You need to file a self-assessment tax return if you: Are self-employed or a sole trader Are a company director Receive income from property or investments Have foreign income Earn over £100,000 per year Have capital gains exceeding the annual allowance Self-employed or a sole trader A company director Receiving rental income from property Earning income from overseas sources A high-income earner over £100,000 per annum Receiving income from savings, investments, or dividends exceeding certain thresholds Making capital gains over the tax-free allowance A partner in a business partnership