As per sec 44AA engineering and technical consultancy are considered as profession and as per sec 44AB tax audit is required if turnover exceeds 15 lakhs in case of profession
CIT Vs. Manmohan Das (Deceased) [1966] 59 ITR 699 (SC).
The expression "profession" involves the idea of an occupation requiring purely intellectual skill or manual skill controlled by the intellectual skill of the operator, as distinguished from an operation which is substantially the production or sale or arrangement for the production or sale, of commodities.
Therefore in my opinion tax audit is required