Design Artefacts Guides
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 They are retained for historical reference only.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Documents are now the single source of truth, and any changes made through Code governance will not appear in the historical documents.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.
The Design Team have developed a series of documents to support understanding of the Design Artefacts, along with some Q&A:
Design Artefacts Guidance & Signposting to help participants identify the Design Artefacts relevant to their organisation
Design Artefacts Matrix to help constituencies understand which Design Artefacts are of most relevance to them
MHHS Knowledge Baseprovides answers to all Design-related questions we've received regarding Design. You can click on the link above, or view the Knowledge Base on the Collaboration Base under 'Programme Information'.
Design Artefacts: DateTime Guidance This guidance is uplifted to v1.4 and has been provided to support the implementation of CR036: Use of Clock Midnight for Appointments and Reads. It does not change the design to CR036 but provides clarity to Programme participants about how to use the DateTime fields in MHHS Flows in line with Interim Release 7 onwards. For more information on CR036, please click here: CR036: Use of Clock Midnight for Appointments and Reads.
Meter Reading Service Guidancehas been provided to support the implementation of Meter Reading Service as part of the Smart Data Service Role and does not change the Design. However, a Design Issue Notification (DIN-1066) has been raised to provide clarifications and there will be a minor amendment of Balancing & Settlement Code (BSC) Code Drafting to make the Design intent clearer.
Data Integration Platform (DIP) Application Programming Interface (API) Message Exchange Guidance has been provided to supplement guidance on the End-to-End Solution Architecture document. This is to support participants with the message exchange with the DIP, including message batching, API/webhook behaviour and message sizes.
Advanced Load Shapes Guidance has been provided to clarify which Load Shapes are applied for the Advanced Market Segment:
- Where a customer has consented to HH readings and;
- Where a customer has opted out of HH readings
Use of Boolean Data Type Guidance has been published following a number of Defects identified in Systems Integration Testing (SIT). This guidance has been provided to clarify how Programme participants should use the Boolean Data Types within the Data Integration Platform (DIP) routed JSON format messages.
If you have any questions about these documents, please email the Design Team at Design@mhhsprogramme.co.uk
Meterless Sites Migration Guidance details how to manage Meter Point Administration Number (MPAN) migrations for sites without meters in four scenarios, and advises installing meters before migration to ensure correct segment assignment and to streamline the process.
Reverse Migration Meter Technical Detail (MTD) Guidance covers how a Metering Service (MS) and Meter Operators (MOPs) exchange MTDs during reverse migrations, including manual transfers if the Supplier does not send a D0205 in time.
