4.3 – Audit Process and Taxpayer Penalties
An IRS audit is simply a review of a taxpayer’s return or supporting financial records to confirm that income, deductions, and credits were reported correctly and that the right amount of tax was paid. Most audits never involve a face-to-face meeting; many are resolved entirely by mail. Alongside the audit function, the IRS also has broad authority to impose penalties on taxpayers who fail to comply with filing, payment, or reporting rules. Understanding how returns get chosen for examination, what the audit process looks like, and which penalties apply in which circumstances helps a taxpayer respond correctly rather than out of fear.
How Returns Get Selected for Audit
The IRS uses several distinct methods to decide which returns to examine. Some returns are chosen through random selection and computer screening, where a statistical sample helps the IRS track broader compliance trends and scoring programs flag returns with a high probability of error based on historical data. A second method is information matching, where the IRS compares what a taxpayer reported against third-party data it independently receives, such as wages on a Form W-2, interest on a Form 1099-INT, or dividends on a Form 1099-DIV; a mismatch between these sources is one of the most common audit triggers.
A third method is the related-examination trigger: if the IRS is already auditing a business partner, investor, or other related party, it may extend the examination to a taxpayer connected to that return. None of these methods require any wrongdoing on the taxpayer’s part; being selected for audit is not itself an accusation, and a large share of audits close with no change to the return at all.
The Three Types of Audits
A correspondence audit is the most common type and is handled entirely by mail. The IRS sends a letter asking for documentation on a small number of specific items, and the taxpayer generally responds by mailing back the requested records. An office audit is more involved: the taxpayer is asked to meet an IRS auditor at an IRS office on a scheduled date to go over a broader range of items than a typical correspondence audit covers.
A field audit is the least common and generally the most complex, involving an IRS auditor visiting the taxpayer’s home, place of business, or accountant’s office. Field audits are usually reserved for businesses or higher-income individuals whose returns involve more moving parts than a correspondence or office audit can efficiently handle.
Stages of the Audit and Taxpayer Rights
The audit process starts with notification: the IRS mails the taxpayer notice of which tax year is being examined and which type of audit will be used. From there the auditor requests documentation and explanations for the specific items under review, and the taxpayer is expected to respond in a reasonably timely way. Throughout this process taxpayers retain specific rights: the right to representation by an attorney, CPA, enrolled agent, or other authorized representative who can deal with the IRS directly on the taxpayer’s behalf; the right to audio-record an in-person interview, provided advance notice is given (the IRS has the same right in reverse); and the right to appeal if the taxpayer disagrees with the findings.
An audit concludes in one of three ways. A no-change outcome means the IRS accepts the return exactly as filed. An agreed-change outcome means the IRS proposes an adjustment and the taxpayer agrees, typically signing a form and paying the additional tax, interest, and any penalty due. A disagreed-change outcome means the IRS proposes an adjustment the taxpayer does not accept, which moves the case into the appeals track described next.
Disagreed Audits: The 30-Day and 90-Day Letters
When a taxpayer disagrees with an audit’s findings, the IRS issues a 30-day letter, formally called a Notice of Proposed Adjustment. This letter details the proposed changes and gives the taxpayer 30 days to file an appeal, which is handled by the IRS Independent Office of Appeals, a body kept separate from the division that conducted the original audit so the review is genuinely independent.
If the taxpayer does not appeal within that window, or disagrees with the outcome of the appeal, the IRS sends a 90-day letter, officially the Notice of Deficiency. This is the IRS’s final determination of the amount owed, and it gives the taxpayer 90 days to petition the U.S. Tax Court to challenge the determination before any tax is formally assessed or collection begins. Letting the 90-day window pass without action generally means the proposed deficiency becomes final and collectible.
