Businesses eligible for the fifth grant of the SEISS based on their tax returns will be contacted by HMRC from mid-July to give a date that the claims service will be available from.
It will be given either by email, letter or within the online service. The online service to claim the fifth grant will be available from late July 2021 and the claim must be made on or before 30 September 2021.
https://www.gov.uk/guidance/claim-a-grant-through-the-self-employment-income-support-scheme
