Most of these companies have been used to launder unaccounted money after the note ban and some of them do not even possess a PAN (permanent account number), according to government sources.
Directors of 15,000 shell companies are also directors of 15,685 companies, all from Kolkata, sources said.
Over the last two weeks, the I-T department has started verification of suspicious transactions post-demonetisation through intensive door-to-door search operations, and Kolkata