Hi,
The final extended filing deadline is now only days away, and there are two surprises about this deadline that catch people off guard every year, one of them is below and the other is near the end, so it’s worth reading through.
October 15, 2026 is the extended federal filing deadline for calendar-year C corporations. Surprise number one: this applies even if the company was dormant, showed a loss, or had no real activity this year, you must still file. Otherwise, federal penalties apply.
The October 15 deadline applies to C corporations filing Form 1120 that submitted a Form 7004 extension. This is the final extended deadline, there is no additional extension beyond this date.
Here is what waiting can cost:
- The late-filing penalty is 5% of any unpaid tax for each month or part of a month the return is late, up to 25% of the unpaid tax
- If the return is more than 60 days late, a flat minimum penalty applies, the lesser of $525 or 100% of the unpaid tax, and this applies to corporate returns the same as individual ones
- A separate late-payment penalty of 0.5% per month (also capped at 25%) applies to any unpaid balance, plus interest that compounds daily
- If the corporation underpaid its quarterly estimated tax during the year, a separate underpayment penalty (calculated on Form 2220) can apply on top of the above
An extension gave the corporation more time to file, not more time to pay. Payment was due back on April 15, and interest has been accruing on any unpaid balance since then, so finishing the return now matters even if the full balance can’t be paid immediately.
Before we can file, this is what usually needs to be addressed:
- Year-end bookkeeping and bank reconciliations
- Payroll, officer compensation, and contractor payments (1099s)
- Fixed-asset purchases, equipment, vehicles, and depreciation
- Business loans, shareholder loans, and related-party transactions
- Inventory and cost-of-goods-sold figures
- Dividends or distributions paid to shareholders during the year
- Retained earnings, corporations that accumulate cash well beyond what the business reasonably needs can trigger a separate 20% accumulated earnings tax, on top of regular corporate tax
- Any credits or deductions the company may not have claimed yet, including the R&D credit
- Foreign subsidiaries, foreign ownership, or international transactions
- Estimated tax payments already made during the year
Fiscal-year corporations, state returns, and companies receiving disaster relief may have different deadlines. That is why the first step is confirming exactly which dates apply to your entity.
Surprise number two: if you also have a dormant shell entity or a nonprofit still operating as a C corporation without a completed tax-exempt election, that entity has its own filing obligation too, mention it when you reply.
Reply to this email by Monday next week, and we will schedule a free 15-minute call with our senior tax advisor. Bring your most recent return, current bookkeeping, and extension confirmation so we can identify what is missing and whether your return can be completed before the deadline.
October 15 is the filing deadline, not the day to begin gathering the records.
Sincerely,
—
George Dimov, CPA
Licensed and Insured
(833) 829-1120 toll free
(212) 994-8081 Fax
www.dimovtax.com