Your bank, employer, cash app and brokerage all report to the IRS so unless you are a drug dealer or similar, yeah for the most part they already know it.

Heres the best bit, people working under the table are going to be making less than 100k generally so it doesn't really matter, anyone making real money will be making big enough waves in the financial system to be detected, small movements of cash doesn't matter at this scale. The highly taxed routes (capital gains) are also already highly policed for tax purposes so no transition is needed there.