How does the IRS review your return?

Asked by: Johanna Carroll II  |  Last update: July 17, 2026
Score: 4.5/5 (46 votes)

The IRS reviews tax returns using automated computer systems to detect mathematical errors, verify income against third-party reports (W-2s, 1099s), and flag discrepancies using a scoring system called the Discriminant Inventory Function (DIF). High-scoring returns, or those chosen randomly, may trigger audits (via mail or in-person) to review records.

What triggers an IRS refund review?

The IRS uses a combination of automated and human processes to select which tax returns to audit. Not reporting all of your income is an easy-to-avoid red flag that can lead to an audit. Taking excessive business tax deductions and mixing business and personal expenses can lead to an audit.

What happens when the IRS is reviewing your tax return?

If the IRS is reviewing your return, it may have questions about your wages and withholding, or credits or expenses shown on your tax return. The review process could take anywhere from 45 to 180 days, depending on the number and types of issues the IRS is reviewing.

How do I know if my tax return has been flagged?

If the IRS decides that your return merits a second glance, you'll be issued a CP05 Notice 1 . This notice lets you know that your return is being reviewed to verify any or all of the following: Your income. Your tax withholding.

What looks suspicious to the IRS?

If the deductions, losses, or credits on your return are disproportionately large compared with your income, the IRS may want to take a second look at your return. Taking a big loss from the sale of rental property or other investments can also spike the IRS's curiosity.

IRS Releases 2026 Tax Brackets + Capital Gains Update — Here’s What You Need to Know

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Will I be notified if something is wrong with my tax return?

The IRS is considering changing an amount on your tax return, due to an examination after it processed your tax return. This is called an audit. If it audits your return, the IRS will notify you by mail, and the notice will tell you if the audit will be handled by mail or in person.

How can you tell if the IRS is investigating you?

You know the IRS might be investigating you through official mail (first contact), phone calls (often with automated messages to IRS.gov), or in-person visits, but signs of a criminal probe include contact with IRS Criminal Investigation (CI) agents, subpoenas to you or your bank, questions to your accountant/bank, unusual account activity (freezing/refusing transactions), or agents suddenly going silent after an audit. Key indicators are official IRS letters, contact from CI special agents, third-party inquiries, and formal summonses for records, signaling serious scrutiny beyond a simple audit. 

What are 5 red flag symptoms?

Here's a list of seven symptoms that call for attention.

  • Unexplained weight loss. Losing weight without trying may be a sign of a health problem. ...
  • Persistent or high fever. ...
  • Shortness of breath. ...
  • Unexplained changes in bowel habits. ...
  • Confusion or personality changes. ...
  • Feeling full after eating very little. ...
  • Flashes of light.

Why would my return be under review?

The IRS reviews some federal tax returns to determine if income, expenses, and credits are reported accurately. The IRS selects returns for review using various methods; including random sampling, computerized screening, and comparison of information received by the IRS such as Forms W-2 and 1099.

What are common reasons for IRS reviews?

Common IRS audit triggers

  • Making math errors.
  • Failing to report income.
  • Claiming too many charitable donations.
  • Reporting too many losses on a Schedule C.
  • Deducting too many business expenses.
  • Claiming a home office deduction.
  • Using nice, neat, round numbers.

Does IRS manually review returns?

Employees will review and either manually release the refund or confirm the error. If an error is confirmed, a notice will be sent to the taxpayer either requesting additional information or informing the taxpayer the error has been corrected through the IRS's math error authority.

Why is my IRS letter saying they are reviewing my return?

Why is my return being reviewed? We select some returns to review so we can determine whether income, expenses, and credits are reported correctly. This doesn't mean you made an error or were dishonest.

Will the IRS tell you if something is wrong with your refund?

Once the IRS reviews your return, they will process your tax return and notify you of any changes, if any. You can use the following link to track your refund.

How do I tell if I have red flags?

Red flags in relationships are warning signs that indicate unhealthy or manipulative behavior. Examples include controlling behavior, lack of respect, love bombing, and emotional or physical abuse. These behaviors may start subtly but tend to become more problematic over time, potentially leading to toxic dynamics.

How do you know if you're in trouble with the IRS?

Should your account be selected for audit, we will notify you by mail. We won't initiate an audit by telephone. Assistance is available to help you understand the letter/notice received: Understanding your IRS notice or letter.

Will you be notified if you are under investigation?

The government has no legal obligation to notify you that you're under investigation. There is no constitutional right to know that prosecutors are building a case against you.

Should I be worried if my refund is still being processed?

You generally shouldn't worry if your refund is "still being processed," as it means the IRS is working on it, but it might take longer than the typical 21 days due to common issues like errors, incomplete information, or claiming credits like the EITC/ACTC. Worry only becomes necessary if you receive an IRS letter requesting more information or if the "Where's My Refund?" tool shows a specific problem like fraud, but typically, it just means a longer wait, not no refund at all. 

How long does the IRS have to catch a mistake?

Legal answer: Three years. First, the legal answer is in the tax law. Technically, except in cases of fraud or a back tax return, the IRS has three years from the date you filed your return (or April 15, whichever is later) to charge you (or, “assess”) additional taxes.

What are the most common errors on tax returns?

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