HM Revenue and Customs No Self Assessment late filing penalty for those who file online by 28 February Self Assessment customers who cannot file their tax return by the 31 January 2021 deadline will not receive a late filing penalty if they file online by 28 February. Self Assessment customers will not receive a penalty for their late online tax return if they file by 28 February, HM Revenue and Customs’ (HMRCs’) Chief Executive Jim Harra has announced. More than 8.9 million customers have already filed their tax return. HMRC is encouraging anyone who has not yet filed their tax return to do so by 31 January, if possible.