Last reviewed: June 2026 | Source: HMRC / gov.uk
TL;DR- The 2026/27 UK tax year runs from 6 April 2026 to 5 April 2027.
- Online Self Assessment deadline for 2025/26 returns: 31 January 2027. Paper return deadline: 31 October 2026.
- Second payment on account for 2025/26: due 31 July 2026.
- P11D benefits in kind deadline: 6 July 2026.
- Making Tax Digital for Income Tax starts 6 April 2026 for sole traders and landlords with income over £50,000.
Key Dates 2026/27
●6 April 2026: 2026/27 tax year begins
●6 July 2026: P11D and P11D(b) deadline
●22 July 2026: Class 1A NIC payment deadline
●31 July 2026: Second payment on account (2025/26)
●5 October 2026: Register for Self Assessment (new)
●31 October 2026: Paper Self Assessment deadline (2025/26)
●31 January 2027: Online Self Assessment + balancing payment (2025/26)
●5 April 2027: 2026/27 tax year ends
When Does the UK Tax Year Start and End
The UK tax year runs from 6 April to 5 April the following year. The 2026/27 tax year began on 6 April 2026 and ends on 5 April 2027. All income, capital gains and most tax allowances and thresholds are assessed within this April-to-April window. The unusual 6 April start date is a legacy of the 1752 calendar reform, when Britain adopted the Gregorian calendar and the Treasury adjusted the year-end forward to avoid losing tax revenue.
This differs from the calendar year (1 January to 31 December) and from most company financial years. Employees paid through PAYE have their tax calculated automatically within the tax year, but those with income outside PAYE must file a Self Assessment tax return covering the same period.
Self Assessment Deadlines 2025/26
The Self Assessment tax return for the 2025/26 tax year (6 April 2025 to 5 April 2026) has two filing deadlines depending on the method. Paper returns must be submitted by 31 October 2026. Online returns must be submitted by 31 January 2027, which is also the deadline for paying any tax owed (the balancing payment) and the first payment on account for 2026/27.
Missing the 31 January deadline triggers an automatic £100 penalty, even if no tax is owed. After three months, daily penalties of £10 per day accrue for up to 90 days (maximum £900). At six months and twelve months, further penalties of 5% of the tax due or £300 (whichever is greater) apply. Interest is charged on unpaid tax from the day after the deadline.
Payment on Account Dates
Self Assessment taxpayers who owe more than £1,000 in tax make payments on account towards the following year's liability. There are two payment on account dates each year: 31 January (first payment, coinciding with the balancing payment for the previous year) and 31 July (second payment). Each payment on account is half of the previous year's tax bill. For 2025/26, the second payment on account is due on 31 July 2026.
Employer Deadlines: P11D, PAYE and NIC
Employers have their own set of HMRC deadlines within the tax year. The P11D form, reporting benefits in kind provided to employees (such as company cars, private medical insurance and loans), must be submitted to HMRC by 6 July 2026 for the 2025/26 tax year. The P11D(b) form, which declares the employer's Class 1A National Insurance liability on benefits in kind, has the same deadline. The Class 1A NIC payment itself is due by 22 July 2026 (19 July for cheque payments).
Monthly PAYE and employee National Insurance payments are due to HMRC by the 19th of each month following the payroll month (22nd for electronic payments). These run continuously throughout the tax year regardless of the April year-end.
VAT Return Deadlines
VAT-registered businesses submit VAT returns quarterly (or monthly for those on monthly returns, or annually for those on the Annual Accounting Scheme). The deadline for submitting and paying is one month and seven days after the end of the VAT accounting period. VAT periods do not necessarily align with the tax year -- they depend on the VAT registration stagger group assigned by HMRC.
Making Tax Digital for Income Tax: From 6 April 2026
Making Tax Digital for Income Tax Self Assessment (MTD ITSA) began on 6 April 2026 for sole traders and landlords with qualifying income over £50,000. These taxpayers must use MTD-compatible software to keep digital records and submit quarterly updates to HMRC, replacing the annual Self Assessment return. The threshold reduces to £30,000 from April 2027 and £20,000 from April 2028. Businesses and individuals below the relevant threshold continue under the existing Self Assessment regime.
Why the Tax Year Starts on 6 April
The 6 April start date is one of the more unusual features of the UK tax system. Before 1752, England used the Julian calendar and the legal and tax year began on Lady Day, 25 March. When Britain adopted the Gregorian calendar in 1752, eleven days were dropped from the calendar. The Treasury, unwilling to lose eleven days of tax revenue, moved the year-end forward by eleven days to 4 April. A further one-day adjustment in 1800 shifted it to 5 April (year end) and 6 April (year start), where it has remained ever since.
Frequently Asked Questions
When does the 2026/27 UK tax year start and end?
The 2026/27 tax year runs from 6 April 2026 to 5 April 2027. All income and gains within this period are assessed for income tax and capital gains tax under the 2026/27 rules and allowances.
When is the Self Assessment deadline for 2025/26?
The online filing deadline for the 2025/26 Self Assessment return is 31 January 2027. Paper returns must be filed by 31 October 2026. Any tax owed must be paid by 31 January 2027 to avoid interest and penalties.
When is the second payment on account due in 2026?
The second payment on account for the 2025/26 tax year is due on 31 July 2026. This is the second of two advance payments towards your tax liability, each equal to half of the previous year's Self Assessment bill.
What is the P11D deadline for 2025/26?
P11D and P11D(b) forms for the 2025/26 tax year must be submitted to HMRC by 6 July 2026. The Class 1A National Insurance payment arising from the P11D is due by 22 July 2026.
