S corp tax return late filing penalty under IRC 6699

What the IRC 6699 charge counts

IRC 6699 imposes a penalty on an S corporation that does not file its Form 1120-S by the due date. The charge is a dollar amount for each month or part of a month the return is late, multiplied by the total number of persons who were shareholders in the corporation. The Form 1120-S instructions use that multiplier wording, so the shareholder count is the number that drives the bill.

A partial month counts as a full month. A 2026 return due March 15, 2027 and filed in early June 2027 is counted as three months late. The 12-month cap stops the count, so the per-shareholder maximum is twelve times the monthly rate.

The charge does not depend on tax. For returns on which no tax is due, the penalty still applies at the full monthly rate. An S corporation with no income tax liability that files six weeks late still owes the per-shareholder charge.

Which rate applies to which return

The rate follows the year the return was required to be filed, not the year it is actually filed. A 2025 Form 1120-S, due March 16, 2026, carries the $255 monthly rate in the Form 1120-S instructions. A 2026 Form 1120-S, due March 15, 2027, carries $260 under Rev. Proc. 2025-32, section 4.56, which sets the section 6699(b)(1) amount for returns required to be filed in 2027.

Decision rule: pull the due date from the return header, not the filing date. A 2025 return filed in late 2026 is still a 2025 return priced at $255. Do not carry the $260 figure into any return due in a later year without looking up that year's amount first.

Work out the bill before you call the client

Count shareholders from the Schedule K-1 list and the stock ledger, not from the year-end cap table. The instructions say the charge is multiplied by the persons who were shareholders in the corporation, which can include a shareholder who sold out mid-year. Read that wording against the current instructions before you put a count in writing to the client.

Worked example, 2026 return: three shareholders, filed two months late. Multiply $260 by 2 months and by 3 shareholders. A return filed more than 12 months late stops at the cap, which is $260 times 12 times the number of shareholders.

Worked example, 2025 return: four shareholders, filed three months late. Multiply $255 by 3 months and by 4 shareholders. The client should see the rate, the months, the shareholder count, the due date the count started from, and the filing date that stopped it.

Add the K-1 charge and any tax due

A late Schedule K-1 is a separate charge. The Form 1120-S instructions say a penalty of $340 may apply to each Schedule K-1 that is not furnished when due. Rev. Proc. 2025-32, section 4.58(1), sets the general rule at $340 per statement for statements required to be furnished in 2027 by a person with more than $5,000,000 in average annual gross receipts. Four late K-1s add four times $340 on top of the return charge.

Section 4.58 has a second table for smaller businesses. Check that table before you apply the $340 figure to a business below the $5,000,000 test.

If the return also shows tax due, the general failure-to-file rule applies on that tax. The IRS failure-to-file page states it as 5% of the tax due for each month or partial month late, up to a maximum of 25%. Tax due on an S corporation return is uncommon, but built-in gains tax can produce it, and that amount is separate from the per-shareholder charge. Show the client the two amounts on separate lines.

Extensions and what they do not cover

Form 7004 must be filed by the regular due date of the return. It gives an automatic extension, generally six months, for the time to file. For a 2026 return, that moves the filing deadline six months past March 15, 2027, and a return filed inside that window is not late for this charge.

Form 7004 does not extend the time to pay any tax due. A client with a balance owing should pay the estimated tax by the original due date. The extension gives no payment relief.

Decision rule: if the Form 7004 was filed after the regular due date, treat the return as having no extension. The late-filing count runs from the original due date.

Reasonable cause: what the request needs to show

The Form 1120-S instructions say the penalty applies unless each failure is due to reasonable cause. The IRS failure-to-file page says the same thing for the general penalty: it does not apply if you show the failure was due to reasonable cause. The burden is on the request to show the cause, with dates.

A request that says only "we forgot" rarely works. The letter needs an event that stopped the filing, the dates it happened, the steps taken once it was known, and the documents that prove each date. Departure of the bookkeeper holding the ledger, a fire or flood that destroyed the books, and a late K-1 from an upstream partnership are the kinds of event that can be documented.

Sample wording for the request, with the bracketed items filled in: “The 2025 Form 1120-S for [entity name] was late because our bookkeeper left on [date] and the general ledger was not reconciled until [date]. We filed on [date] when the reconciliation was complete. Copies of the departure notice and the reconciliation are attached.” Name the notice number and the tax year in the first line.

First-time abatement: the three-year test

First-time abatement (FTA) is the IRS's most common administrative penalty relief for individuals and businesses with a history of timely compliance. The IRS page says FTA applies to taxpayers with three years of timely compliance history. The same return type as the original return must have been timely filed for the prior three years.

The penalty history also has to be clean. No penalty, except the estimated tax penalty, may have been assessed in the prior three years. A penalty from those years also passes the test if it was removed for reasonable cause or IRS error.

Decision rule: pull the account transcript for each of the three prior years first. If all three show timely filing of the Form 1120-S and no penalty, request FTA. If any year has a penalty that stayed on the account, request reasonable cause instead.

How to ask: call the phone number on the notice, or send a written statement or Form 843, Claim for Refund and Request for Abatement. Name the notice, the tax year and the penalty amount. If FTA is denied and the facts support it, send the reasonable-cause statement on the same account.

Failure modes and the fix for each

Wrong shareholder count. The common error is using the year-end owner list. Rebuild the count from the K-1 list and the stock ledger, then compare it with the count on the penalty notice before you respond.

Wrong year rate. A 2025 return filed in 2027 is still priced at $255, and a 2026 return due March 15, 2027 is priced at $260. Pull the due date from the return and apply the rate for that year.

FTA requested with a prior penalty on the account. Pull the transcripts first. One old penalty on the account stops the FTA request, so switch to reasonable cause for that year.

Extension filed after the due date. Treat it as no extension and quote the penalty from the original due date, because a late Form 7004 does not stop the count.

What to tell the client

Give the client the rate, the months and the shareholder count in one sentence, then the next step with its date. For example: “The 2025 Form 1120-S was filed three months late with four shareholders at $255 a month. We are checking first-time abatement and will send the request by the date on the notice.” Keep the total out of the first message until the count is confirmed.

Do not promise abatement before the transcripts are pulled. A client who hears that it will be removed and then receives a denial has less reason to trust the next estimate.