New Delhi: The goods and services tax (GST) evasion investigation agency will complete its probe into 30 insurance companies by November. The Directorate General of GST Intelligence (DGGI) has already completed the investigation into 15 of them, detecting input tax credit discrepancies to the tune of `3,500 crore so far. It is in the process of sending notices to the remaining 15, people aware of the details told ET.