In accordance with extant norms, OBC Certificate is to be obtained from the authority where the person is ordinarily resident, the term ordinarily resident having the same meaning as in the Representation of Peoples Act, 1950 -
Section 20 in The Representation of the People Act, 1950
20. Meaning of “ordinarily resident”.—
(1) A person shall not be deemed to be ordinarily resident in a constituency on the ground only that he owns, or is in possession of, a dwelling house therein.
(1A) A person absenting himself temporarily from his place of ordinary residence shall not by reason thereof cease to be ordinarily resident therein.
(1B) A member of Parliament or of the Legislature of a State shall not during the term of his office cease to be ordinarily resident in the constituency in the electoral roll of which he is registered as an elector at the time of his election as such member, by reason of his absence from that constituency in connection with his duties as such member.]
(2) A person who is a patient in any establishment maintained wholly or mainly for the reception and treatment of persons suffering from mental illness or mental defectiveness, or who is detained in prison or other legal custody at any place, shall not by reason thereof be deemed to be ordinarily resident therein. 2[(3) Any person having a service qualification shall be deemed to be ordinarily resident on any date in the constituency in which, but for his having such service qualification, he would have been ordinarily resident on that date.]
(4) Any person holding any office in India declared by the President in consultation with the Election Commission to be an office to which the provisions of this sub-section apply, shall be deemed to be ordinarily resident on any date in the constituency in which, but for the holding of any such office, he would have been ordinarily resident on that date.
(5) The statement of any such person as is referred to in sub-section (3) or sub-section (4) made in the prescribed form and verified in the prescribed manner, that 8[but for his having the service qualification] or but for his holding any such office as is referred to in sub-section (4) he would have been ordinarily resident in a specified place on any date, shall, in the absence of evidence to the contrary, be 8[accepted as correct].
(6) The wife of any such person as is referred to in sub-section (3) or sub-section (4) shall if she be ordinarily residing with such person be deemed to be ordinarily resident on in the constituency specified by such person under sub-section (5).
(7) If in any case a question arises as to where a person is ordinarily resident at any relevant time, the question shall be determined with reference to all the facts of the case and to such rules as may be made in this behalf by the Central Government in consultation with the Election Commission.]
(8) In sub-sections (3) and (5) “service qualification” means—
(a) being a member of the armed forces of the Union; or
(b) being a member of a force to which the provisions of the Army Act, 1950 (46 of 1950), have been made applicable whether with or without modifications; or
(c) being a member of an armed police force of a State, who is serving outside that State; or
(d) being a person who is employed under the Government of India, in a post outside India.
In light of the facts and circumstances, in my considered opinion, you cannot be considered as an 'ordinary resident' of Bihar, and ineligble to seek OBC Certificate from the comepetent authority in that State.