US UK Tax Returns

Forms & Filings

What each form asks, who has to file it, when it is due and what happens if it is missed. Every guide links to the official instructions.

US tax forms and a pencil

The US Return

Form 1040U.S. Individual Income Tax ReturnThe annual federal return for US citizens, green card holders and US residents, reporting worldwide income wherever the filer lives.Form 1040-NRU.S. Nonresident Alien Income Tax ReturnThe federal return for people who are not US citizens or residents but have US-source income, a US business or a refund to claim.Form 1040-XAmended U.S. Individual Income Tax ReturnThe form for correcting a Form 1040 already filed, whether to add missed income, switch relief methods or claim a refund.Form 4868Automatic Extension of Time to FileA short application that extends the time to file Form 1040 or 1040-NR, though not the time to pay any tax due.Schedule 2Additional Taxes (Form 1040)The schedule that totals taxes beyond regular income tax, including self-employment tax, NIIT and the alternative minimum tax.

Relief From Double Tax

Form 2555Foreign Earned Income ExclusionThe election to exclude a capped amount of foreign earnings from US tax, with a separate housing exclusion or deduction.Form 1116Foreign Tax CreditThe form that turns UK income tax into a credit against US tax on the same income, with carryovers for unused amounts.Form 8833Treaty-Based Return Position DisclosureThe disclosure required when a US return relies on the US-UK treaty to override or modify the ordinary US tax rules.

Foreign Accounts & Funds

FinCEN 114Report of Foreign Bank and Financial Accounts (FBAR)The annual report of foreign accounts filed with FinCEN, separate from the tax return, once combined balances pass the threshold.Form 8938Statement of Specified Foreign Financial Assets (FATCA)The FATCA asset statement attached to the tax return, with higher thresholds for filers who live abroad than for those in the US.Form 8621PFIC Shareholder ReturnThe annual return for US persons holding passive foreign investment companies, which includes most UK funds, unit trusts and ETFs.

Companies & Partnerships

Form 5471U.S. Persons With Respect to Certain Foreign CorporationsThe information return a US citizen or green card holder files for a UK limited company they own, control or have acquired an interest in.Form 547225% Foreign-Owned U.S. CorporationReporting for US corporations with a significant foreign owner, and for single-member US LLCs owned by someone outside the US.Form 8858Foreign Disregarded Entities and Foreign BranchesThe information return for a foreign entity the IRS disregards, or a foreign branch, such as a UK operation of a US business.Form 8865U.S. Persons With Respect to Certain Foreign PartnershipsThe information return for US persons with interests in a foreign partnership, including many UK partnerships and some UK LLPs.

Trusts, Gifts & Exit

Form 3520Foreign Trusts and Receipt of Certain Foreign GiftsReporting for US persons who receive large gifts or inheritances from abroad or who deal with a foreign trust.Form 3520-AForeign Trust With a U.S. OwnerThe annual information return for a foreign trust treated as owned by a US person, normally filed by the trustee.Form 709United States Gift Tax ReturnThe US gift tax return, which Americans in the UK often need for gifts to a non-US spouse, children or property bought jointly.Form 8854Initial and Annual Expatriation StatementThe form that closes out US tax status after renouncing citizenship or giving up a long-term green card, and sets whether the exit tax applies.

Withholding & Tax IDs

Form W-8BENCertificate of Foreign Status (Individuals)The certificate a non-US individual gives a US payer to confirm foreign status and claim treaty-reduced withholding on US income.Form W-8BEN-ECertificate of Foreign Status (Entities)The certificate a non-US entity gives a US payer to confirm its foreign status, FATCA classification and any treaty claim.Form W-7Application for an ITINThe application for an individual taxpayer identification number, for people who need a US tax number but cannot get an SSN.

UK Forms

SA100UK Self Assessment Tax ReturnThe main UK Self Assessment return, with supplementary pages for foreign income, property, gains and residence.SA109Residence, Remittance Basis etc.The Self Assessment pages for residence status, split-year treatment, treaty residence claims and foreign income and gains claims.

Guides

TreatyThe US-UK Income Tax TreatyHow the US-UK income tax treaty allocates taxing rights, and where its saving clause limits what US citizens can claim.183 DaysThe Substantial Presence TestHow the IRS decides whether a non-citizen without a green card is a US resident for tax, and the exceptions that change the count.State ReturnsUS State Tax Returns for People Who Have LeftWhy a move to the UK does not always end a US state tax obligation, and how states decide who remains a resident.US v UKHow US and UK Income Taxes DifferThe structural differences between the US and UK income tax systems that cause most cross-border problems, from tax years to ISAs.

The calendar

US dates are for tax year 2025. UK dates are for 2025/26, which runs from 6 April to 5 April. Interest on US tax runs from 15 April even where the filing date is extended.

US return due: 15 April
US return, filers abroad: 15 June
US extended deadline: 15 October
FBAR: 15 April, extended automatically to 15 October
Register for Self Assessment: 5 October
UK online return: 31 January

28 forms and guides. Not sure which apply to you?

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