The December 15 extension: two more months past 15 October

If you are a US taxpayer abroad who has already filed Form 4868 and 15 October is still not enough time, there is a second extension that almost nobody uses. You can ask for two more months, to 15 December, but not with a form. You write the IRS a letter, and it has to arrive by 15 October. No fee, no approval notice, and a very specific set of things it does and does not cover.

Who can actually use it

It is available to US taxpayers living abroad who already hold the automatic extension — that is, who filed Form 4868 by the original deadline, 15 June for expats. If your extension came through Form 2350 instead — used by people who expect to qualify for the foreign earned income exclusion but have not yet met the physical presence or bona fide residence test — this route is not the one for you; Form 2350 has its own extension mechanics.

There is no form. Here is what the letter contains

Unlike every other extension in the expat calendar, this one has no IRS form behind it. The letter is the entire application, and it needs:

• Your full name, address and taxpayer identification number — SSN or ITIN.
• The tax year the request covers.
• Your signature.
• A specific reason the extra time is needed.

The reason carries real weight

“I need more time” is a weaker request than a specific one. The guidance points at concrete circumstances: a foreign tax assessment that has not been issued yet, or documentation still in progress with a foreign institution or employer. A few precise sentences about what you are waiting on do more work than a general appeal for patience.

Where it goes, and when it has to be there

Mail the letter to the address where you would file a paper return — the one listed in the Form 1040 instructions for your situation. It has to reach the IRS by 15 October, the same date you are trying to extend past. Posting it on 15 October and hoping the postmark carries it is closer than this needs to be; send it with enough time that a postal delay does not cost you the extension outright.

It extends filing, not payment

This is the part that matters most, and it is the same rule that governs every extension in the sequence: it moves the filing date, not the payment date. Interest on unpaid tax has been running since 15 April 2026 regardless of any extension, and it keeps running through 15 December if the balance is still outstanding.

To keep a failure-to-pay penalty off the top of that interest, the expectation is that at least 90% of what you actually owe is paid by 15 October. If the reason you need the extension is that a number has not arrived yet — a foreign tax credit figure, typically — pay your best reasonable estimate in October rather than waiting for the precise one in November.

How you know it was approved

You do not. The IRS writes only if the request is refused. No letter by 15 December means the extension stands. That is uncomfortable if you are used to a confirmation, but it is how this particular extension works: silence is the approval.

If this one passes too, 15 December is the last discretionary extension available, and what follows is set out inwhat actually happens if you miss the deadline. For the whole sequence of dates and which applies to you, see the2026 expat tax deadlines.

What you owe, what you are waiting on and whether Form 2350 already covers you all change the answer here. A fifteen-minute call before 15 October gets you a clear yes or no, and the wording of the letter if the answer is yes.