The clock is running out. Anyone who filed Form 4868 this spring has until October 15, 2026 to get their 2025 federal tax return in. Miss it, and the IRS starts adding penalties that grow every single month. Here is exactly who this deadline applies to, what the penalties look like in real numbers, and the smartest move you can make this week.

1. Who Must File by October 15, 2026

October 15 is the final extended deadline for filing your 2025 federal income tax return. It applies to you if you submitted IRS Form 4868 earlier this year and received the automatic six month extension.

This is the last stop. There is no second extension for most filers after October 15. Taxpayers in a federally declared disaster area or serving in a combat zone may have a different, later deadline, and should confirm directly with the IRS.

If you already filed your 2025 return, this deadline does not apply to you. If you did not request an extension back in April, your return was due April 15, 2026, and penalties have already been running.

2. An Extension to File Is Not an Extension to Pay

This is the most misunderstood part of the extension, and the most expensive one. Form 4868 gave you six extra months to file the paperwork. It did not give you extra time to pay.

1. Any 2025 tax you owed was still due on April 15, 2026
2. Interest has been accruing on unpaid balances since April 15, compounded daily
3. Failure to pay penalties have also been running since April 15 on any unpaid amount

Filing your return by October 15 stops the failure to file penalty from growing further. It does not erase interest or penalties that already accrued on tax you should have paid in April.

3. The Failure to File Penalty: 5% Every Month

The IRS charges a failure to file penalty of 5% of your unpaid tax for each month, or part of a month, that your return is late. The penalty caps at 25% of the unpaid amount.

In plain numbers: if you owe $10,000 and file one month late, the penalty is $500. Five months late, and it hits the $2,500 maximum.

1. Calculated on the unpaid tax only, after subtracting withholding, estimated payments, and credits already applied
2. If your return is more than 60 days late, a minimum penalty applies: $525 or 100% of the tax owed, whichever is less (for returns due after December 31, 2025)
3. No penalty at all if you are due a refund, since the penalty is a percentage of unpaid tax

The 60 day rule is the trap. Even a small unpaid balance can trigger the full $525 minimum once you cross 60 days late.

4. The Failure to Pay Penalty and Daily Interest

Separate from the filing penalty, the IRS charges a failure to pay penalty of 0.5% of the unpaid tax per month, up to 25%. When both penalties apply in the same month, the combined charge is 5% per month (4.5% filing plus 0.5% paying).

1. Interest accrues on the unpaid balance and compounds daily from April 15, 2026, at the federal short term rate plus 3%
2. If you set up an IRS installment agreement, the failure to pay rate drops to 0.25% per month while the agreement is in effect
3. Filing your return on time is what stops the larger 5% monthly penalty, even if you cannot pay the full balance yet

   5. What To Do Right Now

With days left, here is the priority order:

1. File your return by October 15, even if you cannot pay in full. Filing stops the 5% per month failure to file penalty, which is ten times larger than the failure to pay penalty.
2. Pay as much as you can with the return. Every dollar paid reduces the base on which penalties and interest are calculated.
3. If you cannot pay the rest, contact the IRS about a payment plan, including short term options.
4. Disaster area or combat zone? Check whether you qualify for a postponed deadline before assuming October 15 applies.
5. Double check estimated payments and withholding credits so you are not penalized on tax you already paid.

What Should Your Business Do Now?

• Confirm whether anyone on your team or in your family filed Form 4868 and still has an unfiled 2025 return
• Gather all income documents now, including corrected 1099s and K-1s that arrived late
• File by October 15 even with a balance due, then arrange a payment plan for the remainder
• Review your withholding and estimated payments for 2026 so you are not in this position next April
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Do these now, and the deadline becomes a non event instead of a penalty notice.

How Funds to Function Can Help

This is the work we do every day at Funds to Function. When a deadline is days away, you do not need general advice. You need a team that can pick up your return, file it correctly, and deal with the IRS on the balance. That is exactly what we do.

• Last minute return preparation: we prepare and file your 2025 federal return accurately before October 15, even if your documents arrived late or incomplete.
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• Penalty review: we calculate exactly which penalties apply to your situation and check every relief option you may qualify for, including reasonable cause relief.
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• Payment plans: we set up IRS installment agreements for you, which can reduce your failure to pay penalty rate while the agreement is active.
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• Withholding and estimated tax tune up: we fix your 2026 withholding and quarterly estimates now, so you never face this last minute scramble again.
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• Bookkeeping cleanup: our bookkeeping team gets your records clean and IRS ready, so every future filing is fast and painless.
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Disclaimer :

The information shared in this article is for educational and informational purposes only.

While Funds To Function, LLC ensures accuracy from reliable sources, readers should verify details independently before applying them to personal or business decisions.

Funds To Function, LLC is not responsible for any actions taken based on this content, it is provided solely to enhance your knowledge.