Tokyo MoU: Asia-Pacific Port State Control

The Tokyo Memorandum of Understanding on Port State Control is the primary regional port state control (PSC) regime for the Asia-Pacific, with 22 member authorities conducting over 35,000 ship inspections per year across a region that handles more than 40 percent of global seaborne trade, running a risk-based New Inspection Regime since 2014 and publishing annual flag and recognized-organization performance lists.

Port state control gives coastal nations the legal authority to inspect foreign-flagged ships in their ports and to detain vessels that pose a safety or environmental risk. The Tokyo MoU formalizes that authority across the Asia-Pacific through a treaty-level agreement that harmonizes inspection standards, shares inspection data through the APCIS database, and coordinates Concentrated Inspection Campaigns (CICs) with sister organizations, particularly the Paris MoU in Europe.

The secretariat sits at Ascend Shimbashi 8F, 6-19-19 Shimbashi, Minato-ku, Tokyo, Japan. All governance flows through the Port State Control Committee (PSCC), which meets annually and adopts amendments, guidelines, and inspection indices.

Origins and the 1993 founding

The chain that eventually produced the Tokyo MoU began not in Asia but off the coast of Brittany, France. The March 1978 grounding of the supertanker Amoco Cadiz released 223,000 tonnes of crude oil onto 360 kilometres of coastline, triggering a European political response that resulted in the Paris Memorandum of Understanding on Port State Control in 1982. The Paris MoU was the first binding regional PSC framework, setting out procedures for inspecting foreign-flagged ships in the ports of its 14 founding European authorities.

The IMO recognized immediately that the Paris model could scale. At its 17th Assembly session in 1991, the IMO adopted resolution A.682(17), “Regional Co-operation in the Control of Ships and Discharges,” urging maritime nations outside Europe and the North Atlantic to consider establishing analogous frameworks. Japan took the lead in the Asia-Pacific.

The Japanese Ministry of Transport convened a preparatory meeting in 1992, drawing together maritime authorities from across East Asia, Southeast Asia, Oceania, and the Pacific. Three further preparatory meetings followed. At the fourth meeting, in Tokyo in December 1993, 18 authorities signed the Memorandum of Understanding on Port State Control in the Asia-Pacific Region. The instrument entered force on 1 April 1994, giving the region its first unified PSC system.

The original 18 signatories were Australia, Canada, China, Fiji, Hong Kong (China), Indonesia, Japan, Republic of Korea, Malaysia, New Zealand, Papua New Guinea, Philippines, Russian Federation, Singapore, Solomon Islands, Thailand, Vanuatu, and Viet Nam. Membership has since grown to 22 authorities, with Marshall Islands, Mexico, Panama, and Peru joining over the intervening three decades.

The 30th anniversary report (2023) noted that maritime accident frequency in the region had fallen to approximately one-eighth of 1993 levels over that period, though causation is complex and overlaps with broader IMO convention entry-into-force timelines.

Member authorities and geographic scope

The Tokyo MoU covers one of the most commercially dense sea lanes on the planet. The Strait of Malacca, the South China Sea, the waters around the Korean Peninsula, and the East China Sea all fall within the region, together handling container, bulk, tanker, and ro-ro traffic that dwarfs any other regional PSC jurisdiction in volume.

The 22 member authorities as of 2026 are set out below. Each authority implements the MoU through its own national legislation, designates port state control officers (PSCOs), and submits inspection data to APCIS.

Seven observer authorities attend PSCC meetings without voting rights: Cambodia, Democratic People’s Republic of Korea, Macao (China), Samoa, Solomon Islands, Tonga, and the United States Coast Guard. Ten international organizations hold observer status, including the IMO itself, IACS, and the ILO.

The US Coast Guard’s observer status is significant. The USCG runs the largest independent PSC program outside the MoU system, inspecting thousands of vessels annually under 33 CFR Part 160 and 46 CFR. Coordination between the USCG and Tokyo MoU authorities, particularly for vessels transiting between Pacific ports, prevents duplication and lets both systems share deficiency intelligence.

