The IRS does not really know much of that at all unless you receive money through a source that files a 1099 or 1099k. They can certainly find out a lot of stuf

The IRS does not really know much of that at all unless you receive money through a source that files a 1099 or 1099k. They can certainly find out a lot of stuff through an audit. But they don't know that someone wrote you a check for $30k to pay you for your side gig unless the payor files a 1099 for the payment.