Attention, Signers for Slot Winnings over $1,200

[Aslan]

Excel is fine. A lot of these regs/cases were before spreadsheets became popular.

And even with a journal, it may or may not be held sufficient depending on other evidence, such as receipts, bank statements, etc. The IRS is pretty much in the driver's seat on gambling winnings. A journal is only your word on it if not backed by other evidence, as a person might deliberately fudge his journal to produce losses (similar to the practice of rat-holing to keep the casino from knowing what you won or lost). If I were a bigtime gambler, I would certainly be aware of what I put in and took out of my bank accounts, as this may come into play to substantiate that real losses did actually occur. Again, IRS is in the driver's seat unless you have incontrovertible evidence, and I don't know what that would be. As a practical matter, I believe they usually accept a well kept journal, lack of proof notwithstanding.

Dealing with IRS is never entirely predictable.