IRS Penalties for Overstating Deductions: 20%, 40%, and 75%

If you overstated deductions on a federal return, the IRS penalties for overstating deductions run from 20% of the underpaid tax in ordinary cases to 40% for badly inflated property values and 75% when the IRS proves you did it on purpose. On top of the penalty, you owe the underpaid tax itself and daily-compounding interest that starts on the return’s original due date. Which tier you land in depends on how the overstatement happened, not just how big it was.

The 20% Accuracy-Related Penalty

This is the default penalty and the one most taxpayers face. Section 6662 of the Internal Revenue Code lets the IRS add 20% of the tax you underpaid because of the overstated deduction.¹ Two triggers matter for overstated deductions: negligence and substantial understatement.

Negligence means you didn’t make a reasonable effort to get the return right. Claiming a deduction with no records to back it up, using round-number estimates, or ignoring rules you should have known about all qualify. The IRS also treats careless or intentional disregard of its regulations as negligence.

Substantial understatement is a math test, not a judgment about your behavior. For an individual, the understatement is substantial when it’s more than the greater of $5,000 or 10% of the tax that should have been on the return.² Cross that line and the 20% applies whether or not you were careless.

The IRS doesn’t stack these two triggers. If the same underpayment counts as both negligent and substantially understated, the penalty is still 20%, not 40%. And if the civil fraud penalty applies to any part of the underpayment, the 20% accuracy penalty drops off that same part.¹

The 40% Penalty for Inflated Property Values

Some overstated deductions come from inflating the value of property rather than fabricating an expense. Non-cash charitable donations — artwork, real estate, vehicles — are the most common setting. The IRS applies a stiffer penalty tier here.

A substantial valuation misstatement exists when the value you claimed is 150% or more of the property’s actual value, and the resulting underpayment is more than $5,000.³ At that level, the standard 20% accuracy penalty applies.

The penalty doubles to 40% for a gross valuation misstatement — a claimed value at least 200% of the correct amount.⁴ So if you donated a painting actually worth $10,000 and deducted $25,000, you’ve crossed the 200% line and the resulting underpayment carries a 40% penalty.

The usual reasonable cause defense is harder to invoke here. For a gross valuation overstatement on donated property, reasonable cause doesn’t apply unless you based the value on a qualified appraisal by a qualified appraiser and also conducted a good faith investigation of the property’s value on your own.⁵

The 75% Civil Fraud Penalty

When the IRS concludes you deliberately overstated deductions to evade tax, the civil fraud penalty under Section 6663 kicks in at 75% of the underpayment attributable to fraud.⁶ It’s the most severe non-criminal sanction the agency can impose.

The IRS has to prove fraudulent intent by clear and convincing evidence, a higher bar than the preponderance standard that governs most tax disputes. The indicators it looks for include keeping two sets of books, destroying records, filing false documents, hiding income or assets, and a pattern of overstated deductions across multiple years. No single indicator is decisive; the agency builds the case by accumulation.

Once the IRS proves fraud on any portion of the underpayment, the whole underpayment is presumed fraudulent, and the burden shifts to you to prove the rest wasn’t. On a joint return, fraud must be shown separately for each spouse — one spouse’s fraud isn’t automatically pinned on the other.⁶

Criminal Exposure

Civil penalties are money. Criminal prosecution is a separate track, and the IRS can run both at the same time. Willfully attempting to evade tax is a felony carrying up to five years in prison and a fine of up to $100,000.⁷ Filing a return you know to be false — which covers knowingly inflating or fabricating deductions — is a separate felony punishable by up to three years and the same fine.⁸

Criminal cases are rare relative to civil audits. They typically start when a revenue agent flags possible fraud during a civil examination and refers it to IRS Criminal Investigation, where at least two layers of management must sign off before a formal investigation opens.⁹ The threshold is high, but any civil fraud case carries some risk of referral.

Interest and Late-Payment Charges

The penalty isn’t the whole cost. Interest runs on both the unpaid tax and the assessed penalty, compounding daily, and it starts on the return’s original due date without regard to extensions.¹⁰¹¹ It doesn’t stop until you pay in full.

