International Maritime Organization (IMO)

International Maritime Organization (IMO)

The International Maritime Organization (IMO) interest is safety at sea. Until 1982, it was called the Inter-Governmental Maritime Consultative Organization (IMCO). A United Nations conference in 1948 adopted a Convention that established IMO, making it the first-ever international body devoted exclusively to maritime matters.

The International Maritime Organization (IMO) came into being in 1958. Four years prior to this an international convention dealing with the threat of marine pollution from ships (particularly from oil in tankers) was adopted.

The International Maritime Organization (IMO) took on the responsibility of upholding this convention, ensuring that from the start, the improvement of maritime safety and the prevention of marine pollution have been IMO’s most important objectives.

The International Maritime Organization (IMO) updated a number of existing treaties, notably the International Convention for the Safety of Life at Sea (SOLAS), a 1960 Convention superseded the 1948 version. Its measures include: machinery and electrical installations; the safety of navigation; the development of dangerous goods; and nuclear ships.

The International Maritime Organization (IMO) is the only United Nations specialized agency to have its headquarters in the United Kingdom. It is based at 4 Albert Embankment, London.

The governing body of The International Maritime Organization (IMO) is the Assembly, which meets once every two years. It consists of all 132 Member States and one Associate Member. A Council (32 Member Governments elected by the Assembly) acts as IMO’s governing body between the Assembly sessions.

The International Maritime Organization (IMO) is a technical organization and committees and sub-committees, such as the Maritime Safety Committee (MSC) and The Marine Environment Protection Committee (MEPC) conduct most of its work. Such committees have contributed to promoting the adoption of some thirty conventions and protocols, and it has adopted well over 600 codes and recommendations concerning maritime safety, the prevention of pollution, and related matters. Evidence would show that the International Maritime Organization (IMO) measures have already proved beneficial in many areas. For example, the number of collisions between ships has been greatly reduced in is where IMO-approved traffic separation schemes have been introduced.

More recently the International Maritime Organization (IMO) has been responsible for implementing the International Safety Management (ISM) Code for ships, imposing mandatory standards on safety procedures for all types of seagoing ships and their operating companies. Updated information on the IMO’s conventions, codes, rules, and publications can be found on the organization’s formidable website:

The International Maritime Organization (IMO) itself has no direct power to enforce its conventions. When they have been adopted, it is required they be incorporated into the laws of flag states, who are then responsible for ensuring conformity. The actual work of surveying and the issuing of certificates of compliance is likely to be dealt with by Classification Societies. Inspection and enforcement is normally undertaken by Port State Control organizations operating under the direction of flag states and maritime nations.

Main Roles of International Maritime Organization (IMO)

The International Maritime Organization (IMO) is a specialized agency of the United Nations responsible for regulating shipping. Established in 1948 as the Inter-Governmental Maritime Consultative Organization (IMCO) and coming into force in 1959, it was later renamed to its current name in 1982. The IMO is dedicated to ensuring safe, secure, and efficient shipping on clean oceans. Its main roles include:

