IMO Data Collection System: fuel oil reporting guide

The IMO Data Collection System is the mandatory annual fuel-oil reporting regime under MARPOL Annex VI Regulation 27. Every ship of 5,000 GT and above on international voyages collects fuel consumption by fuel type, distance travelled, and hours underway for each calendar year, documents the measurement method in the SEEMP Part II, submits the aggregated data to its flag Administration by the end of February, and receives a Statement of Compliance not later than 31 May. The flag state then uploads that data to the IMO Ship Fuel Oil Consumption Database in GISIS by 30 June. Since 2023, the same data drives the ship’s annual CII rating.

This article covers the legal foundation of the DCS, who must comply and exactly what data they must collect, how the SEEMP Part II works as the measurement framework and what its nine mandatory plan elements require, the full reporting and verification chain from ship to GISIS, what the Statement of Compliance records and when it can be withheld, how DCS data feeds the Carbon Intensity Indicator, the 2025 enhanced granularity amendments under MEPC.385(81) and what the new Appendix IX form records, and the structural differences between the DCS and the EU MRV Regulation that operators must reconcile when a ship trades into Europe. For a side-by-side rule comparison, see IMO DCS vs EU MRV. For the full SEEMP document family, see SEEMP I, II and III.

Legal foundation

MARPOL Annex VI Regulation 27 and Resolution MEPC.278(70)

The legal basis for the DCS is Regulation 22A of MARPOL Annex VI, introduced by Resolution MEPC.278(70), adopted at the 70th session of the Marine Environment Protection Committee on 28 October 2016. The regulation entered into force on 1 March 2018, with the first full calendar-year reporting period running from 1 January 2019 to 31 December 2019. The current consolidation of MARPOL Annex VI renumbers the provision as Regulation 27, which is the identifier used in contemporary flag-state circulars and class-society guidance.

Resolution MEPC.278(70) amended MARPOL Annex VI to insert Regulation 22A and Appendix IX, which sets out the standardized data reporting format. The companion resolution, MEPC.282(70), adopted at the same session, issued the 2016 Guidelines for the development of a SEEMP Part II, prescribing how ships should document their chosen measurement methodology.

The DCS sits inside Chapter 4 of MARPOL Annex VI, the chapter that deals with regulations on energy efficiency for ships. Regulation 26 of the same chapter requires ships to carry a SEEMP; Regulation 27 builds on that by requiring the SEEMP to contain a Part II data collection plan before any data reporting can begin.

Purpose and policy context

The DCS was adopted as the second phase of a three-phase approach the IMO announced at MEPC 70. Phase one was the Energy Efficiency Design Index (EEDI) and SEEMP (2013). Phase two was the data collection system (DCS, in force 2018). Phase three was the operational carbon intensity framework including the CII and the EEXI, which entered force on 1 November 2022 under Resolutions MEPC.328(76) and MEPC.333(76). The DCS was never designed as an end in itself; from the outset, Resolution MEPC.278(70) described the database as a tool to “inform further IMO measures to reduce GHG emissions from ships.” The transition from data collection to carbon intensity rating confirmed that design intent.

Scope: which ships must comply

The 5,000 GT threshold

Regulation 27 applies to ships of 5,000 GT and above engaged on international voyages. That threshold is consistent with the CII requirement under Regulation 28 and the EEXI under Regulation 24. The IMO estimates that ships above 5,000 GT are responsible for approximately 85% of CO2 emissions from international shipping, so the threshold captures the bulk of the emissions signal while keeping the administrative burden proportionate.

The obligation attaches to the ship, not the flag state. A vessel flagged to a non-MARPOL-party still falls within DCS scope if it calls at ports of MARPOL-party states, because port-state control authorities can check for the Confirmation of Compliance and the Statement of Compliance. In practice, 105 of 135 flag administrations submitted DCS data for reporting year 2023, covering 28,620 ships with a combined gross tonnage of 1,301 million GT.

