A tax position is any specific conclusion you reach about how the tax code applies to an item on your return. Every deduction you claim, every dollar of income you exclude, and every credit you take reflects a position about what the law allows. Some are routine. Others involve real uncertainty about how the IRS would read the same facts, and those are the ones that carry consequences if you get them wrong.
Everyday Examples of a Tax Position
The scope is broader than most people realize. Claiming a home office deduction is a tax position. So is treating payments from a legal settlement as nontaxable, classifying a worker as an independent contractor rather than an employee, or reporting business income on a Schedule C instead of through a partnership return. Any determination that changes the amount of tax you owe qualifies.
Positions also show up in timing choices: whether to recognize income this year or next, which depreciation method to apply to equipment, or how to allocate costs between personal and business use. For businesses, the stakes multiply. A multinational deciding how to split income across jurisdictions, or a company claiming a research credit on certain activities, is taking positions that can involve millions of dollars.
Signing the return means you stand behind every one of those choices. If the IRS later disagrees, the question becomes whether your position had enough legal support to avoid a penalty.
How Strong the Position Needs to Be
Federal regulations recognize three tiers of legal support, and each triggers different consequences.
Reasonable Basis
This is the floor. A reasonable basis exists when your position rests on at least one recognized legal authority, such as a statute, regulation, court case, or IRS ruling. The Treasury regulations describe the standard as “significantly higher than not frivolous or not patently improper,” and specifically note that a position which is “merely arguable” does not qualify.1GovInfo. 26 CFR 1.6662-3 – Penalties for Negligence or Disregard of Rules or Regulations
Reasonable basis matters because it is the minimum for avoiding penalties when you disclose the position. Fall below it, and disclosure alone will not save you.
Substantial Authority
This is the standard that matters most in everyday penalty avoidance. The regulation defines it as an objective analysis comparing the authorities that support your position against those that contradict it. It is more demanding than reasonable basis but less demanding than “more likely than not.”2eCFR. 26 CFR 1.6662-4 – Substantial Understatement of Income Tax
The authorities you can weigh include the Internal Revenue Code, Treasury regulations (proposed, temporary, and final), revenue rulings and procedures, tax treaties, court cases, congressional committee reports, private letter rulings issued after October 31, 1976, and other IRS pronouncements published in the Internal Revenue Bulletin.3U.S. Government Publishing Office. 26 CFR 1.6662-4 – Substantial Understatement of Income Tax If a position is supported by substantial authority, you avoid the accuracy-related penalty on that item without disclosing anything extra.
More Likely Than Not
This is the highest standard, requiring a greater than 50% probability that the position would be upheld on its merits.2eCFR. 26 CFR 1.6662-4 – Substantial Understatement of Income Tax It applies primarily to tax shelters, which the Code defines as any partnership, entity, investment plan, or arrangement where a significant purpose is avoiding federal income tax.4Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments For shelter items, the usual escape hatches of disclosure and reasonable basis are not available. You either clear this higher bar or face the penalty.
What It Costs When a Position Fails
The consequences depend on how far off the position was and whether the IRS treats it as careless, aggressive, or frivolous.
The 20% Accuracy-Related Penalty
The most common penalty is a flat 20% of the underpayment tied to the problematic position. It applies when the underpayment results from negligence, disregard of rules, or a substantial understatement of income tax.4Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments
For individuals, a “substantial understatement” means you understated your tax by the greater of 10% of the correct tax or $5,000. If you claimed a qualified business income deduction under Section 199A, the percentage drops to 5%, though the $5,000 floor stays the same. For C corporations, the understatement must exceed the lesser of 10% of the correct tax (or $10,000 if greater) and $10 million.5Internal Revenue Service. Accuracy-Related Penalty
The Frivolous Return Penalty
Positions that cross from aggressive into absurd carry a separate $5,000 penalty per return. The IRS imposes it when a filing either lacks enough information to verify the self-assessment or contains information that is clearly wrong on its face, and the position has been identified by the IRS as frivolous. The same $5,000 penalty applies to frivolous submissions such as collection due process hearing requests based on tax-protester arguments. You can avoid the penalty only by withdrawing the submission within 30 days of notice from the IRS.6Office of the Law Revision Counsel. 26 USC 6702 – Frivolous Tax Submissions
Penalties on Your Preparer
Penalties do not fall on the taxpayer alone. A return preparer who takes an unreasonable position (one lacking substantial authority, or lacking reasonable basis when disclosed) faces a penalty equal to the greater of $1,000 or 50% of the income the preparer earned from that return. If the preparer’s conduct was willful or showed reckless disregard for the rules, the penalty jumps to the greater of $5,000 or 75% of the income derived from the return.7Office of the Law Revision Counsel. 26 USC 6694 – Understatement of Taxpayer’s Liability by Tax Return Preparer
How Disclosure Changes the Math
Disclosure is the most underused tool for managing the risk of a shaky position. The mechanism is simple. If your position has substantial authority, you avoid the accuracy-related penalty automatically. If it falls short of substantial authority, you can still escape the penalty by adequately disclosing the position and showing that it has at least a reasonable basis.4Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments Disclosure without a reasonable basis does nothing, and disclosure of tax shelter items provides no protection at all.