  1. Developing and Maintaining a Comprehensive Regulatory Framework: The IMO creates a wide range of regulations to ensure that the global shipping industry is safe, environmentally sound, efficient, and secure. These include conventions on Safety of Life at Sea (SOLAS), Prevention of Pollution from Ships (MARPOL), and Standards of Training, Certification, and Watchkeeping for Seafarers (STCW).
  2. Safety and Security: The IMO focuses on ensuring the safety of life at sea by setting safety standards for ship design, construction, equipment, operation, and manning.
  3. Environmental Concerns: It addresses environmental issues in the maritime sector, especially those related to pollution. The MARPOL convention, for example, aims to minimize pollution of the seas, including dumping, oil, and exhaust pollution.
  4. Legal Matters: The International Maritime Organization (IMO) is also involved in legal matters, helping to develop international maritime law. This includes addressing liability and compensation issues related to international shipping.
  5. Technical Cooperation and Training: The organization helps with the implementation of its regulations, particularly in developing countries, through technical assistance and training programs.
  6. Security: Post-9/11, the International Maritime Organization (IMO) has also focused on enhancing the security of international shipping, leading to the adoption of the International Ship and Port Facility Security Code (ISPS).
  7. Continuous Update and Improvement: The International Maritime Organization (IMO) continually updates its policies and regulations to respond to new challenges and technological advancements in the shipping industry.
  1. Responding to Emerging Challenges: The IMO adapts its strategies and regulations in response to emerging maritime challenges. This includes addressing issues like Arctic shipping, the increase in size of ships, and the use of new technologies in navigation and ship design.
  2. Global Standards Setting: The IMO ensures that its regulations provide a level playing field for the global shipping industry. This uniformity is crucial for international trade, as it prevents individual countries or regions from implementing less stringent safety and environmental standards that could lead to ‘flags of convenience’, and other practices that might compromise safety and environmental integrity.
  3. Promoting Maritime Education and Awareness: The organization works towards raising awareness about the importance of maritime security, safety, and the marine environment. It encourages a culture of safety and environmental consciousness within the industry.
  4. Facilitating International Cooperation: The IMO fosters cooperation among its member states and facilitates dialogue between various stakeholders in the maritime sector, including governments, shipping companies, and environmental groups.
  5. Monitoring and Enforcement: While the IMO is not an enforcement body, it provides guidelines and frameworks for its member states to implement and enforce its regulations. The effectiveness of IMO conventions largely depends on the commitment of member states to adopt and enforce them.
  6. Addressing Seafarer Rights and Welfare: The IMO also focuses on the wellbeing and rights of seafarers. This includes standards for living conditions, work hours, and training, which are crucial for the safety and efficiency of shipping operations.
  7. Climate Change and Sustainability: In recent years, the IMO has been increasingly involved in efforts to combat climate change. This includes initiatives to reduce greenhouse gas emissions from ships and promote sustainable shipping practices.

The IMO’s work is a continuous process of review, assessment, and adaptation to ensure that global shipping remains safe, secure, and environmentally responsible. It’s an essential cog in the machinery of global trade and environmental stewardship, playing a pivotal role in shaping the future of international maritime activity. The International Maritime Organization (IMO) plays a critical role in international trade and global efforts to sustainably use and protect our oceans. Its regulations and standards are crucial for ensuring that the massive and vital industry of global shipping operates safely and with minimal environmental impact.


What is International Maritime Organization (IMO)?

Every significant development in world history is driven by certain factors that evolve over time, and the establishment of the International Maritime Organization (IMO) is no exception. Among the many industries thriving worldwide, “Shipping” stands out as a genuinely international sector. It facilitates over 90% of global trade through the transportation of cargo and merchant ships, doing so efficiently and cost-effectively. Consequently, individual ships may fall under the management of a multinational chain, spending most of their time at sea traversing various jurisdictions. Hence, there arose a need in the early 20th century for a universal governing body that could establish rules and standards to regulate shipping processes and the industry on a global scale. This led to the creation of the International Maritime Organization.

The first international treaty of its kind between nations can be traced back to the “Safety of Life at Sea” (SOLAS) treaty, which was adopted by several nations following the Titanic disaster. Although the IMO was established in 1948 in Geneva, it did not become enforceable until 1959 during a meeting held in London, where its headquarters are located.

The primary mission and responsibility of the International Maritime Organization are to develop and uphold a comprehensive framework of regulations and policies for the shipping industry. This framework covers various aspects, including maritime security, safety, technical cooperation, environmental concerns, and legal matters. The IMO has effectively carried out this task since its inception through specialized committees and sub-committees operating at its headquarters. These committees’ sessions are attended by numerous delegates and experts from member countries, as well as non-governmental and intergovernmental organizations.

The governing body of the IMO convenes biennially and consists of all member states. In the periods between Assembly sessions, a council serves as the governing body, comprising 40 member states elected by the Assembly for specific terms. These governing bodies oversee and monitor the various committees responsible for specific tasks and duties. The Secretariat, led by the Secretary-General elected by the Assembly, plays a vital role in IMO’s daily operations.

The International Maritime Organization has been successful in regulating key areas, including accident prevention, the establishment of safety standards for ships and ships (including design and materials), adherence to established safety and security treaties, pollution prevention, and addressing other preventable human disasters. The IMO also facilitates technical cooperation among member states, implements an audit and monitoring system for rules and standards, and monitors liabilities and compensation in the event of breaches of regulations.

In summary, the International Maritime Organization plays a pivotal role in advancing modern society toward a more robust and environmentally friendly commercial and transportation environment.