Voyages in scope

The regulation applies to international voyages, defined consistently with the SOLAS convention as voyages between ports in different states. Domestic voyages between ports in the same state are excluded. There is no geographic weighting by voyage category: unlike the EU MRV, which distinguishes between intra-EEA, extra-EEA arriving, and extra-EEA departing legs, the DCS counts all fuel consumed on board across all international voyages in the calendar year, aggregated into a single annual figure.

Excluded vessel categories

Ships not propelled by mechanical means, government vessels on non-commercial service, and vessels exempt from MARPOL Annex VI under Regulation 3 are outside the DCS scope. Fishing vessels, warships, and naval auxiliaries fall into Regulation 3 exemptions. Platforms and drilling rigs are typically excluded because they don’t engage in international voyages as defined.

Data elements required under Regulation 27

The original three parameters (since 2019)

Appendix IX of MARPOL Annex VI (as amended by MEPC.278(70)) specifies three measured quantities that ships must report annually:

“Fuel oil” covers every hydrocarbon fuel used for propulsion or auxiliary purposes: HFO, VLSFO, LSMGO, MGO, LNG, LPG, methanol, and any other fuel type the ship uses. The full list of fuel types and their CO2 emission factors is contained in Appendix IX.

Consumption is reported regardless of operational status: a ship burning HFO at anchor for auxiliary power must count that fuel in its annual total. The distance and hours fields, by contrast, capture only the periods under own propulsion.

The 2025 enhanced granularity additions (from data year 2026)

Resolution MEPC.385(81), adopted at MEPC 81 on 22 March 2024, amended Appendix IX of MARPOL Annex VI. These amendments entered into force on 1 August 2025, with early implementation permitted from 1 January 2025. Ships must collect data at the enhanced level from 1 January 2026 (for new deliveries after 1 August 2025, from delivery date).

Three new data fields join the existing three:

Fuel consumption by consumer type. The annual fuel total must now be disaggregated by consumer group: main engines, auxiliary engines/generators, oil-fired boilers, and other consumers. The amended Appendix IX form requires that each consumer-type subtotal further distinguish between fuel consumed while the ship is under way and fuel consumed while not under way. The four consumer categories match the terminology in MEPC.282(70) Appendix 2 section 3, which already listed main engines, auxiliary engines, boilers, and inert gas generators as the standard consumers to document in the Data Collection Plan. This granularity allows the IMO secretariat and member states to model where efficiency improvements are occurring in the fleet and compare auxiliary-load profiles across ship types.

Transport work. Ships subject to Regulation 28 (those to which CII applies) must report the annual sum of transport work, calculated as the product of cargo carried and distance sailed per voyage. The metric varies by ship type: bulk carriers, tankers, gas carriers, and general cargo ships report in tonne-miles; containerships report in both TEU-miles and tonne-miles; cruise ships and ro-pax vessels report in passenger-miles. This transport work figure is the denominator that turns a raw CO2 mass into a carbon intensity ratio, so having it in the DCS database for the first time closes a longstanding gap between the IMO dataset and what the EU MRV has collected per voyage since 2018. The amended Appendix IX form shows the transport work field only for ships to which Regulation 28 applies, alongside the attained CII, required CII, applicable CII metric (AER or cgDIST), and the A-to-E rating.

Onshore power supply. Total electricity received from shore-side connections, expressed in kilowatt-hours, recorded from supplier documentation. This captures the operational efficiency benefit of cold ironing.

MEPC.1/Circ.913, approved at MEPC 82 on 4 October 2024, provides application guidance for these amendments. It confirms that the SEEMP must be revised to incorporate the enhanced-granularity measurement methodology before the start of data collection at the new level: before 1 January 2026 for ships under administrations that implement on the standard 1 August 2025 entry-into-force date, or before 1 January 2025 for those under early-implementing administrations.

The SEEMP Part II: the measurement framework

What SEEMP Part II contains

The SEEMP Part II is the data collection plan for the DCS. Resolution MEPC.282(70) Appendix 2 sets out the nine mandatory plan sections in a sample form that administrations and ROs use as the reference template:

Section 1: Ship particulars. Name of ship, IMO number, company, flag state, ship type, gross tonnage, net tonnage, deadweight, EEDI (if applicable), and ice class. These identifiers link the plan to the statutory certificate record.

