How many ladies submit 1040's to report a stated income? (Asking for a friend... no, really! She is new to the business and new to the US.She has dreams of buying a house, and I told her she needs a good credit history to obtain a mortgage.)
If a high-earning, cash-only individual wants to buy a house or a car, or sign up for a credit card, she’ll need to report some income. To avoid the stiff IRS penalties, as well as the payment of unpaid taxes, that individual should file IRS Form 1040 Schedule C and pay (quarterly) self-employment tax in addition to ordinary income taxes.
The down-side, of course, is that you are paying 30% of your stated income to the IRS. The plus-side is that you are substantiating that you have an income, and can justify why you have so much money in the bank. The greatest benefit is that this annual loss of 30% protects you from the IRS. If they find that you have money, and don't pay taxes, their penalties for Tax Evasion are much worse than sex crime violations by the local authorities, and easier to prove. (Just ask Al Capone).
How does the IRS learn that you have un-taxed income? When you pay for a car in cash (over $10,000), the Dealer will file Form 8300. If you lease a vehicle where that 12-month payments are more than $10,000, again, the Dealer will file Form 8300 with the IRS. If you make a Bank deposit of more that $10,000, the Bank reports that to the IRS.
My on-line research says that many providers do, indeed, file taxes, to obtain loans and credit cards, and avoid evasion charges. I'm just curious what the real world experience is...