Technical expert evidence: obtain and disclose expert opinion before framing assessments in complex, high revenue tax cases. Assessing Officers must obtain and record formal technical expert opinions and technical evidence in assessments involving complex technical issues and substantial revenue, identifying such cases early and initiating proceedings before limitation. CCIT/DGIT shall monitor complexities and assist in securing timely expert opinions; evidence must be provided to the assessee with a reasonable opportunity before assessment. After referral, Board must be informed via Member (IT) with case particulars, expert details and tax effect.