By ShipCalculators.com · Published 9 May 2026

Tokyo MoU: Asia-Pacific Port State Control regional framework

The Tokyo Memorandum of Understanding on Port State Control in the Asia-Pacific Region (Tokyo MoU) is the regional cooperative framework under which twenty-one Asia-Pacific maritime authorities harmonise the inspection of foreign-flagged merchant ships calling at their ports. Signed in Tokyo on 1 December 1993 and operational from 1 April 1994, the Tokyo MoU is the world’s largest regional port state control framework by inspection volume, conducting between 30,000 and 35,000 inspections per year with between 1,000 and 1,500 detentions annually. Member authorities apply a common New Inspection Regime (NIR) active since 1 January 2014 that replaced the earlier 75 percent regional target with risk-based selection through the Ship Risk Profile (SRP) placing every visiting ship into Low, Standard or High Risk categories. The Secretariat sits in Tokyo and operates the Asia-Pacific Computerised Information System (APCIS) that aggregates inspection results from all twenty-one authorities and feeds the white-grey-black flag list, the Recognised Organisation performance list and the Concentrated Inspection Campaign (CIC) programme. Verification covers SOLAS Chapter I general provisions, the MARPOL Convention Annex I to VI, the STCW Convention, the ISM Code, the ISPS Code, the Ballast Water Management Convention and MLC 2006. The Tokyo MoU operates a Cooperation Memorandum with the Paris MoU sharing detention and deficiency data, and is the principal Asia-Pacific implementation channel for the IMO III Code (Implementation of IMO Instruments) and the IMO Member State Audit Scheme. Recognised-Organisation performance places IACS members and notably DNV consistently at the top of the RO list.

Contents

Background: 1982 Paris MoU precedent

The Tokyo MoU is a direct descendant of the Paris Memorandum of Understanding on Port State Control signed at Paris on 26 January 1982 by fourteen European maritime administrations as a coordinated reply to the Amoco Cadiz disaster of 16 March 1978. The Paris MoU created the template that all subsequent regional PSC instruments followed: a non-binding administrative agreement among maritime authorities, a centralised electronic database, a percentage-of-foreign-calls inspection target, a harmonised PSCO training scheme, a published annual report, and a methodology classifying flag administrations on a white-grey-black list.

By the late 1980s the Paris MoU had demonstrated measurable impact on substandard shipping in European waters. Several Asia-Pacific administrations had observed the Paris MoU process directly, with Japan sending observers to the Paris MoU Committee. IMO Resolution A.682(17) of 1991 on Regional Co-operation in the Control of Ships and Discharges set out the IMO expectation that further regional MoUs would cover unmonitored shipping regions. The Asia-Pacific region, accounting for an increasing fraction of world ship calls, was the obvious next region to constitute a regional PSC framework.

1993 Tokyo signing + 1994 operations start

A preparatory ministerial meeting was convened in Tokyo in late 1993 under joint Japanese and Australian leadership. The instrument was signed on 1 December 1993 in Tokyo by eighteen maritime authorities of the Asia-Pacific region. The text drew heavily on the Paris MoU architecture: a Committee meeting at least annually, a Secretariat hosted by Japan in Tokyo, an Information System operated initially through Russian Federation development (becoming APCIS), inspection targets stated as a regional aggregate, and a methodology for rating flag administrations on a white-grey-black list.

The Tokyo MoU entered into operations on 1 April 1994 with the Secretariat opening at the Ministry of Transport offices in Tokyo. The initial regional inspection target was set at fifty percent of foreign-flagged ship calls, raised to seventy-five percent in 2000, and replaced after 2014 by the risk-based NIR. The Tokyo MoU Committee met for its first session in 1994 in Tokyo and has since rotated its annual meeting among member capitals. The Tokyo MoU swiftly became the operationally largest regional MoU because the Asia-Pacific region carries the highest density of cargo ship calls of any region.

The 21 contracting authorities as of 2026

The membership has grown by accretion over more than three decades. As of 2026 the twenty-one contracting authorities are: Australia, Canada (Pacific waters only, with Atlantic-coast PSC sitting under the Paris MoU), Chile, China (the People’s Republic of China together with Hong Kong, China, the latter operating its own marine department within the Tokyo MoU framework), Fiji, Indonesia, Japan, the Republic of Korea, Malaysia, Marshall Islands, New Zealand, Panama, Papua New Guinea, Peru, the Philippines, the Russian Federation (Pacific authority distinct from its Paris MoU membership for the Baltic and Arctic), Singapore, Solomon Islands, Thailand, Vanuatu and Vietnam. Founding members of 1993 included Australia, Canada, China, Fiji, Hong Kong (then under separate British-administered status that translated into Chinese-Hong Kong status from 1997), Indonesia, Japan, Korea, Malaysia, New Zealand, Papua New Guinea, the Philippines, Russia, Singapore, Solomon Islands, Thailand, Vanuatu and Vietnam. Subsequent admissions added Chile, Peru and Panama in the 2000s as Latin American Pacific-coast states sought a Pacific-Asia PSC link distinct from the Acuerdo de Viña del Mar that already covered them, and the Marshall Islands acceded in the 2010s reflecting that flag’s dual role as a major open registry and a Pacific archipelagic state.

The geographic span runs from the western Pacific (Japan, Korea, China) across south-east Asia (Singapore, Malaysia, Thailand, Vietnam, Philippines, Indonesia), through the south Pacific island states (Papua New Guinea, Solomon Islands, Vanuatu, Fiji, Marshall Islands), Australia and New Zealand, the Russian Pacific Far East (Vladivostok, Nakhodka, Sakhalin), the Canadian Pacific (Vancouver, Prince Rupert), and the South-American Pacific (Chile, Peru, Panama). Cooperative arrangements link the Tokyo MoU with adjacent regional frameworks: the Indian Ocean MoU on the western flank, the Acuerdo de Viña del Mar overlapping in the eastern Pacific, the Black Sea MoU and Mediterranean MoU through Russia and Panama respectively, and the Paris MoU through formal inter-MoU cooperation.

