EU ETS 2031: What Awaits Ships of 400 to 5,000 GT
For four years, operators of workboats, offshore support vessels and small coasters have been able to watch the European carbon market from a comfortable distance. The EU Emissions Trading System, extended to shipping in 2024, currently applies only to ships of 5,000 GT and above. Below that threshold, there is no obligation to surrender allowances. That boundary is now moving.
On 17 July 2026, the European Commission published its proposed revision of the maritime framework in two instruments: the revised ETS Directive, COM(2026) 616, and the regulation amending MRV and FuelEU Maritime, COM(2026) 620. One of the most consequential changes for Europe's working fleet is stated plainly: several categories of ship between 400 and 5,000 GT would enter the carbon market in 2031. Nothing is settled, since the texts follow the ordinary legislative procedure and must still clear the Council and the Parliament. Even so, for anyone running support vessels, the deadline deserves to be read as something other than a distant date.
Key points
Lower threshold. The Commission proposes extending the EU ETS to ships of 400 to 5,000 GT from 2031, against 5,000 GT and above today.
An obligation that already bites. General cargo ships and offshore vessels in that band have been reporting emissions under MRV since 1 January 2025.
A two-step timetable. Tankers, chemical carriers and gas carriers of 400 to 5,000 GT would enter MRV in 2029, then the ETS in 2031.
Offshore redefined. The notion of an offshore ship would give way to an activity-based test, with revised port of call rules applying from 1 January 2032.
Financial support. Up to 110 million allowances would be set aside between 2028 and 2040 for sustainable bunker fuels, electric propulsion and wind assistance.
Process. A political agreement is targeted for the first quarter of 2027, with final texts expected around 2029.
What the Commission has put on the table
At the heart of the proposal lies a lowered threshold. General cargo ships and offshore vessels of 400 to 5,000 GT, already covered by the MRV Regulation, would move into the ETS in 2031. Tankers, chemical carriers and gas carriers in the same band would follow a two-stage path: MRV in 2029, then the ETS in 2031. Passenger ships and ro-pax units of 400 to 5,000 GT, by contrast, would join MRV in 2029 without the Commission's documents providing for their automatic entry into the carbon market, a feasibility report being expected before any decision is taken.
The sequencing is telling. It makes reasonably clear that Brussels proceeds in stages and always begins with the same step: measure before you charge. That is precisely what makes 2031 less remote than it looks.
Many ships are already reporting, sometimes without seeing the stake
The point most often missed in discussions about the ETS concerns a date that has already passed. Since 1 January 2025, according to the European Commission's official FAQ, companies must report emissions for offshore and general cargo ships of at least 400 GT and below 5,000 GT. Those ships remain outside the ETS, and therefore free of any surrender obligation, but they sit squarely within MRV.
In practice this means three things. Each ship must hold a monitoring plan drawn up on the Commission's updated templates, which now cover methane and nitrous oxide, submitted through THETIS-MRV, assessed by an accredited verifier and then approved by the competent authority. Emissions must subsequently be monitored in line with that plan. Finally, an annual emissions report must be produced for each ship and verified by 31 March of the following year, or by 28 February where the competent authority so requires.
For part of the fleet caught by the 2031 extension, in other words, the question is not whether measurement will be required, since measurement is already mandatory. What changes in 2031 is that this measurement stops being a reporting exercise and becomes the basis of a bill.
For offshore, the perimeter changes in nature
The proposal does more than shift a threshold: it changes how an offshore vessel is identified in the first place. The category, currently defined by ship type, would be replaced by an activity-based test, covering vessels carrying out or supporting an offshore operation at a worksite located in the waters of a Member State. Offshore installations in European waters would moreover be treated as port calls, with the revised port of call rules applying from 1 January 2032.
That shift from type to activity is far from neutral for an owner whose vessels alternate between offshore worksites, port works and assorted charters. The IMCA, which represents marine contractors, welcomes the emergence of a dedicated offshore framework but notes that the definitions of offshore operations and offshore worksite still need sharpening. The association also points to the absence of interim guidance and calls for clarity on how the EU ETS and the UK ETS interact, so that a single voyage is not penalised twice. For UK-linked operators the question is immediate rather than theoretical, since both schemes apply to ships above 5,000 GT from January 2027.
For the operators concerned, the practical consequence is straightforward: fuel consumption will have to be attributable to an operation and an area, not merely to a vessel and a period.
Three years of history cannot be manufactured in three months
This is where 2031 stops being comfortable. Building a defensible baseline requires consumption data that is reliable, continuous and tied to identified operations, across several reporting years. A history cannot be back-filled; it has to be accumulated. A company that waited until 2030 to organise itself would enter the carbon market with a single year of data, no basis for comparison, no means of explaining a variance and no leverage in discussion with a verifier.
Nor is the matter purely regulatory. Opsealog, a French specialist in offshore fleet performance monitoring, quantified in late September what it calls the conversion gap, the distance between data collected and decisions taken: 732 m³ of fuel and 1,984 tonnes of CO2 saved in a year on a single anchor handling tug supply vessel. The figure comes from a market participant and should be read as such, yet it illustrates a mechanism technical departments know well, namely that the gains do not come from the sensor but from what is done with it.
Owners who start early therefore pursue two aims at once. They prepare for an obligation, certainly, but above all they recover operating margin that the regulatory constraint will later put a price on.
Counterparts worth noting
The proposal is not solely a tightening. A support mechanism, SMAP, would reserve up to 110 million allowances between 2028 and 2040 to fund sustainable bunker fuels, electric propulsion and wind assistance, a subject we have documented through the operational data of equipped ships. Temporary exemptions covering ice-class vessels, island routes and outermost regions would meanwhile be extended from 2030 to 2035.
Brussels finally promises administrative simplification, merging ETS, MRV and FuelEU Maritime reporting into a common database under a single responsible entity. The Commission estimates the reduction in annual MRV compliance costs at between 10 and 20 per cent. Yet such simplification assumes clean data going in: a unified declaration does not repair patchy monitoring, it exposes the gaps faster.
What this means for recordkeeping on board
For an operator of support vessels, preparing comes down to making a handful of simple but demanding things reliable over time:
Consumption per vessel and per operation, time-stamped and tied to an identified worksite or voyage, rather than reconstructed after the fact from bunker invoices.
Up-to-date technical particulars for every vessel and every engine, since emission factors and consistency checks are built on them.
Traceability of interventions on propulsion lines and measuring equipment, because an undetected drifting flow meter can distort a full year of reporting.
The supporting evidence a verifier will ask for, retained and retrievable without a manual reconstruction at every campaign.
Continuity of monitoring across changes of crew, manager or charterer, which are precisely the moments when data series break.
This is exactly the material the BoatOn Book brings together: a digital logbook, maintenance tracking and document management in one tool, with a carbon reporting module developed in partnership with ADEME, the French environment agency. The habits described in our guide to preventive maintenance apply here too: what is not recorded at the moment of the intervention is never recovered afterwards. Operators of marine works fleets and passenger shuttles, whose vessels never run the same way twice, understand better than most what a hastily reconstructed history costs. The same logic underpins the choice of a marine CMMS.
The proposal of 17 July 2026 is not adopted law, and its thresholds and dates may yet move during negotiation. The direction of travel, however, is hardly in doubt: the perimeter of the European carbon market is shifting towards smaller ships, and it always begins with reporting. For a support fleet, the real question is not whether 2031 will arrive, but with what quality of data it will be met.
Photo credits: Pexels, free licence.
