The U.S. sports-betting market is in the hundreds of billions of dollars a year and the beginning of football season is typically when interest peaks, according to the IRS. For advisors and their clients, dealing with losses and protecting winnings in tax planning is crucial.

The IRS treats professional gamblers as self-employed taxpayers who must file a Schedule C with their tax return; their winnings constitute income at individual income tax rates and their business activities have all the regular Schedule C deductions.

The IRS has other rules for “casual” gamblers, where income includes winnings from lotteries, raffles, horse races and casinos in the form of cash or prizes.

The federal tax rate on winnings of at least $5,000 from gambling venues such as football pools is 24%, compared with a $1,200 threshold for bingo and slot machines. The rate is applied as either a standard withholding or a “backup withholding” if a winner fails to furnish a correct taxpayer identification number, regular gambling withholding hasn’t been withheld and the winnings are at least $600 and at least 300 times the wager.

“Gambling winnings aren’t just subject to federal taxes; state and local income taxes can also apply, with specific rules varying by location,” said Paul Brahan, financial advisor at Fort Pitt Capital Group in Pittsburgh. Also, “offshore or out-of-state betting can trigger tax reporting requirements with the IRS.”

Though reporting thresholds can differ, states generally tax gambling winnings from both online and retail outlets; the rates for both are the same in the many states. Tax rates for online winnings include single-digit percentages in Indiana, Iowa, Mississippi, Tennessee and Wisconsin but up to about 50% in New Hampshire, New York and Rhode Island.

States and some localities generally tax sports winnings if the money was made on a wager in that state. Depending on the size of the win, a client may have to file a tax return in a state where the bet was placed if that state has an income tax.

The IRS draws no distinction between retail and online gambling.

“While most people are aware that substantial winnings are taxable, they often forget that even smaller sports betting wins must be reported,” Brahan said.

Clients who’ve won on sports contests or any other gambling activity will receive an IRS Form W-2G if the winnings were reported to the agency. Advisors say clients should earmark at least a quarter of their winnings for taxes.

“If you win a significant amount, you may need to pay estimated taxes throughout the year to avoid penalties,” Brahan said.

Another common misconception is the tax deductibility of losses. Advisors note that many taxpayers may not realize that their losses can also be deducted against gambling winnings.

“Losses are only deductible if you itemize your deductions and, again, are limited only to the amount of your gambling winnings,” said Richard Koenigsberg, a CPA and partner in EisnerAmper’s private client services group and national leader of the firm’s entertainment and media practice.

To claim these deductions, a client must itemize them on IRS Schedule A with their tax return—which fewer clients have generally done since 2017’s tax reform.

“Let’s take an example of someone who won $500 and lost $100. If the person is not itemizing, they still pay tax on $500. If they itemize, [they pay tax on] $400. Another individual had no winnings and lost $500. Zero deduction,” Koenigsberg said.

As with many potential tax problems, sports wagering comes down to paperwork, advisors say.

“Keep detailed records of your gambling activities, including winnings, losses and dates of wagers,” Brahan said. “Most betting platforms keep records of your wagers including the date and time of the bet, the amount wagered, the odds and the outcome. It’s still important to keep your own records as well, as betting platform records may not be accurate or stored indefinitely.”