From what has been published, people who haven't filed their 2020 return by Midnight on the 2nd of March will miss out on the 4th and 5th SEISS grant.
Is it me, or is this really unfair? Last year, Rishi announced the SEISS and gave late filers until the 23rd of April to file. This was so they could be included in the first SEISS. This year it wasn't widely known (if it was at all) that the 2nd of March was D day. Many people haven't filed simply because they haven't had any money, and now they find out they are not getting any money because they haven't filed.