It depends a lot on what you mean by "the secret cottage industry I have crafted to hide play funds." If you're talking about an off-the-books business that generates cash that you don't tell your family about and don't report on your tax return, yeah, that is exactly the type of thing the IRS would want to know about. [*] In fact, the single largest component of the so-called "tax gap" -- the difference between what the IRS should received under the tax law as written and what they actually receive -- is almost certainly not agressive tax planning, fancy offshore tax shelters, multi-national corporations with hordes of expensive tax lawyers, or "the filthy rich." It's small, Mom-and-Pop cash-based businesses that just take some of that cash under the table and never report it. Yep, those are the most typical "tax cheats."That is exactly the answer I was looking for my situation--thank you.
The IRS would like to catch those folks, but it's not at all easy. The overall effort required versus likely return is not cost-efficient. The individual taxpayer like that is avoiding taxes, but not a huge amount; they account for a large portion of the tax gap only because there are so damned many of them compared to, say, the number of multi-national corporations with assets of $1 billion or more.
If you are selected for an audit, the IRS often just asks for substantiation of your deductions and then checks your income to, e.g., information returns from your employers, brokers, banks, etc. as to how much income you earned. If you run a business, they'll likely ask to review the business' accounting records. Definitely if you run a business, and maybe even if you purport to be a wage-earner only, they can and will get bank statements, brokerage account statements, etc. (possibly credit card statements as well, not to mention Ebay or PayPal) looking for deposits and making sure that all of them are "accounted for." If you have deposits of $150,000 shown in your bank accounts but report income of only $120,000, they'll require you to explain where the other $30,000 came from and they'll want documentation. Saying it was a gift or loan from family members won't be enough. Essentially, they start with the presumption that any accretion to wealth (e.g., deposit to your bank account) = income and you'll have to prove it isn't. So, if your bank statements include unreported income, you'll wind up having to pay tax (and penalties and interest) on it. And the audit result itself will raise the visibility and may lead to questions from SO and family.
If you are audited, whether they're likely to turn something up which would be a surprise to your SO or family depends a lot on the specific details of that "cottage industry." Trading on eBay? Easy to find. Day-trading? Easy to find. Under the table sales from a business you report on Schedule C (or a separate corporation)? If they become suspicious, easy to find. Asking for extra money back on a credit card purchase, for something that you don't deduct? Unlikely they'll even look or care. Withdrawals from the ATM that you don't mention to your SO? Unlikely they'll even look or care -- it's deposits into your bank accounts, rather than withdrawals, that they're concerned about.
[*] If you are reporting that income on your tax return, but your SO isn't aware of it, the audit could create a problem. If you tell the IRS "I earned $30,000 from trading on eBay, for which there was no information return, but here is where I reported it on the return" . . . the IRS is happy. But if your SO wasn't aware you were doing that, and asks what happened to the money you earned, you still have a problem. Originally Posted by Chevalier