I am astonished that you didn't check this out before you went though. If the US taxman can get Al Capone, they'll get you. 'I'll probably be OK' seems a rather naive position to take.
Fuck me. Calm down mate.

Jumping to conclusions seems a rather naive position to take. To put you straight I have lived in the US for almost 7 years. I came here as a maths teacher not a poker pro, but have worked in finance for the past 4 years or so.
If only I could judge the tone of posts as well as Red-Dog I wouldn't get into these situations.

You're right - I started off giving an answer to your post, then wandered down a road where I had forgotten what you'd actually written, and had started answering the post that I've seen people post a million times on other poker forums about US tax law on gambling income. Sorry about that.
By the way surely the IRS would find Al Capone a bigger target on their radar than one of several million anonymous online poker players!
Currently, there are quite a few pro internet poker players in US who wish that the US Governement
would find a bigger target to pick on instead of legislating their jobs away.