A Self Assessment Return is a form that must be completed and submitted to HM Revenue and Customs (HMRC) by certain individuals in the UK each year. These individuals typically include self-employed people, landlords, and those with income from savings, investments, or overseas sources. The form requires individuals to report their income, capital gains, and other relevant financial information for the tax year. Based on this information, HMRC calculates the individual's tax liability and determines if any tax is owed or if a refund is due. Self Assessment Returns are usually filed online and have a deadline of January 31st following the end of the tax year. Late filing can result in penalties and interest charges, so it's important to submit the return on time. To complete a Self Assessment Return, individuals need to maintain accurate records of their income and expenses throughout the tax year.