CII Corrective Action Plan

The CII Corrective Action Plan is the document required by MARPOL Annex VI Regulation 28.10 from any ship of 5,000 GT or above engaged on international voyages that has been rated D for three consecutive years or E for one year under the Carbon Intensity Indicator (CII) regime. The plan is incorporated into the ship’s SEEMP Part III and must specify the additional operational, technical and fuel-switching measures by which the ship will return to a C rating, the target attained CII for each year of the corrective period, an implementation timeline and a self-monitoring procedure. The implementing guidance is set out in MEPC Circular MEPC.7/Circ.16 of 17 June 2022 and in the consolidated SEEMP guidelines under Resolution MEPC.346(78). The corrective action plan must be approved by the Administration or its Recognised Organisation at the next IAPP renewal survey and must be implemented in the calendar year following its approval. Failure to produce, approve and implement an acceptable plan can result in port-state-control detention and (under the BIMCO CII Clause for time charters) commercial consequences for both shipowner and charterer. ShipCalculators.com hosts the principal computational tools: the CII 3-year corrective action plan trigger calculator determines whether the trigger has been pulled; the new CII corrective trajectory calculator projects the attained CII forward over the plan period under user-set annual improvement assumptions and identifies the year of expected return to a C rating; the CII attained, CII required, CII rating, CII voyage adjustment and CII year-on-year improvement calculators provide the underlying CII framework; the SEEMP combined operational measures calculator quantifies the combined effect of the operational levers used in a typical corrective action plan. A full listing is available in the calculator catalogue.

Contents

Background and history

Origin in the 2021 amendments

The corrective action plan requirement was introduced by Resolution MEPC.328(76) of 17 June 2021, which inserted Regulation 28 (CII) into MARPOL Annex VI Chapter 4 with effect from 1 January 2023. Regulation 28.10 specifies that:

Ships rated D for three consecutive years or rated E shall develop a plan of corrective actions to achieve the required CII (rated C, B or A) and incorporate it as part of the SEEMP. The revised SEEMP shall be subject to verification according to paragraph 11 of regulation 26 of this Annex.

The trigger logic recognises that a ship rated D for a single year or E once may be experiencing a transient operational disruption (an unusual cargo pattern, a significant repair downtime, weather-driven inefficiency in a particular year). However, persistent D rating (three years) or a single E rating indicates a structural underperformance that requires deliberate corrective action.

MEPC Circular MEPC.7/Circ.16

The detailed structure of the corrective action plan is set out in MEPC Circular MEPC.7/Circ.16 of 17 June 2022, Guidelines on the development of a CII corrective action plan. The Circular requires the plan to address:

Root cause analysis of the underperformance.
Specific additional measures to be implemented (technical, operational, fuel switching).
Implementation timeline, with year-by-year milestones.
Target attained CII for each year of the plan, calibrated to achieve a C rating by the end of the corrective period.
Self-monitoring procedure, integrated with the SEEMP Part III self-evaluation.
Approval and verification procedures, integrated with the annual IAPP survey.

The Circular also provides templates for the principal sections of the plan, allowing standardised approval workflow at flag administrations and Recognised Organisations.

Integration with SEEMP Part III

The corrective action plan is not a standalone document but is incorporated into the ship’s SEEMP Part III (the CII operational plan). The relationship is:

SEEMP Part III is the standing operational plan setting target CII and operational measures for each calendar year.
CII corrective action plan is the supplementary section added to SEEMP Part III when the Regulation 28.10 trigger has been pulled, specifying the additional measures over and above the standing plan.

The corrective action plan remains in force until the ship has achieved a C rating for at least one year, at which point it is deemed completed and the standing SEEMP Part III becomes the operative document again.

Trigger logic

D for three consecutive years

The “three consecutive D rating” trigger applies when a ship has received a D rating in three consecutive calendar years. The first time this can occur is the calendar year 2025, requiring D ratings in 2023, 2024 and 2025. Approximately 8% to 12% of the global fleet was rated D in 2023 (the first reporting year), suggesting that approximately 1% to 3% of the fleet will trigger the corrective action requirement based on three consecutive D ratings by the end of 2025.

The “consecutive” requirement means that a B or C rating in any year of the period resets the count. A ship rated D-D-C-D-D-D would not trigger the requirement until 2027 (the third consecutive D after the C reset).

E for one year

The “single E rating” trigger applies as soon as a ship receives an E rating in any single calendar year. This is the more aggressive of the two triggers: a single E rating immediately requires a corrective action plan, without the “three years” patience period.

