The calculation period for annual operational CII and what happens on transfer (MARPOL Annex VI Regulation 28)

CII is an indicator that counts a whole year. Which raises the question of who counts that year, and how, when the flag or the company changes mid-year. The 2021 revised MARPOL Annex VI answers that differently in regulation 27 and in regulation 28. This article reads the difference.

The calculation period runs 1 January to 31 December

shall calculate the attained annual operational CII over a 12-month period from 1 January to 31 December for the preceding calendar year, using the data collected in accordance with regulation 27 of this Annex, taking into account the guidelines to be developed by the Organization.

It applies to ships of 5,000 gross tonnage and above falling into one of the categories the Annex lists. The period is the 12-month calendar year and the input is the data collected under regulation 27. The calculation runs from the end of calendar year 2023 and every year after.

The reporting deadline is three months after the year ends

2 Within three months after the end of each calendar year, the ship shall report to its Administration, or any organization duly authorized by it, the attained annual operational CII via electronic communication and using a standardized format to be developed by the Organization.

The recipient is the flag Administration or an organization duly authorized by it. The method is electronic communication in a standardized format.

A change of flag or company does not split the year

3 Notwithstanding 1 and 2 of this regulation, in the event of any transfer of a ship addressed in regulations 27.4, 27.5 or 27.6 completed after 1 January 2023, a ship shall, after the end of the calendar year in which the transfer takes place, calculate and report the attained annual operational CII for the full 12-month period from 1 January to 31 December in the calendar year during which the transfer took place, in accordance with regulations 28.1 and 28.2, for verification in accordance with regulation 6.6 of this Annex, taking into account guidelines to be developed by the Organization.

This is where it parts from regulation 27. Regulation 27 has the period split on a transfer. On a change of Administration the ship reports the aggregated data for the losing Administration’s portion on the day the transfer completes or as close to it as practical; on a change of company it reports the portion corresponding to that company. Where both happen at once, the Administration rule governs.

Regulation 28 does the opposite. For the calendar year in which the transfer happened, it calculates and reports the full 12-month period. Ratings are not to be built out of fragments.

Regulation	How it sees the year a transfer falls in
Regulation 27 (fuel oil consumption data)	Period split by Administration and by company, each aggregated and reported
Regulation 28 (operational CII)	The whole 1 January to 31 December calculated and reported as one

And the same paragraph adds a line: nothing in the regulation relieves any ship of its reporting obligations under regulation 27 or under regulation 28. Counting the year whole does not replace reporting it split.

The required CII comes from a reference value and a reduction factor

Regulation 28 paragraph 4 defines the required annual operational CII by applying an annual reduction factor to a reference value. The reduction factor is the value that keeps improvement running inside a given rating level, and it and the reference value are set by guidelines developed by the Organization. The provision carries the shape of the formula; the numbers are in the guidelines.

The rating splits five ways around the required CII

6 The attained annual operational CII shall be documented and verified against the required annual operational CII to determine operational carbon intensity rating A, B, C, D or E, indicating a major superior, minor superior, moderate, minor inferior, or inferior performance level, either by the Administration or by any organization duly authorized by it, taking into account the guidelines developed by the Organization. The middle point of rating level C shall be the value equivalent to the required annual operational CII set out in paragraph 4 of this regulation.

Two places to read. First, the procedure is documented and verified. It does not end at the operator’s own calculation; the Administration or an authorized organization verifies. Second, the middle point of rating C equals the required CII. Hitting the required CII exactly puts the ship in the centre of C.

Three consecutive D ratings or an E rating leads to a plan of corrective actions carried into the SEEMP, and Administrations, port authorities and other stakeholders are encouraged to provide incentives to ships rated A or B.

The regulation carries its own review date

Paragraph 11 has the Organization complete a review by 1 January 2026. What that review assesses includes the effectiveness of the regulation in reducing the carbon intensity of international shipping. The self-check date sits inside the regulation.

Worth confirming

The passages above come from page 44 of the 2021 revised MARPOL Annex VI (MEPC.328(76)). The reduction factor, the reference value and the rating boundaries come from guidelines developed by the Organization, so the text alone does not produce numbers. Whether that ship is in a regulation 28 category, whether a change of flag or company fell inside this year, and whether the twelve months of data survive without a gap are where the actual judgement starts.