IRC 6651: Failure to File and Failure to Pay Penalties

1. Overview and Statutory Basis

IRC 6651 is the primary civil penalty provision governing a taxpayer's failure to satisfy two distinct filing and payment obligations: (1) the duty to file a return on or before its due date and (2) the duty to pay the tax shown on that return when due. Although both penalties are codified within the same section, they arise from separate obligations, accrue at different rates, and carry independent maximum caps. They also interact through a statutory offset mechanism that prevents the combined burden from doubling during the months that both run simultaneously.

The penalties are additions to tax, not separate tax assessments. They are assessed and collected in the same manner as the underlying tax under IRC 6665. Interest under IRC 6601 also accrues on the penalty amount from the due date forward, compounding the total liability for non-compliant taxpayers.

Treas. Reg. 301.6651-1 provides the interpretive framework for determining net tax due, computing the penalty base, and evaluating the reasonable cause exception. The IRS coordinates penalty administration through IRM 20.1.1 (Failure to File/Failure to Pay Penalties), with the 2025 revision of IRM 20.1.1.3 updating First-Time Abatement qualification criteria and escalation procedures.

2. Failure to File: IRC 6651(a)(1)

The failure-to-file (FTF) penalty applies when a required tax return is not filed by the statutory due date, including any extension period. The base penalty is 5% of the amount of tax required to be shown on the return that is not shown, for each month or fraction of a month that the failure continues, up to a maximum of 25% of that amount.

Net tax due computation. The penalty base is the "net tax due," defined as the tax required to be shown on the return, reduced by: (a) the amount of tax paid on or before the due date; (b) credits allowable under Subtitle A that are not refundable credits; and (c) amounts imposed as additional tax under chapter 1. Withholding credits and estimated tax payments made before the return's due date reduce the base directly.

Extension to file vs. extension to pay. An approved extension of time to file (Form 4868 for individuals; Form 7004 for businesses) suspends the FTF penalty during the extension period. However, an extension to file does not extend the time to pay. Tax not paid by the original payment due date will accrue the FTP penalty under IRC 6651(a)(2) even during an approved filing extension. Practitioners must advise clients that an extension of time to file is not an extension of time to pay.

Fraction-of-month counting. Any fraction of a month is counted as a full month for penalty accrual purposes. A return due April 15 and filed on May 2 has been late for two months (April 15 to May 1 = one month; May 1 to May 2 = a fraction counted as one additional month).

3. Failure to Pay: IRC 6651(a)(2)

The failure-to-pay (FTP) penalty applies when a taxpayer fails to pay the tax shown on a return by the due date of that return. The penalty rate is 0.5% of the unpaid tax for each month (or fraction of a month) that the failure continues, up to a maximum of 25% of the amount of tax initially unpaid.

Start date and ongoing accrual. The FTP penalty begins accruing on the first day after the payment due date. It continues to run on the outstanding balance -- not the original balance -- so payments that reduce the principal also reduce the accruing penalty base going forward. Full payment of the underlying tax stops the FTP penalty from accruing further; interest on the penalty balance continues until paid.

Penalty base during assessed-but-unpaid periods. The FTP penalty under IRC 6651(a)(2) applies to tax "shown on" a return. Tax assessed through a Substitute for Return (SFR) under IRC 6020(b) is treated as tax shown on a return for FTP purposes, because the SFR assessment is deemed a return filed by the taxpayer under the statute. Non-filers who are in the SFR pipeline face FTP accrual from the original payment due date even though no return was voluntarily filed.

Installment agreement rate reduction. When a taxpayer enters into an installment agreement that is approved and in effect, IRC 6651(h) reduces the FTP rate from 0.5% to 0.25% per month. The reduced rate applies only during the period the agreement remains in force. Default on the agreement -- through missed payments, failure to file returns, or other noncompliance -- reinstates the 0.5% rate from the date of default.

