CGT on BTL property sale with a deed of trust

Hi, I have just sold a BTL property which I have owned for approx 20 years. I agreed a legal deed of trust on the property with my ex partner in 2022 as we had planned to continue renting out the house. It has now been sold and I am trying to understand how we do the CGT - the deed of trust (DOT) is 50% each. When we agreed the DOT I paid my CGT up to that point as this is classed as me "selling" 50% of the property. I am now not sure how we allocate costs such as estate agents, solicitors or how we complete the forms at the HMRC CGT page online - for example, what purchase price am I meant to use - the initial one when actually bought or the one when agreed the DOT - any help or should I call HMRC to discuss this? Thanks.

Hi Mark,
More information is needed on this to give a definitive answer, please call 0300 200 3310.
Thank you.