1 Or an approved entity responsible for verification as delegated by the flag state. GUIDANCE FROM BRITANNIA P&I CLUB / JUNE 2025 This guidance is part of our comprehensive Maritime Emissions Regulations section written in consultation with the law firm HFW. This publication was written in consultation with Alessio Sbraga, Partner and Alex Andreou, Senior Associate, from leading global law firm HFW. Whilst care has been taken to ensure the accuracy of this information at the time of publication, the information is intended as guidance only. It should not be considered as legal advice. The definitions for technical terms used can be found in the glossary on page 8. REGULATORY OVERVIEW OF CARBON INTENSITY INDICATOR (CII) AND ENERGY EFFICIENCY EXISTING SHIP INDEX (EEXI) 1. The IMO has imposed operational requirements for ships to improve their carbon intensity, the Carbon Intensity Indicator (CII), and technical design requirements so that ships meet an energy efficiency baseline, Energy Efficiency Existing Ship Index (EEXI) (together the CII Regulations). The CII Regulations were imposed through amendments to Annex VI of MARPOL Chapter 4, via MEPC Resolution 328(76) (Revised MARPOL Annex VI) together with guidelines. KEY FEATURES OF CII 1.1 CII is an operational tool used to measure the carbon intensity generated by the operational performance / commercial activities of individual ships. It applies to all ships above 5,000 gt. 1.2 From 1 January 2023, in each reporting period (one full calendar year), each ship has a target annual operational energy efficiency value (required CII) which it should aim to achieve. Up to 2026, the required CII becomes more challenging to attain each year, requiring a continuous improvement of approximately two percent annually. 1.3 During the reporting period, ships must record and report fuel consumption data and other relevant data relating to greenhouse gas (GHG) emissions in accordance with the IMO Data Collection System (DCS). This data is then verified by 31 March in the year following the reporting period (verification period). The fuel consumption data is calculated on the basis of the annual efficiency ratio (AER) metric, which is total annual CO 2 emissions over deadweight ton miles (gCO2/dwt.nm) and assumes a continuous cargo carriage, even during ballast voyages. The AER metric does not factor in cargo carriage efficiency. In consequence, operational adjustments, such as slow steaming, alternative sustainable maritime fuel and routing, as well as improved fuel consumption efficiency, may be required to comply with the CII regulations depending on the age, type, sector and trade of a ship. 1.4 Using the fuel consumption data, a ship calculates its actual annual operational energy efficiency in accordance with the AER metric, expressed on a gCO2/dwt.nm basis for a reporting period (attained CII) which is to be submitted to the flag state by 31 March of the verification period. In this article, we refer to the in-year-to-date notional attained CII (pre-verified) as the indicative CII value. 1.5 A ship is required to develop (and keep updated) an enhanced ship energy efficiency management plan (SEEMP), which may form part of the ship's safety management system (SMS). The SEEMP must, amongst other requirements, set out the methodology used to monitor and calculate the attained CII and include an implementation plan describing how the required CII will be achieved over the next three years, starting fr