Tax Planning Calendar

Key facts

The UK tax year runs from 6 April to 5 April.
31 January is the deadline for online Self Assessment filing, balancing payment, and first payment on account.
31 July is the deadline for the second payment on account.
Most personal tax allowances and exemptions are use-it-or-lose-it each tax year.
Late filing incurs an automatic £100 penalty, even if you owe no tax.

April – June: New Tax Year

Date	Event / Action
6 April	New tax year begins (2026/27). New allowances, rates, and thresholds take effect.
6 April	Start using your ISA allowance (£20,000), CGT exemption (£3,000), and pension allowance (£60,000) for the new year.
19 April	Deadline for final PAYE submission for the previous tax year (employers).
31 May	Employer must provide your P60 for the previous tax year.

Planning opportunity: Review your tax position at the start of the new year. Set up regular ISA contributions, plan pension contributions, and identify assets to sell using your CGT exemption.

July – September: Mid-Year

Date	Event / Action
6 July	Employer must provide P11D forms (benefits in kind) for the previous tax year.
31 July	Second payment on account due for Self Assessment (previous year’s liability).^[3]
August	MTD quarterly update deadline (Q1: 6 April – 5 July) — due by 7 August.

October – December: Filing Season

Date	Event / Action
5 October	Deadline to register for Self Assessment if you have a new source of income.^[1]
31 October	Deadline for paper Self Assessment returns (previous tax year).
November	MTD quarterly update deadline (Q2: 6 July – 5 October) — due by 7 November.
30 December	Deadline to file online if you want HMRC to collect tax owed (under £3,000) through your PAYE code.

Don’t wait until January: Filing early does not mean paying early — the payment deadline is still 31 January. Filing early gives you more time to plan and avoids the last-minute rush.

January – March: Year-End Planning

Date	Event / Action
31 January	Online Self Assessment deadline + balancing payment + first payment on account for the current year.^[1]
February	MTD quarterly update deadline (Q3: 6 October – 5 January) — due by 7 February.
March	Last chance for year-end tax planning actions before 5 April.
5 April	End of tax year. Last day to use ISA allowance, CGT exemption, pension allowance, and gift exemptions.

Penalty Summary

Lateness	Filing Penalty	Payment Penalty
1 day late	£100 automatic	Interest accrues daily
3 months late	£10/day (up to 90 days = £900)	5% surcharge on tax outstanding at that date
6 months late	5% of tax due or £300 (whichever is higher)	Further 5% surcharge
12 months late	Further 5% of tax due or £300	Further 5% surcharge

^[2]

Key Year-End Actions (Before 5 April)

Use your ISA allowance — £20,000 per person, cannot be carried forward
Make pension contributions — £60,000 annual allowance (plus carry forward)
Use your CGT annual exemption — sell assets to crystallise £3,000 of gains tax-free
Make gifts — use your £3,000 annual IHT exemption and small gift exemptions
Transfer assets to spouse — use both personal allowances and basic rate bands
Review dividend timing — use the £500 dividend allowance

Frequently Asked Questions

What is the most important tax deadline?

31 January is the most critical date for most taxpayers. It is the deadline for filing your online Self Assessment return, paying any balancing tax owed for the previous year, and making your first payment on account for the current year. Missing it triggers an automatic £100 late filing penalty and interest on unpaid tax.

What are payments on account?

Payments on account are advance payments towards your next tax bill. Each payment is 50% of your previous year’s tax liability. The first is due on 31 January and the second on 31 July. If your circumstances change and you expect a lower tax bill, you can apply to reduce your payments on account.

When does the Self Assessment registration deadline fall?

You must register for Self Assessment by 5 October following the end of the tax year in which you started a new source of income. For example, if you started self-employment in 2026/27, you must register by 5 October 2027.

What happens if I file my tax return late?

A £100 penalty applies immediately if your return is even 1 day late. After 3 months, an additional £10 per day is charged (up to 90 days, maximum £900). At 6 months late, 5% of the tax due or £300 (whichever is higher) is added. At 12 months late, a further 5% or £300 penalty applies, potentially rising to 100% of the tax due in serious cases.

Sources

Self Assessment tax returns — GOV.UK
Self Assessment: penalties — GOV.UK
Pay your Self Assessment tax bill — GOV.UK