Section 11(2)(b) in The U.P. Recognised Basic Schools (Junior High Schools) (Recruitment And Conditions Of Service Of Teachers) Rules, 1978
(b)The appointment letter shall clearly specify the name of post, the pay scale and the nature of appointment, whether permanent or temporary, and shall also specify that if the candidate does not join within 15 days from the date of receipt of the appointment letter his appointment shall be cancelled.