Section 2: Record of revision. A table logging each revision date and the provision revised. Every approved update to the plan must be entered here so the verifier can trace when the methodology last changed.

Section 3: Ship engines and other fuel oil consumers, and fuel oil types used. A listing of every consumer on board by type and model, rated power output, and the fuel oil types each consumer can burn, together with the CO2 conversion factor (CF) for each fuel type from the Appendix IX Table 1 list. The 2016 guidelines give CF factors for diesel/gas oil (3.206), light fuel oil (3.151), heavy fuel oil (3.114), LPG propane (3.000), LPG butane (3.030), LNG (2.750), methanol (1.375), and ethanol (1.913).

Section 4: Method to measure fuel oil consumption. The specific method the ship will use, described in enough detail that the verifier can reproduce the calculation. MEPC.282(70) section 7.1 describes four accepted approaches: (a) bunker delivery notes plus tank soundings, the mass-balance method; (b) flow meters; (c) bunker fuel oil tank monitoring using daily soundings; and (d) direct CO2 exhaust-gas measurement (rarely used). A ship may use different methods for different fuel types on board, provided each is fully documented.

Section 5: Method to measure distance travelled. The approach for recording nautical miles: GPS log, chart log, or other Administration-accepted method. MARPOL Annex VI requires distance travelled over ground under own propulsion; canal transits at anchor or under tow are excluded.

Section 6: Method to measure hours underway. The procedure for aggregating the duration of periods under own propulsion, typically derived from the bridge watch log entries at departure from and arrival at port.

Section 7: Processes to report data to the Administration. Who compiles the year-end Appendix IX summary, to whom it is submitted, by what means, and by what date. This section names the responsible officer and the reporting channel (direct to the flag or through the authorized RO).

Section 8: Reporting format. A confirmation that the ship will use the standardized Appendix IX form as required by Regulation 27.3 of MARPOL Annex VI, which requires data to be communicated electronically using the Organization’s standardized form.

Section 9: Data quality. The procedures for identifying data gaps and correcting them. MEPC.282(70) section 7.6 specifies two minimum requirements: the procedure for identifying gaps and the procedure for filling them when monitoring data is missing, for example when flow meters malfunction. The data quality section must integrate with the ship’s safety management system. Any correction applied to the raw data, such as density or temperature adjustments, must be documented in this section.

The nine-section structure is prescribed. A SEEMP Part II that omits any section will not receive a Confirmation of Compliance.

Approval and the Confirmation of Compliance

Before data collection began on 1 January 2019, each ship needed an approved SEEMP Part II on board and a Confirmation of Compliance issued by the flag Administration or authorized Recognized Organization (RO). MEPC.1/Circ.914, approved at MEPC 82 on 4 October 2024 and revoking the earlier MEPC.1/Circ.876, provides the current revised sample format. The Confirmation states that the ship’s SEEMP has been developed and “complies with regulation 26.2 of Annex VI of the Convention,” taking into account the 2024 SEEMP Guidelines adopted by resolution MEPC.395(82).

Regulation 5.4.5 of MARPOL Annex VI is explicit: the Administration must ensure that for each ship to which Regulation 27 applies, the SEEMP complies with Regulation 26.2 “prior to collecting data under regulation 27 of this Annex in order to ensure the methodology and processes are in place prior to the beginning of the ship’s first reporting period.”

Ships delivered after 1 March 2018 need the SEEMP Part II and the Confirmation of Compliance before their first international voyage. Ships switching flag states must update their SEEMP Part II documentation with the new Administration before the plan is revalidated. The Confirmation records the ship’s name, IMO number, port of registry, gross tonnage, and the date of the most recent SEEMP Part II revision.