Asia-Pacific geographical scope

The geographical scope is defined functionally rather than by maritime boundary: any port within the territory of a contracting authority is within scope, and inspections are conducted on foreign-flagged ships of three hundred gross tonnes or above, with exclusions for fishing vessels, pleasure yachts, warships and government non-commercial ships. The combined trade footprint of Tokyo MoU ports includes Singapore, Shanghai, Ningbo-Zhoushan, Busan, Hong Kong, Guangzhou, Qingdao, Tianjin, Yokohama, Kobe, Nagoya, Tokyo Bay, Klang, Tanjung Pelepas, Laem Chabang, Manila, Jakarta, Tanjung Priok, Sydney, Melbourne, Brisbane, Auckland, Vancouver, Vladivostok, Valparaiso, Callao and the Panama Canal terminal ports. The aggregate annual call count across these ports runs to several hundred thousand vessel arrivals, of which the Tokyo MoU samples approximately one in nine to one in ten under NIR risk-based selection.

Secretariat in Tokyo

The Tokyo MoU Secretariat is hosted by Japan in central Tokyo, with a Secretary and a small permanent staff supplemented by seconded officers from member authorities. The Secretariat convenes the annual Committee meeting and inter-sessional Working Groups, maintains the APCIS database, publishes the annual report and statistical analyses, administers the white-grey-black flag list and RO performance list, coordinates the Concentrated Inspection Campaign programme, liaises with the Paris MoU, IMO and ILO, administers the harmonised PSCO training scheme, and publishes technical guidance and PSC Information Sheets. The Tokyo MoU Information Centre is reachable at tokyo-mou.org with the public ship search portal and publications archive, and at apcis.tokyo-mou.org for the inspection-data search interface.

New Inspection Regime (NIR) since 2014

The New Inspection Regime entered into force in the Tokyo MoU on 1 January 2014, three years after the Paris MoU adopted its analogous NIR. The NIR replaced the prior fixed regional target of seventy-five percent with a risk-calibrated regime under which each ship is assigned a Ship Risk Profile (Low, Standard or High Risk) and the inspection priority follows the profile. High-Risk ships are inspected far more frequently than Low-Risk ships, with the HR window two to four months and the LR window twenty-four to thirty-six months. Ships overdue for inspection are flagged on the APCIS for selection at the next port call.

The NIR delivers two operational outcomes. Regulatory burden falls on quality operators: a well-managed Low-Risk vessel may sail two to three years between inspections. Regulatory pressure concentrates on substandard operators: a High-Risk vessel cannot avoid the next-port inspection because every Tokyo MoU port reads the APCIS overdue list before each arrival. The PSC Officer conducts an Initial Inspection on every selected ship covering documents, certificates, the visible material condition and the deficiency-history check, proceeding to a More Detailed Inspection only when clear grounds exist as enumerated in the Memorandum.

Ship Risk Profile (SRP) calculation

The Ship Risk Profile is calculated automatically by the APCIS for every ship of 300 gross tonnes or above visiting a Tokyo MoU port. The calculation is updated whenever a new inspection result, change of flag, change of class society, change of company or change of ship-particulars record is entered. The SRP is a points-based system with weighted contributions from a defined set of factors, and the resulting numerical score is mapped to one of three risk categories.

The calculation draws on inspection records aggregated across all Tokyo MoU authorities and synchronised under the Cooperation Memorandum with the Paris MoU. Owners can verify their ship’s current SRP through the public APCIS ship-search portal. Operators planning a port-call schedule typically consult the SRP to anticipate which port is most likely to host the next NIR-scheduled inspection.

Risk categories: Low (LR), Standard (SR), High (HR)

The three Ship Risk Profile categories carry distinct inspection-frequency consequences. Low Risk Ship (LR) is the category of well-performing ships under quality flags with quality classification societies, modern construction, low or zero deficiency history and no detentions in recent windows; LR window is 24 to 36 months. Standard Risk Ship (SR) is the default category, with window 10 to 12 months. High Risk Ship (HR) is the category of ships under poor-performing flags or ROs, older tonnage, repeat-deficiency history or recent detention, with window 2 to 4 months.

Threshold mapping uses point bands defined in Annex 10 of the Memorandum. Crossing from SR to LR requires a sustained record of clean inspections, a white-list flag and a high-performing RO; falling from SR to HR can be triggered by a single detention. The category is recalculated on each inspection close and on each flag-list publication.

SRP factors: ship type, age, flag, RO, company, deficiencies, detentions

The Ship Risk Profile factors enumerated in Annex 10 are: Ship type, with chemical tankers, gas carriers, oil tankers, bulk carriers and passenger ships attracting higher weighting; Ship age, with ships above twelve years attracting higher points and ships above twenty years higher still; Flag performance, with white-list flags attracting fewer points, grey more, black the most; Recognised Organisation performance, with high-performing ROs (typically IACS members) attracting fewer points; Company performance, calculated on the company-fleet-aggregate detention rate; Deficiency history within the last 36 months; Detention history within the last 36 months. The points sum is mapped to the three categories. Factor weights are reviewed periodically by the Tokyo MoU Committee alongside Paris MoU NIR review to maintain inter-MoU coherence.

~30,000-35,000 inspections per year

The Tokyo MoU annual inspection volume has run between 30,000 and 35,000 inspections per year in the post-NIR era, making it the largest regional PSC framework worldwide by inspection count. The Paris MoU runs 17,000 to 19,000 inspections per year by comparison; the United States Coast Guard 8,000 to 10,000; the Indian Ocean MoU around 5,000; the Black Sea MoU around 4,500; the Mediterranean MoU around 3,500. The volume reflects the density of foreign ship calls in Asia-Pacific ports: Singapore alone accounts for more than 5,000 inspections per year, the Chinese ports collectively for more than 8,000, and Japan, Korea, Australia and Russian Pacific each between 2,000 and 4,000.

~1,000-1,500 detentions per year

The detention count runs between 1,000 and 1,500 ships detained per year across the region, corresponding to a detention rate of approximately three to four percent of inspections. The rate has trended downward from close to ten percent in 1995-2000, to five to six percent in the 2000s, to the current three to four percent under the NIR, reflecting both improving overall fleet quality and better targeting under the SRP. The annual report disaggregates detentions by ship type, flag, RO, age and deficiency category, providing the empirical input to the flag-list methodology and the RO performance list. Black-listed flags typically run detention rates of five to fifteen percent; white-listed flags typically below two percent.

