Referring to ClassNK Technical Information No. TEC-0497 on the summary of ship identification number marking required by the amended SOLAS Regulation XI-1/3, given in section 3, please find details of the requirements hereunder.

1. The ship identification number to be marked
The number is the one given in the IMO Assembly Resolution A. 600 (15) and known as the "IMO Number". A reference is made to in the text of the SOLAS Regulation XI-1/3 in this regard. The number starts with the pre-fix "IMO" and is then followed by 7 digits, which are assigned to individual ships and printed on various statutory certificates. By this amendment to the SOLAS Convention, the number is now required to be marked on the hull of the ship. It must be noted that in marking the number on the hull, the prefix "IMO" must not be omitted. (E.g., "IMO8712345")

2. Ships to which this regulation applies
The same range as existing SOLAS Reg. XI/1/3 applies, the regulation applies to all passenger ships of 100 gross tonnage and upward and to all cargo ships of 300 gross tonnage and upwards. (Note: Cargo ship means ships which are not passenger ships.) It should be noted that the regulation applies to, in principle, ships engaged on international voyages.

3. How to mark the number
(1) Location
Outer side of the hull and inner side of the hull as given hereunder:
(I) One of the following positions (option 1 ? Option 5) on the outer side of the hull where the number is visible:
(a) if the number is marked on the hull, it must be located on:
option 1. The stern of the ship; or
option 2. Either side of the hull, amidships port and starboard, above the deepest assigned load line
(b) if the number is marked on the superstructure, it must be located on:
option 3. Either side of the structure, port and starboard, or
option 4. On the front of the superstructure
(c) in case of passenger ships, the following location can be acceptable:
option 5. On a horizontal surface visible from the air.
(To be continued)
(ii) In addition to the location in (I) above, at the one of following location ((a) ? (d)) where accessible:
(a) either on one of the end transverse bulkheads of the machinery spaces, as defined in regulation II-2/3.30; or
(b) on one of the hatchways, or
(c) in the case of tankers, in the pump-room or,
(d) in the case of ships with ro-ro spaces, as defined in regulation II-2/3.41, on one of the end transverse bulkhead of the ro-ro spaces
(2) Methods of marking
Methods of marking are regulated as follows:
(I) Colours etc.
The marking must be plainly visible, clear of any other marking on the hull and must be painted in a contrasting colour.
(ii) Size
For the marking on the outer side of the ship, it must not be less than 200mm in height. For marking on the inner side of the ship, it must not be less than 100mm in height. The width of the marks must be proportionate to the height.
(iii) Letter writing methods
(a) The permanent marking may be made by raised lettering or by cutting it in or by centre punching it or by any other equivalent methods of marking the ship identification which ensure that the marking is not easily expunged.
(b) On ships constructed of material other than steel or metal, the Administration must approve the methods of marking the ship identification number.

4. Date of implementation
For ships to be built on or after on 1 July 2004, at the time of construction, and for ships built prior to the date,