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 2023-26 Business Plan, trading parties have approved a cleanse of non-eligible supply points and a proof of concept on a centrally managed cleanse service of premises and address data.

As the programme moves into year two, it has been been renamed from Data Cleanse Service to Data Assurance Service, to more accurately reflect the deliverables of the programme.


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 reduces 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.

2023/24 deliverables

The key deliverables for 2023/24 can be found below. Please note these dates are subject to change:

 Updated 2023 24 Data Cleanse Service deliverables

For further information on these deliverables, please read the Central Cleanse Service section of MOSL's 2023-26 Business Plan.

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

Market Eligibility Assurance Review

From 22 November, the non-household market will begin 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.

From 22 November, trading parties will have 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. 

The full process is outlined within the specification document, which is available via the Key documents page. It also includes further information on file formats, roles and responsibilities, and reporting.

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

'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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