International Maritime Organization (IMO) Structure:

The IMO’s work is carried out by several entities, including the IMO Secretariat, Member States, Intergovernmental Organizations (IGOs), and Non-Governmental Organizations (NGOs). Here is a breakdown of these components:

  • IMO Secretariat: The daily operations of the IMO are managed by the IMO Secretariat, led by the Secretary-General and supported by approximately 300 international civil servants. They coordinate meetings, prepare documents, and ensure the organization’s smooth functioning.
  • Member States: Each Member State is represented at IMO meetings, including the Assembly, Council, Committees, and Sub-Committees. Delegations typically consist of the Head of Delegation and advisors.
  • Assembly: The Assembly serves as the highest Governing Body of the IMO, consisting of all Member States. It meets biennially to approve the work program, vote on the budget, and elect the Council.
  • Council: The Council acts as the Executive Organ of the IMO and supervises the organization’s work under the Assembly’s authority. It performs various functions between Assembly sessions.
  • Committees: There are five policy-making Committees responsible for developing, reviewing, and approving the IMO’s guidelines and regulations. These Committees report to the Council and Assembly.
  • Sub-Committees: Seven technical Sub-Committees support the work of the policy-making Committees. They operate under the direct instructions of the Maritime Safety Committee (MSC) and the Marine Environment Protection Committee (MEPC).

The IMO’s structure and functions ensure the effective regulation of international maritime activities and the development of safety, security, and environmental standards in the shipping industry.


What is the role of International Maritime Organization IMO?

The International Maritime Organization (IMO) plays a vital role in global maritime affairs. Its primary responsibilities include:

  1. Developing International Maritime Regulations: The IMO creates and maintains a comprehensive regulatory framework for shipping, encompassing safety, environmental concerns, legal matters, technical cooperation, maritime security, and efficiency.
  2. Ensuring Maritime Safety: It sets standards for ship design, construction, equipment, operation, and manning to ensure the safety of life at sea.
  3. Environmental Protection: The IMO addresses environmental issues in the maritime sector, particularly those related to pollution, through conventions like MARPOL for the prevention of pollution from ships.
  4. Legal Framework for Maritime Affairs: The organization develops international maritime law, dealing with aspects such as liability and compensation issues related to shipping.
  5. Technical Cooperation and Capacity Building: The IMO assists countries, especially developing ones, in implementing its standards through technical assistance and training programs.
  6. Maritime Security: It enhances the security of international shipping, including measures adopted post-9/11 like the International Ship and Port Facility Security Code (ISPS).
  7. Global Standards Setting: The IMO ensures uniformity in regulations, which is crucial for international trade, avoiding practices like ‘flags of convenience’ that might compromise safety and environmental integrity.
  8. Responding to Emerging Challenges: The organization continually updates its policies and regulations to address new challenges in the shipping industry.
  9. Monitoring and Enforcement Guidelines: While not an enforcement body itself, the IMO provides guidelines and frameworks for member states to enforce its regulations.
  10. Seafarer Welfare: It focuses on the rights and welfare of seafarers, setting standards for living conditions, work hours, and training.
  11. Tackling Climate Change and Promoting Sustainability: The IMO is involved in efforts to reduce greenhouse gas emissions from ships and promote sustainable maritime practices.

Through these roles, the IMO ensures that international shipping remains safe, secure, and environmentally responsible, contributing significantly to global trade and environmental stewardship.

How become a member of the IMO?

Becoming a member of the International Maritime Organization (IMO) is a process that involves several steps, typically initiated by a sovereign state. Here’s a general outline of how a country can become a member:

  1. Expression of Interest: A country expresses its interest in joining the IMO. This is usually done through diplomatic channels, such as the country’s foreign affairs ministry or its embassy in the United Kingdom (since the IMO is headquartered in London).
  2. Formal Application: The interested country submits a formal application to join the IMO. This application is typically directed to the IMO Secretary-General.
  3. Requirement Compliance: The applicant country needs to comply with certain requirements. These requirements usually involve agreeing to abide by the conventions and regulations established by the IMO. The country may need to demonstrate its ability and commitment to implementing and enforcing these regulations.
  4. Review by the IMO: The application and the country’s compliance with the requirements are reviewed by the IMO. This review process may involve assessments or discussions to clarify the country’s maritime capabilities and commitment to maritime safety, security, and environmental standards.
  5. Approval by the IMO Assembly: The final step involves the approval of the membership by the IMO Assembly, which is the highest governing body of the organization. The Assembly meets once every two years, and its approval is typically a formality once the applicant country has met all the necessary criteria.
  6. Accession to Key Conventions: Often, new members are also expected to accede to key IMO conventions, such as the International Convention for the Safety of Life at Sea (SOLAS) and the International Convention for the Prevention of Pollution from Ships (MARPOL).
  7. Official Membership: Once the above steps are completed and the IMO Assembly approves the application, the country becomes an official member of the IMO and is expected to participate in its activities and comply with its regulations.

