(b)an authorisation, [* * *] [Omitted 'approval or certificate of competency' by Notification No. G.S.R. 832(E), dated 30.6.2017 (w.e.f. 23.3.1937).] shall remain valid for a period specified therein, subject to a maximum period of one year in each case, and may be renewed for another one year at a time on receipt of application for renewal, provided the applicant has engaged himself in the performance of the tasks for a period of three months in the preceding one year.