Tax questions

[gooseisloose08]

Not sure if this is the right place for this...

Are taxes required to be paid on earnings or cashouts in a given year? For example if this year I win $20,000 and cashout $10,000 and keep the other $10,000 online for building my br, can I only pay taxes on the 10k cashed or do I have to pay on the 20k total? Also if this year's winnings are used to pay off previous year's gambling debts, can any type of write-off be made there. Thanks for any insight in advance.