Major deficiency: structural (hull + watertight)

Structural deficiencies in the Tokyo MoU classification cover the hull plating, structural fire protection openings, watertight doors and hatch covers, and the integrity of the main structural envelope of the ship. The deficiency code series in this category falls under the 10xxx range in the Tokyo MoU coding scheme, and the typical sub-categories include hull cracking and corrosion under SOLAS II-1 and the Enhanced Survey Programme, hatch cover deficiencies under the Load Line Convention and SOLAS II-1, watertight integrity deficiencies under SOLAS II-1, and the special structural-survey items mandated under the IACS Common Structural Rules and the IMO Goal-Based Standards regime applicable to bulk carriers and oil tankers above 150 metres in length.

A structural deficiency is among the most consequential outcomes because severe corrosion or hatch-cover non-watertightness can ground a detention immediately. Bulk carriers in particular face heightened scrutiny on hatch covers, hold-frame brackets and topside-tank corrosion, with the Tokyo MoU PSC Manual incorporating the IACS UR Z10 ESP guidance for the inspection-procedure detail.

Major deficiency: fire safety

Fire-safety deficiencies span SOLAS Chapter II-2, the FSS Code (Fire Safety Systems), the 2010 FTP Code (Fire Test Procedures), the IGC Code for gas carriers and the IBC Code for chemical tankers. The Tokyo MoU coding for this category falls under the 11xxx range and sub-categories include fixed fire-extinguishing system deficiencies (CO2, foam, sprinkler), portable fire-extinguisher deficiencies, fireman’s outfit deficiencies including SCBA and EEBD, fire-control plan deficiencies, fire-pump deficiencies, fire-detection-system deficiencies, fire-damper deficiencies, and structural-fire-protection deficiencies including A-class and B-class divisions.

Fire-safety deficiencies are one of the highest-frequency Tokyo MoU deficiency categories, frequently topping or co-topping the annual deficiency-frequency table together with safety-of-navigation and life-saving categories. A poorly maintained CO2 system, an expired SCBA cylinder hydrostatic test or a missing fireman’s outfit will all be picked up in the Initial Inspection. The PSC Officer typically conducts a brief functional test of the emergency fire pump and at least one fire-detection circuit during the Initial Inspection.

Major deficiency: lifesaving + radio

Life-saving and radio deficiencies span SOLAS Chapter III (Life-Saving Appliances) and SOLAS Chapter IV (Radiocommunications) and the LSA Code. The deficiency-code ranges are 12xxx for life-saving appliances and 04xxx for radio. Sub-categories include lifeboat deficiencies (engine, davit, falls, release gear), liferaft deficiencies (hydrostatic release, certification), immersion suit deficiencies, lifejacket and lifebuoy deficiencies, EPIRB deficiencies (battery, hydrostatic release, registration, GMDSS-A1 to A4 area assignment), SART deficiencies, AIS-SART deficiencies, GMDSS console deficiencies (DSC, MF/HF, VHF, Inmarsat-C terminal), GMDSS battery and source-of-energy deficiencies, and radio-log deficiencies.

Lifesaving and radio deficiencies are particularly visible on PSC inspection because the LSA equipment is physically inspected and the radio-room equipment is functionally tested. Expired EPIRB batteries, missing SART registration, lifeboat-engine failure on test-start and lifeboat on-load-release-gear seizure are typical detention-grade findings. The 2022 amendments to LSA Code lifeboat-on-load-release-gear (LRRS) requirements have generated a particular surge in 12xxx deficiencies.

Safety-of-navigation deficiencies cover SOLAS Chapter V and the carriage-requirements regime for navigation equipment. The deficiency-code range is 13xxx. Sub-categories include ECDIS deficiencies (chart currency, software version, backup arrangement, training, performance test), magnetic compass deficiencies (deviation card current, illumination), gyro-compass deficiencies, AIS deficiencies (transmission, receiver, MMSI, voyage data), voyage data recorder VDR deficiencies (annual performance test, battery, capsule), echo-sounder deficiencies, radar deficiencies (S-band, X-band, ARPA, performance test), Bridge Navigational Watch Alarm System (BNWAS) deficiencies, navigation-light deficiencies, sound-signalling deficiencies and chart-correction deficiencies. The Tokyo MoU has run multiple Concentrated Inspection Campaigns on safety of navigation reflecting the continuing high frequency of 13xxx deficiencies.

Major deficiency: cargo + ballast

Cargo-and-ballast deficiencies cover the loading, stowage, securing and discharge regime under the IMSBC Code (solid bulk cargoes), the IMDG Code (dangerous goods), the IBC Code and IGC Code (chemical and gas carriers), the CSS Code (cargo stowage and securing), the Grain Code, the Timber Code and the Ballast Water Management Convention. The deficiency-code ranges include 03xxx (cargo) and adjacent series. Sub-categories include cargo securing manual deficiencies, dangerous goods documentation deficiencies, hold cleanliness for solid bulk cargo, IMSBC compliance for IMSBC-coded cargoes, ballast water management deficiencies (BWM record book, ballast water management plan, BWMS performance), tank-cleaning deficiencies for chemical tankers, ESP deficiencies for tankers and bulk carriers, segregation of dangerous goods, fumigation procedures, and CSM-related deficiencies on container ships including lashing and twistlock condition.

Major deficiency: ISM + ISPS

ISM Code deficiencies fall under the 14xxx range and ISPS Code deficiencies under the 15xxx range. ISM deficiencies cover Document of Compliance and Safety Management Certificate validity, the Safety Management System on board (master’s responsibility, designated person ashore evidence, safety meetings, drills, near-miss reporting, internal audits, non-conformity tracking, corrective-action records, master’s review of the SMS), shipboard documentation under SOLAS IX/4, and the deficiency category that escalates to a full major non-conformity if the SMS is shown not to be functioning effectively. A confirmed major non-conformity in ISM Code terms triggers a detention under the Tokyo MoU procedures and a parallel notification to the flag administration and the Recognised Organisation that issued the SMC.

ISPS deficiencies cover the International Ship Security Certificate, the Ship Security Plan implementation, the Ship Security Officer designation and training, security drills, the Continuous Synopsis Record, security-level changes management, the Declaration of Security on ship-shore interface, and the Pre-Arrival Notification (PAN) of security-related information twenty-four hours before arrival. ISPS deficiencies similarly escalate to detention if the Plan is shown not to be implemented, and trigger flag-state notification and possible refusal-of-entry consequences in subsequent ports.

