The IRS generally has three years from the date you file to audit a return, and most examinations start within the first 12 to 18 months after filing. So the practical answer to when the IRS audits is: usually soon after you file, rarely more than three years later, and almost never at random. In fiscal year 2024 the agency closed about 505,000 individual audits out of more than 150 million returns filed, which puts the base rate well under one percent. What pushes your return above that base rate is a mix of computer scoring, mismatches with documents third parties send in about you, certain deduction patterns, and occasionally pure chance.
The Three-Year Clock and When It Changes
Federal law gives the IRS three years to begin an audit, measured from the date you filed or the return’s due date, whichever is later. File your 2025 return on February 15, 2026 and the clock still runs from April 15, 2026. Once those three years pass, the IRS loses its authority to assess additional tax or penalties for that year.1Office of the Law Revision Counsel. 26 USC 6501 – Limitations on Assessment and Collection
The window doubles to six years when you leave out a substantial amount of income. The threshold is more than 25 percent of the gross income reported on your return. If your return shows $80,000 in gross income and you failed to report another $25,000, the IRS gets six years instead of three.1Office of the Law Revision Counsel. 26 USC 6501 – Limitations on Assessment and Collection
Two situations remove the deadline entirely: never filing a return, and filing a fraudulent return with intent to evade tax. In either case the IRS can act five, ten, or twenty years later.1Office of the Law Revision Counsel. 26 USC 6501 – Limitations on Assessment and Collection Fraud also carries a civil penalty of 75 percent of the underpayment tied to the fraud, on top of the back tax itself.2Office of the Law Revision Counsel. 26 US Code 6663 – Imposition of Fraud Penalty
You can also agree to extend the deadline. When an audit is already underway and the three-year period is about to run out, the IRS may ask you to sign Form 872 or 872-A consenting to more time. You’re not required to sign. Refusing may push the IRS to issue an assessment based on whatever it already has in hand.
How Returns Get Picked for Audit
Every individual return is scored by the Discriminant Function System, known as DIF. The score reflects how likely the return is to produce a change if examined, based on patterns the IRS has observed across similar returns. The highest-scoring returns go to a human classifier who decides whether an audit is worth the effort.3Internal Revenue Service. The Examination (Audit) Process
What raises a DIF score is generally deductions or credits that look large relative to income. Someone earning $55,000 who claims $18,000 in charitable contributions is far outside the norm for that income band, and the system notices. The same is true of outsized business expense deductions, home office claims, and casualty losses. The exact formula is not published, and that’s on purpose. If taxpayers knew where the line sat, gaming it would be trivial.
A separate track handles document mismatches. Before anyone at the IRS looks at your return, computers have already cross-checked what you reported against forms filed by people who paid you. Employers submit W-2s on your wages.4Internal Revenue Service. About Form W-2, Wage and Tax Statement Banks send 1099-INT forms for interest. Brokerages report dividends and capital gains. Companies that hired you as a contractor file 1099-NEC forms.5Internal Revenue Service. Am I Required to File a Form 1099 or Other Information Return? All of it gets compared to what you filed.
When something doesn’t line up, an automated notice called a CP2000 goes out. It proposes specific changes and calculates the added tax. You can agree, partly agree, or dispute the proposal with documentation. If the numbers are large or the pattern looks broader than a single missing form, the case can move from a notice into a full examination.
A small number of returns are pulled at random through the National Research Program. These audits feed data back into the DIF models and measure overall compliance.6U.S. Government Publishing Office. Tax Administration – IRS Is Implementing the National Research Program as Planned Being picked doesn’t mean anything is wrong on your return, but the examination is thorough: the auditor may ask you to substantiate every line rather than one or two.
Self-Employment and Schedule C Red Flags
Schedule C filers face notably more scrutiny than W-2 wage earners. The IRS compares deductions against industry averages for your type of business and income level, and returns that fall outside the norm get flagged. Common triggers include claiming 100 percent business use of a vehicle with no mileage log, deducting meals and travel that mix personal and business purposes, and writing off equipment that dwarfs the revenue reported.
