Special audit and inventory valuation may be directed where complex accounts require deeper scrutiny in the interest of revenue. Special audit or inventory valuation may be directed by the Assessing Officer where the nature or complexity of accounts, volume of accounts, doubts about correctness, multiplicity of transactions, or specialized business activity make such examination necessary in the interest of revenue. The direction requires prior approval of the specified higher authority and an opportunity of being heard. The audit or valuation report must be furnished within the period specified by the Assessing Officer, subject to a maximum limit of 180 days, and may relate to a particular segment of the accounts.