Do I have to explain the source of *all* income on my taxes?
You can report it as illegal income and you don't have to elaborate any further.  For instance, spirit the cash off to a state where pot is legal and set up a dispensary.  That is not legal at the Federal level, so it is in fact "illegal income" vis-a-vis your Form 1040 and that's all you say. Make sure you look, walk, and quack like a fairly successful pot distributor. That will most likely be the end of their inquiry, since they're not terribly driven to investigate the income you do report.  Having to give 33% of it to the IRS is generally strong motivation for folks to not report fake income.  You're not claiming the money is from pot, you're allowing them to infer it.
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### Instruction:
Do I have to explain the source of *all* income on my taxes?

### Response:
You can report it as illegal income and you don't have to elaborate any further.  For instance, spirit the cash off to a state where pot is legal and set up a dispensary.  That is not legal at the Federal level, so it is in fact "illegal income" vis-a-vis your Form 1040 and that's all you say. Make sure you look, walk, and quack like a fairly successful pot distributor. That will most likely be the end of their inquiry, since they're not terribly driven to investigate the income you do report.  Having to give 33% of it to the IRS is generally strong motivation for folks to not report fake income.  You're not claiming the money is from pot, you're allowing them to infer it.