Transfer of crypto to spouse

Hi I sold crypto via an exchange in my sole name but transferred an element of the held crypto to my spouse before selling on the exchange. My spouse isn't tech savvy and due to the volatile nature of crypto prices felt there wasn't sufficient time to go through the lengthy process to create an account. Thus a letter confirming the transfer was written and signed. Is the letter sufficient to confirm the transfer of crypto to my spouse? Thank you

Hi,

It would need to be a deed of trust that was submitted and this should have been sent to HMRC prior to any sale to ensure that evidence was held that you were not the beneficial owner of all the crypto. It cannot be applied retrospectively.

Thank you.