Major deficiency: STCW (CoC, hours of rest)

STCW Convention deficiencies fall under the 02xxx range and cover certificate-of-competency validity, certificate-of-proficiency for specialised functions, English-language proficiency for safety-critical roles, manning compliance with the Minimum Safe Manning Document (MSMD), watchkeeping arrangements, hours-of-rest compliance under STCW Regulation VIII/1 (consolidated minimum 10 hours of rest in any 24-hour period and minimum 77 hours of rest in any 7-day period), and STCW endorsement validity for masters and chief engineers serving on flags other than the issuing authority. The hours-of-rest sub-category has been a consistent Tokyo MoU CIC focus, including the 2014 and 2021 hours-of-rest CICs that found widespread record-falsification across the inspected sample. STCW deficiencies are graded under the standard severity scale and may result in detention if a certificate is forged, expired or absent, or if hours-of-rest non-compliance is so severe that fatigue is reasonably expected to compromise watchkeeping safety.

Major deficiency: MARPOL Annex I-VI

MARPOL deficiencies fall under the 18xxx range and span all six Annexes. Annex I covers oil-record-book deficiencies, oily-water separator integrity, oil-content monitor calibration and operability, sludge-tank capacity, and the IOPP certificate. Annex II covers chemical-tanker noxious-liquid-substance compliance, P&A Manual implementation and the NLS certificate. Annex IV covers sewage-treatment-plant operability, sewage-discharge record and the ISPP certificate. Annex V covers garbage management plan, garbage record book, on-board waste-segregation procedures and discharge compliance. Annex VI covers air-pollution prevention including the MARPOL Annex VI Regulation 14 sulphur cap (0.50 percent globally outside ECA, 0.10 percent in ECA), fuel-oil change-over records on entering ECA, sulphur compliance demonstration through Bunker Delivery Notes and onboard sample analysis, EEDI-EEXI-CII technical-file documentation, NOx Tier I/II/III engine compliance under EIAPP and the IAPP certificate, ozone-depleting-substance record, VOC management on tankers, and the ship-energy-efficiency-management plan SEEMP. MARPOL deficiencies are typically among the top three deficiency categories by frequency in any given year and increasingly so since IMO 2020 sulphur cap entry into force.

Major deficiency: BWM Convention

BWM Convention deficiencies cover ballast water management plan implementation, ballast water record book maintenance, ballast water management certificate, BWMS (Ballast Water Management System) operability and crew familiarisation, sampling procedure compliance and the D-1 / D-2 standard transition status. Since the BWM Convention’s full D-2 entry into force across the global fleet in September 2024 (under the relevant amendments), the Tokyo MoU has applied increasing scrutiny to BWMS maintenance and crew operation. Sub-categories include malfunctioning UV-treatment lamps, electro-chlorination cell failures, by-pass valve mis-handling, sampling-port deficiencies, and ballast water log-book entries inconsistent with the AIS-derived voyage record. The Tokyo MoU 2025 BWM CIC raised the visibility of these sub-categories.

Concentrated Inspection Campaigns (CIC)

The Concentrated Inspection Campaign (CIC) is a three-month annual programme during which the PSC Officers across all twenty-one Tokyo MoU authorities apply a structured CIC Questionnaire in addition to the standard Initial Inspection on every ship selected for inspection during the campaign window. The questionnaire is designed by the Tokyo MoU Technical Working Group (typically jointly with the Paris MoU under the Cooperation Memorandum to ensure inter-MoU consistency), focuses on a single regulatory or operational area selected by the Committee, and produces structured data feeding both the Tokyo MoU annual report and a dedicated CIC report published after the campaign close. The CIC produces three outputs: an empirical baseline of compliance in the chosen area; targeted detentions where serious non-compliance is found; and educational pressure on the global fleet to address the chosen topic in the months leading up to the campaign and afterward.

CIC 2017 RFOs, 2020 sulphur, 2021 STCW

The CIC programme has run annually since 2008 covering progressively the priority compliance areas as identified by the Committee. The 2017 CIC focused on Safety of Navigation including ECDIS, identifying widespread deficiencies in chart currency, ECDIS software version, route-monitoring set-up and crew familiarisation training. The 2020 CIC focused on the IMO 2020 sulphur cap under MARPOL Annex VI Regulation 14, applied in the second half of 2020 after the 1 January 2020 entry-into-force date, and verified through Bunker Delivery Note review, Fuel Oil Non-Availability Reports, fuel-changeover records and on-board sample analysis. The 2021 CIC focused on the STCW Convention hours of rest, replicating a 2014 CIC on the same topic, and finding continuing widespread record-keeping anomalies. The 2018 CIC focused on MARPOL Annex VI emissions; the 2019 CIC on Emergency Systems; the 2015 CIC on Crew Familiarisation for Enclosed Space Entry following multiple fatal-incident histories on bulk carriers and tankers.

CIC 2022 stability, 2023 MARPOL Annex VI, 2024 fire safety

The 2022 CIC focused on stability in general including damage stability, the loading computer and ballast-water management interface, the trim-and-stability booklet, and the lashing arrangements that underpin the ship’s effective stability assumption. The 2023 CIC focused on MARPOL Annex VI (returning to the 2018 topic with expanded coverage to include Carbon Intensity Indicator (CII) under the IMO 2023 short-term measure, EEXI Technical File evidence, and SEEMP Part III on operational measures). The 2024 CIC focused on fire safety, returning attention to the highest-frequency Tokyo MoU deficiency category and covering structural fire protection, fixed extinguishing systems, fire detection, drills and crew familiarisation. The Committee announces the next-year CIC topic at its annual meeting in October-November of the preceding year, giving the global fleet approximately twelve months’ notice to prepare.

Cooperation with Paris MoU

The Tokyo MoU and the Paris MoU concluded a formal Cooperation Memorandum in the late 1990s and have updated and extended it several times. The Cooperation provides for two-way data exchange between APCIS (Tokyo MoU) and THETIS (Paris MoU) so that the Ship Risk Profile of any ship reflects inspection history from both regions seamlessly: a ship inspected in Rotterdam under the Paris MoU appears in the APCIS with that inspection result entered into the SRP calculation, and vice versa. The Cooperation also covers harmonised CIC topic selection, joint Technical Working Group meetings, observer attendance at each other’s Committee meetings, exchange of PSCO trainers and training materials, joint research projects, and aligned positions in IMO sub-committee submissions. The two MoUs together account for approximately fifty percent of global PSC inspection volume and exercise commensurate influence on flag and operator behaviour. The non-cooperating regional MoUs each maintain bilateral arrangements with both Paris and Tokyo to limited extents.

