It’s your responsibility to send a tax return if, in the last tax year (6 April to 5 April), you were self-employed as a ‘sole trader’ and earned more than £1,000 (before taking off anything you can claim tax relief on).
Be aware, you’ll get a fine if you need to send a tax return and you miss the deadline for submitting it or paying your bill.
Failing to meet the deadline could result in a £100 fine, or more if the deadline is missed by more than 3 months. You’ll have to pay more if it’s later than that, or if you pay your tax bill late. You will also be charged interest on late payments.
You can find the deadlines for Self Assessment tax returns on this page.