A Self Assessment tax return isn’t just a way for HMRC to ensure you’re paying the correct level of taxes, it is also an opportunity to claim tax allowances and tax reliefs on any eligible expenses, which could reduce your tax liability. If you’re the director of a limited company, self-employed or have received income during the tax year which hasn’t been taxed at source, you must complete a Self Assessment tax return. However these aren’t the only reasons why you may need to complete an annual Self Assessment return.