It is difficult to remove an auditor before expiry of his term since adequate grounds must exist to prove that the auditor is unsuitable for continuing as an auditor.
The auditor appointed under section 139 may be removed from his office before the expiry of his term ●only by a special resolution ●after obtaining the previous approval of the CG ●by making an application in Form ADT-2
Thus, such stringent provisions provides that auditor cannot be removed at will by management or shareholders. Such provisions ensure independence of auditors.
Tenure of auditor is till the conclusion of upcoming AGM (in case of casual vacancy).