The long‑awaited Market‑wide Half‑Hourly Settlement (MHHS) is officially commencing this September 2025, marking a significant turning point for the UK energy industry. From 22 September 2025, major code changes under Milestone 8 (M8) come into force, laying the groundwork for a smarter, more accurate electricity settlement system.
Why It Matters to Brokers and Their Clients
• True‑to‑use billing: All energy consumption will be settled using smart half‑hourly data, eliminating guesswork and estimated reads. 
• Operational precision: MPAN formats (like MTC and LLFC) will update to SSC ID and DUoS Tariff ID from 22 September 2025. Brokers should anticipate where these changes appear on bills and contracts. 
• New systems live: Central settlement systems begin operating from late September, with the formal migration window opening in late October 2025. 
Implementation Timeline
| Date | Milestone |
|---|---|
| 22 Sept 2025 | Milestone 8 (M8): Code changes & MPAN format updates go live |
| Late Oct 2025 | Migration window opens |
| May 2027 | Final migration deadline—every MPAN must be settled half‑hourly |
| July 2027 | Full new settlement timetable in effect |
FAQs
1. What is MHHS and why does September 2025 matter?
Market-wide Half-Hourly Settlement (MHHS) is the UK’s transition to using half-hourly electricity consumption data for all customers, powered by smart and advanced meters. Instead of relying on estimates or infrequent reads, energy use will be settled every 30 minutes, creating a more accurate and flexible market.
From 22 September 2025, Milestone 8 (M8) comes into effect, triggering major code changes across the industry. This date is important because it marks the point where brokers, suppliers, and businesses must begin aligning systems and processes with MHHS requirements. For brokers, it’s an opportunity to demonstrate thought leadership and reassure clients through this shift.
2. How will this impact MPANs and billing?
The most immediate visible change will be in MPAN formatting. From September 2025:
- The Meter Timeswitch Code (MTC) is being replaced by the Standard Settlement Configuration (SSC) ID.
- The Line Loss Factor Class (LLFC) is being replaced by the DUoS Tariff ID.
These changes won’t directly affect energy prices but will appear on invoices, supply contracts, and broker quotes. Brokers should familiarise themselves with these new identifiers so they can clearly explain them to customers who may be confused by the updated formats. Transparency here will build client trust and prevent unnecessary disputes.
3. When does the actual migration start, and how long will it last?
The migration period officially begins in late October 2025, shortly after the September code changes. It will run for around 18 months, with the final deadline for full migration set for May 2027.
This means brokers will need to manage clients through a staged process:
- Early adopters may transition sooner to unlock tariff opportunities.
- Others may wait until closer to the deadline, but risk bottlenecks if suppliers and data service providers are overwhelmed.
Brokers who stay proactive during the migration will be able to offer smoother transitions, better tariff options, and improved client retention.
4. What should brokers advise clients to do?
Energy brokers can add real value by guiding clients through MHHS preparation. Key advice includes:
- Audit current metering: Check whether clients have smart meters or AMR meters that support half-hourly data. Where gaps exist, support the upgrade process.
- Check supplier readiness: Not all suppliers are equally prepared for MHHS. Confirm their plans and timelines to avoid client disruption.
- Track milestones and deadlines: Share regular updates on MHHS developments, so businesses stay ahead of regulatory change.
- Plan for tariff flexibility: Highlight that MHHS will allow businesses to benefit from time-of-use tariffs—ideal for those who can shift usage to off-peak times.
By positioning these actions as a structured “readiness checklist,” brokers can strengthen their advisory role.
5. What benefits can businesses expect?
Businesses will gain several practical benefits from MHHS, including:
- Accurate billing: Half-hourly data eliminates reliance on estimates, reducing billing disputes.
- Access to innovative tariffs: Time-of-use pricing could help businesses cut costs by shifting energy-intensive operations to cheaper periods.
- Improved energy management: Clients can use real-time consumption data to identify inefficiencies and make smarter operational choices.
- Net-zero alignment: Half-hourly settlement supports renewable integration, enabling businesses to demonstrate sustainability credentials and meet ESG targets.
For brokers, these benefits are key selling points when communicating the value of MHHS to clients.
6. How can brokers support businesses?
Brokers have a unique opportunity to become trusted advisors during this transition. Support can include:
- Clear communication: Regularly update clients on what MHHS means, when changes will happen, and what action is required.
- Metering support: Guide clients through smart meter rollouts, ensuring compatibility and minimal disruption.
- Supplier liaison: Act as the client’s representative in conversations with suppliers, clarifying contract changes and migration timelines.
- Paperwork and compliance: Simplify the administrative side of MHHS-handling forms, technical queries, and code references—so clients don’t feel overwhelmed.
- Strategic advice: Use MHHS as a platform to discuss long-term energy strategy, cost optimisation, and sustainability planning.
By being proactive and visible, brokers can turn MHHS into a relationship-building exercise rather than a compliance headache.