HMRC have advised that agents can obtain SEISS grant information with specific consent from their client in writing.. (The form 64-8 does not cover SEISS, so we must apply taxpayer confidentiality rules).
Agents can ask their clients for the SEISS grant figures which remain accessible to claimants via the SEISS online portal. Agents also may be able to identify SEISS grant information from their clients’ bank statements as part of their analysis of receipts and expenditure undertaken to draw up business accounts.
Please note that HMRC have a back log of work. If you write to them be aware you may not get a reply in time. If there is any uncertainty we suggest a note is entered on the tax return.