Design Overview
Please note that as of 1 September 2025, the MHHS Programme Design mailbox, Design artefacts and the Design Issues Notification (DIN) log on the MHHS website are no longer monitored or updated. They are retained for historical reference only.
Following Milestone 8 (M8), the Target Operating Model (TOM) and MHHS Design were fully codified, and the Code Bodies no longer maintain standalone Programme artefacts. The live Code and Code Subsidiary Documents are now the single source of truth, and any changes made through Code governance will not appear in the historical documents.
You can view the latest artefacts online, directly from the respective Code Bodies websites, listed below:
Balancing & Settlement Code (BSC)
Retail Energy Code (REC)
Distribution Connection and Use of System Agreement (DCUSA)
For the latest information or to raise queries, please use the Elexon Support Portal or contact the respective Code Bodies directly.
Design Baseline Approved
On 31 October 2022, the Design Advisory Group (DAG) approved the Physical Design Baseline, thereby completing Milestone 5: Physical baseline delivered. This approval was subject to the Programme delivering the remaining elements of the design included in the Work-Off Plan.
On 16 February 2023 DAG approved the re-baseline of the Design Artefacts.
Accessing the Design
Design information is aligned across the different design areas and formats, so you can choose whichever works best for you as a participant:
- Baselined Design Artefacts in document form, as stand-alone documents
- Design Models as integrated views of the baseline Design
- Red-lined Design Artefacts as changes and tracked-changed versions for each release
- Transition Design in document form, as stand-alone documents
- Migration Design in document form
The full set of the Baselined Design Artefacts are available on the Baselined Design Artefacts page of this website.
The Design Models are available on the Collaboration Base.
The Artefacts and Models will be updated as required, and will remain in alignment.
Design Baseline and Interim Releases
The Design was re-baselined on 16 February 2023 following completion of the Design Work-Off Plan.
Design Artefacts (including all five areas mentioned above) are updated in accordance with the Design Review Process. The Baselined Design Artefacts will be updated as part of a release schedule, and you can view details of the Interim Releases on the Red-lined Design Artefacts page of this website.
Design Review Process
The Programme has established a new process for updating Design Artefacts.
For more information, visit the Design Review Process page of this website.