Legal basis: the conventions the MoU enforces

The Tokyo MoU does not create new substantive safety standards. It is an enforcement mechanism for existing IMO and ILO instruments. The Memorandum specifies which conventions member authorities inspect against, and that list has expanded over the decades as new instruments entered force.

The current suite of instruments includes:

• SOLAS 1974/78 (International Convention for the Safety of Life at Sea, as amended), covering structural fire protection, life-saving appliances, radio communications, navigation equipment, stability, grain loading, and dangerous goods
• MARPOL 73/78, all six annexes, covering oil (Annex I), noxious liquid substances (Annex II), packaged harmful substances (Annex III), sewage (Annex IV), garbage (Annex V), and air pollution including sulfur caps and the Energy Efficiency Design Index (Annex VI)
• STCW 1978 as amended (Standards of Training, Certification and Watchkeeping for Seafarers), covering officer certificates, rest-hour records, and watch arrangements
• Load Lines Convention 1966 and its 1988 Protocol
• COLREG 1972 (International Regulations for Preventing Collisions at Sea)
• IBC Code (International Bulk Chemical Code) and IGC Code (International Gas Carrier Code)
• ISM Code (International Safety Management Code), Annex I Part B of SOLAS IX
• ISPS Code (International Ship and Port Facility Security Code), SOLAS Chapter XI-2
• MLC, 2006 (Maritime Labour Convention), covering seafarer employment agreements, wages, rest hours, medical care, accommodation, and repatriation rights
• BWM Convention (Ballast Water Management Convention, 2004), covering ballast water treatment systems and record books
• AFS Convention (Anti-Fouling Systems Convention, 2001)
• CLC Protocol 1992 (Civil Liability Convention for oil pollution damage)

A PSCO inspecting a vessel under the NIR checks compliance across this entire stack, not just one convention. A deficiency under any of these instruments can generate a detention if the condition poses a serious threat to safety, health, or the environment.

For more on the foundational instruments, see the articles on the SOLAS convention, MARPOL convention, ISM Code, and STCW convention.

The New Inspection Regime (NIR)

From quotas to risk-based targeting

The Tokyo MoU’s original inspection system was quota-based: each authority committed to inspecting a target percentage of ships calling at its ports. That approach treated a modern tanker with a clean three-year record identically to an aging bulk carrier with two recent detentions. The Paris MoU moved to risk-based targeting with the introduction of its own NIR on 1 January 2011. The Tokyo MoU followed on 1 January 2014, adopting a harmonized framework that uses the same logical architecture as the Paris system while calibrating the inspection windows to Asia-Pacific traffic volumes.

The NIR replaced the old “ship targeting factor” with a Ship Risk Profile (SRP). The SRP is calculated automatically by the APCIS database, updated at each port arrival, and shared across all 22 member authorities in real time. A PSCO opening a vessel on APCIS sees the current SRP category, the inspection window status, the last inspection record, and any outstanding deficiencies before the vessel has tied up at the berth.

The Ship Risk Profile: six factors

The SRP aggregates six parameters over a rolling 36-month reference period into one of three categories: Low Risk Ship (LRS), Standard Risk Ship (SRS), or High Risk Ship (HRS).

Generic factors (structural characteristics of the vessel and its operators):

1. Ship type: Certain types carry a higher inherent risk weighting. Bulk carriers, gas tankers, chemical tankers, and passenger ships attract a heavier weighting than general cargo vessels or container ships of equivalent age.
2. Ship age: Vessels over 12 years old attract the highest age weighting. Age alone does not override the overall profile, but it pushes borderline SRS ships toward HRS.
3. Flag state performance: The flag’s position on the Tokyo MoU performance list directly feeds the SRP. A ship flagged to a Low Performance (formerly Black) flag state automatically receives a heavier generic-factor score.
4. Recognized Organization (RO) performance: The classification society that issued the ship’s statutory certificates is scored by the RO Performance List. An RO with a poor detention-to-survey ratio pushes the generic score up.
5. Company ISM performance: The ISM DOC holder’s fleet-wide detention and deficiency record over 36 months contributes to the score. A company whose managed fleet shows systemic problems raises the SRP of every ship it operates.

