The EU MRV Regulation requires ships to record a specific data set for every voyage that departs from or arrives at a port in the European Economic Area. That data set covers fuel consumption by type, CO2 emissions, methane and nitrous oxide since 2024, sailed distance, time at sea, cargo or passenger load, and the transport work calculated from them. It is compiled per voyage, aggregated annually, verified by an accredited third party, and submitted through THETIS-MRV, where it directly determines how many EU Allowances a shipping company must surrender under the EU ETS.
This article examines the voyage-level data architecture: which parameters are captured, how each is measured, how the per-voyage records aggregate into an annual emissions report, and how that report flows downstream to the EU ETS for shipping and FuelEU Maritime. For the broader legal history and enforcement provisions of the regulation as a whole, see the companion article on the EU MRV Regulation 2015/757. For a structured comparison of MRV versus the parallel IMO Data Collection System, see IMO DCS vs EU MRV.
Why per-voyage granularity matters
The choice to require per-voyage data rather than annual aggregates was deliberate. The IMO’s parallel Data Collection System, which took effect 1 January 2019, collects only annual totals submitted at the flag-State level and not accessible at the individual ship level. The EU Commission, publishing Regulation (EU) 2015/757 in May 2015, wanted ship-level data broken down by voyage category: intra-EEA legs count differently from legs arriving from outside the EEA under the EU ETS for shipping. You cannot reconstruct that split from an annual aggregate. Per-voyage records also allow energy efficiency to be tracked by cargo load factor trip by trip, which supports the EU’s broader decarbonization policy tools including FuelEU Maritime and the Carbon Intensity Indicator.
The regulation describes a “first step of a staged approach.” What started as a CO2-only monitoring framework in 2018 has since been extended to cover methane and nitrous oxide (from 1 January 2024), and the scope has widened to smaller vessels from 1 January 2025. The voyage data set has grown with each stage.
Scope: which ships and which voyages
Ships in scope
The original threshold is 5,000 GT. Ships at or above that mark calling at any EEA port in the course of commercial cargo or passenger transport have been required to compile EU MRV voyage data since 1 January 2018. The regulation applies regardless of flag state: a Bahamas-flagged bulk carrier calling at Rotterdam falls under exactly the same obligations as a Greek-flagged tanker.
Regulation (EU) 2023/957, published 16 May 2023 and in force 5 June 2023, extended the scope in two directions from 1 January 2025:
- General cargo ships between 400 GT and 4,999 GT (reporting obligation, not yet the full ETS obligation that applies above 5,000 GT).
- Offshore ships of 400 GT and above. A delegated act published 27 December 2024 (Commission Delegated Regulation (EU) 2024/3214) clarified which offshore vessel types are caught: offshore support vessels, pipe-layers, crane vessels, and drilling ships, among others, but not icebreakers.
A small category of vessels is excluded regardless of size: warships, naval auxiliaries, fishing and fish-processing vessels, wooden ships of primitive construction, ships not propelled by mechanical means, and government vessels used for non-commercial purposes.
Voyages in scope
A “voyage” under the regulation is any movement of a ship originating from or terminating at a port of call. A “port of call” is defined as a stop for loading or unloading cargo, or for embarking or disembarking passengers. Stops solely for bunkering, dry-docking, repairs, emergency shelter, or crew changes do not count as ports of call and do not trigger a voyage record.
The geographic scope covers voyages between two EEA ports (intra-EEA) and voyages arriving from or departing to a port outside the EEA (extra-EEA). Both categories generate per-voyage records. The distinction matters downstream: under the EU ETS, 100% of intra-EEA voyage emissions and 50% of extra-EEA voyage emissions count toward the allowance obligation. The MRV system flags each voyage with its category so the ETS calculation can split them correctly.
