Who must send in a tax return

From self-employment to rental income, there are many reasons you may need to file a Self-Assessment return. Know the triggers and register with HMRC by 5 October if this is your first time.
There
Tax rules for savings interest

You could earn up to £18,570 in tax-free savings interest in 2025-26, thanks to the personal allowance, starting rate for savings, and the Personal Savings Allowance.
If your taxable income for the