October 15: What You Need Ready if You're on Extension

If you filed for an extension on your 2025 individual return, the deadline is October 15. There is no further extension available.

This is worth stating plainly because a number of people treat October 15 the way they treated April 15 — as a date that can be moved. It can't.

What the extension did and didn't do

An extension extends the time to file. It never extended the time to pay.

If you owed tax for 2025 and didn't pay it by April 15, interest has been accruing since then, along with a failure-to-pay penalty. Those charges continue until the balance is paid. The extension protected you from the much larger failure-to-file penalty, which is the point of filing one.

The difference is significant. The failure-to-file penalty is generally 5% of the unpaid tax per month, up to 25%. The failure-to-pay penalty is generally 0.5% per month, also capped at 25%. Failing to file is roughly ten times more expensive per month than failing to pay.

That means: if you can't pay, file anyway. File on time and pay what you can. The penalty structure rewards filing far more than it rewards waiting until you have the money.

What to send us, and what people forget

The standard items are usually in hand by now. The ones that hold up returns in October are almost always the same:

K-1s from partnerships and S corporations. These are the single most common reason an October return isn't finished. Entity returns were due September 15 on extension, and K-1s often arrive close to that date or later. If you're waiting on one, tell us now rather than on October 13 — knowing what's outstanding lets us complete everything else.

Basis information. If you're a partner or S corporation shareholder, particularly if the entity had losses or you took distributions, basis calculations matter and often require records going back years.

Foreign account information. If you have signature authority over or an interest in foreign financial accounts exceeding the reporting threshold at any point during the year, there's a separate filing. The penalties in this area are severe and disproportionate to the effort of reporting.

Cryptocurrency and digital asset activity. Every sale, exchange, or use of a digital asset to buy something is a taxable event. Exchanges provide varying quality of records, and transfers between wallets complicate basis tracking. This takes longer than people expect.

Documentation for large or unusual deductions. Charitable contributions above certain amounts require specific substantiation, including a contemporaneous written acknowledgment for gifts of $250 or more and appraisals for certain non-cash gifts. Missing paperwork can cost the deduction entirely.

Records for a home office, vehicle, or business meals. These are ordinary deductions with specific substantiation requirements, and reconstructed records are weak.

Other October 15 items

The extended deadline also applies to certain other filings, and a few things become final around this time. If you have a SEP-IRA and you extended, the contribution deadline generally runs to the extended due date of the return, which means there may still be a deduction available if you fund it before you file. That's one of the few remaining levers for a prior year, and it disappears the moment the return is filed.

If you're going to be late

Talk to us before the deadline, not after.

If the issue is a missing K-1, there are approaches. If the issue is that you owe money you don't have, filing on time and setting up a payment arrangement is far better than not filing. The IRS offers short-term payment plans and longer installment agreements, and the terms are considerably better than the penalty math of simply not filing.

If you're in a federally declared disaster area, deadlines may be automatically postponed. That relief is specific to particular counties and dates, so it's worth confirming rather than assuming.

And then, immediately: 2026 planning

Once the 2025 return is filed, there are roughly ten weeks left in 2026 during which planning can still change the outcome.

This year has an unusual number of items worth reviewing: a mid-year mileage rate change, new W-2 requirements for tips and overtime, a new 1099 threshold taking effect for payments made this year, and equipment expensing rules that are more favorable than they've been in years.

The clients who get the most out of us are the ones who file in October and then book a planning conversation in November.

This article is general information, not tax advice for your specific situation. Deadlines shift for weekends, holidays, and disaster declarations. Please talk with us before acting on anything here.