It doesn’t take the Panama Papers to expose tax cheats — plenty of people report questionable tax behavior to the IRS every year. Here’s what you need to know if you want to report a possible tax crook and perhaps get a reward.

File the right form. The IRS received more than 87,000 reports of alleged misdeeds during the 2015 fiscal year, according to the Government Accountability Office.

You can file IRS Form 3949-A to report the alleged cheater and walk away. But if you want a reward, file Form 211 instead, says Bob Gardner, a consultant and former manager in the IRS whistleblower office.

Whistleblowers can get 15% to 30% of the amount collected if the case involves more than $2 million in taxes, penalties, interest and other amounts. (If the suspected cheater is an individual, he or she must also make more than $200,000 a year.) Below those thresholds, the award is discretionary. In 2015, the rewards totaled more than $103 million for 99 whistleblowers.

Provide solid evidence. Proof is key, according to former IRS attorney Thomas Pliske, who is now a principal at the Tax Whistleblower Law Firm in St. Louis. Bank statements, invoices, emails or that second set of books can be hard to obtain without access, which is why most whistleblowers are people exposing their employers, he says.

You’ll need to mail your completed form and evidence to the IRS — whistleblowing can’t be done online or over the phone. And don’t wait too long: The statute of limitations on audits or assessments is generally three years after the shady return is filed, though there are lots of exceptions, Pliske says.

Work with a lawyer. Reports prepared by professionals may get more attention, experts say.

“The IRS examiners have a huge stack of cases that sits on their desk. When they get something new … if it’s put together by someone who doesn’t really speak the language very well, or who can’t communicate very effectively or can’t lay out a road map for how the IRS should investigate the fraud, it’s going to the bottom of the stack,” says whistleblower attorney Eric Havian, a partner at Constantine Cannon in San Francisco.

Know that you may be outed. You can’t file a whistleblower claim (Form 211) anonymously, according to Susan Coler, a whistleblower attorney at Halunen Law in Minneapolis. Also, the IRS can reveal your identity publicly by calling you as a witness.

“If you’re really afraid about having your identity known, you really need to talk to an attorney about whether or not you should proceed,” she says.

Providing names of others who know about the cheating might encourage the IRS to call them to the stand instead of you, Pliske says.

Don’t expect constant updates. The IRS will likely tell you only that the case is open or closed, Coler says.

The IRS is equally tight-lipped with suspected cheaters. Unless the whistleblower’s identity is revealed, the suspected cheater likely won’t even know a case exists. The investigations look like regular audits, Gardner says.

Be ready to lose your job — or worse. There are no federal protections regarding workplace retaliation against an IRS whistleblower, which makes getting fired a possibility if your employer discovers you made a report. State-level protections may exist but they vary, Havian says.

There’s another caveat: no guaranteed immunity. If you materially participated in the scheme, the IRS may reduce or eliminate the reward — or even come after you, Gardner warns.

However, it depends on the circumstances. “I have yet to see a case where the person has ever gone to jail, but again it depends on your participation: What did you do about it, how much were you involved in it, when did you come forward?” Gardner says.

You may not see a reward for five to seven years. “You really aren’t going to fund next spring break’s vacation with this activity,” Coler cautions. If and when there’s a judgment against an alleged cheater, the cheater still has the right to appeal, she says. Plus, the IRS pays out whistleblower awards only once it actually collects the money from the violator.

And if that reward ever does come, remember: It’s taxable.