To prove gambling losses on taxes, you need a contemporaneous diary of every gambling session backed by documents like W-2Gs, casino win/loss statements, losing tickets, and bank records, and you have to itemize on Schedule A to claim the deduction at all. Starting with tax year 2026, the deduction is limited to 90% of your losses and still cannot exceed your gambling winnings for the year.1Office of the Law Revision Counsel. 26 US Code 165 – Losses Records are what turn a claimed loss into a deductible one; without them, the IRS will disallow the deduction and tax you on every dollar of winnings.
What the IRS Wants to See
Two things, working together. First, a diary or log of your gambling activity kept as you go. Second, third-party documents that corroborate what the diary says.
The diary is the backbone. Revenue Procedure 77-29 sets out what each entry should contain, and the IRS still points to that framework today.2Internal Revenue Service. Notice 2015-21 A log written months later, in a rush before an audit, carries far less weight than one updated the same day. Tax courts have thrown out gambling deductions on exactly that basis. “Contemporaneous” is close to a magic word here.
Before any of this matters, check whether you’ll itemize. Gambling losses are an itemized deduction on Schedule A. If you take the standard deduction, you deduct nothing, but you still owe tax on every dollar of winnings.3Internal Revenue Service. Topic No. 419, Gambling Income and Losses For 2026 the standard deduction is $16,100 for single filers and $32,200 for joint filers.4Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Itemizing only pays off when your gambling losses plus your other itemizable expenses (mortgage interest, state and local taxes, charitable giving, and the rest) exceed that floor. Run the comparison before assuming the deduction will help.
What Goes in the Diary
Each session entry should include:
- The date and the type of gambling. “March 12 — blackjack” is the baseline. “Casino trip” is not.
- The name and address of the venue.
- The names of anyone with you who can corroborate your presence.
- The amounts won and lost in that specific session, not a monthly running total.
A spreadsheet or a notes app works fine. What matters is that the entries are specific and that they exist before you need them.
Supporting Documents by Game Type
The diary carries more weight when it lines up with paper (or digital) trails from the venue and your bank.
Slots, Bingo, and Keno
For slot machines, note the machine number and time played. The single most useful piece of backup for electronic games is the annual win/loss statement from the casino’s player rewards program, so use your card and request the statement. For bingo, keep card-purchase receipts. For keno, keep your tickets and the payout slips showing the game number.
Table Games
Table games leave a thinner paper trail because no machine tracks each hand. Casino marker records, check-cashing receipts, and chip-purchase records tie your activity to specific dates and dollar amounts. Using a player’s card at the table lets the casino estimate your play, which shows up on the year-end win/loss statement.
Racing and Sports Betting
At the track, keep losing tickets. Most people throw them away; don’t. Official programs and payment stubs help too. Online sportsbooks provide downloadable transaction histories with every wager, outcome, and running balance. Pull them at least once a year. If the platform shuts down or you close the account, the data can vanish with it.
Lotteries and Pools
Keep losing lottery tickets and the receipts for the purchases. For office pools and similar arrangements, keep any written record of the terms and your buy-in, plus statements from whoever runs the pool.
W-2Gs and Bank Records
Gambling venues report certain winnings to the IRS on Form W-2G. For 2026, the reporting threshold for slots, bingo, and keno is $2,000, and that figure is now indexed for inflation.5Internal Revenue Service. Instructions for Forms W-2G and 5754, Rev. January 2026 Keep every W-2G you receive. Also hold on to bank statements showing cash withdrawals at or near gambling venues; those help demonstrate that you actually had money in play. One warning: the W-2G threshold is not a tax-free threshold. A $500 slot win that never triggers a W-2G is still taxable, and your diary needs to capture it.
Use the Session Method
Rather than reporting every single bet, the IRS lets you net wins and losses within a continuous gambling session. Sit at a machine for three hours, hit $15,000 on one spin, and give back $10,000 over the rest of the session, and you report a $5,000 net win from that session rather than $15,000 gross.
What counts as one session depends on the game. A day of slots at one casino is generally a session. A poker tournament is a session. Individual sports bets are each their own session. This matters beyond the gambling numbers themselves, because gross winnings feed your adjusted gross income, and AGI drives eligibility for tax credits, student loan repayment plans, and Medicare premium surcharges. Session-level tracking in the diary is what makes the method defensible.
How the Records Turn Into a Deduction
Gambling winnings go on Form 1040 as income. Losses go on Schedule A under “Other Itemized Deductions.”3Internal Revenue Service. Topic No. 419, Gambling Income and Losses The deductible figure is 90% of your losses, capped at your total gambling income.1Office of the Law Revision Counsel. 26 US Code 165 – Losses
Two quick examples show how the cap works. If your diary shows $12,000 in losses against $10,000 in winnings, 90% of $12,000 is $10,800, which then gets capped at your $10,000 in winnings; you deduct $10,000. If your losses are $8,000 against $10,000 in winnings, 90% of $8,000 is $7,200, which is below the cap, so you deduct $7,200. Under the new law, even a gambler who breaks even at the tables ends up with some phantom taxable income.
You don’t attach the diary or receipts to the return. Keep them ready. If you mail a paper return, send it certified so you have proof of timely filing.6Taxpayer Advocate Service. Options for Filing a Tax Return
How Long to Keep Everything
The IRS generally requires you to keep tax records for three years from the date you filed. If you underreport income by more than 25% of the gross shown on the return, the window stretches to six years.7Internal Revenue Service. How Long Should I Keep Records For gambling specifically, six years is the safer floor. Underreporting is common in this area and the IRS knows it.
What Happens If You Can’t Produce the Records
If you claim gambling losses and can’t produce the diary or supporting documents in an audit, the IRS will disallow the deduction. You’ll owe tax on the full amount of reported winnings with no offset. On top of that, the IRS can add a 20% accuracy-related penalty on the underpayment.8Office of the Law Revision Counsel. 26 US Code 6662 – Imposition of Accuracy-Related Penalty on Underpayments Interest runs from the original due date of the return.
Patterns That Attract Scrutiny
Some claimed deductions look wrong on their face. Losses that exactly or nearly exactly equal reported winnings suggest a taxpayer working backward from W-2Gs rather than tracking real activity. Claiming losses on a return with no gambling income at all suggests unreported winnings. The strongest defense against both is boring: a detailed, dated diary, casino win/loss statements, losing tickets, and bank records that all tell the same story. Organized records prove the deduction and, just as usefully, discourage the auditor from looking further.
A Note on Professional Gamblers and State Taxes
Everything above applies to recreational gamblers filing on Schedule A. If you gamble regularly with the intent to make a profit and meet the standard the Supreme Court set in Commissioner v. Groetzinger (1987), you may qualify as a professional and report on Schedule C instead, with a different set of rules; the 90% cap now also sweeps in business expenses like travel and entry fees.1Office of the Law Revision Counsel. 26 US Code 165 – Losses Separately, several states either disallow gambling loss deductions or limit them beyond federal law, so a properly documented federal deduction does not automatically carry over to your state return. Check your state’s specific rules before filing.