Missing a key tax date costs money. Whether it is a late filing penalty, a missed allowance, or an unprepared payroll run, the UK tax year has a fixed rhythm that every taxpayer and business owner needs to understand. Knowing exactly when the tax year starts, ends, and what falls in between puts you firmly in control of your tax position.
This guide covers the UK tax year dates, the deadlines that matter most, and how to prepare for each one.
What Is the UK Tax Year and Why Does It Matter?
The UK tax year, also called the fiscal year, is the twelve-month period HMRC uses to calculate your tax liability. Every allowance, every threshold, and every deadline resets within this period. Personal allowance, ISA limit, capital gains exempt amount, and pension annual allowance all tie directly to it.
For employees, it determines PAYE deductions. For the self-employed, it sets the reporting period for profits. For investors, it defines when gains are taxed and which year’s allowances apply. Getting the dates wrong, even by one day, can mean missed allowances, late filing penalties, and unnecessary tax bills.
What Date Does the UK Tax Year Start and End?
The UK tax year runs from 6 April to 5 April the following year.
| Tax Year | Start Date | End Date |
| 2023/24 | 6 April 2023 | 5 April 2024 |
| 2024/25 | 6 April 2024 | 5 April 2025 |
| 2025/26 | 6 April 2025 | 5 April 2026 |
| 2026/27 | 6 April 2026 | 5 April 2027 |
The current tax year for 2025/26 runs from 6 April 2025 to 5 April 2026.
Why does the UK tax year start on 6 April?
The 6 April start date is a historical quirk rooted in the 18th century. Prior to 1752, the UK used the Julian calendar, and the tax year began on 25 March, Lady Day, the traditional start of the new year. When Britain adopted the Gregorian calendar in 1752, eleven days were lost from the calendar. To avoid losing eleven days of tax revenue, the Treasury moved the tax year start date forward, eventually settling on 6 April, where it has remained ever since.
Key Tax Dates and Deadlines Every UK Taxpayer Should Know
The tax year is punctuated by a series of critical deadlines. Missing them triggers penalties, interest charges, and unnecessary stress.
| Date | Deadline / Event |
| 6 April | New tax year begins, allowances and thresholds reset |
| 31 July | Second payment on account due for Self Assessment taxpayers |
| 5 October | Deadline to register for Self Assessment for the previous tax year |
| 31 October | Deadline for the paper Self Assessment tax return submission |
| 31 January | Online Self Assessment return filing deadline and balancing payment due |
| 31 January | First payment on account due for the current tax year |
| 5 April | Tax year ends, final day to use annual allowances |
| 5 April | Last day to make pension contributions for the current tax year |
| 5 April | Last day to use ISA allowance for the current tax year |
| 19 April | Deadline for final PAYE submissions for the tax year |
| 31 May | Deadline for employers to issue P60S to employees |
| 6 July | Deadline for employers to submit P11D forms to HMRC |
Self Assessment Payments On Account
Payments on account are advance payments toward your next tax bill. They are due on 31 January and 31 July each year. Each payment is 50% of your previous year’s tax bill. Missing these deadlines triggers interest charges from the due date, not from year-end.
The 5 April Allowance Deadline
The final day of the tax year, 5 April, is one of the most financially significant dates in the calendar. ISA subscriptions, pension contributions, capital gains tax planning, and charitable giving all need to be completed by this date to count for the current tax year. Unused allowances do not carry forward.
How Businesses Should Prepare for the Start of a New Tax Year
The start of a new tax year on 6 April triggers a series of practical responsibilities for employers and business owners.
1. Update Payroll For New Thresholds And Rates
From 6 April, new income tax thresholds, National Insurance rates, National Minimum Wage rates, and statutory pay rates come into effect. Payroll software must be updated before the first payroll run of the new tax year. Processing payroll on outdated rates creates compliance errors that are time-consuming to correct.
2. Issue P60S to all employees by 31 May
Every employee on your payroll on 5 April must receive a P60 by 31 May. The P60 summarises their total pay and tax deducted for the year. Late or inaccurate P60S create problems for employees filing their own tax returns and can trigger HMRC queries.
3. Review And Update Employee Tax Codes
HMRC issues updated tax codes ahead of the new tax year. Check that all employee codes have been updated in your payroll system. Any codes carrying over incorrectly from the previous year should be queried with HMRC promptly.
4. Submit Final RTI Returns For The Previous Tax Year
The deadline for submitting the final Full Payment Submission (FPS) and any outstanding Employer Payment Summaries (EPS) for the previous tax year is 19 April. Late submissions attract penalties and can trigger HMRC compliance queries.
5. Review Company Financial Year Alignment
Many businesses choose a company accounting year that ends on 31 March or 5 April to align with the tax year. If your company’s year-end falls at a different point, ensure your accountant is clear on the overlap between your accounting period and the tax year for corporation tax purposes.
6. Use Remaining Allowances Before 5 April
In the weeks leading up to 5 April, review whether any remaining tax-efficient opportunities should be actioned before the year closes. Pension contributions, salary sacrifice arrangements, dividend declarations, and capital loss harvesting are all worth reviewing before the tax year-end deadline.
A well-prepared business does not scramble at year’s end, it arrives at 6 April with clean records, updated payroll, and every allowance already used. The time invested in preparation now saves significantly more time fixing compliance errors later.
Common Confusion Around the UK Tax Year Start Date and How to Avoid It
The UK tax year start date generates more confusion than almost any other aspect of the tax system. Here are the most common sources of misunderstanding.
