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IMO DCS Reporting Guide

MARPOL Annex VI Regulation 27 explained end-to-end — required fields, deadlines, Cf factors from Appendix IX, Statement of Compliance issuance, penalties, and the link to CII from 2023.

MARPOL Annex VI Reg. 27

Effective 2019

CII layer from 2023

What is IMO DCS?

The IMO Data Collection System (DCS) is the mandatory annual fuel-oil consumption reporting system for ships of 5,000 gross tonnage and above on international voyages. Adopted by IMO in 2016 as part of MARPOL Annex VI, took effect 1 March 2018, first submission required by 31 March 2019 covering 2018 data.

Three-tier data flow: ship → flag state administration → IMO GHG database. Ships log fuel consumption per fuel type, distance travelled, and hours underway. At year-end, aggregate is submitted to the flag state, which issues a Statement of Compliance (SoC) and forwards anonymised data to the IMO Ship Fuel Oil Consumption Database.

From 1 January 2023, MARPOL Annex VI Regulation 28 layers the operational carbon-intensity indicator (CII) on top of DCS. Same fuel + distance data feeds CII, which produces an annual A–E rating.

Compliance timeline

1 January

Reporting period starts

All fuel consumption, distance, and hours-underway data captured per calendar year.

31 December

Reporting period ends

Ship crew closes the year's dataset. Reconciliation begins.

31 March (next year)

Ship-to-Administration deadline

Aggregate submitted to flag state in prescribed format. Missing this is a MARPOL Annex VI violation.

31 May

Statement of Compliance issued

Flag state verifies data and issues SoC. Ship must carry valid SoC on board — checked in Port State Control.

30 June

Administration-to-IMO submission

Flag state anonymises data and submits to IMO Ship Fuel Oil Consumption Database.

Required data fields

Per Appendix IX to MARPOL Annex VI Regulation 27, each annual submission must contain:

Ship identification — IMO number, name, flag, ship type, gross tonnage, deadweight, ice class
Technical characteristics — from EEDI/EIV technical file (installed engine power, main + auxiliary)
Reporting period — start + end date of calendar year
Fuel consumption per type — total mass in metric tonnes for each fuel (HFO, LFO, MGO/MDO, LNG, LPG, methanol, ethanol, biofuel)
Distance travelled — nautical miles underway (excluding drift, anchor, berth)
Hours underway — total hours main engine running for propulsion
Measurement method — BDN + tank monitoring / flow meters / bunker tank monitoring
CII (from 2023) — Attained CII, Required CII, rating letter A–E

Cf factors — Appendix IX

CO₂ emissions calculated as fuel mass × Cf. Same set as CII and EEDI.

HFO

3.1144

tCO₂/tFuel

LFO / VLSFO

3.1510

tCO₂/tFuel

MGO / MDO

3.2060

tCO₂/tFuel

LNG

2.7500

tCO₂/tFuel

LPG-Propane

3.0000

tCO₂/tFuel

LPG-Butane

3.0300

tCO₂/tFuel

Methanol

1.3750

tCO₂/tFuel

Ethanol

1.9130

tCO₂/tFuel

Ammonia (TtW)

0.0000

tCO₂/tFuel

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IMO Number

Reporting Year

Fuel #1 Type

Fuel #1 Mass (tonnes)

Fuel #2 Type

Fuel #2 Mass (tonnes)

Distance (nm)

Hours underway

DWT (tonnes)

Ship Type

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Frequently asked questions

What is the IMO DCS deadline?

Ship must submit annual data to flag state by 31 March each year for the preceding year. Flag state issues Statement of Compliance (SoC) by 31 May. SoC must be on board and is inspected during Port State Control.

Is IMO DCS the same as EU MRV?

No, but they overlap. EU MRV (Regulation 2015/757) applies to voyages calling EU ports; IMO DCS applies globally to all ships ≥5,000 GT. Fields collected are similar. MRV per-voyage to verifier + THETIS-MRV; DCS annual aggregate to flag state.

How does IMO DCS connect to CII?

From 1 January 2023, MARPOL Annex VI Regulation 28 requires ships to calculate CII from the same DCS data. Attained CII = (Fuel × Cf) / (Capacity × Distance). See our CII methodology guide.