History factors (the vessel’s own inspection record over 36 months):

6. Deficiency and detention history: Number and type of deficiencies recorded across all member-authority inspections, plus any detention events. A prior detention is the single heaviest history-factor weighting.

The database adds the weighted generic and history scores, then places the ship in one of the three tiers. The precise numeric boundaries are updated periodically by the PSCC. As of the period through 30 June 2026, the PSCC has set the Detention Index at 3.70 and the Deficiency Index at 2.45.

Inspection windows and priority

The risk tier determines the inspection window, the time band within which a member authority is expected to inspect the ship.

Priority I vessels are subject to mandatory inspection. A Port I ship calling at a member-authority port will not be permitted to depart until PSCOs have boarded and cleared it. This is the primary detention-prevention lever: the system flags the vessel before deficiencies escalate into a dangerous condition at sea.

Priority II vessels are subject to inspection when they fall within their window. If a port is congested or resources are limited, a Priority II ship may be deferred to the next port call within the same member authority, provided the window has not expired.

Overriding factors bypass the window entirely. A ship whose Class has been suspended or withdrawn, a ship involved in a recent collision, grounding, or pollution event, or a ship reported by another PSC authority as having clear grounds for inspection is treated as Priority I regardless of its last inspection date.

Inspection types

A PSC inspection under the NIR takes one of three forms:

Initial inspection: The PSCO boards the vessel, examines the ship’s documents and certificates, makes a general visual assessment of the vessel’s condition, and assesses crew competence through observation and brief questioning. If no clear grounds for a more detailed inspection emerge, the initial inspection closes with any minor deficiencies noted and a port-call record entered in APCIS.

More detailed inspection: Where the initial assessment reveals deficiencies or where the PSCO identifies clear grounds, a more detailed inspection follows. The PSCO examines the relevant areas of the ship, tests equipment, reviews logbooks and records, and questions crew members on their duties and emergency procedures. This is the most common form of substantive PSC inspection.

Expanded inspection: Mandatory for specific ship types: passenger vessels, oil tankers, gas carriers, chemical tankers, and bulk carriers above 12 years of age. An expanded inspection follows a prescribed checklist covering areas such as fire detection systems, bilge-water management, cargo hold structure (for bulk carriers), inert-gas systems (for tankers), and stability documentation. It is more time-intensive than a more detailed inspection and typically covers all decks and machinery spaces.

Deficiencies and detention

What counts as a deficiency

A deficiency is any condition that does not conform to the requirements of the applicable convention. Deficiencies are coded using a five-digit system that identifies the convention, the area, and the specific sub-issue. In 2025, Tokyo MoU PSCOs recorded 90,168 deficiencies across 35,546 inspections, an average of 2.54 per inspection.

The four deficiency categories that together accounted for 53% of all 2025 deficiencies were fire safety measures (18,020), life-saving appliances (11,818), working and living conditions (9,108), and safety of navigation (8,936). Fire safety and life-saving appliances have led the deficiency table in the Tokyo MoU region for over a decade, a pattern driven partly by aging fleets in certain flag-state registries and partly by the complexity of automatic sprinkler systems and liferaft release mechanisms.

Grounds for detention

Not every deficiency results in detention. A detention requires that the deficiency (or a combination of deficiencies) poses a serious threat to the safety of the ship, the health of the crew, or the marine environment, and that correction at sea would be impracticable or unreasonably dangerous.

Deficiency severity codes 17, 18, and 30 are the three codes that trigger automatic detention assessment. Code 17 covers deficiencies where the ship is “clearly unfit to proceed to sea.” Code 18 covers conditions that require rectification before departure. Code 30 is applied when a deficiency is not immediately dangerous but is recurrent across two or more inspections.

In 2024, 1,189 ships (registered under 67 flags) were detained, giving a detention rate of 3.71% of all inspections. That rate fell to 3.53% in 2025, when 1,255 ships from 73 flags were detained. The seeming contradiction of more detentions at a lower rate reflects the record inspection volume in 2025: 35,546 inspections against 32,054 in 2024.

