The Internal Revenue Code provides that the IRS shall abate any penalty for failure to file, failure to pay, or failure to deposit when the taxpayer establishes that the failure was due to reasonable cause and not to willful neglect. The phrase is statutory — drawn from IRC §6651, §6656, §6664(c), and §6724(a) — and the standard is interpreted through Treasury Regulations and the Internal Revenue Manual.
The legal standard
Reasonable cause exists when the taxpayer exercised ordinary business care and prudence in determining and meeting their tax obligations, but was nevertheless unable to comply due to circumstances beyond their control. The IRS examiner reviews:
- What the taxpayer's ordinary process was — internal records, advisor relationships, calendaring practices
- What event interrupted that process — and when it began, how long it lasted, how it specifically prevented compliance
- What the taxpayer did once the event resolved — speed of corrective action, voluntary compliance
- Whether ordinary business care would have anticipated or insured against the event
What the IRS accepts
Recurring patterns the IRS has accepted as reasonable cause:
- Serious illness or incapacity of the taxpayer or an immediate family member responsible for tax matters
- Death of an immediate family member during the filing window
- Casualty, disaster, or theft — both federally declared (automatic relief) and undeclared (case-by-case)
- Unavoidable absence — military deployment, hospitalization, incarceration without ability to delegate
- Records destroyed or unobtainable — fire, flood, third-party custodian failure
- Reliance on incorrect written IRS advice (statutory exception under §6404(f))
- Reliance on a tax professional — narrow but applies when the failure was the professional's error rather than the taxpayer's neglect
The Supreme Court's 1985 United States v. Boyle decision established that a taxpayer's reliance on a professional to file a return generally is NOT reasonable cause — filing is a non-delegable duty. Reliance on a professional's substantive tax advice, however, CAN be reasonable cause when the advice was based on a full disclosure of the facts. The line is between "the CPA forgot to mail it" (no relief) and "the CPA advised an incorrect filing position" (relief possible).
What the IRS rejects
- Ignorance of the filing requirement — generally not reasonable cause for sophisticated taxpayers
- Lack of funds — alone, not reasonable cause for failure-to-pay; circumstances causing the lack of funds may qualify
- Vague employee mistakes without documentation of the specific error and the taxpayer's internal controls
- Generic "forgot" or "was busy" claims — not the standard
How to substantiate
The reasonable-cause statement attached to Form 843, Line 7 should:
- State the penalty being challenged and the tax period
- Describe the taxpayer's normal process for ensuring timely compliance
- Describe the specific event that interrupted compliance — with dates
- Explain how the event prevented timely action — causally, not just temporally
- Describe corrective steps once the event resolved, with dates
- Attach supporting documents — medical records, FEMA notices, death certificates, correspondence, etc.
See the letter examples for five drafted reasonable-cause statements covering common scenarios.