The hidden challenges of reconciling online gambling records

Online gambling is showing up on more client returns every season, and the tax issues run deeper than reporting one big win. Sports betting apps generate high transaction volume, apply partial withholding and issue year-end summaries that rarely match what the client thinks they won or lost. Add prediction platforms and event-based contracts to the mix, and reconciliation gets even more interesting.

Before our upcoming webinar, here's a quick refresher on the core rules and the trouble spots that trip up even seasoned preparers.

Start with the code

Under Internal Revenue Code (IRC) §61, all gambling winnings are gross income. It doesn't matter if the client cashed out, left the money in the app or lost it the following week. If they won it, they've earned it for tax purposes.

Losses get different treatments. Under §165(d), as amended by the One Big Beautiful Bill Act, a taxpayer can deduct wagering losses only up to 90% of the loss amount and only to the extent of wagering winnings, and only if they itemize on Schedule A (Form 1040), Itemized Deductions. This replaces the pre-2026 rule under the Tax Cuts and Jobs Act of 2017, which allowed 100% of losses to be deducted against winnings. Casual gamblers can't net winnings against losses on Form 1040, U.S. Individual Income Tax Return. Gross winnings flow through Schedule 1 (Form 1040), Additional Income and Adjustments to Income, and any allowable losses land separately on Schedule A.

That distinction matters more than ever, because platforms love to hand clients a single "net" figure that has no home on the return.

Where W-2Gs fit, and where they don’t 

Form W-2G, Certain Gambling Winnings, is triggered only when specific thresholds and payout ratios are met. Most sports betting activity never crosses those thresholds, so a client may walk in with thousands of dollars in winnings and no W-2G in hand. Absence of a form doesn't mean absence of income.

When a W-2G does appear, check federal withholding in Box 4 and reconcile the win amount to the platform's raw transaction log, not the year-end summary. The two often disagree, and the summary usually wins the argument in the client's head.

Prediction platforms and event contracts

Event-based activity on prediction platforms is where things get genuinely new. Depending on how the contract is structured and regulated, the activity may not be treated as traditional wagering at all. If the contracts qualify as §1256 contracts, the client faces mark-to-market treatment at year-end and the 60/40 long-term and short-term capital gain split. Straddle rules under §1092 may also apply.

Some platforms even issue Form 1099-B, Proceeds From Broker and Barter Exchange Transactions, which is a strong hint the account isn't being treated as gambling at all. The main key: don't assume every "bet" a client places is gambling income. Ask what platform the activity happened on and how the contracts are classified.

Intake questions worth asking

A few questions on the client intake sheet can save hours of cleanup later:

• Did you use any sports betting, casino, poker or prediction platforms during the year?
• Can you pull a full transaction history, not just the year-end summary?
• Did any platform withhold federal or state tax?
• Do you keep a session log or contemporaneous record of play?

Encourage clients to download raw transaction data before their appointment. Rev. Proc. 77-29 still guides recordkeeping, and contemporaneous logs remain the strongest support if the return is examined.

Documenting the position

When paperwork is incomplete, document the workpapers thoroughly. Note which reports were used, how gross winnings and losses were calculated, and why the return numbers differ from any platform summary. A clean audit trail protects both the client and the preparer.

Join us for the webinar Reconciling Online Gambling Records. We’ll walk through real reconciliation examples, W-2G mismatches and how to handle prediction platform reporting with confidence. Bring your questions, and we'll bring the workflow.