4. Concurrency and the IRC 6651(c)(1) Offset Rule

When both the FTF and FTP penalties apply for the same calendar month, IRC 6651(c)(1) reduces the failure-to-file rate by the failure-to-pay rate applicable for that month. This offset prevents the taxpayer from being charged the full 5% FTF and the full 0.5% FTP independently during the same month.

During concurrent months, the effective rates are:

• FTF (after offset): 4.5% per month (5% minus 0.5%)
• FTP: 0.5% per month
• Combined: 5.0% per month

The offset continues for as long as both penalties run in the same month. Practitioners should note that the maximum FTF penalty (25%) is reached based on the unreduced 5% rate. Once the FTF cap is hit, that penalty stops accruing. The FTP penalty continues independently at 0.5% per month until it separately reaches its 25% ceiling at 50 months of accrual.

5. Extension to File vs. Extension to Pay: A Critical Distinction

Practitioners frequently need to clarify for clients that a Form 4868 extension does not relieve the taxpayer of the obligation to pay estimated tax by the original due date. The FTF penalty suspension that comes with an approved extension applies only to the obligation to file the return; the FTP penalty begins accruing on any unpaid balance the day after the original payment due date, extension or not.

Under Treas. Reg. 301.6651-1(b), a taxpayer who files a valid extension and pays at least 90% of the tax shown on the return by the original due date avoids the FTP penalty for the period through the extension date. Any remaining balance not paid by the extended due date begins accruing FTP from that date forward. The 90% safe harbor is an important planning tool: if a client cannot pay the full amount, computing the estimated balance and remitting 90% eliminates FTP exposure through the extension date.

Estimated tax payments vs. extension payments. Timely estimated tax payments (Form 1040-ES) reduce the net tax due on the original due date and therefore reduce both the FTF and FTP penalty bases. A client who fully satisfies the tax liability through timely estimated payments has no FTP exposure, even if the return is filed late, because the penalty base (unpaid tax) is zero.

6. Substitute for Return: IRC 6020(b) Pipeline Interaction

When a taxpayer fails to file a return and the IRS prepares a Substitute for Return (SFR) under IRC 6020(b), the assessment that results is treated as a return filed by the taxpayer for most purposes, including the accrual of the FTP penalty. The SFR does not stop the FTF penalty, which continues to accrue until the taxpayer actually files a return or the FTF maximum is reached.

Effect of filing a superseding return. A taxpayer who files a delinquent original return after an SFR assessment stops the FTF penalty from the date the delinquent return is filed (going forward). The FTF penalty already accrued to that date remains. If the delinquent return shows a lower tax liability than the SFR, the penalty base retroactively adjusts to the correct net tax due, which can reduce the penalty already assessed.

Reasonable cause on delinquent filing. Even when the IRS has prepared an SFR, a taxpayer who files a delinquent original return and requests penalty abatement based on reasonable cause or FTA can obtain relief on both the FTF and FTP penalties. The SFR pipeline does not foreclose abatement; it merely means the penalty has already been assessed and abatement must be pursued through the established request procedures (Form 843 or written request to the service center).

For detailed guidance on SFR procedures and the strategy for challenging or superseding an SFR assessment, see IRS Substitute for Return (SFR): IRC 6020(b) and Practitioner Strategy.

7. Reasonable Cause Defense

IRC 6651(a) provides that no penalty applies if the taxpayer shows that the failure to file or pay was due to reasonable cause and not due to willful neglect. The statute places the burden of proof on the taxpayer. Reasonable cause is evaluated under a facts-and-circumstances standard based on whether the taxpayer exercised ordinary business care and prudence and was nonetheless unable to comply.

IRM 20.1.1.3 factors. The IRS manual provides a non-exhaustive list of circumstances that may support reasonable cause: (a) serious illness of the taxpayer or an immediate family member; (b) natural disaster, fire, or casualty that destroys records or prevents compliance; (c) unavoidable absence of the taxpayer; (d) inability to obtain records despite diligent effort; (e) erroneous advice from the IRS itself; and (f) a taxpayer's reasonable reliance on professional advice regarding the amount of tax owed (as distinct from the filing deadline).