The voyage data parameters
The table below lists every data point Regulation (EU) 2015/757 (as amended by 2023/957 and the delegated Regulation (EU) 2016/2071) requires a company to monitor and record per voyage and to aggregate for the annual emissions report.
| Parameter | Per-voyage | Annual total | Unit | Notes |
|---|---|---|---|---|
| Port of departure | Yes | n/a | n/a | With departure date and time |
| Port of arrival | Yes | n/a | n/a | With arrival date and time |
| Fuel consumption | Yes | Yes | Metric tonnes | Per fuel type (e.g., HFO, MDO, LNG, methanol) |
| CO2 emissions | Yes | Yes | Metric tonnes CO2 | Fuel consumption x emission factor per fuel type |
| Methane (CH4) emissions | Yes (from 2024) | Yes | Metric tonnes CH4 | Required from 1 January 2024 per 2023/957 |
| Nitrous oxide (N2O) emissions | Yes (from 2024) | Yes | Metric tonnes N2O | Required from 1 January 2024 per 2023/957 |
| Distance sailed | Yes | Yes | Nautical miles | Log distance or GPS-based; excludes port maneuvers |
| Time at sea | Yes | Yes | Hours | Port departure to port arrival under way |
| Time at berth (within EEA ports) | Yes | Yes | Hours | Reported separately per port |
| Cargo carried | Yes | Yes | Metric tonnes, TEU, or passengers | Ship-type dependent (see proxy rules below) |
| Transport work | Yes | Yes | Tonne-nautical miles | Distance x cargo carried |
| Energy efficiency (four indicators) | n/a | Yes | g CO2/t·nm or g CO2/nm | Fuel/distance, fuel/transport work, CO2/distance, CO2/transport work |
| Ice class and ice navigation | Yes (if applicable) | n/a | n/a | Recorded when navigating in ice conditions |
Cargo measurement and proxy methods
For bulk carriers, tankers, and container ships, cargo carried is measured from loading documents or, where those are unavailable, from a ship-specific proxy agreed in the monitoring plan. Article 9 of the regulation permits using 70% of the deadweight tonnage as a proxy for cargo when actual cargo figures cannot be reliably obtained or when the company has chosen the simplified “proxy” method during plan preparation. Container ships may use TEU figures rather than metric tonnes. Passenger vessels record passenger numbers and, where available, passenger-nautical miles.
Transport work, which multiplies cargo by distance, drives two of the four mandated annual average energy efficiency indicators: fuel consumed per tonne-nautical mile and CO2 emitted per tonne-nautical mile. Those indicators are the core efficiency metrics the European Commission publishes in its annual MRV fleet reports.
Emission factors and the CO2 calculation
CO2 emissions per voyage are not directly measured under the default methods. Instead, they are calculated: fuel consumption in metric tonnes multiplied by the mass-based emission factor for the fuel type. Annex I to the regulation and Delegated Regulation (EU) 2016/2071 specify the default emission factors: 3.206 tonnes CO2 per tonne of heavy fuel oil, 3.151 per tonne of diesel/gas oil, 2.750 per tonne of LNG (as methane), and so on. Companies may use specific emission factors certified by the fuel supplier if the verifier confirms they are more accurate than the defaults.
Methane and nitrous oxide carry their own emission factors. For LNG-fueled ships, methane slip from unburned fuel in the exhaust is a significant source of CH4 emissions and must be quantified separately. The monitoring plan must identify the methodology for each gas from each emission source on the ship.
The four monitoring methodologies
Annex I to Regulation (EU) 2015/757 defines exactly four methods a company may use to determine fuel consumption for the voyage record. Only one method may be used per ship per reporting period; the choice is locked in when the monitoring plan is assessed.
Method A: BDN plus tank stocktakes. Fuel consumption is the quantity on the bunker delivery notes since last port of call, corrected for tank inventory changes by physical sounding at the start and end of each voyage. This is the most widely used method because bunker delivery notes (BDNs) are mandatory under MARPOL and already exist. The method’s weakness is that BDN-based consumption accumulates over multiple bunkering events rather than measuring what a specific voyage actually burned. Tank stocktakes at every port departure and arrival reduce this error.
Method B: Bunker tank monitoring. Fuel consumption is measured by daily tank soundings while the ship is under way. Consumption for each voyage is the sum of daily differences between soundings, corrected for any bunkering during the voyage. The method demands high-frequency sounding discipline and is subject to thermal expansion errors in tanks that are partially full at varying temperatures.
Method C: Flow meters. Fuel mass flow is measured continuously on the fuel supply lines to each engine or boiler. This gives the highest spatial and temporal resolution: consumption can be attributed to specific machinery and to specific watches or speed regimes. Flow meters must be calibrated and their calibration certificates submitted with the monitoring plan. Any engine or fuel consumer not covered by a meter must be accounted for by a supplementary method.
