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UNITY Messenger CSS

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A High-Performance CSS Adapter for Electricity Market Registration

UNITY Messenger CSS is C&C Group’s cloud-native CSS Adapter, purpose-built to enable seamless integration between the electricity Metering Point Registration System (MPRS) and the UK Energy Central Switching Service (CSS).

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Introduced by Ofgem in 2022, the Central Switching Service was designed to streamline supplier switching across the retail energy market, acting as the central hub for electricity and gas registrations. UNITY Messenger CSS ensures that MPRS environments can interact securely, reliably and at scale with CSS — providing compliant, real-time message exchange within a fully managed Azure-hosted architecture.

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C&C Group was the first organisation to exchange live files with the DCC, and today our software underpins 99.2% of all IDNO MPANs, reinforcing our position as the market-leading CSS MPRS adaptor provider.

Purpose-Built Cloud Architecture

UNITY Messenger CSS is built as a series of microservices hosted within Microsoft Azure UK West and South regions, ensuring high availability, redundancy and resilience.

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Core components include:

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  • Message Validator API — Validates structure and syntax prior to processing

  • From CSS Function — Translates and processes inbound CSS messages for MPRS

  • To CSS File Function — Converts MPRS outputs into CSS-compatible file formats

  • To CSS Message Function — Formats and prepares outbound CSS messages

  • Reporting Function — Provides operational and service-based analytics

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Secure data handshakes are managed via SFTP public keys stored in Azure Key Vault, with private keys retained by (I)DNOs, ensuring compliant and secure communications.

High-Performance Messaging at Scale

UNITY Messenger CSS is engineered for high-volume, low-latency performance:

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  • 202 status response within 750 milliseconds (95th percentile)

  • Hourly throughput of up to 720,000 messages

  • Load-tested to 200 messages per second

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This performance profile ensures reliable handling of peak switching activity without operational disruption.

Operational and Compliance Benefits

UNITY Messenger CSS delivers:

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  • Seamless MPRS–CSS integration

  • Real-time, validated message exchange

  • Automated error handling and structured retry mechanisms

  • Secure message signing aligned to CSS processes

  • Comprehensive performance and monthly reporting

Market-Leading Adoption

SWIM-SOAK, powered by UNITY Messenger CSS, is the leading CSS MPRS adaptor service and is adopted by the majority of Electricity DNO and IDNO organisations.

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By combining cloud-native architecture, proven market adoption, and enterprise-grade performance, UNITY Messenger CSS provides a secure, compliant and future-ready solution for electricity market switching operations.

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