It’s important to note that the specific details and requirements for membership may vary and can be subject to change. Countries interested in joining the IMO should engage directly with the organization for the most current and detailed information regarding the application process.


What is IMO for a Ship?

The International Maritime Organization (IMO) is crucial for ships and the shipping industry as it sets the global standards for safety, security, and environmental performance of international shipping. Here’s how the IMO impacts a ship and its operations:

  1. Safety Regulations: The IMO’s International Convention for the Safety of Life at Sea (SOLAS) is one of the most important international treaties concerning the safety of merchant ships. It sets minimum safety standards in the construction, equipment, and operation of ships.
  2. Environmental Protection: The International Convention for the Prevention of Pollution from Ships (MARPOL) is the main international convention covering the prevention of pollution of the marine environment by ships from operational or accidental causes. It includes regulations aimed at preventing and minimizing pollution from ships – both accidental pollution and that from routine operations.
  3. Security Measures: The International Ship and Port Facility Security (ISPS) Code is an amendment to the SOLAS Convention and prescribes responsibilities to governments, shipping companies, and port authorities to detect and deter threats to maritime security.
  4. Training and Certification Standards: The International Convention on Standards of Training, Certification, and Watchkeeping for Seafarers (STCW) sets qualification standards for masters, officers, and watch personnel on seagoing merchant ships.
  5. Load Lines Convention: The International Convention on Load Lines establishes the maximum depth to which a ship can be loaded, depending on its size and type, to ensure its stability and safety.
  6. Tonnage Measurement: The International Convention on Tonnage Measurement of Ships ensures that a universal system is applied to the measurement of ship tonnage, which is used to calculate the fees for using ports and canals and other related matters.
  7. Operational Guidelines: The IMO also provides guidelines and frameworks for various operational aspects, including ship routing, the transport of dangerous goods, and maritime traffic management.
  8. Legal Framework: The IMO establishes a legal framework within which shipping operates, handling issues like liability and compensation, especially in cases of accidents involving ships.
  9. Ship Certification: Compliance with International Maritime Organization (IMO) standards often necessitates specific certifications for ships, such as the International Oil Pollution Prevention Certificate or the International Air Pollution Prevention Certificate, which are part of MARPOL.
  10. Climate Change and Emissions: The International Maritime Organization (IMO) also works on reducing greenhouse gas emissions from ships, with ongoing efforts to improve ship energy efficiency and support the transition to low-carbon maritime transport.

For a ship, the IMO represents a comprehensive set of standards and regulations that govern nearly every aspect of its design, construction, equipment, operation, and disposal. Compliance with International Maritime Organization (IMO) regulations is essential for ships not only for legal operation in international waters but also for ensuring safety, environmental protection, and maritime security.


Who gives IMO number to Ships?

The IMO Ship Identification Number System, managed by S&P Global Market Intelligence (formerly IHS Markit, Maritime and Trade, or Lloyd’s Register-Fairplay), is a vital tool for maritime safety and regulation. This unique number is assigned, without charge, to qualifying ships:

