By USA law, in almost all circumstances, you have to pay taxes on any money you make regardless of how you make it. On your taxes you can file it as "other income - gambling winnings" or schedule C business if you think you quality as a "professional gambler". You can arguably save a lot of taxes by filing as pro, but there are some stipulations that you would have to make sure you fit into.
When you file as "gambling winnings", you have to itemize all of your winnings and this net revenue determines your tax bracket. Then you pay this percentage on your gross profit.
When you file as "professional gambler", your tax bracket is determined by your gross profit, not your net revenue.
So this can drastically reduce your tax bracket.
For instance,
if you have $480,000 in tournament buyins, with $500,000 in cashes, your gross profit is $20,000 and your net revenue is $500,000.
When filing "gambling winnings", you would be in highest tax bracket (I think it's 39.5% now).
So you would pay 39.5% of $20,000.
If you file as professional gambler, you would be in a tax bracket $20,000. Which is probably about 10% or 15%, so you would pay 10% of $20,000.
I have filed "professional gambler" and "gambling winnings" in multiple years and I think what I stated was accurate by my accountants, but:
I'm not a CPA or qualified professional, consult your accountant to determine what is lawfully accurate for yourself.