Method D: Direct CO2 measurement. Exhaust gas CO2 concentration, measured by continuous emissions monitoring equipment on each stack, is multiplied by the exhaust volume flow to give CO2 mass per unit time. This method inverts the usual chain of calculation: instead of computing CO2 from fuel consumed, it measures CO2 directly and back-calculates fuel. It is the most demanding to calibrate and certify and is uncommon in commercial shipping outside certain cruise and ferry operators with sophisticated onboard monitoring systems.
Most bulk carriers, tankers, and general cargo ships use Method A, sometimes combined with a secondary flow meter read for cross-check purposes.
The monitoring plan
No company may begin reporting per-voyage data without a monitoring plan assessed by an accredited verifier. The plan documents exactly how the company will gather each parameter listed above for each ship. It identifies:
- Each emission source on the ship (main engines, auxiliary engines, boilers, gas turbines, emergency generators where relevant).
- The fuel types used at each source.
- The monitoring method chosen (A, B, C, or D) and any supplementary method for gaps.
- The emission factors applied per fuel type.
- How cargo and transport work will be calculated, including any proxy method.
- Procedures for handling data gaps and anomalies.
- Data quality management and control procedures.
An accredited verifier assesses the plan before submission and confirms it is in conformity with the regulation before the first reporting period begins. The verifier does not approve the plan; that approval sits with the administering authority. But no ship can begin a reporting cycle without first having its plan assessed as conforming.
Monitoring plan deadlines under 2023/957
The original planning deadline under the 2015 regulation was 31 August 2017, with first monitoring from 1 January 2018. The 2023/957 amendment added new deadlines for the expanded scope:
- Companies must have submitted updated monitoring plans incorporating CH4 and N2O monitoring requirements by 1 April 2024.
- For ships entering EEA ports for the first time after 1 January 2024, the monitoring plan must be submitted within three months of the first call.
- The administering authority must approve plans by 6 June 2025.
Ships brought into scope from 1 January 2025 (400-5,000 GT general cargo and offshore) must submit monitoring plans and have them assessed before their first EEA port call under the new obligations.
The administering authority
Each company subject to EU MRV has a single “administering authority” responsible for oversight, determined by where the company is registered or, for non-EEA companies, by a flag-state or call-pattern tie-breaker rule set by Implementing Regulation (EU) 2023/2599. The administering authority receives the monitoring plan, receives the annual emissions report, issues or oversees the issuance of the Document of Compliance, and is the enforcement body for penalties.
Per-voyage data collection in practice
A ship running from Hamburg to Rotterdam to Algeciras to Las Palmas generates four voyage records: Hamburg-Rotterdam, Rotterdam-Algeciras, Algeciras-Las Palmas, and one for the return (or wherever next). Each leg gets its own fuel consumption entry derived from the chosen method, its own CO2 (and from 2024, CH4 and N2O), its own distance from GPS or log, its own cargo figure, and its transport work.
The Hamburg-Rotterdam leg is intra-EEA and counts 100% under the EU ETS. The Rotterdam-Algeciras leg is also intra-EEA (both in EEA). Algeciras to Las Palmas is intra-EEA. Las Palmas in the Canary Islands is in Spain and therefore in the EU, but a voyage from Las Palmas to a Moroccan port would be extra-EEA and attract the 50% factor.
Data for each voyage must be kept by the company for at least five years and made available to the verifier and the administering authority on request.
Aggregation into the annual emissions report
At the end of each reporting period (31 December), the company aggregates all per-voyage records into an annual emissions report. The structure mandated by Implementing Regulation (EU) 2023/2449 requires:
- Totals by category: emissions from intra-EEA voyages, emissions from voyages departing the EEA, emissions from voyages arriving at the EEA, and emissions within EEA ports (at berth).
- Emissions disaggregated by gas (CO2, CH4, N2O from 2024), with CH4 and N2O expressed in metric tonnes of each gas and also in CO2-equivalent using the global warming potentials specified in the monitoring plan.
- Annual average energy efficiency: the four indicators (fuel per distance, fuel per transport work, CO2 per distance, CO2 per transport work) for the aggregate fleet of voyages.
