Deadlines by entity
Calendar-year entities:
- S-corp (1120-S): March 15, extended to September 15
- Partnership (1065): March 15, extended to September 15
- C-corp (1120): April 15, extended to October 15
- Trust (1041): April 15, extended to September 30
Why pass-throughs file a month early
S-corps and partnerships pay no federal income tax themselves; they issue K-1s that feed the owners' personal returns. The March deadline exists so those K-1s arrive before April. An entity that extends pushes its K-1s toward September, which effectively forces every owner onto personal extensions too. One entity's filing habits cascade across every owner's calendar.
The per-owner late-filing penalty
Miss the pass-through deadline without an extension and the penalty runs per shareholder or partner, per month, for up to twelve months, at a rate that adjusts annually. A three-owner S-corp filed five months late generates a penalty in the thousands even if the business owes no tax at all. First-time abatement applies here too, but the cheap fix is the free, automatic Form 7004 filed on time.
Form 7004 mechanics
One page, no signature, no reason required, e-filed in minutes: the extension is automatic when timely filed. Like the personal version, it extends filing, not payment. That distinction bites C-corps, which owe tax at the entity level and must deposit their estimated balance by the original deadline. For S-corps and partnerships with no entity-level federal tax, the extension is usually consequence-free.
The Florida layer
Florida C-corps file a state corporate return (F-1120) and can extend it with Florida's own Form F-7004; the federal extension doesn't do it automatically. S-corps generally owe no Florida corporate income tax and typically have no Florida return to extend. Annual report filings with the state, due in the spring with late fees attached, run on an entirely separate track that catches business owners every year.
Common questions
- Does the entity extension extend owner personal returns?
- No. Owners still file their personal returns by April 15 or extend separately. Missing K-1s due to late entity filing can leave owners scrambling.
- We're an S-corp with no tax due. Does a late return really cost anything?
- Yes. The late-filing penalty for pass-throughs is assessed per owner per month regardless of tax due. It's among the most avoidable penalties in the code: the extension is automatic and free.
- Does Florida need its own extension?
- For C-corps, yes: Florida's F-7004 extends the state F-1120. Federal S-corps generally have no Florida corporate income tax return, so there's usually nothing to extend at the state level.
- Our fiscal year isn't the calendar year. When are we due?
- Generally the 15th day of the third month after year-end for S-corps and partnerships, and the fourth month for most C-corps, with extensions running six months from there. The pattern is the same; the dates shift with your year-end.
Related
Corporation & Partnership Tax Returns
Forms 1120, 1120-S, and 1065 preparation for corporations, S-corps, and partnerships, plus owner K-1s, shareholder basis tracking, and multi-state filings.
Filing a Tax Extension
Form 4868 extends the filing deadline from April 15 to October 15, not payment. Estimate and pay what you owe by April 15 or penalties and interest accrue.
Related tax topics
Year-End Tax Planning
Roth conversions, tax-loss harvesting, RMDs, and Section 179 purchases must happen by December 31. IRA, HSA, and SEP contributions can wait until April.
Required Minimum Distributions
RMDs from traditional IRAs and 401(k)s are due by December 31 starting at age 73. Missing one costs 25% of the missed amount, 10% with timely correction.
Quarterly Estimated Tax Payments
Quarterly estimates are due April 15, June 15, September 15, and January 15. Safe harbor is 90% of current-year or 100% of prior-year tax. Who has to pay.
Form 1040-X Amended Return
Form 1040-X corrects income, deductions, credits, filing status, or dependents on a filed return. Refund claims have a three-year window from original filing.