First of all, you're seeking tax advice on a sports message board, you'll get what you get lol
I'm not sure why you're focused on an "arbitrage" scenario. I feel I'm fairly active in sports betting and rarely if ever see a scenario like that.
Here's how I think about it, but I'll note that I'm a very small potatoes better so I don't exceed $600 in winnings. I also don't itemize so I don't track or deduct my losses.
You place a $1000 bet on Tampa Bay to win, at +100. Tampa Bay wins! Your net winnings are $1000. You have $2000 in your sportsbook account.
You bet $2000 on Iowa State to beat Kansas at +300. Dumb bet, ISU gets smoked. You have $0 in your sportsbook account.
2021 tax time. You'll get a 1099-MISC showing winnings of $1000. You'll owe income taxes on that $1000.
If you itemize your deductions, you could claim a loss of $1000 (you can deduct up to amount of winnings).
Not being a d!ck but this also isn't that hard to google...
Every year, I join a fantasy football league with my friends and every year, I lose. So for me, unfortunately, my limited sports gambling has no impact on my taxes. But if you frequently place bets on sporting events, and find yourself winning, it may have an impact on your taxes. With the US...
blog.turbotax.intuit.com