Approved measurement methods

Appendix IX allows four approaches for measuring fuel consumption, in descending order of precision:

1. Flow meters on fuel supply lines, with documented calibration records. The SEEMP Part II must identify each meter by location, the consumers it covers, and the backup method if the meter fails.
2. Bunker delivery note (BDN) plus periodic tank soundings, the mass-balance method: opening stock plus deliveries minus closing stock equals consumption. This is the most widely used method because BDNs are already statutory documents under MARPOL Annex VI Regulation 18. The plan must document the tank-reading procedure and how the year-end sounding is reconciled with voyage-extension cases where the year turns mid-passage.
3. Bunker fuel oil tank monitoring using daily automated soundings or dip-tape readings, aggregated to a running total.
4. Direct CO2 exhaust-gas measurement, which multiplies exhaust CO2 concentration by exhaust flow rate, rarely used outside specific research contexts.

A ship may use different methods for different fuel types on board, provided each is documented in the SEEMP Part II. If the actual uncertainty of a method exceeds the documented limit in the Data Collection Plan, that period’s data must be treated as a data gap and filled using the gap-filling procedure in Section 9.

SEEMP Part II update required for 2025 amendments

Ships implementing the MEPC.385(81) enhanced granularity requirements under the standard schedule must submit a revised SEEMP Part II to their flag Administration or RO before 1 January 2026, documenting how they will measure fuel by consumer type and how they will calculate transport work. For ships under early-implementing administrations that chose to apply from 1 January 2025, the revised SEEMP Part II had to be in place before 1 January 2025. Ships delivered on or after 1 August 2025 must collect data at the enhanced level from delivery date.

Reporting and verification flow

Step 1: the ship compiles annual data

During the calendar year, the ship records fuel deliveries via BDN, conducts tank soundings at the start and end of the year (or uses its flow meter data), and logs operational hours from the bridge watch record. By 28 February of the following year (the typical flag-state submission deadline, though administrations may set an earlier date), the ship or the company submits the completed Appendix IX data sheet to the flag Administration or the RO acting on its behalf.

The data sheet contains the three original parameters broken down by fuel type, covering the full calendar year from 1 January to 31 December. From reporting year 2026 it also includes the three enhanced fields described above.

Step 2: flag Administration or RO verifies

The flag Administration, or an RO it has authorized under MARPOL Annex VI Regulation 27.7, reviews the submitted data. MEPC.348(78) section 4 sets out the verification programme. The Administration should request additional supporting documents alongside the annual data report, including: a copy of the verified SEEMP Part II, BDN summaries in sufficient detail to show all fuel deliveries are accounted for, summaries of disaggregated fuel consumption and distance data, information on any data gaps and how they were resolved, and copies of the ship’s logbook or oil record book for cross-check.

The verification checks three attributes per MEPC.348(78) section 4.2:

• Consistency: does the reported total match what can be recalculated from the underlying documents, and is it consistent with prior reporting years?
• Completeness: does the data cover the full calendar year without unexplained gaps?
• Reliability and accuracy: were the data quality procedures in the SEEMP Part II properly followed, and does the reported consumption correspond with expected consumption for that ship’s type, size, and operating profile?

MEPC.348(78) section 6.3 defines a material discrepancy as one “that could influence the reported total by more than ±5%.” If a material discrepancy is found, the Administration must communicate it to the company for clarification or correction; the Statement of Compliance cannot be issued until the discrepancy is resolved. From 2023 onward, the verification also covers the attained CII calculation and the CII rating, per MEPC.348(78) section 5.

The Administration or RO issues the Statement of Compliance not later than 31 May of the year following the reporting year. For reporting year 2019 data, the first Statement of Compliance was required on board by 31 May 2020. The format is prescribed in Appendix X of Resolution MEPC.278(70).

Step 3: data uploaded to IMO GISIS

After issuing the Statement of Compliance, the flag Administration transfers the verified annual data to the IMO Ship Fuel Oil Consumption Database, a module in the Global Integrated Shipping Information System (GISIS), by 30 June. Only Administrations or organizations authorized by them can submit data to the GISIS module.

