Filing a Self-Assessment tax return for the first time can feel intimidating. This guide walks you through the entire process — from registering with HMRC to pressing "Submit" — in plain English. Most first-time filers find it far simpler than expected once they know what to prepare.
Who needs to file?
- Self-employed individuals with income over £1,000
- Anyone earning over £100,000 per year
- Company directors
- People with untaxed income (rental, dividends above £500, etc.)
- Higher-rate taxpayers claiming pension relief
- Parents earning over £60,000 who claim Child Benefit
Step 1: Register with HMRC
You need to register for Self-Assessment before you can file. If you're self-employed, register at GOV.UK — HMRC will send you a Unique Taxpayer Reference (UTR) by post within 10 working days. You also need a Government Gateway login.
Deadline: register by 5 October following the end of the tax year you need to file for. For the 2026/27 tax year, register by 5 October 2027.
Step 2: Keep records throughout the year
- All income (invoices, bank statements, P60, P45)
- Business expenses with receipts
- Pension contribution statements
- Gift Aid donation records
- Student loan statements
You must keep records for at least 5 years after the 31 January submission deadline.
Step 3: Complete the return online
Log in to your HMRC account and work through the sections that apply to you. The system will only show relevant pages based on your answers to initial questions. Key sections include:
- Employment: your P60/P45 figures (often pre-populated)
- Self-employment: turnover, allowable expenses, profit
- UK property: rental income and expenses
- Dividends and interest: from banks, shares, etc.
- Pension contributions: for higher-rate relief claims
Step 4: Submit and pay
Online deadline: 31 January following the end of the tax year (31 January 2028 for 2026/27).
Payment deadline: also 31 January. You can pay via Direct Debit, bank transfer, debit card, or through your tax code (if the amount is under £3,000).
If you owe more than £1,000, you will likely need to make payments on account — advance payments towards next year's bill.
Estimate your bill before you file
Use the income tax calculator to get a quick estimate of your tax liability before you start filling in the return. For self-employed income specifically, see our self-employed tax guide.