This works on every hand except the 1st hand. If you try it on your first hand, you'll lose $20k from your bank.
The game saves after every hand; If you're losing a hand you can quit to the dashboard and restart. You'll lose no money and be able to replay the hand.
I'm guessing this is how there were already people with $1 million+ on the leaderboards by 3pm the day it was released.