Attention, Signers for Slot Winnings over $1,200

[Aslan]

-Generally, taxpayers required to keep records to substantiate deduction: Treasury Regulation § 1.6001–1

-Mayer v. Commissioner (2002): Unsigned statement on casino letterhead was insufficient to prove taxpayer's claimed gambling losses; statement contained no explanation of certain important terms and expressly claimed to be only an estimate

-Norgaard v. Comissioner (1991): Gambler using "bankroll method" and who presented a bunch of betting tickets to substantiate loss had his deduction overturned.

-Stein v. Commissioner (1963): "Win/loss" scribbled on napkins at the end of each day and then entered into a notebook was not reliable evidence to uphold loss deduction

I get your meaning, Moo, but there is no tax "deduction" for gambling losses in the ordinary tax sense, but only in the sense of an "offset" to gambling winnings. There is no tax deduction for gambling losses alone. There are, however, allowable deductions for other kinds of losses, such as, casualty, disaster, theft, and business losses.