Missing a US tax or compliance deadline as an expat in the UK can be costly — penalties, interest, and in serious cases, criminal exposure. Yet the US filing calendar for Americans abroad is more complex than the domestic calendar, with multiple extensions, overlapping deadlines for FBAR, FATCA, and foreign corporation reports, and different rules for expats vs. domestic filers.
This complete 2026 deadline guide for US expats covers every date you need to know — for the 2025 tax year — with specific notes for UK-based Americans.
Key US Tax Deadlines for Expats in 2026
January 15, 2026 — Q4 2025 Estimated Tax Payment
The fourth and final estimated tax payment for the 2025 tax year. If you have US income not subject to withholding (self-employment income, investment income, rental income), you must pay estimated taxes quarterly to avoid underpayment penalties. Expats who paid sufficient UK withholding tax (PAYE) throughout 2025 may not have a US estimated tax obligation — but those with investment income or US-source income should review.
April 15, 2026 — Standard US Tax Return Deadline (Domestic)
The standard Form 1040 filing deadline for US residents. Important: Most US expats do NOT use this deadline — they use the automatic June 15 extension (see below). However, April 15 is still relevant for expats in two situations:
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- If you owe US tax, any balance due after estimated payments must be paid by April 15 to avoid interest charges — even if you plan to file by June 15 or October 15
- If you want to make a 2025 IRA contribution, you must do so by April 15, 2026 (not October 15)
April 15, 2026 — FBAR Original Deadline
The original due date for FinCEN Form 114 (FBAR) for the 2025 calendar year. The FBAR is automatically extended to October 15 — no action is required. See the October 15 entry for the filing deadline most expats use.
June 15, 2026 — Automatic 2-Month Extension for Expats
US citizens and resident aliens living outside the United States and Puerto Rico on April 15 receive an automatic 2-month extension to June 15 to file their Form 1040. No form or application is required — your status as an expat on April 15 qualifies you automatically.
Key limitation: This extension is for filing only, not for payment. Any tax owed must still be paid by April 15 (or covered by estimated payments), or interest accrues from April 15. If you owe tax, you must estimate the amount and pay by April 15 even if you plan to file by June 15.
When you file by June 15, you should attach a statement to your return explaining that you qualify for the 2-month extension.
June 30, 2026 — No Longer an FBAR Deadline
Historically, the FBAR was due June 30 with no extension available. This deadline was changed to April 15 (with automatic extension to October 15) effective for tax years beginning in 2016. If you are using old information, note that June 30 is no longer the FBAR deadline.
September 15, 2026 — Q3 2026 Estimated Tax Payment
Third estimated tax payment for the 2026 tax year (not 2025). If you have 2026 income not subject to withholding, your Q3 estimated payment covers June 1 – August 31, 2026 income. UK-based self-employed expats who pay UK Class 2/4 NICs and are covered by the Totalization Agreement should still assess whether US estimated taxes are needed for non-excluded or non-FTC-covered US income.
October 15, 2026 — Form 4868 Extension Deadline (US Return)
The final deadline to file your 2025 Form 1040 if you filed for an extension using Form 4868 by June 15 (or April 15). This is the deadline most US expats use. Note: You must file Form 4868 by June 15 to get the October 15 extension — you cannot wait until October 15 without the extension form on file.
October 15, 2026 — FBAR Final Deadline (Automatic Extension)
The automatic FBAR extension deadline. All US persons who need to file FinCEN Form 114 for the 2025 calendar year must file by October 15, 2026. No further extension is available after October 15.
December 15, 2026 — Additional Extension for Expats (Rare)
In certain circumstances, expats who have already obtained the October 15 extension can request a further 2-month extension to December 15 by writing to the IRS. This additional extension is discretionary and is granted only in unusual circumstances — it does not apply to the FBAR.
Foreign Corporation and Entity Reporting Deadlines
US expats with UK companies (Ltd, LLP) or other foreign entities have additional reporting obligations:
- Form 5471 (Information Return for Foreign Corporations): Due with your Form 1040 (including extensions). Required for US persons owning 10%+ of a foreign corporation. Penalties: $10,000 per late filing, rising to $50,000 for continued non-compliance.
- Form 8865 (Return for US Persons Regarding Foreign Partnerships): Due with Form 1040. Required for certain US partners in foreign partnerships (including UK LLPs). Penalty: $10,000 per late filing.
- Form 3520 (Foreign Trust/Gift Reporting): Due April 15 (or June 15 for expats). Penalties are among the highest in US tax law — 35% of the value of transactions with foreign trusts for which proper reporting is not made.
UK Tax Deadlines for US Expats in 2026
US expats in the UK must also meet UK obligations:
- January 31, 2026: UK Self Assessment return (paper and online) and payment for 2024/25 tax year — and first payment on account for 2025/26
- April 5, 2026: UK tax year end 2025/26
- April 6, 2026: Start of UK tax year 2026/27
- July 31, 2026: Second payment on account for 2025/26 UK tax year
- October 5, 2026: Deadline to register for Self Assessment for 2025/26 if not previously registered
- October 31, 2026: Deadline for paper Self Assessment return for 2025/26 tax year
- January 31, 2027: Online Self Assessment return and payment for 2025/26 UK tax year
What Happens If You Miss a Deadline?
Late Form 1040 Filing
Failure to file penalty: 5% of unpaid tax per month (up to 25%). If no tax is owed, there is generally no failure-to-file penalty — but the return should still be filed as soon as possible to start the statute of limitations running.
Late FBAR Filing
As described in our FBAR Filing Guide: non-willful penalties up to $10,000 per year (per the Bittner decision); willful penalties up to the greater of $100,000 or 50% of account balance. Streamlined procedures offer amnesty for genuinely non-willful filers.
Catching Up: IRS Streamlined Procedures
If you have missed multiple years of US returns and FBARs, the IRS Streamlined Foreign Offshore Procedures allow you to file 3 years of returns and 6 years of FBARs with zero penalty for non-willful non-compliance. This is the most important compliance catch-up programme for US expats in the UK. See our IRS Streamlined Filing service page for how we can help.
2026 Expat Tax Deadline Calendar: At a Glance
- January 15, 2026 — Q4 2025 US estimated tax due
- January 31, 2026 — UK Self Assessment (2024/25) due
- April 15, 2026 — US balance due payment + IRA contribution deadline + FBAR original due date
- June 15, 2026 — Automatic 2-month extension to file Form 1040 for expats
- July 31, 2026 — UK second payment on account due
- September 15, 2026 — Q3 2026 US estimated tax
- October 15, 2026 — Final US return deadline (with Form 4868) + FBAR final deadline
- October 31, 2026 — UK Self Assessment paper return (2025/26)
- January 31, 2027 — UK Self Assessment online return (2025/26)
Never Miss a US Tax Deadline Again
Our team prepares both US and UK tax returns, ensuring all deadlines are met across both jurisdictions. We proactively remind clients of upcoming deadlines and coordinate US and UK filings to prevent gaps in compliance.
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