If you are a US citizen living or working in Britain, understanding the UK tax year is not optional. It affects how you report income locally, how you plan your finances, and how you coordinate your US tax return.

The UK tax year 2025–2026 runs from:

6 April 2025 to 5 April 2026

That single difference, an April start instead of January, is where most confusion begins for Americans.

Let’s walk through what actually matters.

What Is the UK Tax Year?

The UK tax year does not follow the calendar year. Instead, it runs from 6 April to 5 April of the following year.

For comparison:

• US tax year: 1 January to 31 December
• UK tax year: 6 April to 5 April

The tax authority responsible for administering the system is HM Revenue & Customs (HMRC).

If you are employed, your income tax is typically withheld through PAYE (Pay As You Earn). If you are self-employed or have additional income, you may need to file a Self Assessment return.

Why the UK Tax Year 2025–2026 Matters for Americans

If you are an American abroad, you deal with two governments:

• HMRC in the UK
• The Internal Revenue Service (IRS) in the US

And they operate on different timelines.

The Timing Mismatch

The UK tax year 2025–2026 covers:

• 6 April 2025 to 5 April 2026

Your 2025 US tax return covers:

• 1 January 2025 to 31 December 2025

That means:

• Part of the UK 2025–2026 tax year overlaps two different US tax years.
• You may need to allocate income carefully when claiming the Foreign Tax Credit.
• Planning becomes important to avoid temporary double taxation.

This is one of the most common technical issues US expats in the UK face.

Key Deadlines for the UK Tax Year 2025–2026

Here are the important dates Americans should track:

• 6 April 2025 – Start of the UK tax year
• 5 April 2026 – End of the UK tax year
• 31 October 2026 – Paper Self Assessment deadline
• 31 January 2027 – Online Self Assessment deadline and tax payment due

If you owe tax under Self Assessment, payment is generally due by 31 January following the end of the tax year.

How Income Is Taxed During the UK Tax Year

During the 2025–2026 UK tax year, your income may include:

• Employment salary
• Self-employment income
• Rental income
• Capital gains
• Investment income

If you are employed, tax is typically withheld automatically through PAYE.

If you are self-employed, you report your income through Self Assessment.

Americans must then report that same income to the IRS, even if they already paid UK tax on it.

US Filing Obligations Still Apply

Living in the UK does not remove US filing requirements.

You may still need to:

• File Form 1040 annually
• Report foreign bank accounts (FBAR)
• Claim the Foreign Tax Credit
• Consider the Foreign Earned Income Exclusion

The US-UK tax treaty helps prevent double taxation, but it does not eliminate filing requirements. Relief usually comes through tax credits, not exemption from reporting.

With careful planning, some Americans may use both FTC and FEIE strategies on the same return, depending on their income structure.

Planning Before 5 April 2026

Many tax planning decisions in the UK happen before the tax year ends.

Americans in Britain often review:

• Capital gains timing
• Pension contributions
• ISA usage
• Bonus timing

Because the UK tax year ends on 5 April, planning in March can be financially significant.

Common Mistakes Americans Make

1. Assuming the UK tax year matches the US calendar year
2. Forgetting the 5 April cutoff for allowances
3. Misaligning income when claiming the Foreign Tax Credit
4. Ignoring Self Assessment deadlines
5. Thinking the US-UK treaty eliminates filing requirements

These mistakes are avoidable with proper coordination.

FAQs: UK Tax Year 2025–2026

1. What is the UK tax year 2025–2026?

The UK tax year 2025–2026 runs from 6 April 2025 to 5 April 2026.

2. Why doesn’t the UK tax year follow the calendar year?

The April start date dates back to historical calendar reforms in the 18th century. The structure has remained in place ever since.

3. Do Americans in the UK have to follow both tax years?

Yes. Americans must follow the UK tax year for UK income and the US calendar tax year for US filing purposes.

4. When is the Self Assessment deadline for the 2025–2026 UK tax year?

The online filing and payment deadline is 31 January 2027.

5. Can I avoid double taxation during the UK tax year?

You generally cannot avoid reporting income to both countries. However, you may reduce double taxation through the Foreign Tax Credit, the Foreign Earned Income Exclusion, or treaty provisions.

6. Does paying UK tax mean I do not owe US tax?

Not necessarily. You still must file a US tax return. Whether you owe additional US tax depends on your income, credits, and planning.

Final Thoughts

For Americans living in Britain, understanding the UK tax year is more than a technical detail. It shapes how income is reported, how credits are claimed, and how tax planning works across two systems.

The UK tax year 2025–2026 runs from 6 April 2025 to 5 April 2026. That difference from the US calendar year is where most cross-border complications begin.

If you are earning income in the UK while filing in the US, coordination between both systems is essential to avoid errors and unnecessary tax exposure.