You must keep an accurate diary or similar record of your losses and winnings.

Your diary should contain at least the following information.

• The date and type of your specific wager or wagering activity.
• The name and address or location of the gambling establishment.
• The names of other persons present with you at the gambling establishment.
• The amount(s) you won or lost.

In addition to your diary, you should also have other documentation. You can generally prove your winnings and losses through Form W-2G, Certain Gambling Winnings; Form 5754, Statement by Person(s) Receiving Gambling Winnings; wagering tickets; canceled checks; substitute checks; credit records; bank withdrawals; and statements of actual winnings or payment slips provided to you by the gambling establishment.

This information is found in Publication 529, Miscellaneous Deductions.