Self Assessment — Who Needs to File

You likely need to file if you

• Are self-employed and earned more than £1,000 (before expenses)
• Are a partner in a business partnership
• Earned over £150,000 (or £100,000 for certain income mixes) in total income
• Have untaxed income — rental income, savings/investment income above your allowances, foreign income
• Need to pay the High Income Child Benefit Charge
• Had capital gains above your annual exempt amount
• Are a company director with income not fully taxed through PAYE

You probably don't need to if you

• Are only employed, with tax fully collected through PAYE
• Have no additional untaxed income sources

If you're unsure, HMRC has an online checker tool — or check with an accountant, especially if your situation changed during the year (new side income, property sale, etc).