Don't know if its changed, but this is part of  a letter I gave to my clients who gambled.

Rule 1: Your winnings are taxable. Your gambling income is taxable. And—just as important—it’s reportable.

For example, when you win $1,200 or more from a slot machine, the casino must report your winnings on Form W-2G and send a copy to you and the government. With this tool, the government knows when you don’t report enough gambling income on your tax return.

Rule 2: Keep records of your losses. You can offset your gambling winnings with your gambling losses—but you have to keep good proof of those losses. The IRS and courts expect you to maintain a “contemporaneous gambling diary.”

You face specific rules for a gambling diary depending on the type of gambling. For example, with slot machines, the IRS advises that you record the machine number, date, and time played to support your winnings. Often, you can find the machine number clearly displayed on the machine. If not, simply ask the casino operator for the machine number. (A good player card will automatically do this for you.)