The 3.53% detention rate in 2025 remains higher than pre-pandemic levels from 2017-2019, which averaged around 2.8%. The Tokyo MoU’s 2025 Annual Report attributed the elevated post-pandemic baseline to fleet condition deterioration during the period of COVID-19 inspection suspensions and to emerging concerns about structural conditions, water- and weathertight integrity, and propulsion machinery reliability.

A detained ship cannot depart until the deficiencies are rectified to the PSCO’s satisfaction or until a bail-bond-equivalent condition is met (for certain flag states). The detention record remains in APCIS and feeds the vessel’s SRP history factors for the following 36 months, compounding the commercial impact.

Flag and RO performance lists

The scoring methodology

The flag performance list is published annually and classifies flag administrations based on their cumulative inspection and detention record over the preceding three calendar years. Only flags with 30 or more inspections in the three-year period are included; registries below that threshold cannot be statistically classified and are listed separately.

The classification uses the “excess factor” method, a variant of a statistical control-chart test. For each flag, the ratio of actual detentions to the expected number (given the flag’s inspection count and the regional average detention rate) is compared to two thresholds: the Black-to-Grey limit and the Grey-to-White limit. A flag whose detention ratio exceeds the Black-to-Grey limit is classified as Low Performance (formerly Black). A flag between the two limits is Medium Performance (Grey). A flag below the Grey-to-White limit is High Performance (White).

The 2024 list (valid 1 July 2024 to 30 June 2025) was the last to use the Black/Grey/White color terminology. From 1 July 2025 the PSCC formally adopted the redesignated High Performance / Medium Performance / Low Performance labels, aligning with broader industry preference for performance-based rather than color-coded nomenclature.

The 2025 performance list

The flag performance list valid 1 July 2025 to 30 June 2026 (based on 2022-2024 inspection data) covers 66 flags:

• High Performance: 32 flags (two more than the prior year)
• Medium Performance: 19 flags (one fewer than the prior year)
• Low Performance: 15 flags (two more than the prior year)

The 2025 Annual Report noted concern that the number of under-performing ships (defined as ships with deficiencies “nearly double” the regional average) rose sharply, with 222 detention events involving 52 individual ships listed as chronic under-performers. Under-performing ships in this context are distinct from the flag list: they are specific vessels whose repeated detention history triggers enhanced scrutiny under the NIR’s history-factor scoring.

RO performance list

The Recognized Organization performance list uses the same excess-factor methodology applied to each classification society’s fleet rather than a flag registry. An RO with a statistically worse-than-average detention rate sees its ships receive a heavier generic-factor weighting in the SRP. The RO list is updated annually (valid 1 July to 30 June) and covers 13 recognized organizations.

Company performance lists

Two company-level lists are published quarterly on a trial basis: a High-Performing Company list (companies with 30 or more inspections over 36 months and a statistically superior record) and an Under-performing Company list. These feed directly into the SRP generic-factor scoring for company ISM performance, making fleet-wide safety management a direct commercial factor: a company on the Under-performing list increases the SRP of every vessel it operates until its rolling 36-month record improves.

The APCIS database

The Asia-Pacific Computerized Information System (APCIS) is the technical backbone of the Tokyo MoU. The central APCIS facility is located in Moscow and managed by Russia’s Ministry of Transport, a legacy of the organization’s Cold-War-era desire to include the Soviet Union’s Far Eastern ports as co-enforcers in the region.

APCIS does two things. First, it is the authoritative repository for every PSC inspection conducted by member authorities in the Tokyo MoU region: vessel identity (IMO number, flag, class), inspection date and port, deficiency codes and severity, detention status, and the resulting SRP recalculation. Second, it is a real-time query tool: PSCOs at any member-authority port can search a vessel’s full inspection history across all 22 authorities before deciding whether to board, and what priority category the vessel holds.