  1. Applicable Ships:
    • Ships of 100 gross tonnage and above.
    • Fishing ships with steel and non-steel hulls.
    • Passenger ships under 100 gross tonnage, high-speed passenger crafts, and mobile offshore drilling units on international voyages (as per SOLAS regulation V/19-1).
    • Motorized inboard fishing ships under 100 gross tonnage, down to 12 meters in length overall (LOA), authorized to operate outside national waters.
  2. Exclusions:
    • Ships without mechanical propulsion.
    • Pleasure yachts.
    • Special service ships (like lightships, floating radio stations, search and rescue ships).
    • Hopper barges and floating docks.
    • Warships and troop ships.
    • Wooden ships (except for fishing ships).
  3. Authority and Administration:
    • S&P Global Market Intelligence exclusively identifies and assigns IMO numbers.
    • It validates and issues IMO numbers through fleet data exchanges with maritime administrations.
  4. Extended Use:
    • Some entities mandate IMO Ship Identification Numbers beyond SOLAS regulation X-1/3 requirements, such as certain regional fisheries management organizations (RFMOs).
  5. Collaboration with FAO:
    • The IMO works with the Food and Agriculture Organization (FAO) on the Global Record of Fishing Ships, Refrigerated Transport Ships, and Supply Ships. The IMO Ship Identification Number is essential for the first phase of this Global Record.
  6. Support in Maritime Issues:
    • The system aids in investigating seafarer abandonment cases and fraudulent ship registrations by helping identify the ships involved.

This number system plays a crucial role in enhancing maritime safety, regulatory compliance, and the tracking of global maritime activities.


The IMO (International Maritime Organization) number is a unique identifier for ships, registered ship owners, and management companies. Here’s how the process works:

  1. Application: When a new ship is built, the shipbuilder typically applies for an IMO number for the ship. This can also be done by the shipowner or manager.
  2. Assignment: IHS Markit, upon receiving the application, assigns a unique seven-digit number to the ship. This number stays with the ship throughout its lifetime, regardless of any changes in the ship’s name, ownership, or flag.
  3. Registration: The IMO number is then registered in a database maintained by IHS Markit. This database is accessible and used by various maritime authorities, ship owners, and operators.
  4. Display: Once assigned, the IMO number must be displayed on the ship’s hull and on its safety certificates. This requirement enhances maritime safety and pollution prevention and facilitates the response in case of an emergency.
  5. Permanent Identifier: The IMO number remains linked to the hull of a ship for its entire lifespan, regardless of any changes in the ship’s name, owner, or country of registration. This ensures that the ship’s history can be easily traced, which is important for safety, regulatory compliance, and tracking purposes.

The use of the IMO number system is mandated under the International Convention for the Safety of Life at Sea (SOLAS) and is a key tool in improving maritime safety and security.


Can two Ships have same IMO number?

Two ships cannot have the same IMO number. The International Maritime Organization (IMO) number is a unique identifier assigned to seagoing ships and is designed to be a permanent part of the ship’s identity throughout its life. Here’s why the uniqueness of the IMO number is important:

  1. Unique Identification: Each IMO number consists of seven digits and is assigned by IHS Markit (authorized by the IMO) to each ship upon construction. This number remains with the ship throughout its existence, regardless of changes in the ship’s name, ownership, or flag.
  2. Tracking and Monitoring: The uniqueness of the IMO number allows for efficient tracking and monitoring of a ship’s history and compliance with international regulations. It’s essential for maritime safety, security, and environmental protection.
  3. Regulatory Compliance: The IMO number system is used globally by governments, ship owners, and international organizations to monitor and enforce safety and pollution prevention standards. Duplicate numbers would undermine these efforts.
  4. Record Keeping: The IMO number helps in maintaining accurate records for ships, including their construction, ownership, and management history, as well as their compliance with international conventions.
  5. International Conventions: The IMO number system is mandated by various international conventions, such as the Safety of Life at Sea (SOLAS) Convention, which require ships to have a unique identifier for safety and regulatory purposes.

IMO number system is designed to ensure that each seagoing ship can be uniquely and reliably identified, which is crucial for safety, security, and regulatory purposes in the maritime industry.


What is the purpose of IMO number?

The purpose of the IMO (International Maritime Organization) number is to provide a unique and permanent identifier for a ship, enhancing maritime safety, security, and environmental protection. Key aspects of its purpose include:

