Proposing a Change

Anybody can propose a change to the Market Arrangements Code (MAC) and Wholesale Retail Code (WRC) provided it meets the Initial Acceptance Criteria applied by the market operator (MOSL) and Acceptance & Prioritisation Criteria applied by the Code Change Committee. 

Before submitting a proposal we recommend you review the Code Change Process and contact us on for informal advice and assistance on drafting proposals and their acceptance into the change process. The change charter below provides more information on the service offered by MOSL.

Proposals should clearly articulate the problem statement they seek to address, supported by evidence wherever possible. It is not necessary to provide a solution. When ready to formally submit a change proposal for assessment against the Initial Acceptance Criteria, please complete the Change Proposal Form below and email it to The outcome of assessments against the Initial Acceptance Criteria are shown on the Pipeline Changes webpage. If a proposal does not pass the Initial Acceptance Criteria the proposer can revise and re-submit it. If the proposer disagrees with the market operator's decision and suggested improvements, they can appeal to the Authority by emailing 

Once a proposal has met the Initial Acceptance Criteria, further investigation and analysis may be required before presenting it to the Code Change Committee for assessment against the Acceptance & Prioritisation Criteria. Once the Committee accepts a proposal into the change process, MOSL and the Committee will ratify the approach and timetable for further analysis and development of solutions including whether the proposer wishes to develop their own solution, or has decided to hand over the solution development responsibility to MOSL.

Analysis and development can take from days to years depending on the urgency, priority and complexity of the proposal. It may include input from the market operator, working groups, Strategic Panel committees and wider stakeholder groups. Proposers will be invited to engage and provide their own views and evidence. Once assessed and developed, a recommendation is made to Ofwat on whether the proposal should be approved. All changes to the codes and consequential changes to central systems must be approved by Ofwat.

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