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Annex VI of MARPOL 73/78 entered force in May 2005 and has been progressively tightened ever since. It is the single most consequential regulatory framework in modern shipping operations — every fuel bunker, every port call, every charter conversation, and every PSC inspection now touches Annex VI in some form. This page covers what a chief mate + second engineer need to know to defend the ship's compliance to a charterer or PSC officer today.
Global sulphur cap of 0.50% m/m entered force 1 January 2020 (IMO 2020). Reduced to 0.10% m/m in the four Emission Control Areas (SECAs): Baltic, North Sea, North American, and US Caribbean. Compliance options: (a) burn compliant low-sulphur fuel; (b) use exhaust gas cleaning system (scrubber); (c) alternative fuel (LNG, methanol, ammonia, biofuel). Charterer + PSC focus on Bunker Delivery Note retention (3 years), fuel-sample retention (until vessel next fuels or 12 months), and Fuel Oil Non-Availability Report (FONAR) when compliant fuel unavailable at a bunker port.
Nitrogen oxide emissions tiered by keel-laying date:
Tier III applies only in the North American + US Caribbean ECAs currently; the Baltic + North Sea ECA-NOx zones apply Tier III for ships built after 1 January 2021.
EEXI entered force 1 November 2022 with first compliance at 2023 IAPP renewal. Every existing vessel >400 GT calculates an EEXI value against a reference line specific to ship type + size. Non-compliant vessels must implement power limitation (usually via Engine Power Limitation, EPL, or Shaft Power Limitation, SPL) to reduce theoretical maximum output. The EEXI Technical File — signed off by Recognised Organisation — is now part of the ship's statutory certification portfolio.
Operational carbon intensity rating (A/B/C/D/E scale) — the annual report card. Calculated from IMO DCS (Data Collection System) fuel-consumption data + distance travelled. Ships receiving three consecutive D ratings or a single E rating must submit a Corrective Action Plan (CAP) with the SEEMP Part III. See our CII rating calculator.
The 2023 IMO GHG Strategy (Resolution MEPC.377(80)) commits to net-zero GHG emissions by or around 2050, with indicative checkpoints of 20% reduction (striving for 30%) by 2030 and 70% reduction (striving for 80%) by 2040, both compared to 2008. MEPC 83 (April 2025) adopted the mid-term measures: the Global Fuel Standard (WtW GHG intensity requirement) + the economic measure (bunker levy on emissions above a threshold), entering force 2027. Also see our EU ETS + FuelEU Maritime page for the EU-specific framework.