I'm going to disagree with TaxGuyBill here, maybe more on philosophical grounds as opposed to "practical" grounds, an area I'm sure where he has more experience than I do.
Your obligation as a taxpayer is to report the "correct" amount of income based on your accounting records and based on your accepted accounting method. If you do report the proper, supportable amount of income based on your excellent records and based on your accounting method, then you are completely bullet-proof. There is absolutely nothing that the IRS can, (legally), do to you. (The fact that the IRS often acts in an illegal capacity perhaps should temper that advice.)
But I hope the US population is so not so cowed, not so beaten down and fearful of their government that they feel the need to overstate their income and overstate their deductions to conform their reporting to little pieces of paper that might very well be wrong, in the hope that the black-uniformed IRS police won't break down their door in the middle of the night, spirit them away to a prison in a 3rd-world and water-board them into submission.
As a practical matter the IRS has only a very vague picture of what your income "should be." They know that not all income is reported on 1099-MISC's, even income that should be, they know that 1099-MISC's are prone to error, they know that different accounting methods produce different results. And they don't know - at all - any detail of 1099-MISC's that you might enter in TurboTax because that's simply not part of the income tax return you submit.
I'm sure that as a practical matter that if the IRS's receives 1099-MICS's that amount to "X" times whatever you are reporting as revenue - and I have no idea what "X" is - then your chances of receiving a inquiry about the difference goes up. But I would bet that if "X" is a fraction - 1.25x say - something like that doesn't send up red flags. Even the IRS has a concept of "materiality" in selecting what income tax returns they are going to follow up on. But I still wouldn't advocate doing anything other than reporting the correct amount of income and being prepared to defend it.