- Identity of the ship (IMO number, name, flag), the monitoring method used, and the verifier’s identity.
The report is submitted through THETIS-MRV by 31 March (from 2025; previously 30 April), addressed to the administering authority, and simultaneously to the flag-state authority if the flag is an EU Member State, and to the European Commission.
For companies whose fleet includes ships covered by the EU ETS, a second submission is required: the aggregated company-level report showing total CO2 (and from 2026, CH4 and N2O in CO2-equivalent) across all covered ships, disaggregated to support the allowance surrender calculation. This company-level aggregate is also submitted through THETIS-MRV, separately from the per-ship annual emissions report.
Verification and THETIS-MRV
The verification cycle
Before the annual emissions report is submitted to authorities, a verifier accredited by a national accreditation body (NAB) under Regulation (EC) 765/2008 must audit it. The verifier’s task is to confirm:
- The monitoring plan was actually followed.
- No material misstatements exist in the reported emissions, fuel, distance, cargo, or transport work figures.
- The data credibility checks pass: cross-checks against ship-tracking data (AIS-derived distance estimates, for example) and against independent fuel purchase records flag anomalies that require explanation.
- The monitoring method used matches the one documented in the plan.
A material misstatement is defined as an error, omission, or misrepresentation that, individually or combined, exceeds the materiality level set in the monitoring plan, typically 5% of total reported emissions.
After review, the verifier issues one of three conclusions: satisfactory (no material misstatements found), satisfactory with comments (immaterial issues noted but no error large enough to fail), or not satisfactory (material misstatements found; the report cannot be used for compliance). Only a satisfactory or satisfactory-with-comments conclusion allows the Document of Compliance to be issued.
At least once every four years (and at least once per three consecutive reporting periods starting from the 2024 reporting cycle), the verifier must conduct a physical site visit. The visit can be to the ship itself or to the company’s shore-based management facility, at the verifier’s determination.
What THETIS-MRV does
THETIS-MRV, operated and maintained by EMSA at mrv.emsa.europa.eu, is the central data system for the entire MRV cycle. It is not merely a filing cabinet. The platform:
- Holds the assessed monitoring plan for each ship, accessible to the company, verifier, flag state, and administering authority.
- Accepts the draft annual emissions report uploaded by the company.
- Routes the report to the assigned verifier for audit and conclusions.
- Records the verifier’s conclusion and generates the Document of Compliance once a satisfactory conclusion is entered.
- Transmits the verified data to the administering authority and to the Commission’s public dataset.
- From July 2024, includes a FuelEU Maritime module (built on the same platform) for FuelEU monitoring plan management and compliance balance tracking.
Public data from THETIS-MRV is available at the EMSA portal. The published dataset includes ship identity (IMO number, name, flag), annual CO2 emissions, annual fuel consumption, energy efficiency indicators, the monitoring method used, the reporting period, and whether a Document of Compliance was issued. CH4 and N2O data have been collected since the 2024 reporting year; the Commission’s publication timeline for those gases has not yet been fixed.
The Document of Compliance
The Document of Compliance (DoC) is the compliance certificate issued by the verifier, confirming that the ship’s emissions report for a specific reporting period has been verified as satisfactory. Every ship subject to EU MRV must carry a valid DoC on board at all times.
The DoC is specific to the ship (by IMO number) and to the reporting period. It does not run indefinitely. If the 2024 annual report is verified as satisfactory, the DoC covers the 2024 reporting period. The ship needs a new DoC for 2025 based on the 2025 verified report, and so on.
Port State Control officers (under the Paris MOU regime) check for a valid DoC during inspections. A ship that cannot produce one may be detained. If a ship fails to comply for two or more consecutive reporting periods and other enforcement measures have been exhausted, the administering authority may request that flag states and port states issue an expulsion order barring the ship from EU ports until a valid DoC is obtained.
How voyage data feeds the EU ETS
The EU ETS for shipping under Directive (EU) 2023/959, which took effect 1 January 2024, is structurally downstream of MRV. There is no separate ETS measurement system. The allowance obligation is calculated directly from the verified MRV data in THETIS-MRV.
The calculation works as follows. For a given company and reporting year:
- Take total verified CO2 from intra-EEA voyages: multiply by 100%.
