Self Assessment: step by step

Self Assessment is how HMRC collects tax that isn’t taken automatically through payroll. Here’s who needs to file, the key dates, and how it’s changing.

Updated July 2026 · A general guide, not personal tax advice.

Do you need to file a Self Assessment return?

You usually need to file if, in the tax year, you were:

• Self-employed as a sole trader earning more than £1,000 (before expenses)
• A landlord with rental income to report
• Earning untaxed income — e.g. dividends, savings, or side income above the allowances
• A higher earner affected by the High Income Child Benefit Charge, or with other HMRC reasons to file

Key dates

• The tax year runs 6 April to 5 April.
• 5 October — deadline to register for Self Assessment if it’s your first time.
• 31 January — deadline to file online and pay the tax you owe (and any payment on account).

What you’ll need

Records of your income and expenses, your UTR (Unique Taxpayer Reference), National Insurance number, and details of any other income. Keeping these digitally through the year makes filing far easier — and is required once you’re within Making Tax Digital.

How Self Assessment is changing

Under Making Tax Digital for Income Tax, sole traders and landlords above the income thresholds move from one annual return to quarterly updates plus a Final Declaration, kept and filed through compatible software. If your only income is self-employment and/or property, tools like FTrak can take you through the whole thing without an accountant.