The rate resets quarterly. For individual underpayments, the rate is 7% for the first quarter of 2026 and drops to 6% for the second quarter.¹² An audit that takes two or three years to close can add a meaningful interest charge on top of the underlying penalty, and the IRS almost never abates interest.¹¹

Once the IRS bills you, a separate failure-to-pay penalty of 0.5% per month starts running if you don’t pay, capped at 25% of the unpaid balance. That rate climbs to 1% per month if you fail to pay within ten days of a notice of intent to levy.¹³ When you make a payment, the IRS applies it to the tax first, then penalties, then interest.¹¹

How Long the IRS Has to Come After You

The standard statute of limitations is three years from the date you filed the return.¹⁴ For most overstated-deduction cases, that’s the deadline. Three years without an audit or assessment and the return is generally closed.

The window stretches to six years if you left more than 25% of your gross income off the return. The statute treats an overstatement of cost basis (which shrinks the reported gain on a sale) as an omission of gross income for this purpose.¹⁴ A pure overstatement of deductions — inflated charitable gifts, padded Schedule C expenses — doesn’t trigger the six-year window. Basis overstatements on property sales get six years of exposure; expense padding usually doesn’t.

Fraud has no statute of limitations. If the IRS establishes fraudulent intent, it can assess tax and penalties on returns filed decades earlier. That’s one of the starkest practical consequences of crossing from carelessness into fraud.

Defenses That Can Reduce or Eliminate the Penalty

Reasonable Cause and Good Faith

The accuracy-related penalty doesn’t apply if you show reasonable cause for the underpayment and that you acted in good faith.⁵ In practice, that means demonstrating ordinary care and prudence in figuring your tax.

The strongest version is showing you relied in good faith on advice from a qualified tax professional — CPA, enrolled agent, or tax attorney — and that you gave that adviser complete and accurate information.¹⁵ Handing a preparer a partial set of records and blaming them for the result won’t work. The IRS also weighs your own sophistication, the complexity of the issue, and how much effort you put into getting the treatment right.

Reasonable cause doesn’t defeat the civil fraud penalty. Fraud is defined by intent, so “I tried to get it right” isn’t a coherent defense once fraud is proved.

Adequate Disclosure

The substantial understatement penalty can be reduced or avoided if you adequately disclosed the questionable position on the return and had at least a reasonable basis for it. Disclosure usually means attaching a statement identifying the item and your position on it.¹⁶ The disclosed amount comes out of the understatement calculation, which can drop you below the $5,000 or 10% threshold.

Disclosure won’t help with a frivolous position, and it doesn’t protect against the negligence or fraud penalties. It’s a tool for aggressive-but-defensible positions: you tell the IRS your reasoning upfront and accept that they may disagree.

Fix It Before the IRS Finds It

Filing an amended return to correct overstated deductions before the IRS contacts you about the issue is one of the most useful moves you can make. A “qualified amended return” — one filed before the IRS opens an examination or otherwise notifies you about the item — can eliminate the accuracy-related penalty on the corrected amount. You still owe the additional tax and interest, but the penalty comes off the table.

Once the IRS has already started examining the return or written to you about the specific issue, that door closes. The correction is no longer voluntary. Waiting to see whether you’ll be audited becomes a more expensive gamble the longer it goes on.

1
Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments
2
Internal Revenue Service. Accuracy-Related Penalty
3
Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments – Section: Substantial Valuation Misstatement Under Chapter 1
4
Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments – Section: Increase in Penalty in Case of Gross Valuation Misstatements
5
Office of the Law Revision Counsel. 26 USC 6664 – Definitions and Special Rules – Section: Reasonable Cause Exception for Underpayments
6
Office of the Law Revision Counsel. 26 USC 6663 – Imposition of Fraud Penalty
7
Office of the Law Revision Counsel. 26 USC 7201 – Attempt to Evade or Defeat Tax
8
Office of the Law Revision Counsel. 26 USC 7206 – Fraud and False Statements
9
Internal Revenue Service. How Criminal Investigations Are Initiated
10
Office of the Law Revision Counsel. 26 USC 6622 – Interest Compounded Daily
11
Internal Revenue Service. Topic No. 653, IRS Notices and Bills, Penalties and Interest Charges
12
Internal Revenue Service. Quarterly Interest Rates
13
Internal Revenue Service. Failure to Pay Penalty
14
Office of the Law Revision Counsel. 26 USC 6501 – Limitations on Assessment and Collection
15
eCFR. 26 CFR 1.6664-4 – Reasonable Cause and Good Faith Exception to Section 6662 Penalties
16
Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments – Section: Reduction for Understatement Due to Position of Taxpayer or Disclosed Item