- Take total verified CO2 from extra-EEA voyages (both arriving and departing): multiply by 50%.
- Take total verified CO2 from ships at berth within EEA ports: multiply by 100%.
- Sum the three results to get the ETS-covered CO2 for that year.
- Apply the phase-in percentage: 40% for the 2024 reporting year, 70% for 2025, 100% from the 2026 reporting year onward.
- Surrender that many EU Allowances (EUAs) by the September deadline.
From 2026, CH4 and N2O emissions join the ETS obligation. The global warming potentials for converting those gases to CO2-equivalent are set in the ETS Directive. The per-voyage CH4 and N2O data collected since 1 January 2024 will already be in THETIS-MRV by the time the 2026 ETS obligation crystallizes.
The ETS phase-in percentages and the MRV data categories are not coincidental design choices. They reflect a deliberate policy architecture: MRV was built first (2015-2018) to create a verified dataset, and the ETS was layered on top (2023-2024) once that dataset was mature enough to underpin a financial obligation.
How voyage data feeds FuelEU Maritime
Regulation (EU) 2023/1805, the FuelEU Maritime Regulation, sets greenhouse gas intensity limits on the energy used by ships calling at EU ports. It applies from 1 January 2025. Like the ETS, FuelEU does not build a separate data-collection infrastructure. It runs through THETIS-MRV via a dedicated FuelEU module released by EMSA in July 2024.
The FuelEU monitoring plan is a separate document from the MRV monitoring plan, but it is submitted through the same THETIS-MRV interface and assessed by the same accredited verifier. The data feeds are shared: fuel consumption, fuel type, energy content, and voyage-level disaggregation all come from the underlying MRV per-voyage records. FuelEU adds one layer the standard MRV record does not carry: the well-to-wake greenhouse gas intensity of each fuel, expressed in grams of CO2-equivalent per megajoule. That value drives the FuelEU compliance balance calculation.
A ship that reports accurate per-voyage MRV data with well-documented fuel types and consumption quantities is already most of the way to FuelEU compliance reporting. The practical overlap means shipping companies running the two frameworks from a single data collection operation have reduced administrative duplication. EMSA’s implementation regulations (EU) 2024/2031 and (EU) 2024/2027, adopted July 2024, formalize the shared data and verification templates.
EU MRV versus IMO DCS: key differences
Both the EU MRV system and the IMO Data Collection System (IMO DCS, which took effect 1 January 2019 under MARPOL Annex VI Regulation 22A) collect fuel consumption and related data from ships above 5,000 GT. They differ in architecture, granularity, and downstream use.
| Dimension | EU MRV (Reg. 2015/757) | IMO DCS (MARPOL Annex VI, Reg. 22A) |
|---|---|---|
| Entry into effect | 1 January 2018 | 1 January 2019 |
| GT threshold | 5,000 GT (400 GT from 2025 for general cargo and offshore) | 5,000 GT (international voyages only) |
| Geographic scope | Voyages to/from EEA ports | All international voyages |
| Reporting unit | Per-voyage record | Annual aggregate per ship |
| Report recipient | EU administering authority + EMSA (THETIS-MRV) | Flag state, then IMO |
| Public ship-level data | Yes, via mrv.emsa.europa.eu | No; IMO data not publicly available at ship level |
| Third-party verification | Mandatory by accredited verifier | Flag-state approval only |
| GHGs covered | CO2 from 2018; CH4 and N2O from 2024 | Fuel oil consumption only (no gas-level breakdown) |
| Cargo and transport work | Required per voyage | Not required |
| Downstream financial obligation | EU ETS allowance surrender from 2024 | None directly |
| FuelEU integration | Yes, via THETIS-MRV module | No |
The most operationally significant difference is granularity. The IMO DCS requires companies to report the total fuel consumed by a ship across an entire calendar year for all voyages, submitted to the flag state which then reports aggregate fleet data to the IMO. That annual aggregate is sufficient for the IMO’s purpose of tracking global fleet-level efficiency trends. It is insufficient for the EU ETS, which needs to know how much of each year’s fuel was burned on intra-EEA legs versus extra-EEA legs. Only per-voyage data answers that question.
A second structural difference is verification. Under the IMO DCS, the flag state reviews and accepts the data but there is no mandatory independent third-party audit. Under EU MRV, the accredited verifier is a mandatory step before any report can be used for compliance purposes. That audited data is what makes the MRV dataset the foundation for the financial EU ETS obligation.
