I'm going to have The Talk with my barber.  If I can get away for a haircut.  Here is how it goes. 

"I know you try to keep honest records of all your cash income, for tax preparation.  And you tell me you keep track of tips.  But are you sure of those numbers?  Now remember, if you write one down, you have to pay 15% SE tax on it.  And IRS says they won't give you the deduction that would save you 10% income tax.  So let's say you wrote down $2,000 in tips.  Not that I would doubt you, but IRS would.  Do you want to pay $300 in SE tax, and then another $200 of income tax?  After all, they have no way of knowing the real number unless they pay an auditor to analyze your spending habits.  What with salaries and overhead, that would cost IRS thousands of dollars, which they don't have.  So think about it.  Just make sure you give me the right numbers for that tip income."