Your state may still require you to file a 'corporate' return for your LLC. In my state you wouldn't pay anything if your receipts were under some level, maybe $100K. But if you didn't know you were supposed to file, they'll come looking for you after a few years.
How your membership is organized in an LLC matters too. I assumed pass through, no revenue no taxes no filing, but apparently in my state a two member LLC is a partnership for tax purposes and requires filing.
Okay, I think I have been understanding LLC wrong this whole time. I thought they are the equivalent of SARL in France.