Ships above 5,000 GT on international voyages that call at EEA ports are subject to both systems from 2019 onwards. A single on-board monitoring system feeding both reports is possible, because the fuel consumption data underlying the MRV per-voyage record can be aggregated to produce the IMO DCS annual total. The per-voyage disaggregation required by MRV requires more records than the DCS alone would demand, but the underlying measurements are the same. EMSA has published guidance on aligning the two monitoring plans to minimize double work.
Limitations
The EU MRV system is geographic in scope: it captures only emissions on voyages touching EEA ports. A ship that operates exclusively between Singapore, South Korea, and the United States generates no EU MRV record regardless of how large it is or how much CO2 it emits. This leaves a large share of global maritime CO2 outside the MRV dataset entirely.
Cargo measurement accuracy varies by ship type and monitoring plan method. The 70%-of-DWT proxy, permitted where actual cargo figures are unavailable, can overstate transport work for vessels regularly operating below capacity, making efficiency indicators look better than the actual operational picture. The regulation does not mandate AIS-based cargo verification.
Methane emission factors for LNG-fueled ships carry substantial uncertainty, particularly regarding methane slip, where uncombusted LNG passes through engines at low load. Different engine designs and load profiles generate different slip rates. The default emission factors in Annex I to the regulation are fleet averages, not ship-specific measurements. A ship with high methane slip on its main engines will report lower apparent CH4 emissions if it uses default factors rather than direct stack measurement. The European Commission’s 2025 review of the MRV Regulation explicitly noted this measurement uncertainty.
The verification cycle, while more rigorous than the IMO DCS, does not require physical inspection of fuel tanks or direct metering of every fuel line. Verifiers work primarily from documents and records. A systematic fraud in the bunker delivery note chain, while a serious MARPOL violation in its own right, would propagate through the MRV record uncorrected unless an anomaly check against independent data (AIS-derived speed and consumption estimates, for example) flagged it.
From 2025, the inclusion of general cargo ships between 400 and 5,000 GT creates a two-tier system: ships above 5,000 GT carry the full ETS surrender obligation, while the newly included smaller ships have reporting obligations but are not yet within the ETS scope. The Commission must review whether to include those vessels in the ETS by 31 December 2026.
The non-alignment between EU MRV and IMO DCS parameters means ships produce two sets of records from essentially the same measurement base, increasing administrative cost without producing additional physical data. Proposals to create a single harmonized global system have been discussed at IMO MEPC working groups since 2019 but have not resulted in a binding agreement that would allow the EU to retire the per-voyage granularity requirement.
Practical compliance checklist for companies
A company bringing a new ship into EU MRV scope or reviewing an existing monitoring plan should confirm the following:
The monitoring plan identifies every emission source: main engines, auxiliary engines, boilers, and any other combustion equipment. Each source is matched to a fuel type, an emission factor, and a monitoring method. The plan was assessed by an accredited verifier before the first reporting period and has been reassessed after any material change such as a new fuel type, change of monitoring equipment, or company transfer.
Per-voyage records are captured for every voyage departing from or arriving at an EEA port: fuel consumption per source per leg, departure and arrival port with dates, distance (from GPS or log), time at sea, and cargo or passengers with the transport work calculation. Records are retained for at least five years.
The annual report is compiled, verified by the accredited verifier, and submitted through THETIS-MRV by 31 March. The Document of Compliance is on board before the 30 June deadline. If the ship is above 5,000 GT and covered by the EU ETS, the company-level aggregated emissions report is also submitted by 31 March, and the allowance surrender is completed by the September deadline for the applicable phase-in percentage.
CH4 and N2O have been included in the monitoring plan and per-voyage records from 1 January 2024. The FuelEU Maritime monitoring plan has been submitted and assessed through THETIS-MRV for the 2025 reporting year onwards.
Annual public data publication
Each year by 30 June, the European Commission publishes aggregated ship-level data drawn from the verified THETIS-MRV records. The published dataset is publicly available and covers the preceding reporting year. It identifies each ship by IMO number, name, and flag; reports annual CO2, annual fuel consumption, the four energy efficiency indicators, and the monitoring method; and states whether a valid Document of Compliance was issued.