The first time this trigger can apply is the calendar year 2023 (the first CII reporting year), with the corrective action plan due by the next annual SEEMP review (typically late 2024 or early 2025). Approximately 1% to 2% of the global fleet was rated E in 2023, predominantly older ships in inefficient trade patterns.

The CII 3-year corrective action plan trigger calculator

The CII 3-year corrective action plan calculator implements the trigger logic, taking as inputs the ratings for each calendar year and returning whether the corrective action requirement has been triggered, the trigger date, and the required submission timeline.

Year-by-year reporting cycle

The corrective action plan must be:

Drafted by the ship operator within 3 months of the rating notification.
Submitted to the flag administration or its Recognised Organisation within 6 months of the rating notification.
Approved by the Administration before the next annual IAPP survey.
Implemented in the calendar year following approval.
Verified at each subsequent annual survey through the standard SEEMP Part III verification process.

The CII rating notification typically reaches the ship operator in May or June of the year following the reporting year, giving until November or December for plan drafting and submission. The fast-track approval workflow operated by most major class societies (ABS, DNV, Lloyd’s Register, Bureau Veritas, ClassNK) typically completes plan approval within 30 to 90 days from submission.

Root cause analysis

Common root causes

The 2024 DNV survey of corrective action plans submitted in 2023 to 2024 identified the following recurring root causes:

Root cause	Frequency in surveyed plans	Typical CII penalty
Excessive operating speed under charter pressure	45%	8 to 15% above optimum
Underutilised cargo capacity	30%	5 to 10%
Hull biofouling beyond cleaning interval	25%	5 to 12%
Suboptimal trim for prevailing draft	20%	2 to 5%
Unfavourable trade pattern (long ballast legs)	18%	5 to 8%
Engine performance degradation	15%	3 to 7%
Fuel switching from HFO to MGO without compensation	10%	2 to 4%
Auxiliary engine load profile	8%	2 to 4%

The percentages sum to more than 100% because most plans identify two or three contributing root causes.

The single largest contributor is excessive operating speed under charter pressure, reflecting the well-known principal-agent problem in time charter operations: the charterer pays for fuel and may instruct higher speeds for commercial reasons, while the shipowner bears the regulatory consequence of the resulting CII rating. The BIMCO CII Clause for Time Charters addresses this directly by requiring the charterer to issue voyage instructions consistent with achieving a C rating.

Root cause documentation requirements

The MEPC.7/Circ.16 template requires the root cause analysis to:

Identify each contributing factor and quantify its CII impact (in g CO₂ per cap·nm or as a percentage of the attained CII).
Document the data sources used in the analysis (IMO DCS data, voyage records, charter-party records, weather data).
Identify whether each root cause is within the operator’s control, within the charterer’s control, or arises from external factors (regulation, weather, ECA fuel switching).
Recommend the corrective measure category for each root cause.

The classification of root causes between operator-controlled and charterer-controlled is critical for the BIMCO CII Clause cost allocation; misallocation can result in a charter-party dispute that complicates the implementation of the plan.

Corrective measures

Operational measures

The principal operational corrective measures are:

Slow steaming: the single most powerful operational lever, with typical CII improvement of 8% to 15% for a 10% speed reduction. Frequently combined with EPL or ShaPoLi under EEXI compliance.
Weather routing optimisation: typical CII improvement of 2% to 5% on long-distance voyages, higher in seasonally challenging routes.
Trim optimisation: typical CII improvement of 1% to 4% through trim management software.
Hull cleaning frequency increase: typical CII improvement of 5% to 8% by reducing the biofouling-driven resistance penalty.
Just-in-time arrival: typical CII improvement of 2% to 7% through coordinated port arrival times.
Auxiliary engine load profile optimisation: typical CII improvement of 1% to 3% by minimising auxiliary engine running hours.

The SEEMP combined operational measures calculator implements the standard non-overlapping savings formula for stacking these measures.

Technical measures

The principal technical corrective measures are:

Energy-saving devices (ESDs): pre-swirl stators, propeller boss cap fins (PBCF), Mewis ducts, ducts, kappa fins. Typical CII improvement of 2% to 5% per device, with multiple devices stackable.
Propeller polishing and replacement: typical CII improvement of 2% to 4% from propeller maintenance; up to 5% to 8% from a propeller replacement with optimised geometry.
Engine derating with EPL or ShaPoLi: typical CII improvement of 3% to 8% through limited operation at lower MCR.
Bulbous bow optimisation: typical CII improvement of 2% to 5% from a bulbous bow modification matching the new operating speed range.
Air lubrication systems: typical CII improvement of 5% to 10% on flat-bottomed hulls (bulk carriers, tankers).
Wind-assisted propulsion (Flettner rotors, suction sails, kites): typical CII improvement of 5% to 15% depending on trade route and rotor configuration.

