This modification sought clarification of Section F Paragraph 10.11 to confirm venting of gas between the Metering Point and the Delivery Point is permitted in order to protect the T&S Network from potential off-spec CO2 and enable compliance with the Annexure H – Isolation Procedure Terms of Reference 1(a)(iii) “the requirement for cross-party proof of isolation integrity. i.e., proving zero energy;”

The Modification Panel approved CCS001 on 10 September 2025. As this modification was Authority Determined, the documentation was provided to Ofgem. Ofgem provided a letter on 5 November 2025, confirming that the modification should be implemented. The Secretary implemented this modification on 6 November 2026.