Accuracy-Related Penalties Under Section 6662
IRC Section 6662 imposes a penalty, generally 20% of the underpayment, for several categories of error. Negligence or disregard of rules covers a careless, reckless, or intentional failure to make a reasonable effort to comply with the tax law, including inadequate recordkeeping or a general lack of ordinary care in preparing the return. A substantial understatement of income tax applies when the understatement exceeds the greater of 10% of the tax required to be shown on the return or a fixed dollar floor (currently $5,000 for most individual filers, $10,000 for most corporations other than S corporations or personal holding companies).
A valuation misstatement penalty applies when a taxpayer overstates the value or basis of property to inflate a deduction, or understates the value of property or services in a way that reduces reported tax; the rate can rise to 40% for a gross valuation misstatement, reflecting how much more serious that error is treated compared with an ordinary miscalculation.
Failure-to-File and Failure-to-Pay Penalties
IRC Section 6651(a)(1) penalizes filing a return late: 5% of the unpaid tax for each month or partial month the return is late, capped at 25% of the unpaid tax. If a return is more than 60 days late, a minimum penalty applies, set at the smaller of a fixed dollar amount (indexed periodically, $485 for returns due in 2024) or 100% of the tax required to be shown on the return. The penalty does not apply if the taxpayer can demonstrate reasonable cause for the delay.
IRC Section 6651(a)(2) penalizes failing to pay tax that was actually shown on a timely filed return: 0.5% of the unpaid tax per month or partial month, also capped at 25%. This penalty can likewise be avoided with reasonable cause, provided the taxpayer pays the tax as soon as they reasonably can. A related penalty under Section 6656 applies specifically to businesses that are late depositing employment taxes, with the rate stepping up from 2% for a short delay to 15% for a deposit still outstanding after a delinquency notice.
Fraud Penalties: Civil and Criminal
Fraud penalties are reserved for cases where the IRS concludes a taxpayer intentionally tried to evade or defeat the tax owed, and they are far more severe than the accuracy-related penalties. Civil fraud under Section 6663 adds a penalty of 75% of the underpayment attributable to the fraud, on top of the underlying tax and any applicable interest.
Criminal fraud under Section 7201 and related provisions goes further, exposing a taxpayer to prosecution that can result in fines, imprisonment, or both, separate from the civil penalty. Filing a knowingly false return, concealing income, and destroying records are the kinds of conduct that typically support a criminal fraud case rather than a simple accuracy dispute.
Reasonable Cause Relief and Other Considerations
IRC Section 6664(c) provides an exception to the accuracy-related penalties where the taxpayer had reasonable cause for the underpayment and acted in good faith. Whether reasonable cause exists is determined case by case, weighing all the surrounding facts rather than applying a fixed test, which means the taxpayer generally has to document the circumstances that led to the error to support the claim.
Beyond penalties, interest also accrues automatically on any underpayment from the original due date until the tax is paid, at a rate the IRS adjusts periodically; the IRS pays interest the other way on overpayments as well. Separately, the IRS imposes penalties under Section 6721 for failing to file correct information returns, such as Forms 1099 or W-2, or for failing to furnish correct statements to recipients, with the amount generally scaled to how late the filing is and whether the failure was intentional.
Quick revision summary
- Returns are selected for audit through random screening, information matching against third-party forms, or related-party examinations.
- The three audit types are correspondence (by mail), office (in-person at an IRS office), and field (at the taxpayer’s location), increasing in complexity.
- Taxpayers have the right to representation, to record an interview with notice, and to appeal a disagreed finding.
- A disagreed audit moves through a 30-day letter (appeal within the IRS) and, if unresolved, a 90-day Notice of Deficiency giving 90 days to petition Tax Court.
- Accuracy-related penalties under Section 6662 are generally 20% of the underpayment for negligence, substantial understatement, or valuation misstatement.
- Failure-to-file (5%/month) and failure-to-pay (0.5%/month) penalties can both be avoided with reasonable cause; fraud penalties (75% civil, criminal exposure) apply only to intentional evasion.