Guides
US–UK tax deadlines calendar
If you file on both sides of the Atlantic, the key dates are: the US return on 15 April (automatically extended to 15 June for Americans abroad, then 15 October on request), the FBAR on 15 April (extended to 15 October), and on the UK side the online Self Assessment return and payment by 31 January, with a payment on account on 31 July. US tax owed accrues interest from 15 April even when filing is extended.
Filing in two countries means tracking two sets of deadlines that don’t line up. The US runs on the calendar year; the UK year runs 6 April to 5 April. Miss the overlap and you can face penalties from both tax authorities for the same period — so here are the dates that matter, in one place.
One trap worth highlighting: the automatic extensions that Americans abroad receive push back the filing deadline, not the payment deadline. US tax owed still accrues interest from 15 April, so an extension is not a reason to delay paying.
Key dates
The two calendars side by side
United States
- 15 AprilUS return due (interest on tax owed starts now, even if filing is extended)
- 15 AprilFBAR (FinCEN 114) due — automatically extended to 15 October
- 15 JuneAutomatic filing extension for Americans abroad
- 15 OctoberFinal US return extension deadline (if requested) and FBAR extension deadline
United Kingdom
- 6 AprilNew UK tax year begins
- 31 JulySecond payment on account due (if applicable)
- 5 OctoberDeadline to register for Self Assessment for the previous tax year
- 31 OctoberPaper Self Assessment return deadline
- 31 JanuaryOnline Self Assessment return and balancing payment due
Dates reflect the standard deadlines and automatic expat extensions. Where a deadline falls on a weekend or public holiday it may shift to the next working day, and some dates depend on your circumstances. Always confirm the current year’s deadlines for your specific filings.
Frequently asked questions
The US return is due 15 April, but Americans living abroad get an automatic extension to 15 June, and can request a further extension to 15 October. The FBAR is due 15 April with an automatic extension to 15 October. Importantly, any US tax owed still accrues interest from 15 April even when the filing deadline is extended.
The UK tax year runs 6 April to 5 April. Paper Self Assessment returns are due by 31 October, online returns and the balancing payment by the following 31 January, with a second payment on account due 31 July where applicable. Company Corporation Tax is generally due nine months and one day after the accounting period ends, with the return due twelve months after.
They do not — and that is a common source of confusion. The US uses the calendar year (1 January to 31 December) while the UK year runs 6 April to 5 April. This mismatch affects how income is apportioned, when foreign tax is considered paid for credit purposes, and how a move mid-year is handled, which is why cross-border returns need the two timelines reconciled.
It depends which one. HMRC charges an automatic £200 for a late Self Assessment return plus escalating penalties and interest; the IRS charges failure-to-file and failure-to-pay penalties plus interest, and information returns like the FBAR and Form 5471 carry their own steep penalties. Where a deadline has been missed, acting quickly — and, for missed US filings, considering the Streamlined programme — usually limits the damage.
Never miss a cross-border deadline
We track both calendars for our clients and file on time on both sides. Book a consultation.