1. Confusing The Tax Year With The Calendar Year
The UK tax year does not run from January to December. It runs from 6 April to 5 April. This catches out individuals who assume their ISA allowance or pension limit resets on 1 January. It does not, it resets on 6 April.
2. Confusing The Tax Year With The Company’s Financial Year
A company’s accounting year can end on any date, it does not have to align with the tax year. Corporation tax is calculated based on the company’s accounting period, not the personal tax year. Many business owners conflate the two, leading to errors in tax planning and financial reporting.
3. Assuming The Tax Year Starts On 5 April Rather Than 6 April
The tax year ends on 5 April and starts on 6 April. The distinction of one day matters, particularly for pension contributions, ISA subscriptions, and capital gains planning. A contribution made on 5 April counts for the current tax year. The same contribution made on 6 April counts for the next.
4. Not Knowing Which Tax Year A Transaction Falls Into
For self-assessment purposes, income and gains are allocated to the tax year in which they arise, not the calendar year. A bonus paid in February 2026 falls into the 2025/26 tax year. A dividend declared on 6 April 2026 falls into 2026/27.
5. Mixing Up Self-Assessment Deadlines Across Tax Years
The 31 January deadline refers to the return for the tax year that ended the previous April, not the current one. For example, the 31 January 2026 deadline applies to the 2024/25 tax year return. Confusing which year a deadline applies to is a consistent source of late filing penalties.
Each of these confusions is easily avoided with one simple habit: always confirming which tax year a date, transaction, or deadline actually belongs to before acting on it.
Mistakes Taxpayers Make Around the Tax Year Start and End Dates
These errors are consistently seen across both individual taxpayers and business owners. Most are avoidable with basic calendar awareness.
1. Missing The ISA Subscription Deadline
The ISA allowance, £20,000 for 2025/26, expires on 5 April. It cannot be carried forward. Taxpayers who intend to use their full allowance but delay until after 5 April lose it permanently for that year. Set a reminder well in advance, not on the day.
2. Missing Pension Contribution Deadlines
Pension contributions made by 5 April count toward the current tax year’s annual allowance and attract tax relief in the current year. Contributions made on or after 6 April fall into the next tax year. For higher earners managing the tapered annual allowance, this distinction is financially significant.
3. Failing To Use The Capital Gains Tax Annual Exemption Amount
The CGT annual exempt amount, £3,000 for 2025/26, resets on 6 April and cannot be carried forward. Taxpayers with unrealised gains who could crystallise them tax-free before 5 April often miss this opportunity by not reviewing their portfolio before the year-end.
4. Registering For Self Assessment Too Late
If you received untaxed income in 2024/25 from self-employment, rental income, dividends, or other sources, you must register for Self Assessment by 5 October 2025. Missing this deadline can result in penalties even if your tax return is subsequently filed on time.
5. Submit A Paper Return by 31 October
Paper Self Assessment returns must be submitted by 31 October following the tax year end. Many taxpayers are unaware of this earlier deadline, submitting on paper after 31 October, and receiving an automatic late filing penalty that could have been avoided by filing online.
6. Not Reconciling Payroll At Year’s End
Employers who fail to reconcile their payroll records at year’s end risk submitting inaccurate P60S, incorrect final RTI submissions, and misaligned PAYE accounts. Year-end payroll reconciliation is a critical step, not an optional one.
Every one of these mistakes shares the same root cause, leaving tax planning too late. A simple annual calendar with key dates marked is all it takes to avoid every error on this list.
Final Thoughts
The UK tax year runs from 6 April to 5 April, and that fixed rhythm drives every allowance, every deadline, and every compliance obligation you face. Missing a date does not just cost money in penalties. It means permanently losing allowances that reset and never return.
Put the key dates in your calendar now. Review your allowances before 5 April every year. Prepare your payroll and business records before 6 April. And if your tax affairs are complex, multiple income sources, investments, pension planning, or a business, work with a qualified adviser who ensures nothing slips through the gaps.
FAQs
What Date Does The UK Tax Year Start?
The UK tax year starts on 6 April every year. The 2025/26 tax year began on 6 April 2025 and ends on 5 April 2026.
Why Does the UK Tax Year Start On 6 April?
The 6 April start date originates from an 18th-century calendar change. When Britain adopted the Gregorian calendar in 1752, eleven days were removed from the year. To avoid losing tax revenue, the Treasury moved the tax year start date forward, eventually settling on 6 April.
When Does The 2025/26 Tax Year End?
The 2025/26 tax year ends on 5 April 2026. All income, gains, and allowances for that year must be accounted for by this date.
When is the Self-Assessment Filing Deadline?
The online Self Assessment filing deadline is 31 January following the end of the tax year. The paper return deadline is 31 October. For the 2024/25 tax year, the online deadline is 31 January 2026.
When Does The Isa Allowance Reset?
The ISA allowance resets on 6 April, the start of each new tax year. Unused ISA allowance from the previous year cannot be carried forward. The annual ISA allowance for 2025/26 is £20,000.
What Is The Deadline For Registering For Self Assessment?
You must register for Self Assessment by 5 October following the end of the tax year in which you received untaxed income. For income received in 2024/25, the registration deadline is 5 October 2025.
When Must Employers Issue P60S?
Employers must issue a P60 to every employee who was on the payroll on 5 April by 31 May. The P60 confirms total pay and tax deducted for the completed tax year.
Does The Company’s Financial Year Have To Match The Tax Year?
No. A company can choose any accounting year-end date. However, many businesses align their financial year with the tax year, ending on 31 March or 5 April, to simplify tax planning and reporting.
