Where and how to report suspected tax fraud
The IRS has a dedicated channel for reports of tax fraud or unreported income: the Form 3949-A, which you submit to the IRS Criminal Investigation division, or the online whistleblower form at IRS.gov. You can also call the IRS Criminal Investigation tip line at 1-800-366-4484. The form asks you to describe what you know, provide names and addresses if you have them, and explain why you believe the person is not reporting income or is committing fraud.
You do not need to be certain about the details. The IRS investigates based on the information you provide, and they have access to tax records, bank statements, and other documents you may not see. Your report goes to a specific investigator, not into a general inbox — the IRS takes these reports seriously because tax fraud directly reduces revenue.
If you are reporting a business or employer, include the business name, address, and the type of fraud you suspect (cash-only income not reported, inflated deductions, employee wages paid under the table, and so on). The more specific you can be, the easier it is for the IRS to investigate.
Key Takeaways
- The IRS Criminal Investigation tip line (1-800-366-4484) and the online whistleblower form at IRS.gov are the official channels for reporting suspected tax fraud.
- You can report anonymously, and you do not need proof — the IRS will investigate based on the information you provide.
- Include as much detail as you can: names, addresses, the type of income you suspect is unreported, and how you know about it.
- If you are a whistleblower with direct knowledge of fraud and the IRS recovers money as a result, you may be may have access to to a financial reward under the IRS Whistleblower Program.
Anonymous reporting and your protection
You can report someone to the IRS without giving your name. The online whistleblower form and the tip line both allow anonymous reports. If you choose to remain anonymous, the IRS will not contact you for follow-up questions, but they will still investigate based on what you report.
If you provide your name and contact information, the IRS will keep your identity confidential during the investigation. Your name will not appear in any documents shared with the person being investigated. However, if the case goes to court, you may be called as a witness, which would reveal your identity at that point.
The difference between the tip line and the whistleblower program
The IRS Criminal Investigation tip line (1-800-366-4484) is for reporting suspected fraud. You call, describe what you know, and the IRS investigates. There is no financial reward for this type of report — it is a civic duty channel.
The IRS Whistleblower Program is different. It is for people with direct, firsthand knowledge of tax fraud — usually employees, accountants, or business insiders who have seen the fraud happen. If you report through the Whistleblower Program (Form 211, submitted to the IRS), and the IRS recovers more than $2 million as a result of your report, you receive a percentage of what they recover, typically between 15 and 30 percent. This program is designed for people with inside information, not neighbors or acquaintances who suspect something.
If you are unsure which route fits your situation, start with the tip line. The IRS will direct you to the Whistleblower Program if your report qualifies.
What information to include in your report
The more specific your report, the more actionable it is. Include the person's or business's full name, address, phone number, and any business license or tax ID number you know. Describe the suspected fraud clearly: Is income being hidden? Are deductions inflated? Are employees paid in cash without tax withholding? When did you first notice this? How do you know about it?
If you have documents — a pay stub showing cash payments, a receipt, an email, a bank statement — describe them. You do not need to submit the documents themselves with your initial report, but telling the IRS what documents exist helps them know where to look when they investigate.
If the fraud involves a specific time period (for example, "I worked there from 2021 to 2023 and saw cash payments every week"), include those dates. The IRS uses this information to narrow the scope of their investigation.
What happens after you report
After you submit a report, the IRS Criminal Investigation division reviews it and decides whether to open an investigation. You will not receive a confirmation that your report was received or a status update on any investigation — the IRS does not disclose this information to protect the integrity of the case.
If the IRS investigates and finds evidence of fraud, they may pursue civil penalties (additional taxes owed plus interest and penalties), criminal charges, or both. A criminal investigation can take months or years. You will not be notified of the outcome unless you are called as a witness.
If you reported through the Whistleblower Program and the IRS recovers money, you will receive a letter notifying you of the award. The IRS processes whistleblower awards separately from criminal investigations, so the timeline is different.
Reporting a specific type of fraud: cash businesses
Cash-based businesses — restaurants, bars, retail shops, salons, construction companies — are common subjects of tax fraud reports because income can be underreported more easily. If you suspect a business is not reporting all cash sales, describe what you observed: How many customers per day? What is the typical transaction size? Did you see a register or point-of-sale system? Did the owner or manager ever mention keeping two sets of books or not reporting certain income?
If you worked there, you have stronger credibility. If you are a customer who noticed something unusual, include that context in your report so the IRS understands the basis of your knowledge.
Reporting unreported income from a side job or gig work
If you suspect someone is earning income from a side job, gig work, rental property, or freelance activity and not reporting it, tell the IRS what you know about the income source. For example: "My neighbor rents out a house on Airbnb and told me he makes $3,000 a month but I have never seen him file a tax return." Or: "My coworker does freelance graphic design on the side and has mentioned making $500 to $1,000 per week, but I do not think he reports it."
The IRS cross-references income reported by platforms like Airbnb, DoorDash, Uber, Etsy, and others against individual tax returns. Your report can prompt them to look more closely at a specific person's filings.
Frequently Asked Questions
Can I report someone anonymously?
Yes. You can call the IRS Criminal Investigation tip line at 1-800-366-4484 without providing your name, or submit an anonymous online whistleblower form at IRS.gov. The IRS will investigate based on the information you provide even if you do not identify yourself.
What if I am not sure whether what I saw is actually fraud?
Report it anyway. The IRS investigates to determine whether fraud occurred. You do not need to be certain — you only need to describe what you observed and why you think it may be fraudulent. The IRS has the tools and authority to investigate further.
Will the person I report find out it was me?
Not during the investigation. The IRS keeps your identity confidential. However, if the case goes to criminal court, you may be called as a witness, which would reveal your identity to the defendant and the public record.
Can I get paid for reporting tax fraud?
Only if you report through the IRS Whistleblower Program and you have direct, firsthand knowledge of the fraud. If the IRS recovers more than $2 million as a result of your report, you receive a percentage of the recovery, typically 15 to 30 percent. Routine reports to the tip line do not result in payment.
How long does an IRS investigation take?
Criminal investigations can take months or years. You will not receive updates on the status of your report. If the IRS pursues charges and the case goes to trial, you may be notified that you are needed as a witness.