There is no need for the IRS to do any investigation. Brokerage houses report all trades on a 1099, and after 2011 that includes the cost basis as well. If you ‘forget’, a computer will send you an automated bill.
“There is no need for the IRS to do any investigation”
My spider senses tell me, if the IRS heard about a guy making 77 million, they would probably have someone ‘take a quick peek’ at the guys file.