The Boyle rule for filing deadlines. United States v. Boyle, 469 U.S. 241 (1985), holds that a taxpayer cannot rely on a tax professional's advice regarding the due date of a return as reasonable cause for failure to file. The Court reasoned that the taxpayer has a non-delegable duty to timely file, and filing deadlines are matters of public record. Reliance on an attorney or accountant to timely file does not constitute reasonable cause for the FTF penalty. However, Boyle does not bar reasonable cause defenses based on reliance on professional advice about the amount owed or the correct method of reporting -- those involve substantive judgment questions, not a fixed calendar obligation.

Willful neglect standard. To defeat a reasonable cause defense, the IRS need only show that the failure was due to willful neglect, defined as a conscious, intentional failure or reckless indifference. Evidence of willful neglect includes a pattern of repeated failures, filing only after IRS contact, or concealment of income.

Substantiation requirements. A reasonable cause request should include: a detailed narrative of the circumstances, with dates and supporting documentation (medical records, insurance claims, disaster declarations), and a statement from the taxpayer explaining the connection between the cited circumstances and the inability to file or pay timely. The IRS will evaluate whether the circumstances affected the taxpayer specifically or only generally.

8. First-Time Abatement (FTA)

First-Time Abatement is an administrative waiver policy established under IRM 20.1.1.3.6.1. It permits the IRS to waive the failure-to-file, failure-to-pay, and failure-to-deposit penalties for a taxpayer who has a clean compliance history in the three prior tax years. FTA does not require the taxpayer to demonstrate a specific hardship or unusual circumstance; it is based solely on prior compliance.

FTA eligibility criteria. To qualify, the taxpayer must satisfy all three of the following:

1. Filed (or timely extended and filed) all required returns for the three prior tax years;
2. Has no unpaid penalties assessed in those three prior years (other than the estimated tax penalty under IRC 6654 or 6655); and
3. Has filed the return for the current year (or has an extension on file).

Significantly, FTA is applied to the earliest year for which the taxpayer qualifies. If a taxpayer has penalties for multiple years, FTA eliminates the penalty for only one year (the first eligible year). Subsequent year penalties require a separate grounds-based abatement request.

How to request FTA. The most efficient method is a telephone request to the IRS Penalty Abatement line during a call to the appropriate compliance unit. FTA is a scripted waiver that IRS representatives can apply in real time without supervisory referral in most cases. Alternatively, FTA can be requested in writing via Form 843 (Claim for Refund and Request for Abatement) or in a formal letter submitted to the service center. Written requests take significantly longer to process.

See IRS Penalty Abatement: Reasonable Cause, FTA, and CP 2000 Requests for detailed abatement procedure and escalation strategy.

9. Supervisory Approval Requirement: IRC 6751(b)

IRC 6751(b)(1) requires that no penalty under the Code shall be assessed unless the initial determination of the penalty assessment was personally approved, in writing, by the immediate supervisor of the individual making the determination. This requirement applies to IRC 6651 penalties and is a substantive procedural safeguard, not merely an internal administrative requirement.

Chai and Graev line of cases. The circuit split and Tax Court evolution on this requirement began with Chai v. Commissioner, 851 F.3d 190 (2d Cir. 2017), which held that a penalty notice sent to the taxpayer before supervisory approval was obtained renders the penalty invalid. The Tax Court subsequently aligned with Chai in Graev v. Commissioner, 149 T.C. 485 (2017) (reviewed), and the IRS issued T.D. 10017 to establish updated regulations clarifying the timing of the approval requirement.

Timing of the approval. Under the current rule (post T.D. 10017), supervisory approval must be obtained before the initial determination of the penalty is communicated to the taxpayer. For examination-sourced penalties, this means before the Revenue Agent's Report (RAR) or 30-day letter is issued. For automated penalties, the IRS has argued that computational penalties assessed without examiner involvement do not require individual supervisory sign-off, but practitioners should request and review the approval documentation in any contested penalty case.

