September 15 Is the Deadline for Extended Business Returns
If your calendar-year S corporation or partnership received an extension for its 2025 federal income tax return, the extended filing deadline is September 15, 2026.
That date is approaching quickly, and an extension does not provide additional time beyond September 15.
Which Business Returns Are Due?
The September 15 deadline applies to Form 1120-S for calendar-year S corporations and Form 1065 for calendar-year partnerships that filed valid extensions. (Fiscal-year businesses may have a different deadline based on the end of their tax year.)
The business must also provide the appropriate Schedule K-1 to each shareholder or partner by September 15. The K-1 reports the owner’s share of income, deductions, credits, and other tax items that may affect the owner’s individual return.
Schedule K-1s Matter to the Owners
Shareholders and partners need their Schedule K-1 before they can complete their individual income tax returns. Taxpayers whose personal returns are on extension generally have until October 15, 2026, but that additional month can disappear quickly when a K-1 arrives late or raises questions. Timely business filing gives each owner a better opportunity to review the K-1 and finish the individual return without a last-minute rush.
What Information May Still Be Needed?
Do not wait until the final days to gather missing information. Bank and credit-card statements, bookkeeping records, payroll reports, asset purchases, loan activity, distributions, contributions, and other owner transactions may all be needed. The accounting records should also be reconciled before the return is finalized. Unexplained balances or transactions between the business and its owners can require additional time to review.
An Extension Is Not Extra Time to Pay
A filing extension provides additional time to submit the return, not additional time to pay tax that was due at the original deadline. Although S corporations and partnerships usually pass income through to their owners, an entity can still have certain federal or state tax liabilities. Unpaid balances may continue to accrue penalties and interest.
Late-Filing Penalties Can Add Up
Partnership and S corporation late-filing penalties can increase based on the number of owners and the length of the delay. This means penalties may become significant even when the entity itself owes little or no federal income tax. Filing as soon as possible is better than allowing an overdue return to remain unfinished.
Do Not Wait Until Deadline Week
If your extended S corporation or partnership return has not been completed, contact me soon. We can determine what information is still needed, identify any accounting issues that must be addressed, and evaluate whether the September 15 deadline can be met.
The article is meant for informational purposes only. Please contact me directly to discuss how this applies to your individual tax situation.