HMRC revealed that, as of 24 January 2018, there remained over 3 million taxpayers who had not yet submitted their 2016-17 self-assessment returns. This left a lot of people with a lot of work to do in the final week before the submission deadline.Any taxpayers who missed the filing deadline will receive a £100 fixed penalty if their return is up to 3 months late, regardless of whether they owed tax or not. Taxpayers that do not get their house in order before 1 May 2018 will face far greater penalties. A daily penalty of £10 per day, up to a maximum of £900 (90 days) will be charged from 1 May 2018. Further penalties then apply if the return is still outstanding for more than 6 months after the 31 January 2018 filing deadline. From 1 August 2018 taxpayers will be charged the greater of £300 or 5% of the tax due. If the return remains outstanding one year after the filing deadline, further penalties will be charged from 1 February 2019.Planning noteTaxpayers can appeal against any penalties that have been issued if they feel that they had a reasonable excuse for late filing. This can be done online in some cases or an appeal can be made in writing using the SA370 form. An appeal must usually be made within 30 days of receipt of the penalty.