The online self-assessment deadline is 31 January following the end of the tax year. Miss it and you face an automatic £100 penalty, even if you owe no tax.
- Who needs to file
- Step 1 — Register and get your UTR
- Step 2 — Gather your documents
- Step 3 — Complete the return online
- Step 4 — Pay what you owe
Who needs to file
You need to file if you are self-employed with income above £1,000, a company director, earn over £100,000, have untaxed income from rent or dividends above £10,000, or have income from abroad.
Step 1 — Register and get your UTR
Register at gov.uk/register-for-self-assessment. HMRC will send you a Unique Taxpayer Reference number within 10 working days.
Step 2 — Gather your documents
You will need P60s from any employment, records of self-employment income and expenses, savings interest statements, dividend information, and Gift Aid donation details.
Step 3 — Complete the return online
Log into your HMRC account and work through section by section. The system calculates your tax bill automatically.
Step 4 — Pay what you owe
Tax owed must be paid by 31 January. If your bill exceeds £1,000, you will also need to make payments on account towards next year.
Bottom line
File early — do not wait until January. Filing in April means any mistakes can be corrected without pressure, you know your bill months in advance, and you avoid the January rush.