You need to submit an Income Tax return (for 2024/25) if HMRC send you a Tax Return to complete, or if any of the following apply and you owe income tax or capital gains tax:
Your income from self-employment exceeded £1,000;
You are a Partner in a business partnership;
You received over £1,000 in rental income;
You received more than £1,000 in other income such as undeclared tips or commission;
You received £1,000 (£500 for higher rate taxpayers) or more before tax from savings/investments;
You made Capital Gains in excess of £3,000;
You have received dividends in excess of £500;
Your taxable income exceeds £60,000 and you, or your partner, receive Child Benefit;
If your only taxable income is under PAYE, you are no longer required to do a Tax Return, although it may be a good idea to file one to ensure you receive the correct tax-relief on any personal pension contributions.