Reporting an investment disposal

Hello,
I'm a UK citizen and basic rate tax payer waiting on foreign investment information to enable me to complete my 23/24 self assessment.
In March 2024 I initiated the sale of my South African unit trusts but to date have not received the nett funds due to South African Revenue Service and Exchange Control red tape.
I do have the gross figure (in Rands) from the sale of the unit trusts (approx. £10k equivalent).
I expect there will be a South African non-residents capital gains element to be deducted at source (as historically through the last 34 years of this investment both South African and UK tax has been paid on interest and dividends declared as per the double taxation agreement).
It is now unlikely I will have the nett financial info in time to include this on my self assessment.
My question is:
1) Can this March 2024 disposal and subsequent CGT payment be declared to HMRC in the future and not in the self assessment I'm currently working on?

Hi ,
 

"You can submit your tax return now if you want and include estimates for this income / capital gain.  You tick the box to state there are provisional figures in the return.  You can then amend your return at a later date to declare the actual figures.  This will allow you to submit the return by the due date of 31 January and pay the tax, to avoid penalties and interest and give you the time necessary to obtain the actual figures. Thank you .