Relationship to IMO III Code 2016

The IMO III Code (Code for the Implementation of IMO Instruments) entered into force on 1 January 2016 through SOLAS Chapter XIII, MARPOL Annex VI Regulation 11, the Load Line Protocol, the COLREGs and the Tonnage Convention amendments. The III Code is the global instrument enumerating the obligations of flag states, port states and coastal states under all IMO instruments and is the regulatory backbone of the IMO Member State Audit Scheme. The Tokyo MoU’s PSC procedures are calibrated to the III Code: PSC Officer training, deficiency classification, detention procedures, flag-state notification and Recognised Organisation oversight all map to the III Code obligations, and Tokyo MoU members participate in the Council and IMO sub-committee work that updates the III Code. III Code compliance forms one element of the white-grey-black flag-list methodology because flag administrations falling persistently short of III Code obligations attract the worst PSC performance which translates into list demotion.

Relationship to IMO Audit Scheme IMSAS

The IMO Member State Audit Scheme (IMSAS) is the mandatory audit programme adopted under IMO Resolution A.1067(28) and operating since 2016 under which every IMO member state submits to a periodic audit of its flag, port and coastal-state implementation of IMO instruments. The Tokyo MoU member authorities have been audited under IMSAS and the audit findings are visible to the Tokyo MoU through the III Code performance evidence. IMSAS findings inform the white-grey-black flag list indirectly: an IMSAS audit finding non-compliance with flag-state obligations correlates with elevated detention rates which translates into list demotion. The Tokyo MoU and IMSAS together provide a two-track verification of flag-state performance: external audit (IMSAS) and operational outcomes (PSC inspections and detentions).

White/grey/black flag list 3-year rolling

The Tokyo MoU flag-state performance list classifies every flag administration whose ships have been inspected at least a minimum threshold count over the rolling three-year window into one of three lists: White List (high-quality flags), Grey List (medium-quality flags) and Black List (low-quality flags). The classification is calculated on the excess factor comparing the flag’s detention rate to the regional average detention rate after correcting for ship-type mix and inspection volume. Flags above a defined upper threshold are White, between thresholds are Grey, below a defined lower threshold are Black. The list is published in the Tokyo MoU annual report and is updated annually. The lists feed the Ship Risk Profile factor weighting: White-list flags attract fewer SRP points, Grey more, Black the most.

The methodology is published in detail in Annex 12 of the Tokyo MoU Memorandum and uses a binomial-distribution-based statistical confidence test to avoid spurious list movement on small inspection counts. Flags with fewer than thirty inspections in the rolling window are listed as “Not Listed” rather than Black-listed by default, recognising that small samples cannot reliably support the statistical inference.

2024 white-list flags: Singapore, Korea, Japan, Hong Kong

The Tokyo MoU 2024 White List included: Singapore, Republic of Korea, Japan, Hong Kong (China), Australia, Cayman Islands, Bahamas, Marshall Islands, Liberia, Norway, United Kingdom, Denmark, Netherlands, France, Germany, Italy, Greece, Cyprus, Malta, Antigua and Barbuda, Isle of Man, Bermuda, Gibraltar, the United States, Canada, New Zealand and various other consistently high-performing flags. The White List position confers commercial advantage: charterers, P&I clubs, banks and insurers refer to white-list flag status in vetting and pricing decisions. The White List is broadly stable across years with most movement concentrated in the Grey and Black categories.

2024 black-list flags: historical Tanzania, Togo, Cook Islands

The Tokyo MoU Black List has historically included flags such as Tanzania (Zanzibar Maritime Authority), Togo, the Cook Islands, Comoros, Belize, Sierra Leone, Saint Kitts and Nevis, Saint Vincent and the Grenadines (historical), Mongolia, Cambodia, Honduras and several other small-fleet flags with elevated detention rates. The Black List is the most actively reviewed list because flag administrations under sanctions risk and commercial pressure typically respond to Black List status with reform packages that may lift performance. The Cook Islands moved from Black to Grey in some years following reform of its registry oversight; Tanzania (Zanzibar) has alternated between Black and Not-Listed status depending on sample size. Black-list flags face extra scrutiny on every Tokyo MoU port call (HR Ship Risk Profile by default) and may face refusal-of-entry consequences in some authorities.

RO performance list (IACS members top)

The Tokyo MoU Recognised Organisation performance list ranks classification societies authorised by flag administrations to issue statutory certificates on the flag’s behalf, on the basis of the RO-related detention rate over the rolling three-year window. The list classifies ROs as High Performance, Medium Performance and Low Performance according to a methodology described in Annex 8 of the Tokyo MoU Memorandum. IACS members consistently dominate the High Performance list, with DNV, Lloyd’s Register, ABS, ClassNK, Bureau Veritas, the Korean Register, the China Classification Society, RINA, the Indian Register of Shipping, the Polish Register of Shipping, the Croatian Register of Shipping and the Russian Maritime Register typically all placing in the High or Medium tier. Non-IACS smaller ROs more frequently appear in the Medium or Low tier reflecting smaller fleet samples and different operational profiles. The RO performance enters the Ship Risk Profile factor weighting the same way the flag list does.

Detention code structure (5-digit hierarchical)

The Tokyo MoU uses a five-digit hierarchical deficiency-code structure aligned with the Paris MoU code structure to support inter-MoU data exchange. The first two digits define the principal category. Examples include 01xxx for ship’s certificates and documents; 02xxx for STCW including certificate of competency and hours-of-rest; 03xxx for crew and accommodation under MLC and ILO instruments; 04xxx for Radio communications under SOLAS IV; 05xxx for emergency systems; 07xxx for Stability, structure and related matters; 09xxx for Damage control and propulsion-and-auxiliary; 10xxx for Construction and structure; 11xxx for Fire prevention and SOLAS II-2; 12xxx for Life-saving appliances; 13xxx for Safety of navigation; 14xxx for ISM Code; 15xxx for ISPS Code; 18xxx for MARPOL Annexes I to VI; 19xxx for working and living conditions under MLC. Each top-level category breaks down into three further digits indexing the specific sub-category and individual deficiency. The complete code list is published in the Tokyo MoU PSC Manual and synchronised with the Paris MoU code list for inter-MoU consistency.