  1. Unique Identification: The IMO number is a unique seven-digit number assigned to seagoing merchant ships. This unique identifier helps in distinguishing one ship from another.
  2. Consistency Throughout Ship’s Life: The IMO number remains with a ship throughout its life, irrespective of any changes in the ship’s name, ownership, or flag. This consistency allows for the tracking of a ship’s history and particulars over time.
  3. Safety and Security: The IMO number aids in the effective monitoring and regulation of ships, enhancing safety and security in international shipping. It’s especially useful in search and rescue operations and in investigating maritime incidents.
  4. Regulatory Compliance: The number helps in enforcing international maritime conventions and regulations. It allows authorities to ensure that ships are meeting safety, security, and environmental standards set by the IMO.
  5. Pollution Prevention and Control: The IMO number is crucial in tracking and monitoring ships for compliance with environmental regulations, such as those concerning pollution prevention.
  6. Facilitates Data Sharing: The IMO number system allows for efficient sharing of ship data among governments, shipping companies, and international organizations, facilitating various administrative and operational processes in the maritime sector.
  7. Combat Illegal Activities: By providing a permanent identifier for ships, the IMO number is instrumental in combating illegal activities at sea, such as illegal fishing, piracy, and smuggling, by making it harder for ships to evade detection by changing identity.
  8. Maritime Research and Statistics: For researchers and analysts, the IMO number is a valuable tool for gathering data on global shipping trends, fleet statistics, and maritime safety records.

IMO number serves as a critical tool in the global effort to maintain and improve safety, security, and environmental stewardship in international maritime operations


What is the Difference Between IMO and MMSI?

The growth in worldwide commerce has led to a surge in maritime shipping activity. This bustling activity presents several challenges, including security concerns, communication difficulties, tracking of the fleet and cargo, and efficient coordination of port operations. Consequently, implementing identification systems, like the IMO number and the MMSI number, is crucial. Understanding the functions and distinctions between these two types of numbers is key.

How are the IMO and MMSI numbers utilized by ships in their operations?


What is the IMO number?

The IMO number is a unique identifier assigned to each ship for identification purposes. It consists of the letters “IMO” followed by a seven-digit number, such as IMO9619907 for the Maersk Mc-Kinney Moller.

This number is permanent and remains unchanged throughout a ship’s lifespan, regardless of changes in ownership, registration country, name, or flag. It is distinct and not to be confused with the official number issued by the ship’s flag administration, which is for internal use only.

The IMO number is required to be displayed on the ship’s certificates, including the classification and tonnage certificates, which are necessary for navigating through the Suez and Panama canals.

Mandatory for all propelled seagoing ships of 100 gross tonnage (GT) and above, the scheme applies to cargo ships, fishing ships (since 2013), refrigerated cargo ships, supply ships of 12 meters in length or above, and passenger ships, including smaller and non-steel hull ships (since 2016).

However, certain types of ships are exempt from needing an IMO number, including floating docks, hydrofoils, pleasure crafts, non-motorized ships, special service ships like hopper barges and lightships, self-unloading barges, warships, troopships, and all wooden ships.

Introduced on November 19, 1987, via the IMO Assembly resolution A.600 (15), the IMO number scheme aims to enhance maritime safety, reduce pollution, and prevent maritime fraud.

The IHS Markit, Maritime, and Trade (IHSM) is the exclusive authority for issuing and assigning IMO numbers. This service, provided free of charge, is usually carried out at the time of a ship’s construction or during the issuance of new certificates. Under SOLAS (Safety of Life at Sea) regulations, possessing an IMO number is essential for sailing and trading ships.


What is the MMSI number?

The Maritime Mobile Service Identity (MMSI) is a nine-digit number utilized in marine traffic monitoring systems to recognize a ship. It comprises a three-digit Maritime Identification Digits (MID) representing the ship’s nationality, followed by a six-digit unique identifier, formatted as MIDXXXXXX.

The International Telecommunications Union (ITU) oversees the global rules for MMSI number assignment, which is handled by the competent authorities in the ship’s country of registration.

A key difference between the MMSI and IMO numbers is the MMSI’s potential for change. The MMSI number of a ship may be altered, for instance, if the ship changes its flag due to sale or long-term chartering, since each country has its own MID. Consequently, a single ship can have multiple MMSI numbers throughout its service life. On maritime tracking platforms, it’s common to see one consistent IMO number for a ship associated with several MMSI numbers. This variability is why the MMSI is not primarily used for ship identification.

In the United States, the Federal Communications Commission (FCC) issues MMSI numbers to both recreational and commercial ships equipped with licensed VHF radio gear. Additionally, the FCC, in conjunction with the Coast Guard, maintains a database of MMSI numbers, offering detailed information on each merchant ship, such as ownership and home port, typically gathered during radio station license applications or amendments. For non-commercial ships operating solely in U.S. waters, an MMSI number can be obtained for VHF DSC radio or AIS transponder usage without the need for a Ship Station License.


