Trade Union must receive official notices at its registered head office and notify the Registrar of membership or registration changes. Registered trade unions must receive all communications at the head-office address entered in the Registrar's register, sent in the prescribed manner. Unions must notify the Registrar if membership falls below ten per cent of total workers or one hundred workers, whichever is less, and must inform the Registrar of any change to registration particulars or to their constitution or rules in the prescribed manner.