Deficiency severity: 17 observation, 18 next port, 30 detention

Each deficiency entered by the PSC Officer is assigned a severity code indicating the action required of the master and the consequence for the ship. The principal action codes are: 17 = action observation (the deficiency is recorded but no specific corrective deadline is imposed; the master is expected to address it in due course); 18 = rectify before departure next port (the deficiency must be rectified before arrival at the next port and a notation is sent to that next-port PSC); 30 = detention (the ship is detained until the deficiency is rectified to the satisfaction of the PSC Officer). Other action codes include 15 (rectification before departure from current port), 16 (rectify within 14 days), 19 (rectify within 3 months), and various flag-state-notification codes. A deficiency can be coded with more than one action; for instance, a serious item may be both 30 (detention) and flag-state notification. The severity assignment is the PSC Officer’s professional judgement guided by the Tokyo MoU PSC Manual and the clear grounds definition in the Memorandum.

Typical detention duration: 24-72 hours

The typical detention duration once imposed runs 24 to 72 hours as the master and superintendent arrange the corrective work, supplier delivery, surveyor attendance and PSC Officer release inspection. Short detentions (under 24 hours) typically arise when a single equipment item can be repaired or replaced rapidly (a fire-pump repair, a lifejacket replacement, a navigation chart correction). Longer detentions (3 to 7 days) arise when serious structural, ISM or ISPS findings require extended remedial work, additional surveyor or RO attendance, flag-state representation or even crew rotation. Very long detentions (over 7 days) are rare and usually reflect total-loss-grade findings such as severe corrosion, total ISM Code breakdown or arrest under separate criminal or civil proceedings.

The detention release follows a release inspection by the same or a different PSC Officer who verifies the rectification. The release is recorded in the APCIS and the detention notation enters the ship’s permanent inspection history feeding the Ship Risk Profile.

Appeals via flag-state representation

A shipowner who disputes a Tokyo MoU detention has two principal recourses. The first is on-the-spot dialogue with the PSC Officer and the inspecting authority’s regional PSC office, frequently mediated through the local class surveyor and the company superintendent. The second is flag-state representation: the flag administration of the detained ship may make formal representations to the inspecting authority through diplomatic channels, supported by the flag-state’s own assessment of the ship’s actual condition. The Tokyo MoU Memorandum incorporates a procedure for the inspecting authority to consider flag-state representations and to revise the detention if the evidence supports a different conclusion. The Tokyo MoU Detention Review Panel is the formal review body that addresses contested detentions referred up by member authorities; the Panel meets as required and its findings are published in the annual report. The threshold for overturning a detention on appeal is high: the inspecting authority’s PSCO judgement is presumed correct, and the appellant must demonstrate either a material error of fact or a material error of law.

Singapore + Hong Kong + Japan inspection hubs

The largest individual contributors to the Tokyo MoU inspection volume are the principal Asia-Pacific transshipment and trade hubs. Singapore is the world’s largest bunker port and a major transshipment hub, conducting more than five thousand Tokyo MoU inspections per year through the Maritime and Port Authority (MPA) and ranking consistently as the top-volume Tokyo MoU inspection authority. Hong Kong (China) is the second-largest contributor through the Marine Department, conducting around three thousand inspections per year. Japan through the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) conducts around three to four thousand inspections per year across Tokyo, Yokohama, Kobe, Osaka, Nagoya, and several smaller ports. The mainland Chinese authority (Maritime Safety Administration, MSA) conducts a further large volume across Shanghai, Ningbo, Qingdao, Tianjin, Dalian, Guangzhou and other ports. The Australian Maritime Safety Authority (AMSA) is the most prolific southern-hemisphere PSC authority. Korea, Russia, Canada (Pacific), New Zealand, the Philippines, Indonesia, Malaysia, Vietnam and Thailand all contribute meaningful inspection volumes to the regional total.

COVID-19 2020-22 impact

The COVID-19 pandemic produced a measurable but bounded impact on Tokyo MoU operations from early 2020 through late 2022. Several authorities suspended or restricted on-board PSC inspections for varying periods to protect PSCOs from infection, with virtual or remote inspection trials conducted in some jurisdictions. Inspection volume fell by an estimated fifteen to twenty-five percent during the worst-affected months of 2020-2021, with detention counts falling proportionally. The Tokyo MoU Committee issued joint guidance with the Paris MoU on pandemic-period PSC operations including extended certificate validities, virtual evidence-checking and risk-prioritised on-board attendance. Detention rates as a proportion of (reduced) inspections did not change materially, suggesting that the underlying fleet quality was unchanged and that the suspended inspections would have produced similar outcomes if conducted. By mid-2022 inspection volume had returned to near-pre-pandemic levels and the 2023 annual report showed full restoration of the Tokyo MoU operational tempo. The pandemic accelerated Tokyo MoU consideration of digital evidence-handling, electronic certificates and remote-survey acceptance, several of which have been incorporated into the post-2023 PSCO Manual revisions.

2024 annual report deficiency stats

The Tokyo MoU 2024 annual report (covering the calendar year and published in mid-2025) reported approximately thirty-three thousand inspections, approximately one thousand three hundred detentions, and a total deficiency count of approximately one hundred and twenty thousand individual deficiencies recorded across the inspections. The top deficiency categories by frequency were fire safety (11xxx), safety of navigation (13xxx), MARPOL (18xxx), life-saving appliances (12xxx), ISM (14xxx) and structural-and-construction (10xxx and 07xxx). The detention-rate distribution showed bulk carriers, general cargo ships and oil tankers above twenty years of age as the highest-detention populations. The flag-list movement showed continued stability in the white list, modest movement in the grey list, and a small reduction in the black list count reflecting flag-administration reform across several Black-listed flags. The RO performance list showed continued IACS-member dominance of the high-performance tier. The CIC 2024 fire-safety campaign reported approximately seven thousand inspections under the campaign questionnaire with deficiency-rate findings consistent with prior fire-safety CICs.