The GISIS database holds ship-level records but the data is not publicly available at the individual ship level. The IMO Secretariat produces an anonymized annual report to the Marine Environment Protection Committee where identification of a specific ship is not possible. That report presents aggregate fleet-level fuel consumption and carbon intensity trends by ship type and size category.

MEPC.385(81) added Regulations 27.14 and 27.15 to MARPOL Annex VI, which create two new access paths not available under the original 2016 regime. Regulation 27.14 permits the Secretary-General to share data on an ad hoc basis with “analytical consultancies and research entities, under strict confidentiality rules.” Regulation 27.15 requires the Secretary-General to grant a company access to its own ships’ fuel oil consumption reports in non-anonymized form “to the general public” on request.

Step 4: IMO annual report to MEPC

The Secretariat’s annual DCS report is presented at the MEPC session held in the autumn of each year. For reporting year 2023, the MEPC 82 session (30 September to 4 October 2024) approved the summary covering 28,620 ships, 1,301 million GT, and 105 participating Administrations. Total fuel used by reporting ships was 211 million tonnes in 2023, down from 213 million tonnes in 2022. Of that, 93.52% was HFO, light fuel oil, or diesel/gas oil, with the remaining 6.48% comprising LNG, LPG, methanol, and other non-conventional fuels, up from 5.35% in 2022. CII ratings were reported by 24,653 of the 28,620 reporting ships, a coverage rate of 86.1%. The report feeds the IMO’s fleet carbon intensity dataset, which informs the IMO Strategy on Reduction of GHG Emissions from Ships and the Revised IMO GHG Strategy adopted at MEPC 80 in July 2023.

The Statement of Compliance

The Statement of Compliance is the primary statutory document a ship carries to demonstrate DCS compliance. It must be retained on board for five years from the date of issue.

From 2023, the Statement of Compliance records two items beyond the fuel and distance totals:

• The attained annual operational CII, expressed in grams of CO2 per capacity unit per nautical mile.
• The operational carbon intensity rating, one of five grades: A (major superior), B (minor superior), C (moderate), D (minor inferior), E (inferior).

MEPC.348(78) section 6.2 adds an important conditional: when a corrective action plan is required (because the ship rated D or E) but has not yet been submitted, the Administration must inform the company and must not issue the Statement of Compliance until a revised SEEMP Part III incorporating the corrective action plan has been developed and verified. The Statement of Compliance cannot be issued in that case unless the corrective action plan is “duly developed and reflected in the SEEMP and verified by the Administration.”

A ship rated D for three consecutive years, or E for any single year, must update its SEEMP Part III with a documented corrective action plan before the next Statement of Compliance can be issued. The corrective action plan mechanism is in MARPOL Annex VI Regulation 28 and the 2021 CII Guidelines (MEPC.336(76)).

Port-state control officers check for both the Confirmation of Compliance and the Statement of Compliance during inspections. A missing or expired Statement of Compliance is a deficiency under MARPOL Annex VI that can result in detention.

How DCS data feeds the CII

The Carbon Intensity Indicator entered force on 1 November 2022 under Regulation 28 of MARPOL Annex VI. The CII is calculated from the DCS data collected in the preceding calendar year, making the DCS the direct data source for every ship’s annual CII rating.

The CII calculation chain

The attained CII formula for most ship types is:

where M_\text{CO_2} is the total mass of CO2 emitted during the year, $C$ is the ship’s capacity (deadweight for bulk carriers and tankers; gross tonnage for cruise ships and ferries), and $d$ is the distance sailed during the year. All three quantities come directly from the DCS report: M_\text{CO_2} is derived from the reported fuel consumption totals multiplied by the fuel-specific CO2 conversion factors in Appendix IX, and $d$ is the reported distance travelled.

The addition of transport work data in the MEPC.385(81) amendments will, once fully implemented, allow the IMO to calculate a transport-work-normalized CII variant that adjusts for load factor. This is the same normalization the EU MRV has enabled since 2018 through per-voyage cargo data.

