UK Self Assessment Tax Return 2026

What Is Self Assessment?

Self Assessment is HMRC's system for collecting income tax from people whose tax is not automatically deducted through PAYE (Pay As You Earn). Under PAYE, employers deduct income tax and National Insurance from employees' salaries before they are paid. Self Assessment puts the responsibility on the individual to report their income and pay the correct tax.

Each year, you submit a Self Assessment tax return telling HMRC:

• What income you received during the tax year
• What allowable expenses you incurred
• Any other relevant financial information (pension contributions, Gift Aid donations, etc.)

HMRC then calculates your tax bill — or you calculate it yourself — and you pay any tax owed by the deadline.

Who Needs to File a Self Assessment Tax Return in 2026?

According to GOV.UK, you must send a tax return for the 2025/26 tax year (6 April 2025 to 5 April 2026) if any of the following applied:

You must file if:

You may also need to file if you have untaxed income, such as:

• Money from renting out property or land — the first £1,000 is tax-free; above that, contact HMRC (up to £2,500), and you must file a return if it's more than £2,500 after allowable expenses or £10,000 before
• Tips and commission
• Savings interest
• Dividends, including investments
• Foreign income
• Any taxable UK income, if you're a non-UK resident
• You want to claim tax relief on community investments or some venture capital schemes

You must also send a return if HMRC asks you to, even if none of the above applies.

Key Self Assessment Deadlines for 2025/26

The 2025/26 tax year ran from 6 April 2025 to 5 April 2026. Here are all the critical dates (each deadline is 11:59pm):

Making Tax Digital (MTD) for Income Tax

Sole traders and landlords registered for Self Assessment must use Making Tax Digital for Income Tax once their qualifying income (from self-employment and property) is over a threshold. It means keeping digital records with compatible software and sending quarterly updates to HMRC:

• Over £50,000 in the 2024 to 2025 tax year → use MTD from 6 April 2026
• Over £30,000 in the 2025 to 2026 tax year → use MTD from 6 April 2027
• Over £20,000 in the 2026 to 2027 tax year → use MTD from 6 April 2028

You still send a Self Assessment return for the tax year before you start using MTD. Partnerships will join later, on a timeline HMRC has not yet set.

Step 1 — Register for Self Assessment

If you have not sent a tax return before, you must register with HMRC before you can submit one.

Step 2 — Gather Your Information

Before you start your tax return, collect all relevant documents. The exact information you need depends on your income sources:

Step 3 — Understand Allowable Expenses

If you are self-employed, you can deduct allowable business expenses from your income to work out your taxable profit. You cannot claim expenses if you use the £1,000 trading allowance instead.

Step 4 — Calculate Your Tax Bill

Once you know your total income and allowable expenses, you can calculate your tax liability.

The basic calculation for self-employed people:

Total income
− Allowable business expenses
= Profit (taxable income)

Profit
− Personal Allowance (£12,570)
= Taxable profit

Taxable profit × Income Tax rate
+ Class 4 National Insurance
= Total tax bill

Worked example — freelancer earning £30,000:

Total income:                £30,000
Business expenses:            £5,000
Profit:                      £25,000

Personal Allowance:         −£12,570
Taxable profit:              £12,430

Income Tax (20%):             £2,486
Class 4 NI (6%):             £745.80

Total tax bill:            £3,231.80
Monthly equivalent:       £269.32/month

Step 5 — Submit Your Tax Return Online

The fastest and most common way to file is online via HMRC's Self Assessment service. Online filing deadline: 31 January 2027.

Step 6 — Pay Your Tax Bill

You must pay any tax owed by 31 January 2027 — the same day as the online filing deadline. GOV.UK lists these ways to pay:

Payments on Account

Payments on account are advance payments towards your next bill, made in two instalments by 31 January and 31 July, each usually half of last year's tax. You must make them unless last year's bill was less than £1,000, or you paid more than 80% of it outside Self Assessment (for example through your tax code).

Penalties for Missing the Deadline

HMRC charges penalties for late filing and late payment:

Late filing penalties

Late payment penalties

Common Self Assessment Mistakes to Avoid

Summary — Self Assessment 2025/26 Key Facts

Frequently Asked Questions