The Maritime Emissions Compliance Stack: How CII, FuelEU and EU ETS Fit Together

Three regimes, one tonne of fuel

A decade ago a fleet's emissions obligation was a single annual report. Today the same tonne of fuel, burned on the same voyage, is measured by three separate regimes, each with its own methodology, its own geographic boundary and its own deadline. CII rates the vessel's operational carbon intensity. FuelEU Maritime prices the greenhouse-gas intensity of the energy used on board. EU ETS puts a price on the CO2 itself. None of them was designed to line up with the others.

The consequence is not that compliance is harder. It is that compliance is no longer one task. An operator now reconciles three numbers drawn from the same source data but answering to different rules, and a decision that improves one can leave another untouched. Slow steaming helps the CII rating and cuts the ETS bill, but it does nothing for FuelEU intensity if the fuel itself has not changed.

CII: a rating that travels with the vessel

The Carbon Intensity Indicator is an IMO measure under MARPOL Annex VI. It divides a vessel's annual CO2 emissions by its transport work and assigns a rating from A to E against a reference line that tightens every year to 2030. A D or E rating is not a fine. It is a commercial signal a charterer can read, and it follows the vessel into the next negotiation.

The criticism is worth stating plainly: the metric rewards deadweight-distance, so a vessel that sails further in ballast can rate better than one doing more useful work. Operators manage the methodology they have, not the one they would have designed.

FuelEU Maritime: intensity, not tonnage

FuelEU Maritime, Regulation (EU) 2023/1805, in force from January 2025, prices the well-to-wake greenhouse-gas intensity of the energy a ship uses, against a 2020 baseline that steps down on a fixed schedule. It is fuel-led, not distance-led. That moves the decision off the bunker manager's desk and onto the voyage plan and the charter party. Pooling, banking and borrowing can move the penalty around, but the benefit sits at the vessel and contract level, not the fleet level where operators instinctively look.

EU ETS: a price on the carbon

EU ETS extended to shipping in January 2024, under Directive (EU) 2023/959. The phase-in runs on reported emissions from the prior year: allowances for 40 percent of 2024 emissions were surrendered in 2025, 70 percent of 2025 emissions in 2026, and 100 percent of reported emissions from 2027 onward. Two changes are easy to miss. Methane and nitrous oxide entered scope only from 2026, so the 2026 reporting year covers more than CO2. And the geographic boundary is split: 100 percent of emissions on voyages between two EU ports and while in an EU port, but 50 percent on voyages that start or end outside the EU. For voyages between EEA ports it covers all emissions; for voyages into or out of the EEA, half. The shipping company surrenders allowances for the prior year, and where the charter party is silent on who carries that cost, it lands by default rather than by agreement.

The boundaries and calendars do not match

This is where the stack bites. CII runs on the full calendar year of global operations. FuelEU applies well-to-wake intensity to the EU scope. EU ETS prices CO2 on the EU scope with a phase-in. The clocks differ too: the MRV emissions report falls due on 31 March, EU ETS allowances are surrendered in September, and CII ratings settle early in the year. An operator managing all three is reconciling different scopes against different deadlines, from data captured the same way for each.

It all rests on the noon report

The one thing the three regimes share is their input. Every rating, intensity figure and allowance calculation traces back to the same noon-report and sensor data. When that data is rounded, inconsistent or unvalidated, the error propagates into all three, and it surfaces months later when a verifier or a charterer questions a number nobody can reconstruct. Underneath three regimes sits one problem, and it is a data-quality problem.

What it means for the operator

The job is no longer to comply with a rule. It is to see the three numbers early enough to act on them, on data clean enough to defend. That is a forecasting and data-discipline problem before it is a software one. The regimes will keep tightening to 2030 and beyond. The fleets that manage them well are the ones that already treat the noon report as the evidence document it has quietly become.

Four things commonly got wrong about this stack

These are not pedantic distinctions. Each one changes a number, and each is repeated often enough in circulation that it is worth stating the correction with its source attached.

• •“CII carries a fine.” It does not. There is no financial penalty in the measure. What a D rating for three consecutive years, or a single E, triggers is a plan of corrective actions in Part III of the ship’s SEEMP. The cost arrives through the charter market instead, which is a different mechanism with a different remedy. Source: IMO, EEXI and CII frequently asked questions.
• •“The CII reduction factors after 2026 have not been set.” They have. The 2021 guidelines specified factors only to 2026 and left 2027 onward blank, which is why anything written before April 2025 says the trajectory is undecided. Resolution MEPC.400(83), adopted 11 April 2025, sets 13.625 percent for 2027, 16.25 for 2028, 18.875 for 2029 and 21.5 for 2030 against the 2019 reference line. Nothing is set beyond 2030.
• •“CII and FuelEU count the same emissions.” They do not. CII uses tank-to-wake carbon factors from the IMO DCS. FuelEU Maritime uses well-to-wake greenhouse-gas intensity, which includes producing and delivering the fuel. Applying one regime’s factor to the other produces a plausible number that is wrong, and nothing in the output flags it.
• •“CII corrections cover ballast voyages.” They do not. The interim guidelines on correction factors and voyage adjustments, Resolution MEPC.355(78) adopted 10 June 2022, provide for ice-classed ships and distance sailed in ice, ship-to-ship transfer and shuttle tanker operations, fuel used for electrical power, boiler and other auxiliary consumption, cubic capacity and voluntary structural enhancement. A ballast leg is not among them.

The pattern underneath all four is worth naming: three regimes, three methodologies, four deadlines, and one set of reported fuel and distance figures feeding all of them. An error in the source data propagates into every one of them at a different exchange rate.