The public APCIS portal at apcis.tokyo-mou.org provides a ship-inspection search function accessible to shipowners, operators, charterers, and P&I clubs, returning the last three inspections and the current SRP category for any IMO-numbered vessel. This transparency is intentional: owners can see exactly what their SRP category is and which history factors are suppressing their profile, letting them target deficiency remediation at the highest-weighted items.

APCIS is integrated with the Paris MoU’s THETIS database and shares inspection records with the other regional PSC regimes through bilateral data-exchange agreements. A detention in Rotterdam, for example, flows into APCIS and affects the vessel’s SRP for inspections in Singapore or Shanghai.

Concentrated Inspection Campaigns

Structure and purpose

Each year, the Tokyo MoU selects a thematic focus for its Concentrated Inspection Campaign, conducted between 1 September and 30 November. The CIC adds a standardized questionnaire to every routine PSC inspection during that three-month window, providing the PSCC with a statistically consistent dataset on a specific compliance area.

From 2019 onward, every CIC has been conducted jointly with the Paris MoU, using a shared questionnaire developed by the two secretariats. The joint approach covers roughly two-thirds of world shipping inspections simultaneously (Paris MoU covers Europe and the North Atlantic; Tokyo MoU covers the Asia-Pacific), giving the CIC results a scope that no other PSC data collection can match.

The CIC does not impose requirements beyond existing convention obligations. It selects areas where convention compliance has been uneven or where new regulations are approaching full enforcement.

Recent CIC results

2024 CIC: Crew Wages and Seafarer Employment Agreements (MLC, 2006)

The 2024 CIC, run jointly with the Paris MoU from 1 September to 30 November 2024, assessed compliance with MLC Title 2 provisions on seafarer employment agreements and wage payment. PSCOs used a 10-question checklist covering SEA availability and content, wage calculation records, financial security for repatriation and compensation, and crew access to employment information.

Results: 8,134 PSC inspections, of which 6,580 (80.89%) included the CIC questionnaire. 20 ships were detained as a direct result of MLC-related CIC deficiencies, a CIC-topic detention rate of 0.30%. The most common deficiency was the absence of a signed Seafarer Employment Agreement (SEA), found in 16% of CIC-related deficiency records, followed by deficiencies in crew access to employment-condition information.

2025 CIC: Ballast Water Management Convention

The 2025 CIC, again joint with the Paris MoU (1 September to 30 November 2025), focused on the BWM Convention, examining ballast water treatment systems (BWTS) installation, Ballast Water Management Plans, and Ballast Water Record Books. Of 9,244 PSC inspections, 6,930 (74.96%) included the 10-item CIC questionnaire. 30 ships were detained directly for BWM deficiencies (CIC-topic detention rate 0.43%). Total detentions during the CIC window were 184, a 2.66% detention rate. BWM deficiencies overall tripled in 2025 compared to 2024, driven by systems that met the D-2 biological standard on paper but failed operational verification by PSCOs.

CIC topic selection

Topics are selected by the PSCC at least 12 months before the campaign, allowing the industry and flag administrations time to prepare. Past CIC topics have covered SOLAS fire safety systems (2015), STCW rest-hour records (2016), ISM Code deficiencies (2018), navigation in Polar Waters (2022), and ballast water management (previous campaigns in 2016 and 2025). Announcements appear on the Tokyo MoU website and in joint press releases with the Paris MoU.

Relationship with the Paris MoU

The Paris MoU is the Tokyo MoU’s closest institutional sibling. Both follow the same NIR architecture, use harmonized deficiency codes, conduct joint CICs, and share inspection data. But four operational differences matter to operators:

Inspection windows: The Tokyo MoU windows are shorter than Paris at each risk tier. Under the Paris NIR (in force since 2011), High Risk ships have a 6-month window and Low Risk ships a 24-36 month window. The Tokyo NIR uses 2-4 months for High Risk and 9-18 months for Low Risk. A vessel with a poor SRP faces more frequent inspections in the Pacific than in Europe.

Conventions enforced: Both regimes enforce the same core instrument stack, but the Tokyo MoU added MLC, 2006 enforcement in 2014 and has progressively integrated BWM Convention checking, reflecting the region’s higher proportion of older bulk-carrier tonnage where ballast water compliance is a documented issue.

