Claim EIS Deferral Relief on capital gains from a previous year

I made capital gains in the 21/22 tax year and would like to apply deferral relief to those gains, due to a EIS investments in 22/23. I can see in guidance HS297 that "If the gains against which you are claiming Deferral Relief arose in the tax year to which this return relates, please put ‘OTH’ in box 36 on page CG 2." , but there is no mention of previous years. If this is impossible using the online self assessment form could you please guide me with the paper EIS3 form. The 'Claim to EIS deferral relief' requires you write each asset disposed of date of acquisition and date of disposal, whereas my gains were made over 1000's of cryptocurrency transactions which makes this impractical. Am I really required to attach the details of the 1000's of transactions to the 10's of EIS3 forms I need to fill in, and if so it there a minimum font size I can print in. Regards

Hi Stuart,
You can still amend your 21-22 return to claim EIS Deferral relief until 31/1/24, or you can complete the EIS3 claim forms in relation to each subscription.  
If you are stating that each subscription will defer more individual gains than can be included on 1 claim form you should attach a document to the claim forms highlighting the disposals that have realised gains being that are deferred by the EIS Deferral relief claim.
As per VCM23200 it is a requirement to confirm the chargeable gains against which deferral relief is claimed. I understand it might not be practical to include this in the claim form but this detail should be provided alongside the claim forms. Even if you do decide to amend the 21-22 return we would expect and amended computation to be attached that would outline the same detail.
Venture Capital Schemes Manual VCM23200 - EIS: deferral relief: shares issued on or after 6 April 1998: claims procedure
Thank you.