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TL;DR: Maritime emissions reporting is the annual submission of verified fuel and emissions data to regulators — per voyage under EU MRV and UK MRV, as annual totals under IMO DCS, with EU ETS and FuelEU attaching costs to the same numbers. Every regime draws on the same raw ingredients (fuel, distance, cargo, time), so the fleets that find reporting easy keep one validated dataset and generate each report from it.
Every large commercial ship now has to tell regulators how much it emits. Most ships report to more than one authority, from the same year of sailing, in different formats and on different deadlines.
The rules themselves are not complicated one by one. The difficulty is keeping several of them straight at once.
This guide keeps it simple: what maritime emissions reporting is, which regulations require it, how the emissions number is actually calculated, and what the reporting process looks like in practice.
What is maritime emissions reporting?
Maritime emissions reporting means submitting your ships' verified fuel and emissions data to a regulator, once a year, in the format that regulator requires.
It is the external half of the job. The internal half — tracking emissions continuously so you always know where you stand — is monitoring, which we explain in what is emission analytics.
A useful way to think about it: monitoring is for you, reporting is for them.
The regulations you report under
There are two kinds of rules in maritime emissions reporting: rules that ask for your data, and rules that make you pay for it.
Rules that ask for data. EU MRV covers ships of 5,000 GT and above calling at European ports (smaller general cargo and offshore ships joined in 2025). You report fuel used, emissions and cargo carried for every voyage in scope. IMO DCS is the global version, run through your flag state, and asks for annual totals rather than voyage detail. UK MRV mirrors the EU system for ships calling at UK ports.
Rules that make you pay. The EU ETS puts a price on the emissions you report — you buy and surrender allowances to cover them. FuelEU Maritime works differently: it targets how carbon-intensive your fuel is, not how much you emit in total, and fines ships that miss the limit.
Here is the whole picture in one table:
One ship trading between the UK, Europe and Asia can fall under all five at once — from the same year of operations.
How are ship emissions calculated?
Behind every report is one simple calculation: fuel burned × emission factor = CO₂ emitted.
Every fuel has a fixed emission factor set by the IMO. Heavy fuel oil produces about 3.11 tonnes of CO₂ per tonne burned; marine gas oil about 3.21; LNG about 2.75.
A quick example. A bulk carrier burns 5,000 tonnes of heavy fuel oil in a year. Its reported CO₂ is 5,000 × 3.11 = roughly 15,570 tonnes. That single number feeds its EU MRV report, its IMO DCS submission and its EU ETS bill.
This is why fuel data quality decides everything downstream. If the fuel figure is wrong, every report built on it is wrong — and under EU ETS, a wrong number is a wrong invoice.
What the reporting workflow looks like
In practice, maritime emissions reporting follows the same annual rhythm for most fleets. Here is a typical year for one vessel.
Through the year — collect. The crew logs fuel consumption, distance and cargo on every voyage, through noon reports, flow meters and bunker delivery notes.
As data lands — check. Each figure is validated against physical limits and past patterns. Catching a typo in June takes minutes; finding it in February means reconstructing months of records.
January — compile. The year's voyages are assembled into the reports each regulation needs: per-voyage detail for EU MRV and UK MRV, annual totals for IMO DCS.
February to March — verify and submit. An accredited verifier audits the EU MRV report before it goes to the authorities via THETIS-MRV by 31 March. IMO DCS data goes to the flag state in the same window.
After submission — settle and certify. The ship receives its documents of compliance, and by 30 September the company surrenders EU ETS allowances covering its verified emissions.
The pattern to notice: the deadlines are in spring, but the work that makes them painless happens all year.
One dataset, many reports
Look back at the table and you'll see every regulation asks for the same raw ingredients — fuel, distance, cargo, time. Only the format, scope and deadline change.
That means the smart setup is one validated dataset, with each report generated as a different view of it. Keep separate spreadsheets per regulation and you will reconcile the same voyages five times, and chase every correction through every copy.
One gap to note: these rules cover ships you operate. If you charter ships and need to report the emissions of cargo you move, that is Scope 3 territory — see ZeroNorth Scope 3.
Reporting is the floor, not the ceiling
Maritime emissions reporting is mandatory, but the same verified data can do far more than satisfy a regulator. It can forecast your CII rating, price a voyage's ETS cost before you fix it, and flag a FuelEU deficit while there is still time to act.
That is what Emission Analytics does: one validated dataset producing submission-ready EU MRV, UK MRV, IMO DCS and FuelEU reports — with EU ETS exported straight to THETIS-EU — while the same numbers power live monitoring and forecasting.
The fleets that find reporting season easy didn't work harder in March. They did the work once, all year.
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