Section 26A(2)(ii) in The Bihar Civil Service (Executive Branch) and the Bihar Junior Civil Service (Recruitment) Rules, 1951
(ii)The selection shall be made on the basis of merit to be assessed from the up-to-date service records with due regard for seniority, from amongst the officers of the Bihar Civil Service (Executive Branch) who have completed not less than 5 years of continuous service in the Bihar Civil Service (Executive Branch) on the 1st day of January of the year in which the list is prepared. The above period of service shall be reduced by one year in the case of officers belonging to Scheduled Castes and Scheduled Tribes, if adequate number of officers of those castes with prescribed minimum length of service are not available in the required proportion for the purposes of sub-rule (i):