Key dates at a glance
Dates fall on weekends some years, but HMRC deadlines don't move. Aim to finish a few days early.
| Date | What happens |
|---|---|
| 6 April 2026 | New tax year starts. New tax codes and allowances apply. |
| 31 May 2026 | Employers must give you your P60 for 2025/26. |
| 6 July 2026 | Deadline for employers' P11D forms showing 2025/26 benefits. |
| 31 July 2026 | Second payment on account for 2025/26 due. |
| 7 August 2026 | First Making Tax Digital quarterly update due, if you're in scope. |
| 5 October 2026 | Register for Self Assessment if you need to file for 2025/26 for the first time. |
| 31 October 2026 | Paper Self Assessment returns for 2025/26 due. |
| 30 December 2026 | File online by now to have tax under £3,000 collected through your tax code. |
| 31 January 2027 | Online returns for 2025/26 due. Pay the balance and first payment on account for 2026/27. |
| 5 April 2027 | Tax year ends. Last day to use 2026/27 ISA, pension, CGT and gifting allowances. |
Self Assessment deadlines
If you're new to Self Assessment, register by 5 October after the tax year you need to report. Returns for 2025/26 are due by 31 October 2026 on paper or 31 January 2027 online. Missing the online deadline brings an automatic £100 penalty, even if you owe nothing.
Payments on account usually apply unless your previous Self Assessment bill was less than £1,000 or more than 80% of your tax was paid outside Self Assessment. Each instalment is half the relevant previous liability, excluding Capital Gains Tax and student loans, due on 31 January and 31 July.
When tax codes change
Your code is updated for the new year from 6 April. Most people with one job are on 1257L. HMRC may also change it during the year when your benefits, second job, Marriage Allowance or underpaid tax change.
Check your code on your first payslip after April and after any change at work. A wrong code is the most common reason for paying too much or too little tax through PAYE. You can see and update details in your HMRC online account.
When to use or claim allowances
Some allowances reset on 6 April and can't be carried forward, so use them before 5 April. Others can be claimed for earlier years.
- ISA allowance: £20,000 a year. Unused allowance is lost on 5 April.
- Capital Gains Tax annual exempt amount: £3,000. Consider timing disposals across tax years.
- Dividend allowance: £500 a year.
- Pension annual allowance: generally £60,000, and unused allowance can be carried forward for up to three years.
- Marriage Allowance: can be backdated up to four tax years, so claim before 5 April 2027 to include 2022/23.
- Uniform, work tools and professional fees: tax relief can be claimed for the current year and the previous four.
- Higher-rate relief on personal pension contributions and Gift Aid: claim through Self Assessment or by contacting HMRC.
Making Tax Digital quarterly updates
From 6 April 2026, sole traders and landlords with qualifying income over £50,000 send quarterly updates using compatible software. Updates are due by 7 August, 7 November, 7 February and 7 May, with the final return still due by 31 January.
Turn dates into a records checklist
Keep each deadline alongside the information or action it requires. A reminder to file is more useful when your records, access details and payment plan have been prepared separately.
Try it with your own numbers
Estimate Income Tax and Class 4 National Insurance on self-employed profits for 2026/27, including other employment income.
Frequently asked questions
When does the 2026/27 tax year end?
On 5 April 2027. The 2027/28 tax year starts on 6 April 2027.
Check it on GOV.UK: Income Tax rates and allowances (opens GOV.UK in a new tab) · Self-employed National Insurance rates (opens GOV.UK in a new tab)
What happens if I miss the 31 January deadline?
There's an immediate £100 penalty, rising after three, six and twelve months, plus interest on any tax paid late.
Check it on GOV.UK: Income Tax rates and allowances (opens GOV.UK in a new tab) · Self-employed National Insurance rates (opens GOV.UK in a new tab)
Do I need to do anything when my tax code changes?
Usually not, but check it matches your circumstances. If it looks wrong, tell HMRC through your online account or app.
Check it on GOV.UK: Tax codes (opens GOV.UK in a new tab)
Sources
- GOV.UK: Self Assessment tax returns
- GOV.UK: Tax codes
- GOV.UK: Marriage Allowance
- GOV.UK: Self Assessment deadlines
- GOV.UK: Individual Savings Accounts
Tax year 2026/27. Check these official sources for current rules and deadlines.
Related calculators
- Self Employed Tax Calculator — Estimate Income Tax and Class 4 National Insurance on self-employed profits for 2026/27, including other employment income.
- PAYE Calculator — Estimate PAYE Income Tax and NI using your own tax code for 2026/27.
- Salary Calculator — Convert a gross UK salary into net pay for 2026/27.
Related guides
- Self Assessment Explained — Who needs to file a Self Assessment tax return, what goes on it, the deadlines for 2026/27 and the penalties for missing them.
- Tax Codes Explained — What your tax code means, from 1257L to K codes, BR, D0, NT and emergency codes, and what to do if yours looks wrong.
- Marriage Allowance — Who can claim Marriage Allowance, how much it's worth, how to backdate a claim and how it changes your tax code.
- UK Tax-Free Allowances — A summary of UK tax-free allowances for 2026/27: Personal Allowance, savings, dividends, CGT, trading, property, ISAs and pensions.