Flag list composition: The two regimes publish separate performance lists covering the same flags but drawing on different inspection datasets. A flag that sits on the Paris MoU Grey List may simultaneously appear on the Tokyo MoU White List (now High Performance) if its ships calling at Asian ports have a better record than those calling at European ports. Operators should check both lists when assessing a flag’s SRP impact.

Detention consequences: Both systems allow a ship to sail once deficiencies are corrected. Paris MoU, however, has the explicit refusal-of-access mechanism under Directive 2009/16/EC (Article 16), banning ships with three detentions in 36 months from all EU ports for a rising period (3, 12, then 24 months). The Tokyo MoU has no equivalent formal ban mechanism, though repeated detention records push SRP into HRS territory and make Priority I status nearly permanent.

Both secretariats hold annual bilateral meetings and issue joint press releases for CICs. The Tokyo MoU website cross-links to the Paris MoU’s THETIS database, and the two inspection records are mutually visible at each PSCO terminal.

Relationship with other regional PSC regimes

Nine regional PSC regimes cover the world’s major shipping routes. After Paris (1982) and Tokyo (1994), the others are:

• Indian Ocean MoU (1998): 17 member authorities covering the Indian Ocean and Persian Gulf, headquartered in Mumbai. Operationally relevant for vessels transiting between the Tokyo MoU region and the Middle East or East Africa. The Tokyo and Indian Ocean MoUs share inspection data but run separate flag performance lists.
• Riyadh MoU (2004): Covers the Arabian Gulf states (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, UAE, Yemen, Jordan). Ships calling at Gulf ports before proceeding to Singapore or China pass through both the Riyadh and Tokyo MoU jurisdictions.
• Acuerdo de Viña del Mar: Covers Latin American Pacific and Atlantic ports. Chile, Mexico, Peru, and Panama are also Tokyo MoU members, meaning their ports are subject to the Tokyo NIR, not the Viña del Mar system.
• US Coast Guard: The USCG operates independently under US domestic law (33 CFR Part 160, 46 CFR). It inspects approximately 8,000-9,000 vessels annually at US ports, using its own Automated Targeting System (ATS) to prioritize vessels. Canada, a Tokyo MoU member, coordinates Pacific-coast inspections between Transport Canada and the USCG. The USCG participates in Tokyo MoU meetings as an observer and shares detention data with APCIS.

Vessels on Asia-Pacific routes commonly pass through multiple PSC jurisdictions on a single voyage. A container ship running Hong Kong-Singapore-Colombo-Jeddah-Rotterdam crosses Tokyo MoU, Indian Ocean MoU, Riyadh MoU, and Paris MoU waters. Each regime’s inspection record feeds the vessel’s SRP in the others, creating a de facto global tracking system.

Governance and the Port State Control Committee

The organization’s decision-making body is the Port State Control Committee (PSCC), which meets annually in Tokyo. Each of the 22 member authorities holds a vote; observer authorities and organizations attend but do not vote.

The PSCC amends the Memorandum itself (the 23rd amendments were adopted on 14 November 2024 and entered effect 1 July 2025), sets the annual inspection indices, adopts or modifies inspection guidelines, and selects the CIC topic. Day-to-day operations run through the Secretariat, which maintains APCIS in coordination with Moscow, publishes the annual report, manages the flag and RO performance lists, and coordinates the CIC questionnaire with the Paris MoU.

Working groups convene between PSCC sessions to develop technical guidance. The Flag State Control Working Group, for example, manages the dialogue between the PSCC and flag administrations whose registers appear on the Low Performance list, running targeted seminars and providing remediation guidance to flag state inspectors.