Fuel switching

The principal fuel-switching corrective measures are:

B30 biofuel blend (30% biodiesel, 70% conventional fuel): typical CII improvement of approximately 30% in attained CII for the proportion of fuel switched.
B100 biodiesel (full biodiesel): typical CII improvement of approximately 90% to 95% (depending on feedstock LCA).
Bio-LNG for dual-fuel ships: typical CII improvement of approximately 70% to 80% per tonne switched.
Methanol or ammonia for dual-fuel ships: similar order-of-magnitude CII improvement, with the precise value depending on the WtW intensity of the specific fuel pathway (see the GFI attained calculator).

Fuel switching is typically the most expensive corrective measure but also the most powerful single lever. A ship that needs more than approximately 15% CII improvement will typically need to combine fuel switching with operational and technical measures.

Combined effect calculation

The combined CII improvement from multiple corrective measures is computed using the standard non-overlapping multiplicative formula:

CII_after = CII_before × (1 - Combined saving)

where Combined saving = 1 - Π(1 - s_i ) and s_i is the fractional CII improvement from each measure i.

The SEEMP combined operational measures calculator implements this formula for a standard set of measures; the new CII corrective trajectory calculator takes the resulting CII improvement and projects the attained CII forward over the corrective period to identify the year of expected return to C rating.

Plan structure

Section 1: Ship and rating history

The opening section of the plan documents:

Ship particulars (IMO number, type, capacity, year built).
CII rating history for the most recent 4 to 5 years.
Trigger condition (D-D-D or E).
Trigger year (the year that activated the corrective action requirement).

Section 2: Root cause analysis

The root cause analysis section follows the MEPC.7/Circ.16 template and identifies each contributing factor, its CII impact and the relevant operator/charterer/external classification.

Section 3: Corrective measures

The corrective measures section identifies each planned measure, its expected CII improvement, the implementation timeline and the responsible party.

Section 4: Target trajectory

The target trajectory section provides a year-by-year forecast of attained CII over the corrective period, against the Required CII trajectory and the rating boundaries:

Year	Required CII	Boundary D/E	Target attained CII	Projected rating
Y0 (trigger)	4.50	5.31	5.40 (actual)	E
Y1 (plan year 1)	4.43	5.23	5.00	D
Y2 (plan year 2)	4.36	5.14	4.65	D
Y3 (plan year 3)	4.30	5.07	4.40	C
Y4 (recovery)	4.23	4.99	4.20	B

The trajectory must show the ship reaching a C or better rating by the end of the corrective period (typically 3 to 5 years).

Section 5: Self-monitoring procedure

The self-monitoring procedure documents:

Quarterly review of attained CII trajectory.
Annual review and revision of the plan.
Trigger conditions for plan revision (e.g. failure to meet a year’s target by more than 5%).

Section 6: Approval

The approval section is signed by the master, the ship operator’s designated person ashore (DPA), and the flag administration’s authorised representative.

Approval and verification

Flag administration approval

The corrective action plan is submitted to the flag administration (typically delegated to a Recognised Organisation) within 6 months of the rating notification. The approval workflow:

Initial submission review: Recognised Organisation reviews the plan against the MEPC.7/Circ.16 template and confirms completeness.
Technical review: review of the root cause analysis and the proposed measures for technical feasibility.
Trajectory review: review of the target attained CII trajectory for realism.
Approval or revision request: approval issued if the plan meets the requirements; revision requested if not.
Final approval: documented in the IEE Certificate at the next renewal survey.

The typical approval cycle from submission to approval is 30 to 90 days for a well-prepared plan; longer for plans requiring substantive revision.

Annual verification

The implementation of the corrective action plan is verified at each annual IAPP survey under Regulation 5 of MARPOL Annex VI. The verification confirms:

The corrective measures listed in the plan are being implemented (e.g. evidence of slow steaming, biofuel use, hull cleaning, ESD operation).
The actual attained CII for the year is in line with the target trajectory (within typical ±5% to ±10% tolerance).
The self-monitoring records are complete and current.

A ship that fails to meet its target trajectory by more than the tolerance is required to revise the plan with additional measures, typically at the next annual survey.

Port state control

Port state control inspectors verify the existence and approval of the corrective action plan during port-call inspections. The principal verification is the IAPP / IEE Certificate annotation showing the plan approval status. Where a ship subject to the corrective action requirement does not have an approved plan, port state control may detain the ship until the deficiency is remedied.