What are the respective purposes of IMO and MMSI numbers?

The IMO (International Maritime Organization) number and the MMSI (Maritime Mobile Service Identity) number are two distinct identifiers used in the maritime industry, each serving a specific purpose:

  1. IMO Number:
    • Purpose: The IMO number is a unique identifier for ships, assigned under the International Convention for the Safety of Life at Sea (SOLAS). It is primarily used for safety and regulatory purposes.
    • Assignment: Assigned to each ship upon construction by IHS Markit (authorized by the IMO).
    • Uniqueness and Permanence: The IMO number remains with the ship throughout its life, regardless of changes in name, ownership, or flag.
    • Use: It is used for tracking and monitoring ships for safety compliance, maritime security, and pollution prevention. It’s particularly important for port state control, regulatory enforcement, and maritime safety administration.
    • Display: The number must be displayed on all ships’ hulls and on their safety certificates.
  2. MMSI Number:
    • Purpose: The MMSI is used for radio communications and identification, particularly in the use of digital selective calling (DSC), automatic identification systems (AIS), and other onboard electronic communication equipment.
    • Assignment: Issued by national maritime authorities or designated bodies to ships, as well as to coast stations and individual handheld VHF radios.
    • Uniqueness: Each MMSI is unique to a specific radio or a ship’s communication equipment, and unlike the IMO number, it can change if the ship’s communication equipment changes or if the ship is re-registered under a different country.
    • Use: Primarily used in the Global Maritime Distress and Safety System (GMDSS) for identification in radio communications. It enhances the efficiency and effectiveness of maritime communications, especially in distress situations.
    • Format: The MMSI number is typically a nine-digit code, with the first few digits representing the country code or a specific type of service.

While the IMO number is focused on ship identification for regulatory, safety, and security purposes, the MMSI number is centered on enhancing communication and safety at sea, particularly for distress and safety communication. Both numbers are essential in the global maritime industry for ensuring efficient, safe, and compliant operations.


What is the IMO number used for?

The IMO number is widely acknowledged as the foremost Unique Ship Identifier (UVI) system, recognized by the majority of governments. It is associated with the major part of the ship’s hull that encloses the machinery space. As per the SOLAS regulation XI 1/3, adopted in 1994, this identification number must be permanently and conspicuously marked in a visible area, typically on the ship’s hull or superstructure. Additionally, on passenger ships, it is required to be marked on a horizontal surface visible from the air.

The IMO number serves several vital functions in maritime operations:

  • Assists national authorities in effectively managing ships under their flags and monitoring their territorial waters.
  • Enhances the clarity and reliability of legal records.
  • Improves the efficiency of monitoring, surveillance, and overall operational performance.

On maritime tracking websites, users can conveniently input a ship’s IMO number and click the SEARCH button to access its current or last known location, displayed on an interactive map. This feature underscores the importance of the IMO number in global maritime activities.


What is the MMSI number used for?

Similar to how a cell phone number uniquely identifies a mobile device, the MMSI (Maritime Mobile Service Identity) number serves as a distinctive, internationally standardized identifier for communication and security purposes on ships. It must be programmed into all VHF devices onboard and updated as needed:

  • DSC (Digital Selective Calling) Radio: Used for communication.
  • Automatic Identification System (AIS): For tracking purposes, as the MMSI number is displayed on radar, chart plotters, or electronic chart display information systems (ECDIS).
  • Emergency Position Indicating Radio Beacon (EPIRB): Utilizes the contact information from the MMSI registration in case of emergencies.
  • Man Over Board (AIS MOB) Devices: For immediate alert and location tracking in man-overboard situations.

The ship’s AIS transponder automatically broadcasts its MMSI number and position report every 30 seconds. These signals are detectable by Ship Traffic Services (VTS), the carrier or operator’s shore station agency, the Coast Guard, and other ships equipped with AIS.

All ships traversing international waters require an MMSI number to participate in the IMO’s Global Maritime Distress and Safety System (GMDSS). The GMDSS is an internationally agreed-upon system of coordinated VHF radio communications for merchant ships. It leverages both satellite and terrestrial networks to facilitate continuous and coordinated communication among ships or between ships and shore operators. The system also provides essential alerting means for use in emergencies.