Filing of Form 23B is the responsibilty of the Statutory Auditor and not of the Company.
Further, as per section 224(1A), every company is required to give an intimation of appointment to the Statutory Auditor appointed at the AGM, within 7 days of the AGM.
Within 30 days from the date of receipt of intimation letter from the Company,the Auditor is required to initmate the Registrar in prescribed Form 23B that he has accepted the appointment in so and so Company.
Form 23B is to be filed by the Statutory Auditor irrespective of whether he is appointed as such in a Public Limited Company or a Private Limited Company.