Charter-party considerations

BIMCO CII Clause for Time Charters

The BIMCO CII Clause for Time Charters, published in November 2022, addresses the practical issue that the CII rating is driven primarily by charterer-controlled operational decisions while the regulatory consequence (including the corrective action plan) falls on the shipowner. The clause provides:

The charterer must issue voyage instructions consistent with achieving a C rating, where reasonably practicable.
The shipowner may modify voyage instructions (including reducing speed) to maintain the rating.
Costs of corrective measures (biofuel premium, hull cleaning, ESD retrofit) are allocated between owner and charterer based on responsibility.
A specific procedure is set out for the case where the ship is rated D or E and a corrective action plan is required.

Cost allocation in the corrective action plan

The corrective action plan typically allocates costs between owner and charterer based on the root cause analysis:

Charterer-driven measures (slow steaming, JIT arrival, fuel switching): typically charterer cost.
Owner-driven measures (hull cleaning, ESD retrofit, EPL): typically owner cost.
Shared measures (weather routing, trim optimisation): typically shared cost based on benefit.

The BIMCO clause includes a specific allocation table that operators commonly adapt to their particular trade pattern.

Worked example

A 50,000 DWT bulk carrier (Capacity = 50,000 t DWT, Required CII for 2025 = 5.0 g CO₂/dwt·nm) has the following CII rating history:

Year	Attained CII	Required CII	Rating
2023	6.05	5.30	D (1.14 × Required)
2024	6.10	5.15	D (1.18 × Required)
2025	6.15	5.00	D (1.23 × Required)

The “three consecutive D” trigger is pulled at the end of 2025. Required CII trajectory:

Year	Required CII reduction	Required CII (g CO₂/dwt·nm)
2026	6%	4.94
2027	8%	4.83
2028	11% (post-2026 trajectory TBD)	4.68

The corrective action plan, submitted in mid-2026 and approved in late 2026, specifies the following measures:

Measure	Expected CII improvement	Implementation date
Slow steaming (10% speed reduction, with EPL retrofit)	12%	1 January 2027
Hull cleaning every 9 months (vs current 14 months)	5%	next port call after approval
Weather routing service	3%	from 1 January 2027
Trim optimisation software	2%	from 1 March 2027
B30 biofuel blend on alternate voyages	8%	from 1 July 2027

Combined CII improvement (non-overlapping formula): 1 - (1-0.12) × (1-0.05) × (1-0.03) × (1-0.02) × (1-0.08) = 1 - 0.74 = 26%

Projected attained CII trajectory:

Year	Attained CII	Required CII	Rating
2026	6.15 (no measures yet)	4.94	E (1.24 × Required)
2027	6.15 × 0.74 = 4.55	4.83	C (0.94 × Required)
2028	4.55 × 1.00 = 4.55 (assumed steady)	4.68	C (0.97 × Required)

The plan returns the ship to a C rating by 2027 with an additional buffer for 2028. The CII corrective trajectory calculator implements this projection for arbitrary inputs.

Industry adoption patterns

Plan-submission rates

The 2024 DNV survey of CII corrective action plan submissions identified:

2023 trigger (E rating): approximately 350 ships triggered the requirement; approximately 280 plans submitted by mid-2024; approximately 220 approved by end of 2024.
2025 trigger (D-D-D): approximately 1,200 to 1,500 ships expected to trigger the requirement; approximately 60% of those expected to submit plans within the 6-month window.

The lower compliance rate for D-D-D triggers reflects the fact that some operators view the D rating as a recoverable issue and prefer to invest in measures rather than formal plan documentation.

Common plan deficiencies

The 2024 ABS review of submitted plans identified the following common deficiencies leading to revision requests:

Inadequate root cause analysis: 35% of plans required additional analysis.
Optimistic measure savings: 30% of plans required reduction of claimed savings to industry-typical ranges.
Unclear implementation timeline: 20% of plans required more specific milestones.
Inadequate self-monitoring procedure: 15% of plans required more frequent monitoring.

Plan approval timelines

Class society approval timelines have improved substantially since the introduction of the regime in 2023:

2023: average 90 to 120 days from submission to approval (long queue).
2024: average 45 to 90 days.
2025: average 30 to 60 days, with major class societies operating dedicated CII compliance teams.

Critical assessment

Effectiveness as a regulatory mechanism

The corrective action plan mechanism is widely regarded as a soft regulatory instrument compared with the EU ETS Maritime or FuelEU Maritime regimes, which impose immediate financial penalties for non-compliance. The principal criticisms are:

No financial penalty: a D-rated ship faces no direct financial penalty under the IMO regime; the only consequence is the requirement to produce a corrective plan.
Charter-party cost allocation: the cost of implementing the plan falls on the operator first, with subsequent allocation to the charterer through the BIMCO clause; this introduces commercial complexity.
Plan optimism: operators have an incentive to submit plans with optimistic measure savings; class society review tightens this but not perfectly.