Form 8275 and Form 8275-R
The standard disclosure vehicle is Form 8275, the Disclosure Statement. You attach it to your return and describe items for which you are taking a position that may not meet the substantial authority standard. The form asks for a concise description of the item and the reason for the tax treatment.8Internal Revenue Service. Instructions for Form 8275
If your position directly contradicts an existing Treasury regulation, Form 8275 is not enough. You need Form 8275-R, the Regulation Disclosure Statement, instead.9Internal Revenue Service. Form 8275 (Rev. October 2024) Taking a position contrary to a regulation is inherently aggressive, and the IRS wants that flagged separately.
Adequate Disclosure Built Into the Return
Not every uncertain position needs a Form 8275. The IRS publishes an annual revenue procedure listing items that are considered adequately disclosed simply by filling out the return correctly. For returns filed on 2025 tax forms, Rev. Proc. 2026-12 identifies those items.10IRS.gov. Bulletin No. 2026-7 If your position involves an item not covered by that procedure, you need Form 8275 or 8275-R for the disclosure to count.
When Professional Advice Shields You
Relying on a tax professional can serve as a “reasonable cause and good faith” defense against accuracy-related penalties, but the defense has specific requirements. Simply hiring someone with a CPA license is not enough. The IRS and courts apply a three-part test: the advisor must have been competent in the relevant area of tax law, you must have given all necessary and accurate information, and you must have actually relied on the advice when filing.11IRS.gov. Reasonable Cause and Good Faith
The advice itself must rest on reasonable factual and legal assumptions and must consider all relevant facts you provided. If the advisor relied on assumptions you knew (or should have known) were inaccurate, the defense collapses. The IRS also weighs your own sophistication: a taxpayer with extensive business experience will have a harder time claiming innocent reliance than someone filing a first complex return.11IRS.gov. Reasonable Cause and Good Faith
One boundary matters here. The reasonable cause defense for relying on professional advice applies only to technical tax questions, not to factual matters. If you told your accountant that a personal vacation was a business trip, you cannot blame the accountant for deducting it.
Documenting the Position Before You File
A tax position you cannot explain is a tax position you cannot defend. Assemble your support before you file, not after a notice arrives.
Identify the specific Code sections, regulations, or rulings that authorize the treatment you are claiming. If a court case supports your reading, note the case name, court, and the specific holding that applies to your facts. Private letter rulings and technical advice memoranda can bolster a position, though private letter rulings technically apply only to the taxpayer who requested them.
Legal authority is only half the record. Transaction dates, amounts, parties involved, and the business purpose behind each item all need to be documented in a way an examiner can follow. Positions often fail in audit not because the legal theory was wrong but because the taxpayer could not prove the underlying facts.
The IRS recommends keeping tax records for at least three years after filing. For items tied to property, stock transactions, retirement accounts, or rental income, longer retention is wise because the IRS may have an extended window to challenge those positions.12IRS. Managing Your Tax Records After You Have Filed
How Long the IRS Can Challenge Your Position
The standard window for the IRS to assess additional tax is three years from the later of the return’s due date (including extensions) or the date you actually filed.13Internal Revenue Service. Time IRS Can Assess Tax That clock governs the vast majority of tax positions.
Two situations extend it. If you omitted more than 25% of your gross income from the return, the IRS gets six years.13Internal Revenue Service. Time IRS Can Assess Tax If the return was fraudulent or you never filed at all, there is no time limit whatsoever. The three-year clock also pauses when the IRS issues a formal notice of deficiency or if you file for bankruptcy.
These deadlines drive documentation choices. If you took an aggressive depreciation position on a building you bought this year, you may need to defend it in an audit that starts two or three years from now. Dispose of your records too early and you lose the ability to prove you were right.