Raising the 6751(b) defense. This is a threshold procedural defense that should be raised in the notice of deficiency response, the Tax Court petition, or the CDP hearing request, as applicable. The taxpayer bears no burden on this issue -- if the IRS cannot produce a timely supervisory approval document, the penalty falls. Practitioners should routinely request the approval record through the IRS's administrative file or through a Freedom of Information Act (FOIA) request when a penalty is at issue.

10. One Big Beautiful Bill Act: Penalty Timing Developments

The One Big Beautiful Bill Act (OBBBA), enacted in 2025, introduced several provisions affecting the timing of tax obligations that interact with IRC 6651 penalty accrual. Practitioners working on delinquency matters for tax years 2025 and later should be aware of two specific areas of interaction.

Modified payment deadlines for certain taxpayers. OBBBA provisions that shift the applicable due dates for certain business entities and pass-through returns affect the starting point for FTF and FTP penalty accrual. A return that was due on a modified OBBBA-driven date for tax year 2025 has a different penalty start date than a return governed by the prior-law calendar. Practitioners should verify the correct due date -- including any OBBBA adjustments -- before computing penalty accrual in a delinquency representation matter.

IRM 20.1.1.3 revisions (2025). The 2025 revision of IRM 20.1.1.3 clarified the IRS's internal procedures for processing abatement requests in cases where an OBBBA-related extension or modification affected the original due date. These revisions also updated penalty notice templates to reflect modified dates and introduced a supplemental FTA eligibility check for taxpayers who had returns due on OBBBA-shifted dates in 2024 and 2025.

Because the OBBBA penalty interaction rules are recent and implementation is ongoing, practitioners should confirm current IRM provisions and any interim guidance before relying on penalty computations for OBBBA-affected returns.

11. Practitioner Workflow: From Intake to Resolution

Step 1: Pull compliance transcripts immediately. Before any client conversation about penalties, obtain the Account Transcript (IMRS) and the Wage and Income Transcript for all years at issue. The Account Transcript shows: (a) the filing date and any SFR assessments; (b) all penalty assessments, dates, and amounts; (c) payments applied; and (d) any prior abatement history, including FTA grants.

Step 2: Compute the correct penalty base. Verify that the IRS has computed the FTF and FTP penalties on the correct net tax due. The penalty base is reduced by credits and payments made before the due date, not by payments made later. Common IRS errors include applying withholding credits after the due date when they should reduce the base, or computing FTF on the gross tax liability without credit for timely estimated payments.

Step 3: Assess the 6751(b) defense. Request the supervisory approval record for any penalty that arose in examination. If the IRS cannot produce timely approval, raise this procedural defense before engaging the merits of reasonable cause or abatement.

Step 4: Evaluate FTA first. Pull three years of prior filing history from the transcript. If the client has clean prior compliance (no penalties, no late filing), FTA is the fastest and most reliable abatement path. Call the penalty abatement line with the transcript in hand. FTA waives the penalty without requiring substantiation of circumstances.

Step 5: Build the reasonable cause narrative if FTA is unavailable. If FTA does not apply, construct the reasonable cause request around the specific IRM 20.1.1.3 factors supported by the client's records. Document the causal link between the qualifying event and the inability to file or pay by the due date. Avoid generic hardship language; the IRS evaluates whether the particular taxpayer was unable to comply, not merely inconvenienced.

Step 6: Coordinate filing and payment compliance. Abatement requests are stronger when the client is in current compliance at the time of the request. File all delinquent returns before submitting an abatement request; the IRS's systemic procedures often require all returns to be filed as a prerequisite for penalty resolution consideration. For non-filers with SFR assessments, filing the delinquent original return stops future FTF accrual and may reduce the penalty base.

See IRS Non-Filer Resolution: Voluntary Compliance Strategy and Collection Exposure for the full intake-to-resolution sequence for delinquent filers.

12. Claims and Limitations Notice