It feels like the year just started, but March 15th always sneaks up fast. One day you’re thinking you have plenty of time, and the next you’re staring at a missed deadline wondering what it’s going to cost you. If your business is set up as an S Corporation or a partnership, make sure your calendar is marked for March 15th (in 2026, the filing date is March 16th since the 15th falls on a Sunday).
TL;DR: Missing the March 15th filing deadline for S Corps and partnerships triggers automatic IRS penalties that add up fast. Here’s what actually happens and what you can do about it.
Who Needs to File Taxes on March 15th?
While April 15th is the Tax Day that comes on every calendar, March 15th is the equivalent for S Corps and Partnerships. A full month earlier than when other entities and individuals file.
The March 15th deadline applies to any business that files a Form 1120-S (S Corporation) or Form 1065 (partnership). If your business falls into either of those categories, March 15th is your date.
Are There Penalties For Missing the March 15th Deadline?
As with every major deadline, the penalties start the day after the deadline passes.
For S Corps and partnerships, the penalty is calculated per partner or shareholder, per month. As of March 2026 IRS guidelines, base penalty rates for Forms 1120-S, 1065, 1066 and 8985 are $255 per partner or shareholder per month. So if your S Corp has four shareholders and you file two months late, you’re looking at roughly $2,040 in penalties before you’ve paid a single dollar of the actual taxes due.
The more partners or shareholders involved, the worse it gets. A partnership with ten members filing three months late could be looking at $7,650 in penalties. These are hefty penalties for something that could’ve been easily avoided!
Does the IRS Ever Waive These Penalties?
The IRS has a “reasonable cause” standard, meaning if something genuinely beyond your control caused the delay, you can write in and request relief. A natural disaster, a serious illness, or another similar situation might qualify.
Can You File an Extension for S Corp and Partnership Tax Returns?
Yes, filing Form 7004 gives you an automatic six-month extension, pushing your deadline to September 15th. Once filed, it’s automatically granted by the IRS. But it’s crucial that you file it before March 15th. You can’t file for an extension after the deadline has already passed. Keep in mind: An extension to file is not an extension to pay.
Not sure if you need an extension or ready to get your return filed before the deadline? Our team at JBS handles S Corp and partnership returns year-round, including remote tax preparation for businesses around the country. Book a tax appointment today and let’s get ahead of it.
If you’re interested in becoming a JBS client, contact us about our welcome offer! For new S Corp and Partnership clients, we’ll file your March 15th tax extension for free.
What Else Can Go Wrong When You File Late?
Owners of S Corps and partnerships receive a Schedule K-1 from the business return. That K-1 is what each person needs to file their own personal return. If the business return is late, the K-1s are late. That means the individual owners would need to file late too, which is costly.
Late K-1s can also raise flags. If an owner’s personal return doesn’t match what eventually gets reported on the business return, the IRS takes notice.
Can I File S Corp or Partnership Taxes Remotely?
You don’t have to sit across a desk from someone to get your taxes done right. Remote tax preparation has become completely standard, and for S Corps and partnerships it works the same way as in-person filing.
At JBS, we work with business owners all across Massachusetts and handle everything digitally. You share your documents securely, we prepare the return, you review and sign electronically, and we file. No office visit needed!
If you’re looking for remote tax preparation or in-person tax preparation in Massachusetts and want someone who knows S Corp and partnership returns inside and out, reach out to our team. We’ll make sure your return is accurate and filed on time (or we’ll help you file an extension if needed!).
JBS Corp offers remote tax preparation and filing for S Corporations, partnerships, and individuals across Massachusetts. Contact us to book a tax appointment.
