When are 2026 business tax returns due for an LLC, S corp and partnership, and what are the extension dates?

Key takeaways

• Partnerships, S corporations and multi-member LLCs taxed as partnerships file by March 15, 2027. Everyone else named here files by April 15.

• Extensions run six months: September 15, 2027 for the March group and October 15, 2027 for the April group.

• An extension gives you more time to file and no more time to pay. Interest runs from the original date regardless.

• LLC is not a tax classification. Your due date follows how the LLC is taxed, so confirm that before using any calendar.

• All four 2027 dates fall on weekdays, so the weekend rollover rule does not move anything this year.

Quick answer

• Partnerships, S corporations and LLCs that are taxed as partnerships are due on March 15, 2027, with an extension available to September 15.

• Sole proprietorships, single-member LLCs and C corporations are due on April 15, 2027, with an extension available to October 15.

• File the extension by the original date, and pay what you estimate you owe then too, because the extension covers filing only.

For the 2026 tax year, filed in 2027, there are two dates that matter. Partnerships and S corporations file by March 15, 2027. Sole proprietorships and C corporations file by April 15, 2027. Where an LLC sits depends entirely on how it is taxed, which is the part most owners get wrong.

Numetix closes books monthly so the March date is a handover rather than a scramble, and runs an AI-powered. Experts in the Loop. model. Everything below is taken from Internal Revenue Service guidance and dated accordingly.

What are the dates for each business type?

These are calendar-year dates. A business with a fiscal year that does not end in December sits on a different schedule, which the rule below explains.

Where do those dates come from?

From a rule about months after year end, not from a fixed calendar date, which is why a fiscal-year business cannot use the table above.

The IRS tax calendars publication sets it out: a partnership return is due on the 15th day of the third month after the end of the partnership's tax year, and the S corporation return on the 15th day of the third month after the end of the corporation's tax year. The C corporation return is due on the 15th day of the fourth month after year end, as is the individual return that carries a sole proprietor's business income.

For a December year end, the third month is March and the fourth is April. That is the whole derivation.

The publication also covers what happens when a date lands badly: where a due date for performing any act falls on a Saturday, Sunday or legal holiday, the act is treated as timely if performed no later than the next day. For 2027 this changes nothing, because March 15 is a Monday, April 15 a Thursday, September 15 a Wednesday and October 15 a Friday.

What does an extension actually give you?

Six more months to file, and nothing at all on the payment side. This is the single most expensive misunderstanding on this page.

The instructions for Form 7004 state plainly that the form does not extend the time to pay any tax due, that any balance shown is required by the regular due date of the return, and that interest runs from that original date even where an extension is granted. The form itself generally has to be filed on or before the return's original due date.

So an extension buys time to finish the paperwork. It does not buy time to find the money. If you expect to owe, estimate it and pay by the original date, then file the completed return later. Our note on how much to set aside for taxes each month is the habit that makes that payment unremarkable rather than painful.

Why does the LLC question not have a single answer?

Because an LLC is a legal structure rather than a tax classification, so it has no deadline of its own.

An LLC is taxed as something else, and that something else carries the date. The same two-member consulting LLC could sit on the March row or the April row depending on how it is treated and whether any election has been made. Owners who look up "LLC tax deadline" and act on the first date they see are the ones who miss March 15 by a month.

Confirm your classification with whoever prepares the return before you diarize anything, and confirm it again after any ownership change. It takes one email and it is the difference between the two halves of the table.

What has to happen before the March date?

The return is the last step, not the first. Work backwards from March 15 and the real deadline is considerably earlier.

• By mid-January: December closed and reconciled, so the year is complete rather than nearly complete.

• By end of January: contractor and payroll reporting dealt with, since these run on their own earlier schedules.

• By mid-February: the full document package with your preparer, with any gaps named rather than hidden.

• Late February: questions answered in one batch, which is usually what actually delays a return.

• Early March: review and sign, leaving room for the thing nobody predicted.

What to hand over is set out in our checklist of what your accountant needs to file. If the books are not current, that comes first and it changes the timeline, which our guide to being two years behind on bookkeeping works through. A reliable monthly close through the year is what turns all of this into a handover.

Firms carrying sector-specific reporting on top of the return, as many do in professional services, should add that to the same backward plan. States run their own calendars and they do not all match the federal one. Check the requirements for every state you file in, and do it before February rather than during it.

Common questions

Does filing an extension increase the chance of an audit?

There is no basis for believing it does, and extensions are routine. A rushed return containing errors is the more plausible risk. If the choice is between filing something inaccurate on time and extending to get it right, discuss it with your preparer rather than guessing.

What if my business year does not end in December?

Use the rule rather than the table. Partnerships and S corporations file on the 15th day of the third month after year end; C corporations and sole proprietors on the 15th day of the fourth. Count from your own year end and confirm the result with your preparer.

Can I file the extension myself?

Usually yes, and it can be filed electronically. The part worth getting help with is the estimate of what to pay alongside it, since that figure is what stops interest accruing. Ask your preparer for the number even if you submit the form yourself.

March 15 as a handover, not a scramble

Numetix closes and reconciles the books every month, so the year is finished in January rather than rebuilt in February, with experienced people reviewing before anything reaches your preparer.

See monthly bookkeeping or tax services.

This article is for informational purposes only and does not constitute formal legal or tax advice. Always consult a qualified tax professional regarding your specific situation. Dates shown are for calendar-year filers for the 2026 tax year and are derived from the filing rules published by the Internal Revenue Service, checked in October 2026. Deadlines, forms and rules change, fiscal-year filers follow a different schedule, and state requirements differ from federal ones, so confirm your own dates before relying on them.