According to latest edition of the ICSE Regulations page 11, section 6(ii) a, b & c . No subsequent change in the name/s or date of birth will be permitted, except, if:
A) the Head of the candidate’s School certifies with due justification that he/she made a mistake in entering the Name/s/Date of Birth in the online Registration Form or that after satisfying himself/herself of the need to do so he/she has changed the School records based on a Birth Certificate or any other document issued by a competent authority duly authorised to do so.
B) The onus of responsibility in certifying the necessary changes/corrections lies with the Head of the School who shall be held liable in case of any legal dispute arising in future.
C) If for any reason compliance is not possible by the School as per clause 7 (a), then in order to establish the veracity of the request, the candidate is required to produce a declaratory Court order from a Court of competent jurisdiction recording his or her correct name/date of birth. In the event of the court allowing change/correction of name/date of birth, the same shall be carried out by the Council after obtaining a certified copy of the Court order and other relevant documents from the School/candidates.
There is no other format or steps except this.