S-Corp Late Filing Penalty: Calculation, Waivers, and Abatement

The S-corp late filing penalty is $255 per shareholder for every month, or part of a month, that Form 1120-S is late, capped at 12 months. That rate applies to returns due in 2026.¹ The penalty is charged to the corporation itself, and it applies even if the S-corp owes no federal income tax, because Form 1120-S is an information return. Several relief options exist, and one of them acts as an automatic waiver for most small S-corporations whose shareholders filed their personal returns on time.

How the Penalty Is Calculated

Internal Revenue Code Section 6699 sets the formula: $255 multiplied by the number of people who were shareholders at any point during the tax year, multiplied by the number of months the return is late. A partial month counts as a full month. The meter stops at 12 months, so the maximum per shareholder is $3,060.²

The base amount in the statute is $195, adjusted annually for inflation. $255 is the figure for returns required to be filed in 2026.¹

What the math looks like at different scales:

Single-owner S-corp, 2 months late: $255 × 1 × 2 = $510
Three shareholders, 5 months late: $255 × 3 × 5 = $3,825
Six shareholders, 12 months late (the maximum): $255 × 6 × 12 = $18,360

A return that arrives on time but is missing required information, such as a shareholder’s Schedule K-1 or the financial data called for under Section 6037, triggers the same penalty as filing nothing at all.²

When the Return Is Due

Calendar-year S-corporations must file Form 1120-S by March 15. Fiscal-year S-corps file by the 15th day of the third month after their tax year ends, so a June year-end means a September 15 deadline. When the date falls on a weekend or holiday, it shifts to the next business day.³

Filing Form 7004 on or before the original deadline buys an automatic six-month extension. The extension itself has to be timely. A Form 7004 filed on March 16 does nothing for a March 15 deadline, and the penalty starts running from that original date.⁴

Interest on the Penalty

Interest accrues on the unpaid penalty from the original return due date, without regard to any extension, and it runs until the balance is paid.⁵ The IRS sets the underpayment rate quarterly. For the first quarter of 2026, the rate is 7% for non-corporate taxpayers, compounded daily.⁶

The IRS almost never abates interest. Even a successful penalty abatement can leave the interest that accrued beforehand on the account.

The Automatic Waiver Most Small S-Corps Qualify For

Check this option first. Revenue Procedure 84-35 was written for partnerships, but the IRS applies it to S-corporations too, and the CP162A penalty notice itself points to this relief.⁷

An S-corporation qualifies when all of the following are true:

The corporation had 10 or fewer shareholders during the year, and each shareholder is a natural person or an estate. Trusts and corporate shareholders disqualify the entity.
Each shareholder’s share of every income, deduction, and credit item is proportional to ownership, and that same proportion applies across all items.
Every shareholder timely filed a personal return that reported their full share of the S-corp’s income, deductions, and credits.

A married couple, and their estates, count as one shareholder for the 10-person limit. In practice, a typical one-to-five-owner S-corp where everyone filed their 1040 on time with the right K-1 numbers already qualifies. Minor clerical errors on a shareholder’s return will not defeat the waiver, but a material understatement of income will.

First-Time Abatement If 84-35 Doesn’t Apply

If the small-corporation waiver doesn’t fit, the next option is First-Time Abatement, an administrative policy that requires no explanation of why the return was late. It requires only a clean compliance history.⁸

You qualify when both of these are true:

The S-corporation filed Form 1120-S for each of the three tax years before the penalty year, where a return was required.
No penalties were assessed against the corporation during those three prior years, or any penalty that was assessed was removed for a reason other than First-Time Abatement itself.

You do not have to pay the penalty first. The IRS explicitly allows First-Time Abatement requests on unpaid balances.⁸ The IRS will check your account history when you call; you don’t need to submit documents, though naming the relief by name can move things along.

Reasonable Cause

Reasonable cause is the broadest category and the hardest to win. The corporation has to show the late filing came from circumstances beyond its control, not neglect.² The IRS recognizes situations like these:

Fires, natural disasters, or civil disturbances
Death, serious illness, or unavoidable absence of the taxpayer or an immediate family member
Inability to obtain records needed to prepare the return
System issues that prevented timely electronic filing or payment

⁹

Reliance on a tax professional who missed the deadline is generally not enough. The IRS takes the position that the corporation is responsible for timely filing even when it hires someone else. Not knowing about the filing requirement, making a mistake, and lacking funds to pay a preparer also do not qualify on their own.⁹

A reasonable cause request needs a written explanation with contemporaneous documentation. Medical records, insurance claims, written acknowledgment of fault from a preparer, or outage records from your e-file provider all help. Vague statements about difficult circumstances do not.

How to Request Relief

Any of the three relief options can start with a call to the toll-free number on the penalty notice. Phone requests work well for First-Time Abatement, because the agent can check compliance history on the spot.¹⁰

When the call doesn’t settle it, or when your case needs documentation (which reasonable cause almost always does), send a written request or file Form 843, Claim for Refund and Request for Abatement. Include the corporation’s name, EIN, the tax period, and a clear statement of which relief provision applies, with supporting documents attached for reasonable cause.¹¹

Layer your arguments. Lead with Revenue Procedure 84-35 if you qualify, then First-Time Abatement, then reasonable cause. Nothing stops you from raising all three in one letter, and if the first fails the IRS should move to the next.

If the IRS Denies Your Request

A denied abatement is not the end. The IRS notifies you in writing, and you can request a conference with the IRS Independent Office of Appeals. Appeals officers have broader settlement authority than the initial examiner.

If Appeals also denies relief, the remaining path is to pay the penalty, file Form 843 as a refund claim, and if that claim is denied, sue in U.S. District Court or the U.S. Court of Federal Claims. That route is slow and expensive, so it only makes sense when the penalty is large. For a single-owner S-corp facing $510, litigation costs more than the penalty. For a six-owner corporation hit with the $18,360 maximum, the math is different.

State Penalties Are Separate

Most states with an income tax also require S-corporations to file a state-level return, and many assess their own late-filing penalties. These range from flat fees to percentage-based charges tied to state tax due. A federal extension does not automatically extend the state deadline everywhere, so check the rules in each state where the corporation files.

1
Internal Revenue Service. Rev. Proc. 2024-40 – Inflation Adjusted Items for 2026
2
Office of the Law Revision Counsel. 26 USC 6699 – Failure to File S Corporation Return
3
Internal Revenue Service. About Form 1120-S, U.S. Income Tax Return for an S Corporation
4
eCFR. 26 CFR 1.6081-3 – Automatic Extension of Time for Filing Corporation Income Tax Returns
5
Internal Revenue Service. Topic No. 653, IRS Notices and Bills, Penalties and Interest Charges
6
Internal Revenue Service. Interest Rates Remain the Same for the First Quarter of 2026
7
Internal Revenue Service. Understanding Your CP162A Notice
8
Internal Revenue Service. Administrative Penalty Relief
9
Internal Revenue Service. Penalty Relief for Reasonable Cause
10
Internal Revenue Service. Penalty Relief
11
Internal Revenue Service. About Form 843, Claim for Refund and Request for Abatement