CII rating determination

The attained CII is compared against the Required Annual Operational CII for that ship, which is a function of ship type, capacity, and the year within the reduction trajectory. The reduction factors from 2023 to 2026 are set in MEPC.336(76); MEPC.354(78) extended the trajectory. The resulting rating (A to E) is entered on the Statement of Compliance and in the revised SEEMP Part III.

Ships must document their CII compliance trajectory and, for D and E ratings, a corrective action plan in the SEEMP Part III. The SEEMP Part III links directly back to the DCS because the corrective action plan must reference the attained CII figures from prior reporting years and project a credible path to a C or better rating. Operators can model this trajectory using the CII attained vs required calculator and the CII 3-year corrective plan calculator.

IMO DCS and the EU MRV: two systems on the same ships

Why the comparison matters

Any ship of 5,000 GT and above that calls at a European Economic Area port must comply with both the IMO DCS and EU MRV Regulation 2015/757. The two systems overlap substantially in what they measure but differ in how they report, what they disclose, and what financial consequences they trigger. For a structured rule-by-rule comparison see IMO DCS vs EU MRV.

Side-by-side comparison

The non-alignment problem

The non-alignment between the two systems creates specific operational complications. Three are worth detailing.

Annual vs. voyage granularity. The IMO DCS requires only annual aggregates; the EU MRV requires individual voyage records from which the annual total is built up. A ship that collects EU MRV voyage records can always derive the DCS annual total by summing, but the reverse is not true. Operators must maintain per-voyage records for MRV regardless, so DCS compliance becomes a subset of the MRV data exercise.

Scope weighting. The EU MRV distinguishes intra-EEA legs (100% weight) from extra-EEA legs (50% weight) for ETS purposes. The IMO DCS counts all fuel for all international voyages equally. A ship on a world-trading route with only occasional EEA calls will have a DCS total much larger than its EU ETS-relevant total. A single monitoring plan can share the measurement methodology, but two different annual reports with different totals will emerge.

Cargo and transport work. EU MRV has required per-voyage cargo figures since 2018. The IMO DCS did not require transport work until MEPC.385(81) brought it in for data year 2026. In the intervening seven years, a researcher comparing EU MRV transport-work efficiency metrics with IMO DCS figures was comparing an intensity metric (MRV) against a bare consumption figure (DCS). Post-2026, both systems will include transport work, but the EU MRV per-voyage granularity still allows finer analysis.

Combining the monitoring plan

Most operators maintain one combined monitoring plan document with a small annex covering the MRV-only fields (per-voyage granularity tables, cargo-carried definitions, voyage category classification logic). The four measurement methods accepted by the DCS (BDN mass balance, flow meters, tank monitoring, and direct CO2 measurement) are identical to the four accepted by EU MRV Annex I. A method documented in the SEEMP Part II satisfies the MRV Monitoring Plan requirement for the same parameter, and the MRV verifier can rely on DCS-compliant data. Port-state control inspections check the Statement of Compliance; MRV compliance checks look at the Document of Compliance. Both documents need to be on board.

Enforcement and port-state control

MARPOL Annex VI Chapter 4 gives port-state control officers authority to check for the Confirmation of Compliance and the Statement of Compliance on any ship calling at a port. The Paris MOU, Tokyo MOU, and other regional port-state control organizations include DCS document checks in their standard inspection checklists.

A missing Confirmation of Compliance means the ship’s Data Collection Plan was never approved, which is a major non-conformity under MARPOL Annex VI Regulation 5.4.5. A missing or expired Statement of Compliance is a deficiency that inspectors can cite and, in repeat cases, use as grounds for detention. The Confirmation and Statement are distinct documents with distinct functions: the Confirmation attests that the methodology is in place before data collection begins; the Statement attests that data from a completed calendar year was reported and verified correctly.