Practical implications for ship operators

SRP management

A ship’s SRP is the most direct lever for reducing PSC burden. Operators can lower their SRP by:

1. Clearing deficiency backlogs: History-factor scoring weights open deficiencies and prior detentions over the rolling 36 months. Resolving recorded deficiencies at the next port call prevents compounding.
2. Choosing a High Performance flag: Flag performance feeds the generic-factor score. A flag on the Low Performance list increases the SRP of every ship it registers; migration to a High Performance flag removes that generic-factor penalty.
3. Using a well-performing RO: The RO performance list is updated annually. An RO that has moved from Medium to High performance between list cycles lowers the generic score for every ship it certifies.
4. ISM compliance across the fleet: Company ISM performance is fleet-wide. A single vessel with chronic deficiencies drags the SRP of every ship in the management portfolio if the company falls onto the Under-performing Company list.

Pre-inspection preparation

A PSC inspection is not auditable in advance in the sense of knowing the exact questions. But the five areas that generate the largest deficiency volumes in the Tokyo MoU region (fire safety, life-saving appliances, MLC working and living conditions, safety of navigation, and BWM systems since 2025) should be the focus of internal pre-port-arrival audits. The CIC topic for each year is announced well in advance; a vessel calling at Tokyo MoU ports during September-November should ensure the CIC subject area is specifically checked by its crew.

Charter parties frequently include “first class” PSC record warranties. A detention in Singapore or Yokohama that is recorded in APCIS can trigger off-hire claims under charterparty clauses, compounding the direct cost of the detention.

Detention aftermath

When a vessel is detained, the owner must notify the flag administration, the RO, and (typically) the P&I Club immediately. The flag administration may dispatch its own inspector; the RO must verify that the deficiencies are corrected before re-issuing relevant certificates. The PSCO who ordered the detention must confirm rectification before releasing the vessel. Costs of port charges during detention, crew overtime, and any cargo delay claims run against the owner.

Once released, the detention event remains in APCIS and visible to all member-authority PSCOs for the full 36-month reference period. During that window, the vessel’s SRP will be elevated, inspection frequency will increase, and charterers conducting vessel vetting may flag the detention in their SIRE or CDI screening.

Limitations

The Tokyo MoU’s risk-targeting system operates on a 36-month rolling dataset. A vessel that was well-maintained three years ago but has deteriorated recently will carry a favorable SRP until enough recent deficiency data accumulates. This temporal lag is a recognized structural limitation of all PSC regimes using rolling reference windows.

Member authorities vary in inspection capacity. Smaller economies with limited PSCO resources (Fiji, Vanuatu, Papua New Guinea) inspect a much smaller fraction of calling vessels than high-traffic ports in China, Japan, or Singapore. The NIR’s Port Priority I designation theoretically mandates inspection, but if no PSCO is available, Priority I vessels may proceed with a deferred-inspection flag that is visible to the next port’s authority.

The Tokyo MoU has no enforcement authority over flag states. It can publish a Low Performance designation, but cannot compel a flag administration to improve its survey standards or withdraw certificates from vessels. The IMO’s Member State Audit Scheme (IMSAS) is the primary instrument for flag-state accountability, and a flag that has not completed its IMSAS audit receives a generic-factor penalty in the SRP, but that is the extent of the MoU’s direct reach over flags.

RO and company performance lists are effective only where the rolling inspection dataset is large enough. An RO with fewer than 30 inspections in the Tokyo MoU region cannot be statistically ranked and falls outside the performance list mechanism, potentially leaving its fleet without the flag-style SRP modifier. Similarly, small owner-operators with fewer than 30 inspections in 36 months are excluded from the company performance list scoring.

Finally, the territorial limits of the Tokyo MoU mean that a vessel can accumulate a clean record in one region by avoiding high-scrutiny ports while racking up deficiencies in less well-resourced jurisdictions. The cross-regime data sharing with Paris MoU and the Indian Ocean MoU mitigates this, but the mitigation is imperfect: not all nine regional regimes share data at the same granularity.

For the broader legal and operational context of port state control as a discipline, see the port state control article. For the European regime, see Paris MoU. For the flag-state perspective and flags of convenience, see flag state and flag of convenience. For the ISM Code framework that PSCOs check under SOLAS IX, see ISM Code. For the role of classification societies in the RO performance list, see classification society.