The first dataset covering the 2018 reporting year was published in June 2019. Data since then has tracked how average efficiency across the covered fleet has changed year by year. The 2018 dataset covered 11,900 ships. As of the 2023 reporting year, the dataset covered approximately 13,600 ships. The 2025 publication will be the first to include the expanded scope (400-5,000 GT general cargo and offshore) and the first to include CH4 and N2O emissions data.
The Commission uses the annual publication as a policy monitoring tool, tracking whether the fleet’s average CO2 per tonne-nautical mile is falling at a rate consistent with the EU’s climate targets. Where the data shows stagnation, it can inform amendments to the regulation or adjustments to the ETS carbon price signal.
Interaction with port state control
Port State Control officers under the Paris MOU check for EU MRV compliance during ship inspections. The primary check is the presence of a valid Document of Compliance on board. Officers can request the ship’s annual emissions report and monitoring plan and can verify the monitoring method being used matches the plan.
The MRV Regulation establishes escalating consequences for non-compliance. A ship without a DoC by 30 June of the year following the reporting period may be detained. A ship that has failed to report for two or more consecutive years may receive an expulsion order: entry to EEA ports is refused until the company produces a valid DoC. The Commission maintains a database of ships subject to expulsion orders, accessible to port authorities across the EEA.
Non-EEA flag ships are not exempt from this regime. A Marshall Islands-flagged VLCC calling at any EEA port faces the same monitoring, reporting, and verification obligations and the same enforcement consequences as an EU-flagged ship.
Company change and partial emissions reports
A practical complication arises when a ship changes operating company during a reporting year. Before the 2023/957 amendment, the regulation was silent on mid-year company transfers. The amendment added an explicit mechanism: when a ship changes company, the outgoing company must submit a “partial emissions report” covering only the period under its operation. That partial report is verified and submitted through THETIS-MRV to the incoming company, to the flag state, to the administering authority, and to the Commission. The incoming company is responsible for the remainder of the reporting year. Neither company can submit a single annual report covering the other’s operational period.
The partial report must follow the same format and verification requirements as a full annual report, including third-party verifier assessment. EMSA updated the THETIS-MRV workflow in 2023 to handle partial report submissions and chain-of-custody tracking when a ship changes hands. Shipowners purchasing vessels from operators mid-year should expect to receive a verified partial report as part of the handover documentation and should confirm with the administering authority that the report has been accepted before assuming the monitoring obligation for the balance of the year.
Data retention and audit trail
Regulation (EU) 2015/757 requires companies to retain all data underlying their per-voyage records for at least five years after the end of the reporting period. “All data” covers raw fuel measurements (BDN copies, tank sounding logs, flow meter readings, or CEMS data depending on method), the source documents for cargo and distance, and the working calculations that produced the emission figures submitted to THETIS-MRV.
Verifiers have the right to request this underlying data during the audit. The administering authority and the Commission may also request it. The five-year minimum is designed to allow audits retroactively covering the full period over which a ship might receive a port state control inspection or face an ETS penalty assessment. Companies using third-party data management software that automates per-voyage log entries should ensure the system retains raw inputs, not only final report figures, to satisfy this requirement.
The 2025 Commission review
Article 22 of Regulation (EU) 2015/757 requires the Commission to review the regulation and report to the European Parliament and Council. The most recent review report, published in March 2025, covered two topics: (1) the implementation of the EU ETS in maritime transport during its first year (2024), and (2) the possibility of including additional ships and ship types in the MRV scope beyond the 400-5,000 GT expansion already enacted by 2023/957.
The review confirmed that MRV data quality has improved year-on-year since 2018. It flagged methane emission factor accuracy as an open technical question, particularly for dual-fuel engines where the split between combusted and unburned methane depends on engine load and ambient conditions. The Commission indicated it would work with EMSA and verifier accreditation bodies to develop improved monitoring guidance for CH4 before the 2026 ETS CH4 obligation takes effect.
The review also noted that the ETS phase-in trajectory had not triggered significant evasive behavior: the share of ships calling at EEA ports remained stable in 2024 relative to 2023, and no material rerouting of cargo to non-EEA ports was detected in the THETIS-MRV dataset for the first full ETS year.