We have a massive black market now. We always will- it will just shift.
By the way, in the State of Florida, where we are funded 100% by sales tax, I can tell you confidently that the Dept. of Revenue is nothing like the IRS in terms of intrusiveness. Their tactic is to audit sales receipts, but that's nothing compared to the info needed to determine income.
Watch what happens as more people do business out of their homes.