Into how much trouble could I get if I had an online website that earns me around $ 2k monthly and I don't declare any of that? Hell what if I didn't even had a business registered? Btw I don't live in the US but still.
I don't get why people on this board act like the IRS are harmless. They will eventually come after you if you owe them especially if OP is American and is picking up another income on top of that 2k monthly.
If you're an American OP you will be hearing from them eventually. Depending how much you have withheld you could be looking at serious trouble or just a slap on the wrist. If you aren't American I'd tell them to suck you off.