Reporting a Schedule C loss year after year is its own signal. The general benchmark is three profitable years out of five. Fall short and the activity may be reclassified as a hobby, which strips most of the deductions. Even when losses are legitimate, expect the IRS to look harder.
Payment Apps and the 1099-K Threshold
Payments received through Venmo, PayPal, or credit card processors may generate a Form 1099-K sent to the IRS. Under current law, a 1099-K is required only when gross payments exceed $20,000 and there are more than 200 transactions in a calendar year. A lower threshold enacted in 2021 was reversed, restoring the original $20,000 and 200-transaction rule.7Internal Revenue Service. IRS Issues FAQs on Form 1099-K Threshold Under the One, Big, Beautiful Bill; Dollar Limit Reverts to $20,000
Falling below the threshold does not make the income tax-free. All income is still taxable. The difference is only that the IRS won’t have an automated document to match, which makes it easier for the income to slip off a return and harder for the agency to catch it through data matching alone.
Audits That Follow From Someone Else’s Return
An audit of one taxpayer often reaches others whose finances are tied to it. When the IRS examines a partnership or S corporation, it commonly checks the individual returns of the owners or partners for consistency. Under the centralized partnership audit regime, each partner must report items consistently with the partnership’s return. If a partner’s return doesn’t match, the IRS can treat the inconsistency as a math error and assess the tax immediately.8Internal Revenue Service. Internal Revenue Manual 4.31.9 – Centralized Partnership Audit Regime (BBA) Field Examination Procedures
Investors in real estate syndications, private equity funds, and other pass-throughs carry the same exposure. If the entity’s return is adjusted, the changes flow through to every investor’s K-1. You may not learn about the underlying partnership audit until a notice adjusting your own return arrives.
Worker Classification
Businesses that use independent contractors face a specific audit risk. The IRS weighs three categories of evidence in deciding whether a worker should have been classified as an employee: behavioral control (whether the company directs how the work is done), financial control (who provides tools, how expenses are handled, how payments are structured), and the nature of the relationship (written contracts, benefits, permanence).9Internal Revenue Service. Independent Contractor (Self-Employed) or Employee?
No single factor decides it. But a small business that relies heavily on 1099 workers can face back employment taxes, penalties, and interest going back years if even a few are reclassified as employees. It’s one of the higher-stakes outcomes for small businesses.
What an Audit Actually Looks Like
Audits come in three formats, and the one you get depends on the scope of the issues.
- A correspondence audit is the most common and runs entirely by mail. The IRS asks you to verify one or two items, like a charitable deduction or an education credit. You send documentation, and resolution usually comes within a few months.10Taxpayer Advocate Service. Lifecycle of a Tax Return – Correspondence Audits – Increased Communication Alternatives Are in Progress
- An office audit brings you into a local IRS office with specific records for an in-person meeting. It covers more ground than a mail audit but still focuses on particular issues.
- A field audit sends an IRS revenue agent to your home, business, or accountant’s office. Field audits are the most comprehensive and are generally used for complex returns, high-income filers, and cases where the IRS suspects significant underreporting.
Whatever the format, the IRS must tell you which records it needs and which tax years are under review.11Internal Revenue Service. IRS Audits You aren’t expected to produce documents the IRS hasn’t asked for, and you aren’t required to answer questions outside the scope of the examination.
What Being Audited Can Cost
If an audit produces additional tax, interest and penalties stack on top of the balance.
- The accuracy-related penalty is 20 percent of the underpayment caused by negligence or a substantial understatement of income.12Internal Revenue Service. Accuracy-Related Penalty
- The fraud penalty is 75 percent of the underpayment tied to the fraud when the IRS can prove intent.2Office of the Law Revision Counsel. 26 US Code 6663 – Imposition of Fraud Penalty
- The failure-to-pay penalty runs at 0.5 percent of the unpaid balance per month, up to 25 percent.
- Interest on underpayments is set quarterly. The rate is 7 percent for the first quarter of 2026 and drops to 6 percent for the second quarter.13Internal Revenue Service. Quarterly Interest Rates
Interest runs from the original due date of the return, not from the day the audit ends. On a 2022 return audited in 2025, roughly three years of compounded interest has been building on any additional tax before penalties are even added. That can push the total up by 20 percent or more on its own.