You are required by law to complete a self-assessment tax return if you receive income from any of the following:
- Self-employed/sole trader earnings of over £1,000
- Business partnerships
- Income of over £100,000
- Rental income
- Savings and investments
- Dividends
- Trusts
- Living abroad with any UK income
- High-income child benefit tax charge
You do not need to complete a return if your only income comes from wages or pensions however you do if you are already registered for self-assessment. The only exception being if your income is above £100,000.