Help shape the future of Tariff Interoperability: Phase 1b consultation now open

November 6, 2026

The Department for Energy Security and Net Zero (DESNZ) and RECCo are inviting industry views on the proposed arrangements for sharing account-specific tariff information as part of Tariff Interoperability (TI) Phase 1b.

The consultation is open until 18 December 2026 and asks for feedback on the regulatory, design, technical and implementation arrangements needed to deliver Phase 1b under the Smart Secure Electricity Systems (SSES) programme.

What is TI Phase 1b?

TI Phase 1b builds on TI Phase 1a, which requires TI Energy Suppliers to make public tariff pricing data available through a standardised API from 18 February 2027.

While Phase 1a makes tariff pricing data available, optimisation services also need to know which tariff applies to a consumer’s energy account. TI Phase 1b addresses this gap.

With an account holder’s permission through the Consumer Consent Service (CCS), an authorised Registered Tariff Interoperability (RTI) User will be able to identify the tariff linked to an energy account and receive notifications when relevant account or tariff information changes. This will help Energy Smart Appliances (ESAs), such as smart electric vehicle chargers and heat pumps, and optimisation services respond to current tariff prices. The aim is to help consumers use electricity at cheaper, less-busy times, thereby supporting a smarter and more flexible energy system.

How will TI Phase 1b work?

The proposed TI Phase 1b journey uses the CCS to manage account holder verification, permissions and authorisation. The process involves five main steps:

Permission: The account holder grants permission through the CCS for their account-specific tariff information to be shared
Account verification: The TI Energy Supplier supports account holder verification by confirming that the person referred by the CCS holds the relevant energy supply account, and provides the relevant MPxNs
Information request: The RTI User requests account-specific tariff information from the TI Energy Supplier using a CCS-issued access token, which confirms that permission is in place
Tariff identification: The TI Energy Supplier responds with the Tariff Identifier(s) for the associated MPxNs, which the RTI User then uses to retrieve tariff pricing data through the TI Phase 1a public API
Ongoing notifications: Where the permission includes ongoing notifications, the TI Energy Supplier sends a TI event notification to the RTI User when relevant account or tariff information changes

The decision to implement TI Phase 1b and use the CCS was confirmed in the May 2026 Government Response and is not being reconsidered through this consultation.

The common CCS arrangements were consulted on separately between 7 September and 19 October 2026. This consultation focuses on how those CCS capabilities are used within, and interact with, the TI Phase 1b journey.

What are we consulting on?

We are seeking views from Suppliers, potential RTI Users and other interested parties on whether the proposed arrangements are complete, workable and capable of successful implementation in November 2027. In particular, we welcome views on:

Whether the proposed end-to-end TI Phase 1b design is complete and workable, including its interface with the CCS
Whether the proposed REC obligations, definitions and governance arrangements are sufficient
Whether the TI API Technical Specification, market messages, data items and associated standards capture the required technical arrangements
Whether the implementation plan is achievable and the proposed high-level testing principles provide an appropriate basis for the detailed TI Phase 1b Test Approach and Plan
The proposed approach to multi-rate tariffs where the applicable time-of-use periods depend on meter configuration

Published documents

The consultation letter and questions (Annex A) are published alongside six annexes, which together set out the proposed arrangements for TI Phase 1b:

Annex A – Consultation Letter & Questions
Annex B – Policy and TI Phase 1b Design: the detailed end-to-end design. All reviewers should read this annex.
Annex C – Implementation Plan and Testing Approach: the proposed implementation stages and testing principles
Annex D – REC Schedule 35: Tariff Interoperability Arrangements: proposed drafting for version 2 of Schedule 35, together with new and amended definitions for REC Schedule 1
Annex D – Appendix: Redline
Annex E – TI API Technical Specification: a REC Category 2 document bringing together the TI Phase 1a and Phase 1b technical requirements
Annex E – Appendix
Annex F – Energy Market Data Specification (EMDS): new and amended TI data items and market messages
Annex G – TI Developer Portal: the physical definition of TI interactions, a REC Category 3 artefact building on the portal implemented for TI Phase 1a
Consultation response proforma

How to respond and next steps

Responses should be submitted using the consultation response proforma and emailed to: TariffInteroperability@retailenergycode.co.uk by 18^th December 2026.

Where feedback also relates to the CCS, please explain its effect on TI Phase 1b and state whether you have raised it separately through the CCS consultation.

TI Phase 1a and TI Phase 1b are complementary. Nothing in this consultation changes the obligations or implementation dates for TI Phase 1a, and TI Energy Suppliers should continue to implement TI Phase 1a in line with the published timetable.

DESNZ intends to publish its decision on the proposed TI Phase 1b REC changes following Ofgem’s decision on incorporating the CCS arrangements into the REC. This is currently expected in April 2027, allowing time for industry to build, test and prepare for go-live.