The Big Myth: Filing vs. Paying
Before we dive into the dates, let’s clear up the biggest misconception in US taxation. An extension to file is not an extension to pay.
Even if you successfully request an extension to move your filing date to October, the IRS expects every penny of tax owed to be paid by April 15, 2026. If you miss that payment date, the interest starts accruing immediately. Don’t let a paperwork delay turn into a debt trap.
March 16, 2026: The First Major Hurdle
For many business structures, the first “finish line” isn’t in April: it’s in March. Because March 15 falls on a Sunday in 2026, the deadline moves to the next business day.
Who needs to act now?
- S-Corporations (Form 1120-S): If you’ve elected S-Corp status, your return is due now.
- Partnerships (Form 1065): This includes multi-member LLCs that haven’t elected to be treated as corporations.
The Strategy: If you aren’t ready to file, you must submit Form 7004 by this date to request a six-month extension. Doing this pushes your filing deadline to September 15, 2026. However, remember the rule above: pay any estimated taxes now to avoid the IRS “late payment” sting.
April 15, 2026: The Critical Deadline for Everyone
This is the day the US tax world revolves around. It is the final deadline for several key groups and the mandatory payment date for almost everyone else.
1. C-Corporations (Form 1120)
If your international business operates as a US C-Corp, your federal income tax return is due today. C-Corps are popular for international sellers looking to reinvest profits or eventually seek VC funding, but they come with strict annual filing requirements.
2. Sole Proprietorships and Single-Member LLCs
If you are an individual seller or a “disregarded entity” (a single-member LLC that hasn’t chosen to be taxed as a corp), your personal tax return (Form 1040 or 1040-NR) is due today.
3. Estimated Tax Payments (Q1 2026)
Success breeds tax obligations. If you expect to owe more than $1,000 in taxes for the 2026 tax year, your first quarterly estimated payment is due today. Keeping up with these keeps your cash flow predictable and avoids year-end “tax shock.”
4. Extension Requests (Form 4868)
If you are an individual (including sole proprietors) and need more time, you must file Form 4868 by today. This grants you an extension to file until October 15, 2026.
The “Invisible” Deadline: Form 5472 for International Owners
This is where many international sellers get caught out. If you own a US LLC that is “foreign-owned” (at least 25% owned by a non-US person) and it is a disregarded entity, you have a specific reporting requirement.
You must file Form 5472 along with a pro-forma Form 1120. The IRS uses this to track transactions between the US company and its foreign owner.
- The Penalty for Missing This: In recent years, the penalty for failing to file Form 5472 or filing it incorrectly has started at $25,000.
Don’t guess on this one. If you are an international seller with a US entity, talk to an expert to ensure your Form 5472 is handled correctly.
June 15, 2026: The Expat Advantage
If you are a US citizen or resident alien living and working outside the United States on the April 15 deadline, you get a “free” two-month extension to file your return. You don’t even need to file a form to get this; it is automatic.
The Catch: Again, the IRS is hungry for its money. Interest on any unpaid tax still starts accruing from April 15. If you owe money, the June extension only helps you avoid the “failure to file” penalty, not the “failure to pay” interest.
October 15, 2026: The Final Countdown
If you filed for an extension back in April, today is the day. There are no further extensions for 2025 tax year returns.
FBAR (Foreign Bank Account Report)
This is arguably the most important date for international sellers with global footprints. If you had a financial interest in or signature authority over foreign financial accounts (including bank accounts, brokerage accounts, etc.) that exceeded $10,000 at any time during the 2025 calendar year, you must file FinCEN Form 114.
While the official deadline is April 15, the IRS grants an automatic 6-month extension to October 15 for everyone. You do not need to request this extension; it’s yours by default.
Checklist for International Sellers in 2026
To ensure you stay compliant and keep your business running smoothly, follow this operational checklist:
- Reconcile your books monthly: Don’t wait until March to look at your 2025 data. Accurate bookkeeping throughout the year makes tax season a breeze.
- Confirm your entity type: Are you a disregarded LLC, a C-Corp, or a Partnership? Your deadline depends entirely on this classification.
- Track “Reportable Transactions”: For Form 5472 purposes, keep a log of every time you move money between your personal foreign account and your US business account.
- Check your Sales Tax Nexus: Income tax is only half the battle. Ensure you are also tracking where you have “nexus” for US Sales Tax. Physical or economic presence triggers filing requirements.
- Gather Foreign Bank Data: Start collecting the highest balance of every non-US account held in 2025 for your FBAR filing.
