timeline

The timeline for each of the phases can be found below: 

Data Assurance Service timeline

For further information on what is set to be delivered in 2024/25, please see the Data Assurance Service section of the 2024-27 Business Plan.

Market Eligibility Assurance Review

From 22 November 2023, the non-household market have begun the Market Eligibility Assurance Review phase of the Data Assurance Service.

It involves trading parties reviewing and assuring or deregistering supply points that are considered ineligible for the market.

Trading parties have been given access to CMOS data which has been grouped into assurance levels 1, 2 or 3. Whilst trading parties have access to the entirety of this data, they are only required to review the ‘Level 1’ supply points within 12 months. Level 1 supply points are defined as those that have the highest match against multiple external data source indicators, suggesting that it holds a household status and is therefore ineglible for the non-household market. Trading parties are being asked to review their data and submit to MOSL monthly, to collate the decisions from the wholesaler and the retailer. This data is underpinned by a quarterly Data Quality Audit, which tracks progress and volumes of data..

The full process is outlined within the specification document, which is available via the Key documents page

The assurance files will be available in My Files, which can be accessed via the My MOSL homepage. Access to My MOSL has already been given to Contract Managers. If you require additional access, please contact IT Support via My MOSL.

If you have any questions on the activities required within the Market Eligibility Assurance Review phase, please contact us via IT Support on My MOSL.

To review both market-wide and trading party-specific progress on this assurance activity, please visit the dashboard on My Charts.

View Market Eligibility Assurance dashboard

Premises and Address Assurance Review

MOSL is currently piloting the criteria for the second phase of the Data Assurance Service, the Premises and Address Assurance Review. 

This involves the development of a criteria that identifies missing or incorrect UPRN, VOA and address field data and offers an alternative for trading parties to accept or reject.

We are looking to commence the market-wide assurance activity in June 2024. We will host a webinar and supporting materials for trading parties in due course.

If you are not a Contract Manager but would like to receive updates regarding this phase, please ensure you are signed up to receive 'Data Insight and Analytics' emails.

Project TIDE and the Data Quality Assessment

Project TIDE (Transformation in Data Enrichment) was established in April 2022 by MOSL and Sagacity to assess the quality of premises, address, and customer data within CMOS.

Sagacity, undertook a Data Quality Assessment, which reinforced the extent of the issues in core market data. Key findings were shared with trading parties and the wider market in August 2022, with further detail on the impact of poor data quality provided in the Data Cleanse Consultation document issued in November.

To review the full findings, read the report below.

Read Data Assessment Report

'MOSL Talks'

An interview with former MOSL CIO John Davies on the scope of the programme and the impact on trading parties.


Related documents

Market Eligibility Assurance Review good practice guide v1.1


Data Cleanse Webinar - 051023


Data Cleanse Service Steering Group Terms of Reference


Data Cleanse Service Working Group Terms of Reference


Market Performance Framework (MPF) Reform

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