DESNZ Approves Implementation of Tariff Interoperability Arrangements within the REC
The Department for Energy Security and Net Zero (DESNZ), supported by RECCo, has now published the Tariff Interoperability (TI) Phase 1a arrangements under the Smart Secure Electricity Systems (SSES) Programme.
Tariff Interoperability will support consumer-led flexibility by standardising how electricity tariff pricing data is shared across the market. This will make it easier for optimisation services and Energy Smart Appliances (ESAs), such as electric vehicle chargers, heat pumps and battery systems, to respond to electricity price signals using consistent, machine-readable tariff data, helping consumers reduce bills and optimise energy usage.
The arrangements introduce a new framework requiring electricity Suppliers to make tariff pricing data available through a standardised Application Programming Interface (API) approach. The published arrangements follow the November 2025 industry consultation (https://retailenergycode.co.uk/our-programmes/tariff-interoperability-project/) and subsequent engagement through the Tariff Interoperability Working Group (TIWG).
What has been published
The published package includes:
• Government Response to TI November 2025 Consultation
• new Electricity Supply Standard Licence Condition (SLC11C) requirements;
• REC Schedule 35 – Tariff Interoperability Arrangements;
• the baselined Tariff Interoperability API Technical Specification;
• updates to the Energy Market Data Specification (EMDS); and
• associated governance documentation.
On 18 May 2026, DESNZ will introduce the new SLC11C provisions and will implement REC Schedule 35 into the Retail Energy Code. This begins the implementation period ahead of the Phase 1a go-live date of 18 February 2027.
The updated arrangements reflect consultation feedback received from Suppliers, optimisers, trade bodies and other stakeholders. The Government response to the consultation has been published on the REC website, which outlines the comprehensive rationale for why decisions have been made.
Revised phased implementation approach
Following consultation feedback, DESNZ and RECCo have updated the implementation approach for Tariff Interoperability to support a more manageable delivery timeline and alignment with the Consumer Consent Solution (CCS).
Phase 1a – Public Tariff Pricing Data
Go-live: 18 February 2027
Phase 1a introduces standardised access to Public Tariff Pricing Data through Supplier APIs. This enables optimisation services and Energy Smart Appliances to use tariff pricing data where consumers can share their Supplier and tariff details.
Phase 1b – Consumer Specific Tariff Information
Planned go-live: November 2027
Phase 1b will introduce the ability for consumers to consent to the sharing of Consumer Specific Tariff Information with authorised third-party providers through CCS-aligned arrangements. Further consultation on the Phase 1b arrangements will take place later in 2026.
Tariff Interoperability API Technical Specification
The Tariff Interoperability API Technical Specification has now been baselined to support Supplier implementation ahead of the Phase 1a go-live date.
Baselining the specification gives industry sufficient certainty to begin implementation now. During implementation, updates are expected to focus on defect resolution, clarifications and fixes identified through Supplier testing.
Further consultation planned for later in 2026 will support incorporation of the Phase 1a API Technical Specification into the REC, and a separate consultation for future enhancements and CCS-aligned Phase 1b requirements.
Key updates following consultation feedback
Key changes include:
• introduction of the phased implementation approach;
• extended implementation timelines from 1 January 2027 to 18 February 2027 to support Supplier build and testing activities;
• inclusion of export tariffs within scope;
• updated exemption criteria for certain non-domestic Suppliers; and
• replacement of proposed daily reporting with a monthly reporting approach from Suppliers.
The updated arrangements also now allows Suppliers to voluntarily support additional tariff structures beyond the mandatory minimum scope where they choose to do so.
What electricity Suppliers need to do now
Electricity Suppliers should now begin implementation ahead of the 18 February 2027 Phase 1a go-live date, including:
• reviewing the new SLC11C obligations and REC Schedule 35 requirements;
• assessing impacts to tariff data structures;
• developing and testing Tariff Interoperability APIs;
• preparing Supplier Endpoint registration activities; and
• engaging with RECCo working groups and implementation support.
Under the arrangements, Suppliers will be required to make tariff pricing data available through a standardised API approach in accordance with the REC and associated technical specifications
Industry engagement and support
RECCo and DESNZ will continue to work closely with industry throughout implementation.
To support implementation activities, RECCo has established a Tariff Interoperability Implementation Working Group (IWG), focused on implementation planning, technical delivery and testing coordination.
For further information or to join the Tariff Interoperability Implementation Working Group, please contact:
tariffinteroperability@retailenergycode.co.uk
SSES.Interoperability@energysecurity.gov.uk
Key dates
REC Schedule 35 and SLC11C implementation – 18 May 2026
Phase 1a API Technical Specification consultation – July 2026
Supplier implementation and testing period – May 2026 – February 2027
Further consultation on CCS-aligned Phase 1b arrangements – Later in 2026
Phase 1a go-live – Public Tariff Pricing Data – 18 February 2027
Phase 1b go-live – Consumer Specific Tariff Information – November 2027