Flag-state enforcement varies. Administrations with large open registries (Liberia, Marshall Islands, Panama, Bahamas) have delegated DCS verification to recognized organizations under class society agreements. Class NK, DNV, Lloyd’s Register, Bureau Veritas, and other societies acting as ROs issue both the Confirmation of Compliance and the Statement of Compliance on behalf of the flag on the basis of technical review. The RO acts as an extension of the flag Administration under Regulation 27.7, but the Administration “assumes full responsibility for all tasks conducted” by the RO, per MEPC.348(78) section 3.2. This is a materially different accountability structure from the EU MRV’s independently accredited verifier model, where the verifier is not an agent of the flag state.

MEPC.385(81) added Regulation 27.14 to MARPOL Annex VI, allowing the IMO Secretary-General to share data with analytical consultancies and research entities under confidentiality rules. That provision does not create any new port-state authority, but it does create a channel for independent researchers to obtain fleet-level data that can cross-check the plausibility of aggregate flag-state submissions.

Limitations

The IMO DCS produces a global fleet fuel-consumption dataset that no other mechanism could generate at this scale, but several structural limitations matter in practice.

Annual aggregates obscure operational variation. A ship that slow-steams for six months and sprints at maximum speed for the other six will report the same annual fuel total as one that maintains steady speed throughout, provided the totals are equal. The DCS annual aggregate cannot distinguish these patterns. Per-voyage granularity, which the EU MRV provides, is the minimum needed to link fuel consumption to operational choices.

Fuel-type definitions are not granular enough for new fuels. LNG, LPG, methanol, ammonia, and hydrogen each have distinct energy density and CO2 factors. Appendix IX Table 1 has been updated as new fuels enter service, but classification of blended fuels or co-fueling remains ambiguous in some flag-state implementations. The SEEMP Part II gap-filling procedure allows for estimates, but those estimates carry uncertainty that the annual aggregate conceals.

Verification quality is uneven. The DCS relies on flag Administrations to check the data before uploading to GISIS. Unlike the EU MRV, which requires an independently accredited verifier, the DCS verification quality depends on the rigor applied by the flag or its authorized RO. MEPC.348(78) uses a materiality threshold of ±5%: discrepancies below that level do not block issuance of the Statement of Compliance. The IMO Secretariat cannot reject data once uploaded; it can only produce aggregate statistics. Systematic under-reporting or methodological inconsistencies across flag states are difficult to detect from the anonymized GISIS totals.

No public access at the ship level. The IMO publishes annual reports with fleet-level aggregates by ship type and size category. Individual ship data is not disclosed. Charterers, cargo owners, and financial institutions seeking ship-level carbon intensity data cannot use the DCS database directly; they rely on commercial databases that compile SEEMP Part III disclosures or EU MRV public records.

CII ratings are influenced by cargo factor. The CII denominator is fixed capacity (deadweight or GT), not actual cargo carried. A ship trading at 60% load factor and one at 90% load factor will receive different CII scores even if their fuel efficiency per tonne-mile is identical. The MEPC.385(81) transport work addition addresses this for future years, but historical CII ratings from 2023 to 2025 carry this structural bias.

The non-alignment with EU MRV creates duplicate reporting. Ships trading to Europe run two parallel reporting processes with different deadlines, different verifier models, and different downstream obligations. This is not a DCS deficiency per se, but it is a practical cost of the IMO and EU having developed parallel systems without full harmonization. The alignment of measurement methods (both accept the same four approaches) is a floor, not a ceiling.

Practical guidance for operators

Before the reporting year starts

The SEEMP Part II must be approved and a Confirmation of Compliance on board before 1 January of the first reporting year, or before the ship’s first international voyage for newly delivered vessels. Ships updating to the MEPC.385(81) enhanced requirements need a revised SEEMP Part II approved by the flag or RO before 1 January 2026. The revised format required by MEPC.1/Circ.914 references compliance with the 2024 SEEMP Guidelines (MEPC.395(82)), so an older plan that references MEPC.346(78) or MEPC.282(70) will need a formal re-endorsement to confirm it meets the updated standards.

