Self-assessment
UK system for declaring income and calculating tax owed when you're not taxed at source through PAYE. Required for sole traders, limited company directors, and most freelancers.
Self-assessment is HMRC's annual tax return process for individuals with untaxed income — primarily the self-employed, company directors, landlords, and high earners.
The form (SA100) covers all income sources: self-employment profits, employment income, dividends, rental income, savings interest, and capital gains. From this total, HMRC calculates income tax and National Insurance owed.
The online deadline is 31 January following the end of the tax year. Late filing triggers automatic £100 penalties, increasing with delays. Most freelancers also make payments on account — two advance instalments toward the next year's tax bill, due 31 January and 31 July.
- Tax year: 6 April Y to 5 April Y+1
- Online filing deadline: 31 January following the tax year
- Paper filing deadline: 31 October — most file online for the extra 3 months
- Automatic £100 penalty for late filing, even if no tax is owed