Missing the deadline with result in a penalty where you will be charged, regardless of whether you have no tax to pay or have already paid all of the tax you owe.
IMPOTANT:
Today HMRC has announced they will not charge:1. Late filing penalties for those who file online by 28 February 2022.
Late payment penalties for those who pay the tax due in full or set up a payment plan by 1 April 2022