March 2026 · Taxes, Small Business
The March 16 Deadline for S-Corps and Partnerships
File or extend, get the K-1s out, and the last call for the 2026 S-corp election
If your business is an S-corp or a partnership, your tax deadline is not in April. Calendar-year business returns are due Monday, March 16, a full month before the personal deadline most owners have in mind.[1]
What is due
- Form 1120-S: the S-corp return, with a Schedule K-1 to each shareholder.[1]
- Form 1065: the partnership return, with a K-1 to each partner.[2]
- Form 2553: the last day to elect S-corp status for 2026, if you meant to and have not.[3]
The date is the 16th this year because March 15 lands on a Sunday, and deadlines that fall on a weekend roll to the next business day.[1]
A late business return delays every owner
The K-1 tells each owner their share of the profit, and no owner can file a personal return without it. When the business return runs late, every shareholder or partner waits with it, which is why this deadline sits a month ahead of the personal one.
The penalty is per owner, per month
The late-filing penalty is $260 per owner for every month or part of a month the return is late, up to twelve months.[4] Three owners and three months late is $2,340, charged on a return that usually owes no tax itself.
Reasonable cause and first-time penalty relief exist, but the cheaper move is the next section.
The extension is free and automatic
Form 7004, filed by March 16, moves the deadline to September 15 with no questions asked.[5] It extends the paperwork rather than any tax owed, and most pass-throughs owe no federal tax at the business level anyway.
So if the books are not ready, extend. The penalty math above is the price of skipping a free form.
Last call for the 2026 S-corp election
The January checklist and the myths post both pointed at this date: Form 2553 is due March 16 for the election to count for 2026.[3] Miss it and the election generally waits for 2027, unless you can prove reasonable cause for a late one.
The bottom line
File by March 16, or spend five minutes on the free extension, and get the K-1s out either way. If you are not sure the books can close in time, a free consultation this week costs less than a penalty next month.