March 15, 2027 is the due date for Form 1065 (partnerships and multi-member LLCs taxed as partnerships) and Form 1120-S (S corporations) covering calendar year 2026. It is a month before the individual deadline on purpose: the K-1s these returns produce are what the owners need to file their own returns in April.
What is due
- Form 1065 or Form 1120-S, or Form 7004 to extend either to September 15, 2027.
- Schedule K-1 to every partner or shareholder.
Why the penalty is unusual
Most partnerships and S corporations owe no federal income tax themselves, so people assume a late return costs nothing. It does. The late filing penalty is charged per owner, per month, for up to twelve months. For returns due in 2026 the rate was $255 per partner or shareholder per month, and the figure is indexed each year. A four-owner LLC that files three months late owes about $3,000 for a return that showed no tax.
If you cannot finish by then
File Form 7004. It is automatic, takes five minutes, and moves the deadline to September 15. There is no payment to estimate for most pass-through entities, so there is no reason to miss this one.
Tell the owners
An extended entity return means late K-1s. Every partner and shareholder will need their own extension in April. Say so in March, not on April 14.
Common mistake
Extending the entity and forgetting that the owners' individual returns are still due April 15. The entity extension does nothing for the individuals.
Ready to file it?
You can file a business extension (Form 7004) online in a few minutes with TaxExtension.com, an IRS-authorized e-file provider operated by our publisher. The extension is automatic; the payment is still due on the original date.
Sources
- IRS, About Form 7004
- IRS, Failure to file penalty, partnership base rates
- IRS, Instructions for Form 1120-S