Federal Tax Procedures & Penalties
Filing requirements, estimated tax safe harbors, and preparer penalties under the Internal Revenue Code.
By SimplyCPA · Updated 27 September 2026
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Why this topic matters
Taxation and Regulation (REG) Area I tests filing deadlines, estimated tax requirements, and the penalties that apply to taxpayers and return preparers. Penalty questions are often calculation-based — especially the combined failure-to-file and failure-to-pay penalties.
Filing deadlines (calendar-year taxpayers)
| Return | Due date | Extension |
|---|---|---|
| Individual (Form 1040) | April 15 | 6 months (October 15) |
| C corporation (Form 1120) | April 15 (15th day of the 4th month) | 6 months (October 15) |
| S corporation (Form 1120-S) | March 15 (15th day of the 3rd month) | 6 months (September 15) |
| Partnership (Form 1065) | March 15 | 6 months (September 15) |
| Trust or estate (Form 1041) | April 15 | 5½ months (September 30) |
| Exempt organization (Form 990) | May 15 (15th day of the 5th month) | 6 months (November 15) |
| Gift tax (Form 709) | April 15 | Follows the income tax extension |
| Estate tax (Form 706) | 9 months after death | 6 months |
An extension extends the time to file, not the time to pay. Interest and the failure-to-pay penalty run from the original due date.
Estimated tax
Individuals
- Four installments: April 15, June 15, September 15, and January 15 of the following year.
- No penalty if the tax due after withholding and credits is less than $1,000.
- Safe harbors — pay the lesser of: 90% of the current year's tax, or 100% of the prior year's tax (110% if prior-year adjusted gross income (AGI) exceeded $150,000; $75,000 if married filing separately). The prior-year safe harbor requires a 12-month prior-year return.
- The annualized income installment method helps taxpayers with uneven income.
- Withholding is treated as paid evenly through the year, regardless of when withheld.
Corporations
- Installments on the 15th day of the 4th, 6th, 9th, and 12th months.
- No penalty if the tax is less than $500.
- Safe harbors: 100% of current-year tax, or 100% of prior-year tax (the prior-year safe harbor is not available to a large corporation — taxable income of $1 million or more in any of the 3 prior years — except for the first installment, or if the prior year showed no tax or was a short year).
Taxpayer penalties
| Penalty | Rate | Notes |
|---|---|---|
| Failure to file | 5% of net tax due per month or part of a month, maximum 25% | If more than 60 days late, a minimum penalty applies (the lesser of an indexed dollar amount or 100% of the tax due). Fraudulent failure to file: 15% per month, max 75%. |
| Failure to pay | 0.5% per month or part of a month, maximum 25% | Rises to 1% per month after an Internal Revenue Service (IRS) notice of intent to levy; reduced to 0.25% during an installment agreement for timely filers |
| Both in the same month | Failure to file is reduced by the failure-to-pay penalty — a combined 5% per month | |
| Accuracy-related | 20% of the underpayment | Negligence or disregard of rules; substantial understatement (individuals: exceeds the greater of 10% of the correct tax or $5,000; corporations: the lesser of 10% of correct tax (or $10,000 if greater) and $10 million); substantial valuation misstatements. 40% for gross valuation misstatements. |
| Civil fraud | 75% of the underpayment attributable to fraud | The IRS must prove fraud by clear and convincing evidence; not combined with the accuracy penalty on the same portion |
| Frivolous return | A flat penalty (indexed) | Positions based on frivolous arguments |
| Erroneous refund claim | 20% of the excessive amount | Without reasonable cause |
EXAMPLE: A taxpayer files 2 months and 10 days late, owing $10,000 with no payment, and has no reasonable cause. The partial month counts as a full month, so 3 months apply.
Failure to pay = 0.5% × 3 × $10,000 = $150.
Failure to file = (5% − 0.5%) × 3 × $10,000 = $1,350.
Total = $1,500 (plus interest).
Avoiding or reducing penalties
- Reasonable cause and absence of willful neglect (serious illness, natural disaster, reliance on a competent professional's advice).
- First-time abatement of failure-to-file and failure-to-pay penalties for taxpayers with a clean 3-year compliance history.
- For the substantial understatement penalty: the understatement is reduced by positions with substantial authority, or with a reasonable basis that are adequately disclosed (Form 8275) — not for tax shelters.
Interest
Interest on underpayments runs from the original due date until paid, at the federal short-term rate plus 3 percentage points (plus 5 for large corporate underpayments), compounded daily. Interest is not a penalty and generally cannot be abated for reasonable cause. It also runs on penalties.
Tax return preparer penalties
| Provision | Conduct | Penalty |
|---|---|---|
| §6694(a) | Understatement due to an unreasonable position (the preparer knew or should have known) | The greater of $1,000 or 50% of the income derived from the return |
| §6694(b) | Understatement due to willful or reckless conduct | The greater of $5,000 or 75% of the income derived |
| §6695 | Procedural failures: not furnishing a copy to the taxpayer, not signing, not including a Preparer Tax Identification Number (PTIN), not keeping copies, negotiating a refund check, failing due diligence for refundable credits and head of household status | Per-failure amounts (indexed); negotiating a refund check has its own penalty |
| §7216 / §6713 | Unauthorized disclosure or use of taxpayer information | Civil penalty per disclosure; criminal misdemeanor if knowing or reckless |
| §6701 | Aiding and abetting an understatement | Flat penalty per return |
Standards to avoid the §6694(a) penalty
| Position | Standard needed |
|---|---|
| Undisclosed position | Substantial authority (roughly 40% likelihood of being sustained) |
| Disclosed position | Reasonable basis (roughly 20%) |
| Tax shelter or reportable transaction | Reasonable belief that it is more likely than not (over 50%) to be sustained |
Reasonable cause and good faith is also a defense. A preparer may rely in good faith on client information but may not ignore implications of information furnished and must make reasonable inquiries if it seems incorrect or incomplete.
Criminal provisions
- Willful attempt to evade tax (a felony), willful failure to file or pay (a misdemeanor), and willfully making a false return (a felony).
- Generally a 6-year statute of limitations for criminal prosecution.
How it is tested
- Compute combined failure-to-file and failure-to-pay penalties.
- Apply the estimated tax safe harbors, including the 110% rule.
- Test the substantial understatement threshold.
- Match preparer conduct to the penalty and the standard needed to avoid it.
EXAM TIP: Remember the ladder of certainty: reasonable basis (with disclosure) → substantial authority (without disclosure) → more likely than not (tax shelters). Each step up protects a riskier position.