The late filing penalty for a 1120-S is $255 per shareholder for every month or partial month the return is overdue, capped at 12 months.1Internal Revenue Service. Instructions for Form 1120-S (2025) It applies even when the S corporation owes no federal tax, because Form 1120-S is an informational return and the IRS uses the penalty to force the filing itself. A five-shareholder S corporation that files four months late owes $5,100 before interest or anything else is added.
How the Penalty Is Calculated
Three numbers drive the charge: the monthly rate, the number of shareholders, and the number of months the return is late. Under 26 U.S.C. § 6699, the IRS multiplies a fixed dollar amount by the number of people who were shareholders at any point during the tax year, then multiplies that result by the number of months (or any fraction of a month) the return is outstanding.2Office of the Law Revision Counsel. 26 USC 6699 – Failure to File S Corporation Return The statutory base is $195, adjusted annually for inflation. For returns required to be filed in 2026, the figure is $255.1Internal Revenue Service. Instructions for Form 1120-S (2025) The penalty stops accruing after 12 months, no matter how long the return goes unfiled.
A calendar-year S corporation with three shareholders that files six months past its extended September 15 deadline would owe:
$255 × 3 shareholders × 6 months = $4,590
The partial-month rule catches people off guard. A one-day slip into a new month counts as a full month. If that same corporation filed on September 17, two days past the deadline, the penalty would already be $765 ($255 × 3 × 1). The clock does not wait until the end of the month to start.
Zero Tax Owed Does Not Help
Most S corporations have a $0 balance at the entity level because income passes through to shareholders. The § 6699 penalty exists to enforce filing of the informational return, not to collect tax, so the full per-shareholder charge still applies to a company that lost money all year.3Internal Revenue Service. Failure to File Penalty – Section: S Corporation Returns (Form 1120-S)
When the Corporation Owes Tax at the Entity Level
A few situations create a real corporate tax bill for an S corporation. The two most common are the built-in gains tax, which hits appreciated assets a converted C corporation sells within a five-year recognition period and is taxed at 21%,4Office of the Law Revision Counsel. 26 USC 1374 – Tax Imposed on Certain Built-in Gains and the excess net passive income tax, which can apply when a former C corporation still carries accumulated earnings and profits and more than 25% of its gross receipts come from passive sources like rents, royalties, or interest.5Office of the Law Revision Counsel. 26 USC 1375 – Tax Imposed When Passive Investment Income of Corporation Having Accumulated Earnings and Profits Exceeds 25 Percent of Gross Receipts
When tax is actually owed, the penalty picture changes. The IRS adds 5% of the unpaid tax for each month the return is late, capped at 25%, on top of the per-shareholder charge. A return more than 60 days overdue also triggers a minimum penalty of $525 for the 2026 filing year, or the full tax due if that is less.1Internal Revenue Service. Instructions for Form 1120-S (2025) A separate failure-to-pay penalty of 0.5% per month, also capped at 25%, runs alongside, with interest compounding daily. When both the failure-to-file and failure-to-pay penalties apply in the same month, the IRS reduces the failure-to-file portion by the failure-to-pay amount to prevent full double-charging.6Internal Revenue Service. Failure to Pay Penalty
Late K-1 Penalties Stack on Top
Filing Form 1120-S late also delays the Schedule K-1s shareholders need for their personal returns, and that triggers a separate penalty under 26 U.S.C. § 6722 for failing to furnish correct payee statements on time. For statements due in 2026, the penalty is $340 per K-1 if the failure continues past August 1 of the year the statement was due, and it jumps to $680 per K-1 with no annual cap when the IRS determines the failure was intentional.7Internal Revenue Service. Information Return Penalties These charges are independent of the § 6699 penalty and stack on top of it. An S corporation with 10 shareholders that files months late can face both the $255 per shareholder per month and $340 per late K-1 at the same time.
The Deadline and the Extension That Prevents the Penalty
Form 1120-S is due on the 15th day of the third month after the tax year ends. For calendar-year S corporations, that is March 15.8Internal Revenue Service. About Form 1120-S, U.S. Income Tax Return for an S Corporation Filing Form 7004 before the original due date gives an automatic six-month extension to September 15.9Internal Revenue Service. About Form 7004 The extension covers only the return itself, not payment of any corporate-level tax. The late filing penalty applies only when the return is not submitted by the extended due date, or when no valid extension was requested.
Getting the Penalty Removed
First-Time Abate
If the S corporation has a clean recent compliance history, the easiest route is the IRS First-Time Abate program. It is an administrative waiver, which means you do not need to prove a disaster or emergency. The IRS specifically lists the § 6699(a)(1) S corporation late filing penalty as eligible. To qualify, the corporation must have filed Form 1120-S for the three prior tax years, received no penalties during those years (or had any prior penalty removed for a reason other than First-Time Abate), and be current on all required filings or valid extensions.11Internal Revenue Service. Administrative Penalty Relief
Call the number on the penalty notice. The IRS can often approve First-Time Abate during that call. If you have never been hit with this penalty before, make this your first move before building a reasonable cause argument.
Reasonable Cause
If First-Time Abate is not available, usually because the corporation received a penalty in the prior three years, the fallback is a reasonable cause request. You must show the corporation used ordinary care and prudence but still could not file on time, and that the failure was not due to willful neglect.10Internal Revenue Service. Penalty Relief for Reasonable Cause
The IRS decides reasonable cause case by case. Circumstances it recognizes include fires, natural disasters, or civil disturbances that destroyed records or blocked access to the business; death, serious illness, or unavoidable absence of the person responsible for the filing; inability to obtain necessary records; and system issues that delayed a timely electronic filing. For a business, the IRS looks at whether the circumstances affected the specific person with authority to submit the return.12Internal Revenue Service. Penalty Relief for Reasonable Cause A hospitalized sole officer is compelling. An office manager out sick while the CEO could have filed is much weaker.
Put the request in writing on Form 843 if the IRS cannot resolve it by phone, and attach documentation: hospital records, insurance claims, correspondence showing attempts to obtain records, FEMA disaster declarations. A vague letter saying you had difficulties will be denied. A timeline backed by third-party documents has a real chance. Simply forgetting the deadline, being too busy, or blaming a tax preparer who did not finish on time will not qualify.
State Penalties Are Separate
Everything above is federal. Many states charge their own late filing penalties on S corporation returns, and the structures vary. A late federal return often means a late state return too, because the deadlines usually align, so the combined exposure for a single missed filing can run well beyond what the IRS alone collects. Check your state tax agency for the specific rules.