Firstly only a COP holding C.A. may tax audit. And able to be a director of the company but then he cann't appoint for an auditor of the company as per sec 226.
The disqualification as per sec 226 is -
1. A body corporate
2. An officer or employee of the company
3. A person who is a partner of an officer or employee of the company
4. a person who is an employee of any officer or employee of the company
and A person holding any security of the company. security means any instrument, which carries voting rights.
and many more disqualification are available in sec 226