2030+ outlook: digitalisation + cyber + autonomous ships

Looking forward, the Tokyo MoU faces several modernisation pressures. Digitalisation of inspection workflow is advancing through APCIS modernisation, mobile PSCO application development for tablet-based inspection, electronic certificate acceptance under the IMO 2024-2030 ECT (Electronic Certificate) framework, and remote-witnessing of certain test items. Cyber compliance has entered the inspection scope through the IACS UR E26 and UR E27 cyber-resilience requirements applicable to vessels contracted from 1 July 2024 onwards and through the MSC Resolution MSC.428(98) requirement that ISM Code SMS address cyber-risk management. Autonomous and Maritime Autonomous Surface Ships (MASS) present a future challenge as the IMO MASS Code (under development for adoption around 2028) creates a new vessel category whose PSC inspection cannot follow the traditional crew-interview and crew-document model. The Tokyo MoU is engaged with the Paris MoU and IMO sub-committees on the MASS PSC framework. Decarbonisation through MARPOL Annex VI Chapter 4 and the IMO Net-Zero Framework adds new inspection items including CII verification, alternative-fuel bunker compliance for LNG, methanol, ammonia and hydrogen fuel, and the SEEMP Part III operational measures. The Tokyo MoU 2030 strategic outlook is therefore one of expanded scope, deeper data integration with sister MoUs and IMO IMSAS, and continuing evolution of the Ship Risk Profile and CIC programme to track regulatory entry-into-force dates.

Formula, assumptions, and limits

Formula

Three formulae together summarise the Tokyo MoU operational structure.

Inspection frequency under the New Inspection Regime is a function of Ship Risk Profile category:

T_{\text{insp}}(\text{LR}) \in [24, 36] \text{ months}

T_{\text{insp}}(\text{SR}) \in [10, 12] \text{ months}

T_{\text{insp}}(\text{HR}) \in [2, 4] \text{ months}

Detention rate as the principal performance metric is:

R_{\text{det}} = \frac{N_{\text{detentions}}}{N_{\text{inspections}}}

with the Tokyo MoU regional aggregate:

R_{\text{det,Tokyo MoU}} \in [0.030, 0.040] \text{ (3 to 4 percent)}

Flag-list excess factor for the white-grey-black classification compares an individual flag’s detention rate against the regional aggregate:

E_{\text{flag}} = \frac{R_{\text{det,flag}} - R_{\text{det,regional}}}{\sigma_{\text{regional}}}

with significance tested against the binomial confidence interval at the inspection-count threshold $N_{\text{flag}} \geq 30$ .

Derivation

The twenty-one-authority count derives from the eighteen founding authorities plus subsequent admissions of Chile, Peru, Panama and the Marshall Islands by Committee accession. The 30,000 to 35,000 inspection band derives from the published Tokyo MoU annual reports across the post-NIR years 2014 to 2024 with COVID-affected 2020-2021 outliers excluded. The 1,000 to 1,500 detention band similarly derives from the annual report time series. The three-category Ship Risk Profile derives from Annex 10 of the Tokyo MoU Memorandum point-band thresholds, calibrated against the historical detention-frequency distribution to deliver the targeted inspection-frequency outcomes. The three-year rolling window for flag-list and RO-list derives from the trade-off between sample sufficiency (binomial confidence at typical flag inspection counts) and responsiveness to flag-administration reform.

Assumptions

The framework assumes that Tokyo MoU PSC Officers across all twenty-one authorities apply the PSC Manual consistently after their harmonised PSCO training and qualification course, an assumption supported by the joint training scheme but acknowledged to introduce some variance. It assumes that APCIS data quality is high and that data-entry errors and omissions are infrequent, an assumption reinforced by the periodic data-quality audits run jointly with the Paris MoU on the THETIS database. It assumes that the Cooperation Memorandum two-way data exchange operates without significant lag, with daily synchronisation as the operational target. It assumes that ship and flag identity data (IMO number, flag, classification society, company IMO number, ship type) are recorded accurately at the inspection-data-entry stage. It assumes that the flag-list and RO-list rolling windows do not shift the underlying populations significantly during the window. It assumes that the regional aggregate detention rate is a meaningful baseline against which individual-flag excess factors can be calculated, an assumption that holds for flag administrations with thirty or more inspections in the window and breaks down for smaller flags listed as Not Listed.

Worked example

A 165-metre Panama-flagged general cargo ship of 19 years age, classed by an IACS member, operated by a company with a moderate Tokyo MoU detention history of two detentions in the last three years across a ten-ship fleet, calls at the Port of Singapore. The APCIS Ship Risk Profile draws on: Panama flag (white list under the Tokyo MoU 2024 list), classification by an IACS member (high-performance RO), age 19 years (above twelve years threshold, below the twenty-year threshold, so weighted), ship type general cargo (not in the high-priority sub-list of tankers, gas, chemical, bulk, passenger, so unweighted), company performance (moderate, medium SRP contribution), zero deficiencies in the latest two inspections, no detention in the latest 24 months. The points sum places the ship in the Standard Risk category. The expected next-inspection window is 10 to 12 months from the previous inspection. On arrival at Singapore the APCIS shows the ship overdue by two months and the MPA PSC schedule selects the ship for an Initial Inspection on 09 May 2026. The PSCO conducts the inspection within the first eighteen hours of port stay, finds two minor deficiencies (one fire-extinguisher annual inspection date overdue, one navigation light internal cleaning required), assigns severity code 17 (action observation) and code 16 (rectify within 14 days) respectively, no detention. The result enters the APCIS, the SRP refreshes, and the ship’s next-inspection window resets to 10-12 months from 09 May 2026.

Edge cases and limits

Edge cases include flags with fewer than thirty inspections in the window (treated as Not Listed rather than statistically classified), Ship Risk Profile transitions between categories triggered by single events (a single detention can move SR to HR), and the treatment of newly built ships with no inspection history (assigned Standard Risk by default until a first inspection record exists). The Tokyo MoU does not inspect fishing vessels regardless of size, pleasure craft, warships or government non-commercial ships. The Tokyo MoU framework does not extend to United States ports (covered by the United States Coast Guard PSC programme operating outside any MoU). The Tokyo MoU does not enforce against domestic-flag ships of the inspecting authority (those fall under flag-state survey by the same authority). Detention durations longer than thirty days are extremely rare and typically indicate parallel criminal, civil or arrest proceedings outside the PSC framework. Concentrated Inspection Campaign findings can produce CIC-specific detentions independently of the underlying SRP category if the CIC questionnaire reveals serious non-compliance.

