Annexes I and II: oil and noxious liquids
Annex I, in force since 2 October 1983, governs oil. Machinery space bilge water managed through the oily water separator with its 15 ppm alarm. Sludge retention and disposal. And for tankers, the cargo related requirements including double hulls. The Oil Record Book is the annex's nervous system. Part I covers machinery space operations on every oil tanker of 150 gross tonnage and above and every other ship of 400 gross tonnage and above. Part II covers cargo and ballast operations on oil tankers of 150 gross tonnage and above. Inspectors read both forensically, reconciling entries against tank capacities, port calls, sludge production rates and shore reception receipts. Entries that cannot be reconciled attract far closer examination, and in several jurisdictions they have led to prosecution. Annex II, in force since 6 April 1987, applies the same discipline to noxious liquid substances carried in bulk by chemical tankers, with cargo categorization into categories X, Y, Z and other substances, prewash requirements, and its own Cargo Record Book. Annexes I and II are mandatory for every party to the convention. Annexes III to VI are optional, though in practice they are near universally ratified.
Annexes III, IV and V: packaged goods, sewage, garbage
Annex III, in force since 1 July 1992, covers harmful substances carried in packaged form and works through the documentation, marking, labelling and stowage requirements of the IMDG Code. Annex IV, in force since 27 September 2003, governs sewage. Comminuted and disinfected sewage may be discharged more than 3 nautical miles from the nearest land. Sewage that is not comminuted and disinfected requires more than 12 nautical miles. Separately, sewage that has been stored in holding tanks must not be discharged instantaneously. It must be discharged at a moderate rate while the ship is en route and proceeding at not less than 4 knots. Annex V, in force since 31 December 1988, governs garbage on a strict principle: discharge is prohibited unless expressly permitted. The narrow exceptions cover comminuted food waste at distance, certain cargo residues and cleaning agents, and animal carcasses, each under specific conditions. The documentation requirements have widened. Since 1 May 2024, under resolution MEPC.360(79), every ship of 100 gross tonnage and above engaged on voyages to ports or offshore terminals under the jurisdiction of another Party must carry a Garbage Record Book, down from the previous 400 GT threshold. A garbage management plan is required for ships of 100 gross tonnage and above and for every ship certified to carry 15 or more persons, and placards are required on ships of 12 metres or more in length. All three are standing PSC checks.
Annex VI: air, and now carbon
Annex VI, in force since 19 May 2005, has become the convention's most dynamic front. It caps the sulphur content of fuel oil at 0.50 per cent globally, in force since 1 January 2020, and at 0.10 per cent inside Emission Control Areas, in force since 1 January 2015. A carriage ban on non-compliant fuel oil has applied since 1 March 2020 to ships without an approved equivalent such as a scrubber. The list of ECAs keeps growing. The Mediterranean Sea ECA entered into force on 1 May 2024 and its 0.10 per cent limit took effect on 1 May 2025. The Canadian Arctic and Norwegian Sea ECAs entered into force on 1 March 2026, with the 0.10 per cent sulphur and particulate matter requirements taking effect on 1 March 2027. The North-East Atlantic ECA was adopted at MEPC 84 in May 2026. The amendment enters into force on 1 September 2027 and the ECA takes effect twelve months later in 2028, covering the exclusive economic zones and territorial seas of Greenland, Iceland, the Faroe Islands, Ireland, the United Kingdom, France, Spain and Portugal. NOx limits apply by engine tier and by area, and fuel changeover procedures and bunker delivery note documentation are routine inspection items. The same annex carries the IMO's energy efficiency and carbon regime. EEXI, the operational Carbon Intensity Indicator and the enhanced SEEMP came in through the 2021 amendments, which entered into force on 1 November 2022 with requirements applying from 1 January 2023. Annex VI is also the intended home of the IMO Net-Zero Framework, the fuel intensity and pricing mechanism approved at MEPC 83 in April 2025. That framework has not been adopted. Adoption was adjourned for a year at the extraordinary MEPC session in October 2025 and remained unresolved at MEPC 84 in May 2026. The adjourned session is set to resume on 4 December 2026, subject to confirmation by MEPC 85, and it is that resumed session, not MEPC 85 itself, that is the adoption decision point. This is the position as at August 2026. Operators should plan on the current EEXI and CII rules, watch the framework, and treat any published entry into force date as provisional until adoption actually happens.
The record books are the ship's testimony
Across the annexes one principle repeats. The record books are the ship's own written account of its environmental behaviour, and courts and inspectors treat them as evidence. What inspectors test is consistency: between the record books, the condition of the equipment and the physical quantities on board. Magic pipe prosecutions show how severe the consequences of falsification can be, for individual officers as well as for companies. The operational answer is unglamorous. Train the crews who make the entries. Verify that the equipment actually works. And reconcile the records before someone else does.