Does the Ship Identification Number required by SOLAS XI-1/3 require the prefix “IMO” or is just the seven figure number acceptable?

The ship identification number must include the prefix “IMO”. That is, the number should be in the form “IMO 1234567” and not just “1234567”. This was decided by IMO at MSC 77 in June 2003. The reasoning lies in IMO Assembly Resolution A.600(15) which covered the adoption of Ship Identification Numbers by IMO. The number “1234567” is legally a “Lloyd’s Register Number”, while “IMO 1234567” is the Ship Identification Number as adopted by IMO.