Verify that the SEEMP Part II documents the correct measurement method for each fuel type. The most common non-conformity found during flag-state reviews is a SEEMP Part II that names the BDN method but doesn’t include the tank-sounding procedure or the data-gap policy required by Section 9. If the ship switches fuel types (for example, switching from HFO to LNG for a specific route), the SEEMP Part II must be updated before the new fuel is consumed on an international voyage.

During the reporting year

The practicalities of data collection fall on the ship’s officers and the company’s technical or environmental department. The key documents to maintain during the year:

• Original BDNs for every fuel delivery, including all mandatory BDN fields per MARPOL Annex VI Regulation 18.
• Bunkering tank sounding records immediately before and after each delivery.
• Year-end (31 December midnight) tank ROB (remaining on board) soundings, which close the mass-balance equation.
• Bridge watch logs recording the times under way versus at anchor, in port, or under tow.
• From data year 2026: consumer-type fuel logs separating main-engine burn from auxiliary and boiler burn.

Submitting the annual data report

The completed Appendix IX data sheet, signed by the master and countersigned by the company’s designated person, must reach the flag Administration or the authorized RO by the deadline set by that Administration, typically 28 February or earlier. Late submission can delay issuance of the Statement of Compliance, which creates a compliance gap if port-state control inspects after 31 May.

Companies managing large fleets across multiple flag registries should track Statement of Compliance issuance dates centrally. A ship that changes flag mid-year carries two partial-year records: the outgoing flag issues a partial Confirmation or statement covering its tenure, and the incoming flag takes responsibility for the remainder of the year. The split-year procedure is described in MEPC.1/Circ.876 (now superseded by MEPC.1/Circ.914 for the Confirmation format, though the split-year principles remain).

Annual DCS data and the CII calculation

Since 2023, the CII calculation accompanies the annual DCS data submission. The master or company computes the attained CII from the year’s fuel and distance data before submitting to the Administration. If the ship is rated D or E, the SEEMP Part III corrective action plan must be completed and submitted simultaneously, because MEPC.348(78) section 6.2 bars the Administration from issuing the Statement of Compliance until the plan is verified.

The CII calculation itself is not an optional add-on to the DCS submission; Regulation 28 and MEPC.336(76) make it mandatory for ships of 5,000 GT and above from the 2023 reporting year. The Administration or RO will not issue a Statement of Compliance without a CII rating recorded on it. This means errors in the DCS fuel or distance figures propagate directly into the CII rating. A ship that over-reports fuel consumption (for example by including fuel consumed by a crane barge on charter rather than the reporting ship itself) will receive a worse CII rating than it deserves and may face unnecessary corrective action obligations. A ship that under-reports distance will similarly skew its intensity ratio upward. Both errors should be caught during the SEEMP Part II review, but the master’s sign-off is the last practical quality check before the data leaves the ship.

From 2025 onward, the attained CII figures for individual ships have become available through commercial tracking services that aggregate THETIS-MRV public disclosures and cross-reference them with AIS distance data. Charterers, banks, and cargo owners increasingly use these signals to assess counterparty carbon risk. While the DCS itself produces no public per-ship disclosure, the CII rating on the Statement of Compliance is visible to port-state control and to any RO conducting flag-state surveys.

Operators can use the IMO DCS annual report calculator to check the Appendix IX totals before submission and use the CII rating calculator to project the attained CII and rating. The SEEMP Part II and III tracker maintains a consolidated compliance record across the SEEMP Part II and Part III obligations.

See also

• SEEMP I, II and III: the three-part SEEMP document family, including the Part II data collection plan
• Carbon Intensity Indicator (CII): how attained CII is calculated from DCS data
• IMO DCS vs EU MRV: detailed rule-by-rule comparison
• EU MRV Regulation 2015/757: the parallel EU reporting regime
• EU MRV Voyage Data: the per-voyage data fields required under EU MRV
• MARPOL Annex VI: the parent annex covering all air pollution and energy efficiency regulations
• IMO Net Zero Framework: the 2023 Revised IMO GHG Strategy that the DCS database informs