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September 15, 2026: The S-Corp and Partnership Deadline That Costs $245 Per Owner, Per Month
What is actually due on September 15
Tuesday, September 15, 2026 is the extended filing deadline for calendar-year S corporations filing Form 1120-S and partnerships and multi-member LLCs filing Form 1065. If your entity filed Form 7004 back in March, this is the date that extension runs out.
This deadline arrives a full month before the October 15 deadline that gets all the attention. That timing catches people out every year, because the October date is the one they remember from their personal return. If you own an S corporation or a partnership interest, September is your month, not October.
It matters in a second way too. The Schedule K-1 that your entity produces is what carries the business income onto your personal return. Miss September 15 and you have not just created an entity penalty; you have also jammed your own 1040, which is due October 15 and cannot be finished accurately without that K-1.
The penalty that surprises owners: $245 per owner, per month
Here is the part that catches business owners off guard. The late-filing penalty for a partnership under Internal Revenue Code section 6698, and for an S corporation under section 6699, is currently $245 per month, and it is charged per partner or per shareholder, for each month or part of a month the return is late, for up to twelve months. The figure is adjusted for inflation periodically, so check the current-year amount when you calculate.
The word that does the damage is per. This is not a flat penalty on the business. It multiplies by the number of owners, and it multiplies again by the number of months. A single missed deadline compounds in two directions at once.
Note also that a part of a month counts as a whole month. Filing on the sixteenth of the month is not a day late in the eyes of this penalty; it is a full month late. There is no proration and no grace period built into the statute.
Why it applies even when the business owes no tax
This is the single most misunderstood point about entity returns, and it is the reason owners talk themselves out of filing on time. S corporations and partnerships are pass-through entities. In the ordinary case they pay no federal income tax themselves; the income passes through to the owners, who pay the tax on their personal returns.
Owners reasonably conclude that if the entity owes nothing, filing late cannot cost anything. That conclusion is wrong. The sections 6698 and 6699 penalties are penalties for failing to file a required return on time. They are not calculated on tax due, and they apply in full to an entity with zero taxable income, an entity that lost money, and an entity that had no activity at all during the year but still had a filing requirement.
Work the arithmetic on a straightforward case. A three-shareholder S corporation that files five months late owes 245 dollars, times three shareholders, times five months. That is 3,675 dollars in penalties on a return that may have reported no tax whatsoever. A two-partner partnership that forgets for a full twelve months reaches 5,880 dollars. Nothing about the underlying business changed. The only variable was the filing date.
The Form 7004 trap: rejected is not the same as filed
There is a failure mode worth naming specifically, because it produces the worst version of this problem: an extension that was submitted but rejected. Form 7004 is filed electronically, and it can be rejected for reasons that have nothing to do with your tax situation. The common ones are a mismatch between the entity name and the employer identification number as the IRS has them recorded, an incorrect EIN, or a fiscal-year setting that does not match IRS records.
The trap is that a rejection does not always announce itself the way a person expects. If nobody confirms acceptance, the owner believes the entity is safely extended through September while the IRS considers the return simply unextended and late from the original March deadline. The penalty clock has been running the entire time, silently.
The check takes very little effort and is worth doing this week. Confirm you have an actual acceptance acknowledgment for the 7004, not merely a record that it was transmitted. Those are different things, and only one of them protects you. If it was rejected, the fix is usually to correct the identifying details and file the return itself as quickly as possible, because at that point filing is what stops the accrual.
If you cannot make September 15, file anyway
The most expensive decision available is to delay the return further because it is not perfect or because you cannot pay. The entity penalty is driven by time, not by accuracy and not by payment. Each additional month adds another full multiple of 245 dollars for every owner. Filing a complete and honest return stops that accrual, and a return can be amended later if a number needs correcting.
If a genuine problem is holding the return up, such as missing books or a K-1 you are waiting on from another entity, file with the best information you have and correct it afterward rather than letting the months accumulate. The cost of an amendment is small and predictable. The cost of another month of the entity penalty is a further 245 dollars for every owner on the return.
Once the return is in, penalty relief becomes the next conversation, and it is often a productive one. First-Time Abate is available to entities with a clean compliance history for the prior three years, and it applies to these late-filing penalties. Reasonable-cause relief is a separate route that turns on the specific facts, such as serious illness, a natural disaster, or the loss of records. Relief is normally requested after the penalty has been assessed and you have the notice in hand, which supplies both the amount and the correct address to respond to.
What to do in the next few days
Start by confirming which entities you actually have a filing obligation for. Every S corporation files, and every multi-member LLC treated as a partnership files, whether or not it made money and whether or not it distributed anything. A single-member LLC with no election is generally reported on the owner's personal return instead, which is a different deadline.
Next, confirm the extension was accepted rather than merely submitted, using the check described above. Then get the books to a filing-ready state: bank and credit card accounts reconciled through year end, owner compensation and distributions recorded correctly, and any loans between the owner and the business documented as loans. For S corporations, reasonable compensation to owner-employees deserves particular attention, because it is a frequent audit issue and it needs to be right on the return, not fixed afterward.
Finally, work out the K-1 sequence. Your entity return feeds your personal return, so the order matters when the October 15 personal deadline is only a month behind this one. If several entities stack into a single 1040, the earliest one in the chain has to move first.
Working with an Enrolled Agent on a deadline
An Enrolled Agent is licensed by the U.S. Department of the Treasury and can represent taxpayers before the IRS in every state. For a filing deadline this close, the useful thing is a straight answer about what is achievable in the time remaining and what the exposure looks like if it is not, rather than optimism.
At All State Tax Resolution we prepare 1120-S and 1065 returns, confirm extension status, request penalty abatement where a client qualifies, and handle the personal returns that the K-1s flow into. The work is remote, the fee is quoted before anything begins, and the first conversation is a free fifteen-minute call. If September 15 is looming and you are not sure where your entity stands, that call is the fastest way to find out.
Frequently Asked Questions
What is the deadline for S-corp and partnership returns in 2026?
For calendar-year entities that filed Form 7004, extended Forms 1120-S and 1065 are due Tuesday, September 15, 2026. The original deadline was March 16, 2026, and the extension provided six additional months. This is one month earlier than the October 15 deadline for extended individual returns.
Is there really a penalty if my S-corp owes no tax?
Yes. The late-filing penalties under sections 6698 and 6699 are charged for filing the return late, not for owing tax. They apply in full to an entity with no taxable income, an entity with a loss, and an entity with no activity that still had a filing requirement. The penalty is currently 245 dollars per owner per month, for up to twelve months.
How is the penalty calculated if I have multiple shareholders?
It multiplies. The monthly amount is charged for each shareholder or partner, so a three-owner entity accrues three times the monthly figure. A part of a month counts as a full month, meaning a return filed one day past the deadline is treated as a full month late.
Can this penalty be removed?
Often, yes. First-Time Abate is available to entities with a clean compliance history for the prior three years and applies to these penalties. Reasonable-cause relief is a separate route based on the specific circumstances. Relief is typically requested once the penalty has been assessed and the notice has arrived, since the notice supplies the amount and the correct response address.
What if my Form 7004 extension was rejected?
Then the entity is treated as unextended and the return has been late since the original March deadline, with the penalty accruing the whole time. Rejections commonly stem from a name and EIN mismatch or a fiscal-year discrepancy. Confirm you have an acceptance acknowledgment rather than just a transmission record, and if it was rejected, correct the details and file the return promptly, because filing is what stops further accrual.
Related Reading
Talk to an Enrolled Agent
This article is general information, not individual tax advice. If you want to talk through your specific situation, book a free 15-minute review or call or text us directly.
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