The 2024 ICCT analysis suggested that approximately 30% of submitted corrective action plans would not, in fact, return the ship to a C rating within the corrective period at the claimed measure savings. Tightening the verification requirements and introducing financial consequences for non-compliance is being discussed at MEPC.

Future tightening

The IMO is considering several tightening measures:

Mandatory verification of measure implementation: continuous monitoring of biofuel use, EPL operation, hull cleaning records.
Financial penalties: a per-tonne CO₂e penalty for ships that fail to meet their plan trajectory.
Public disclosure: publication of the corrective action plan on a public IMO database.

A formal tightening proposal is expected at MEPC 86 in mid-2027, with possible entry into force in 2028 to 2029.

Interaction with the Net-Zero Framework

The IMO Net-Zero Framework (Chapter 4 ter, in force from 2027) introduces a financial mechanism (Remediation Units at USD 100 to 400 per tonne CO₂e) that operates in parallel with the CII rating regime. From 2027 onward, ships triggering the corrective action plan will also face financial pressure through the Net-Zero Framework, providing a stronger combined incentive.

The interaction between the two regimes is complementary: the CII regime operates on a per-ship basis with the rating as the operative metric; the Net-Zero Framework operates on a fleet-wide GFI intensity basis with financial transfers as the operative mechanism. A ship in corrective action under CII is likely also in deficit under the Net-Zero Framework, and the corrective measures (fuel switching, operational improvement) will improve both metrics simultaneously.

Future outlook

The principal regulatory developments expected through 2030 are:

MEPC 86 (mid-2027): review of the post-2026 CII reduction trajectory; possible introduction of financial penalties for plan non-compliance.
MEPC 88 (mid-2028): review of corrective action plan submission and approval data; recommendations for tightening.
MEPC 90 (2030): comprehensive review of the CII regime and integration with the Net-Zero Framework.

By 2030 the CII corrective action plan is expected to evolve into a more formalised compliance instrument with financial consequences and potentially public disclosure. Operators and charterers are advised to integrate corrective action planning into their long-term commercial strategy from 2026 onward.

References

IMO MEPC. Resolution MEPC.328(76) - Amendments to MARPOL Annex VI (introducing CII under Regulation 28). IMO, 17 June 2021.
IMO MEPC. MEPC.7/Circ.16 - Guidelines on the Development of a CII Corrective Action Plan. IMO, 17 June 2022.
IMO MEPC. Resolution MEPC.336(76) - 2021 Guidelines on the Operational Carbon Intensity Indicators. IMO, 17 June 2021.
IMO MEPC. Resolution MEPC.337(76) - 2021 Guidelines on the Reference Lines for Use with Operational Carbon Intensity Indicators. IMO, 17 June 2021.
IMO MEPC. Resolution MEPC.338(76) - 2021 Guidelines on the Operational Carbon Intensity Reduction Factors. IMO, 17 June 2021.
IMO MEPC. Resolution MEPC.339(76) - 2021 Guidelines on the Operational Carbon Intensity Rating of Ships. IMO, 17 June 2021.
IMO MEPC. Resolution MEPC.346(78) - 2022 Guidelines for the Development of a SEEMP. IMO, 10 June 2022.
IMO MEPC. Resolution MEPC.347(78) - 2022 Guidelines for Administration verification of CII reporting and rating. IMO, 10 June 2022.
BIMCO. BIMCO CII Clause for Time Charters. BIMCO, Copenhagen, November 2022.
ABS. CII Compliance and the Corrective Action Plan: A Practical Guide. ABS, Houston, 2024.
DNV. CII Corrective Action Plan Survey 2024. DNV Maritime, Oslo, 2024.
Lloyd’s Register. CII Implementation Year-One Review. Lloyd’s Register Marine, London, 2024.
ClassNK. CII Corrective Action Plan Approval Procedures. ClassNK, Tokyo, 2024.
ICCT. CII Year-One Review and Corrective Action Plan Analysis. ICCT, Washington, 2024.
International Chamber of Shipping. ICS CII Implementation Guide (4th ed). ICS, London, 2024.

External links

IMO Energy Efficiency Page - official IMO landing page
IMO MEPC.7/Circ.16 PDF - corrective action plan guidelines
BIMCO CII Clause - standard charter-party clause
DNV CII Page - implementation guidance
Lloyd’s Register CII Page - implementation guidance