Regulatory basis

The regulatory basis is the Tokyo Memorandum of Understanding on Port State Control in the Asia-Pacific Region signed at Tokyo on 1 December 1993 and operational from 1 April 1994, as amended by Committee resolutions through the current consolidated revision. The Memorandum draws PSC authority from the underlying IMO instruments: SOLAS Regulation I/19 (and Chapter XI-1 Regulation 4), MARPOL Annex I Regulation 11 and Annex VI Regulation 10, the Load Line Convention Article 21, the STCW Convention Article X, MLC Title 5 Regulation 5.2, the ISM Code through SOLAS IX/6.3, the ISPS Code through SOLAS XI-2/9, the BWM Convention Article 9, and the AFS Convention. The PSC procedural framework follows IMO Resolution A.1185(33) of 2023 Procedures for Port State Control, which consolidates and replaces all prior IMO PSC procedure resolutions. The flag-state, port-state and coastal-state obligations underpinning the III Code are set out in IMO Resolution A.1070(28). The IMSAS framework is in Resolution A.1067(28). The harmonised system of survey and certification under which inspection-window timing aligns with statutory-certificate cycles is in Resolution A.883(21). The Tokyo MoU operational manuals (PSC Manual, NIR procedures in Annex 10, deficiency code list, severity-action code list, flag-list methodology in Annex 12, RO-list methodology in Annex 8) are published on the Tokyo MoU portal.

Common errors

A frequent confusion treats the Tokyo MoU as binding international law: it is not. It is a non-binding administrative arrangement among maritime authorities, with each authority enforcing through its own national legislation. A second confusion places the Tokyo MoU Secretariat at IMO London: the Secretariat is in Tokyo. A third confusion conflates the Tokyo MoU New Inspection Regime with the Paris MoU NIR: they are similar but separately administered, with their two-way data exchange under the Cooperation Memorandum providing the harmonisation. A fourth confusion treats the white-grey-black flag list as a static ranking: it is recalculated annually on a rolling three-year window. A fifth confusion treats the RO performance list as the IACS dominance list only: non-IACS ROs are listed and can rank in High or Medium performance tiers depending on the data. A sixth confusion treats the Concentrated Inspection Campaign as a separate inspection on top of the standard inspection: the CIC questionnaire is added to the standard Initial Inspection during the campaign window, not a stand-alone visit. A seventh confusion treats detention as the only meaningful PSC outcome: the sequence of action codes 17, 18, 30 and others all carry consequences and feed the Ship Risk Profile.

References

The principal authoritative source on the Tokyo MoU is the Tokyo MoU itself through its Tokyo Secretariat publication portal at tokyo-mou.org, which hosts the consolidated Memorandum of Understanding on Port State Control in the Asia-Pacific Region in its current revision, the PSC Manual setting out the harmonised inspection procedures applicable across all twenty-one contracting authorities, the Annex 10 New Inspection Regime procedures including the Ship Risk Profile calculation factors and points bands, the Annex 8 Recognised Organisation performance list methodology, the Annex 12 flag-state white-grey-black list methodology with the binomial-confidence statistical test, the deficiency code list aligned with the Paris MoU, the severity-action code list including codes 17 action observation, 18 rectify before next port and 30 detention, and the annual report archive covering the operational years 1994 to the most recent published year. The Asia-Pacific Computerised Information System (APCIS) at apcis.tokyo-mou.org provides the public ship-search portal returning the inspection history of any IMO-numbered ship inspected within the Tokyo MoU region. The Tokyo MoU Concentrated Inspection Campaign reports for each annual campaign from 2008 onwards are published on the Tokyo MoU portal including the 2017 Safety of Navigation, 2018 MARPOL Annex VI emissions, 2019 Emergency Systems, 2020 IMO 2020 sulphur cap, 2021 STCW Hours of Rest, 2022 Stability, 2023 MARPOL Annex VI return, 2024 Fire Safety and the 2025 Ballast Water Management programmes. The cooperation framework with the Paris Memorandum of Understanding on Port State Control is documented through the Cooperation Memorandum text and the joint Technical Working Group records on both organisations’ portals at tokyo-mou.org and parismou.org. The IMO procedural framework is supplied by IMO Resolution A.1185(33) of 2023 Procedures for Port State Control, which consolidates and replaces the earlier A.1119(30) and A.1052(27) resolutions on the same subject. The III Code (Code for the Implementation of IMO Instruments) is in IMO Resolution A.1070(28) and entered into mandatory force from 1 January 2016 through SOLAS Chapter XIII and corresponding amendments to MARPOL, the Load Line Protocol, the COLREGs and the Tonnage Convention. The IMO Member State Audit Scheme (IMSAS) framework is in IMO Resolution A.1067(28) and is the global flag-port-coastal-state audit programme covering Tokyo MoU member authorities. The Harmonised System of Survey and Certification under IMO Resolution A.883(21) supplies the statutory-certificate renewal cycle that feeds the inspection-window timing assumptions of the New Inspection Regime. The IACS RO Code adopted as IMO Resolution MSC.349(92) and MEPC.237(65) supplies the regulatory framework under which Tokyo MoU member authorities authorise classification societies as Recognised Organisations whose performance is rated on the Tokyo MoU RO list. The Equasis public maritime database at equasis.org provides per-ship inspection history aggregated across all regional MoUs and the United States Coast Guard PSC programme, supporting independent verification of Ship Risk Profile category. National maritime authority portals for each of the twenty-one contracting authorities provide the operational implementation detail at the national level, including the Maritime and Port Authority of Singapore (MPA), the Hong Kong Marine Department, the Japan Ministry of Land Infrastructure Transport and Tourism (MLIT) and Japan Coast Guard, the Australian Maritime Safety Authority (AMSA), the China Maritime Safety Administration (MSA), the Korea Maritime Safety Tribunal and the Korea Coast Guard, the New Zealand Maritime Authority, the Russian Ministry of Transport Maritime Safety service for the Pacific Far East, Transport Canada Pacific Region, and the Panama Maritime Authority. The Tokyo MoU is supported in its information-system development by ongoing cooperation with the Paris MoU THETIS database operations and the European Maritime Safety Agency (EMSA), with the inter-MoU two-way data exchange running on a near-real-time synchronisation. Historical reference for the regional PSC architecture and the Hague-Paris-Tokyo lineage is in the Paris Memorandum of Understanding on Port State Control archives covering the 1978 Hague Memorandum, the 1982 Paris MoU founding, the proliferation of regional MoUs through the 1990s, the IMO Resolution A.682(17) of 1991 on Regional Co-operation in the Control of Ships and Discharges, and the contemporaneous IMO Maritime Safety Committee discussions that led to the 1993 Tokyo signing.