If you filed an extension back in April, October 15 has probably been living comfortably in the back of your mind as "plenty of time." Here's the wake-up call: there is no extension after the extension, the clock on penalties has been running since April, and the return you postponed is now the very first one filed under the biggest tax law change in years. Time to finish it — and here's exactly what Frederick County extension filers need to know.
The six-month extension is the only one the IRS gives. Miss October 15, and the failure-to-file penalty kicks in at 5% of your unpaid tax per month, up to 25% — ten times the rate of the late-payment penalty. Go more than 60 days past the deadline and there's a minimum penalty of $525 or 100% of the tax owed, whichever is smaller, even on modest balances.
The single most expensive mistake extension filers make is not filing because they can't pay. Filing and paying are separate problems with separate penalties — and the filing penalty is ten times worse. File by October 15 no matter what; we can solve the payment side afterward.
And October 15 isn't the only date on the fall calendar. Here's the map:
| Date | Who it applies to | What it means |
|---|---|---|
| September 15 | S-corps & partnerships on extension | Extended business returns (1120-S, 1065) are due — a full month before your personal deadline, and your K-1 comes from this return |
| September 15 | Anyone paying quarterly estimates | Q3 2026 estimated payment due — a separate obligation for this year's taxes |
| October 15 | Individuals & C-corps on extension | Final deadline for 2025 returns — also the last day to fund a SEP-IRA or employer solo 401(k) contribution for 2025 |
| After October 15 | Anyone who missed it | No more extensions; the 5%-per-month late-filing penalty starts stacking |
Business owners, note the trap in rows one and three: if your S-corp or partnership return isn't done by September 15, you won't have the K-1 you need to finish your personal return by October 15. The two deadlines are a relay race, and September is the handoff. Our small business tax team runs both legs together for exactly this reason.
The extension moved your filing deadline. Your payment was due April 15 — and if you didn't pay in full then, the meter has been running ever since. Right now that means the late-payment penalty of 0.5% per month plus IRS interest at 7% per year, compounded daily, on whatever's unpaid. On a $10,000 balance, that combination adds roughly $100 every month you wait.
Two pieces of good news. If you paid at least 90% of your actual tax by April, the late-payment penalty is generally waived for the extension period — one more reason to finish the return and find out where you actually stand. And if you can't pay in full, an IRS payment plan cuts the penalty rate in half and stops collection letters; a short-term plan costs nothing to set up.
Maryland's extension mostly piggybacks on the federal one — if you filed Form 4868 and owed Annapolis nothing, your state extension to October 15 was automatic, no separate form needed. But if you owed Maryland tax, that payment was due April 15 with Form PV, extension or not. Maryland charges its own interest on unpaid balances — at an annual rate that has historically run well above the IRS's — and its late-payment and late-filing penalties can each reach 25% of the tax due.
Both governments have been charging you since April 15 — the extension never paused either meter. If you know you owe and haven't paid, sending a payment today, before the return is even finished, stops the bleeding on every dollar you send.
Here's the part nobody mentions in the deadline reminders: 2025 returns are the first filed under the sweeping federal tax law passed last summer. Extension filers are doing them now, with brand-new rules that didn't exist the last time you filed — the tip income deduction, the overtime deduction, the $6,000 senior deduction, and a SALT cap that quadrupled to $40,000, which changes the itemize-or-not math for a lot of Maryland homeowners who've been taking the standard deduction on autopilot. We keep a running plain-English breakdown in our 2025 Tax Law Guide.
Software will update the forms, but it won't notice what changed for you — whether your W-2 tips qualify, whether itemizing beats the standard deduction this year, whether your withholding matched the new rules. And if you're one of the thousands of Frederick County residents who commute into DC, Virginia, or Montgomery County, the multi-state layer stacks on top; our commuter tax guide covers that terrain.
Bring us what you have — even if it's incomplete, even if you owe, even if your last preparer vanished. We'll tell you exactly what's missing, what it will cost, and get it filed well before October 15. Call (301) 662-6992.
Book a ConsultationThere's no second extension — the late-filing penalty starts at 5% of your unpaid tax per month, up to 25%, plus a minimum penalty of $525 if you're more than 60 days late and owe tax. The answer is to file as soon as possible, even late; every month you wait adds another 5%. If you're already past deadlines from prior years, our back taxes guide covers catching up.
Yes — emphatically. Filing on time eliminates the 5%-per-month late-filing penalty, which is ten times the late-payment penalty. Then an IRS installment agreement handles the balance: it halves the ongoing penalty rate, stops collection activity, and a short-term plan (up to 180 days) has no setup fee. Filing broke, then paying over time, costs a fraction of hiding.
Usually not. If you filed a federal extension and owed Maryland nothing as of April, your state extension to October 15 was automatic. If you owed Maryland tax, the payment itself was due April 15 — and if it wasn't made, interest and penalties have been accruing on the state side regardless of the extension. Paying the state balance now, before filing, limits the damage.
One big lever remains: self-employed filers on extension can fund a SEP-IRA for 2025 up until October 15 and deduct it on this return. Traditional and Roth IRA contributions closed on April 15, but the SEP window follows your extended deadline — for a profitable sole proprietor or single-member LLC, it's often a four- or five-figure deduction still on the table. This is exactly the kind of move we check for in every extension return we prepare.
By Roy Cogliandolo, CPA · Mercer Flanagan · July 25, 2026
This article is general information, not tax advice for your specific situation. Penalty and interest figures cited are current as of July 25, 2026, and change quarterly.