Regarding noc for tax audit


(Guest)

A query regarding tax audit:
A CA is appointed as tax auditor of a proprietorship concern. The letter for communication with previous auditor and for objection is sent by registered post acknowledgement due. The incoming auditor got the receipt of acknowledgement from postal dept. but no communication from previous auditor is received in writing.
My query: within how much time the incoming auditor can start work on tax audit i.e. for how many days should the auditor wait after receiving the receipt from post dept.