Occupation= (1) a person’s occupation, work, or trade: ‘She is thinking to change his occupation and become a writer.’ (2) the state of being held or possessed: ‘The office is ready for occupation.’ ‘Occupation of a building without a certificate of occupancy is illegal.’
Job = a specific piece of work required to be done as a duty or for a specific fee: ‘It used to be difficult for women to get good jobs.’ ‘The important thing is to be happy in your job.’
Occupation and Job have similar meaning but occupation is mainly used in formal and official styles.