If you run an S corporation, partnership, or multi-member LLC taxed as a partnership, your federal tax return for 2025 is due Monday, March 16, 2026. The usual March 15 deadline shifted by one day because March 15 falls on a Sunday this year.
Calendar-year partnerships, LLCs taxed as partnerships, and S corporations must file their 2025 returns by March 16, 2026. Partnerships and LLCs taxed as partnerships file IRS Form 1065, while S corporations file IRS Form 1120-S.
Schedule K-1s must be issued to owners and partners by this date, since individual owners need K-1 data to prepare their own April 15 personal returns.
These are information returns, meaning pass-through entities generally do not pay federal income tax at the business level. Instead, taxable income, deductions, and credits pass through to the owners. Even though these entities typically do not owe federal income tax themselves, they are still required to file.
Penalties add up fast
The penalty for a late Form 1065 is $255 for each month or part of a month the failure continues, multiplied by the total number of persons who were partners during the tax year, for up to 12 months. Because S corps usually do not owe tax at the entity level, the IRS penalizes simply for filing the informational return late. For the 2025 tax year, the late filing penalty is $245 per shareholder, per month, for up to 12 months. These penalties apply even if the business owes no tax.
For a 3-owner S corp that files 3 months late, the bill comes to roughly $2,200. A 5-partner LLC filing 3 months late could face nearly $3,825.
Not ready? File an extension by March 16
Pass-through entities may request an automatic 6-month extension by filing IRS Form 7004 by March 16, 2026, extending the filing deadline to September 15, 2026. Form 7004 grants 6 more months to file your return, but it does not give you an extension to pay. If your entity owes any tax, it generally must still be paid by the March 16 deadline.
If the entity return is extended to September 15, 2026, that date also becomes the deadline for issuing Schedule K-1 forms to owners. That delay typically means owners will also need to extend their personal returns to October 15.
For the full IRS tax calendar, see IRS Publication 509. Block Advisors and Berndt CPA also have helpful breakdowns of what’s due and when.
If you haven’t already, talk to your accountant or tax preparer today. The March 16 deadline is firm, and the clock on penalties starts the day after.
