The house has a number, which is assigned by authorities. The owner may sell the house & the new owner can change the name, but the number is permanent. The same scenario is found in shipping as well.

The Ship has a name. It can be changed. The ship has the flag. The flag can change if the port of registry is changed. The IMO number of the ship is permanent & it cannot be changed. This prevents maritime fraud activities.

In the early time, ships were only provided with official number, which was issued by the Flag state. This will change if the ship’s flag is changed. Now it is replaced with the IMO number. This scheme was introduced in 1987. The ideas behind this scheme were to enhance maritime safety, pollution prevention & to facilitate prevention of maritime fraud. The IMO number is inserted in ship’s certificates.

The passenger vessels of 100 GRT & upwards, all cargo ships 300 GRT & upwards must have an IMO number. It is mandatory for all ships as of 1st January 1996. In 2005 IMO adopted a new SOLAS regulation, which makes the company & registered owners to have IMO numbers as well.

Who issues the IMO number? IHS Fairplay is the sole authority to assign & identify IMO number. The IHS Fair play is combined of three major business partners. They are Lloyds Register, Fairplay & IHS.

The IMO number consists of three letters IMO, followed by seven digits. The final digit is known as the Check digit.

For example the vessel M/T OMEGA QUEEN’s IMO number is IMO 9283679.




9 X 7 = 63

2 X 6 = 12

8 X 5 = 40

3 X 4 = 12

6 X 3 = 18

7 X 2 = 14

9 X 1 = 9 (Check digit)

Now add 63 + 12 + 40 + 12 + 18 + 14 = 159. The final digit of the sum & check digit have to match. The above IMO number is a true number.

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