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