Section 126(12) in The Naval Ceremonial, Conditions Of Service And Miscellaneous Regulations, 1964
(12)Promotion to Lieutenant.(a)Depending on the marks obtained in the examination, Sub-Lieutenants shall serve a period of 1½ years to 2½ years in the rank of Sub-Lieutenant (including the period served as Acting Sub-Lieutenant) before promotion to the rank of Lieutenant.(b)No officer shall be promoted to the rank of Lieutenant unless he has obtained a certificate of competency on completion of sea training :-Provided that where the Chief of the Naval Staff is satisfied that any officer has been unable to obtain a certificate of competency owing to the exigencies of Service, such officer may be promoted to the rank of Acting Lieutenant on the due date, and confirmed in the rank of Lieutenant on obtaining the requisite certificate with seniority of date of promotion to Acting Lieutenant.
