Every date that matters, both systems.
Two tax years that do not align, two sets of deadlines, and extensions that apply automatically if you live abroad but are widely missed.
The tax years do not line up
The US tax year is the calendar year. The UK tax year runs 6 April to 5 April. That offset is the source of a great deal of avoidable confusion, because income earned in one UK year can straddle two US years.
It also means the two returns are never prepared at quite the same moment, which is exactly why sequencing them deliberately matters when credits on one depend on figures from the other.
Living abroad buys you time
US filers abroad get an automatic extension to mid-June without asking for it, and can extend further to mid-October on request. The extension is to file, not to pay — interest still runs on anything owed from the April date.
That extra room is genuinely useful. A US return prepared before the UK position is settled often has to be revisited, and the extension usually removes the need to do it twice.
- US return: 15 April, automatic extension to 15 June from abroad
- Further US extension available to 15 October on request
- FBAR: 15 April, with an automatic extension to 15 October
- UK Self Assessment online: 31 January following the tax year end
- UK paper return: 31 October following the tax year end
- UK payments on account: 31 January and 31 July
Dates change, so check yours
Where the current cycle stands: the 2025 US return was due 15 April 2026, automatically extended to 15 June from abroad, and 15 October 2026 if you filed for the further extension. The 2025 FBAR carries the same 15 October 2026 backstop. The UK 2025/26 year ended 5 April 2026, so a paper return is due 31 October 2026 and an online return 31 January 2027.
The pattern above is stable, but individual dates shift when they fall on a weekend or public holiday, and extension rules are amended more often than people expect. Treat this as orientation for a specific year rather than advice. If a deadline is close and you are unsure, ask rather than assume.
Last reviewed . Thresholds and rates change annually — check figures against the current tax year before relying on them.
Deadline coming up?
Tell us where you stand and we will confirm what is due, when, and whether an extension is worth filing.