Hi,
The SA108 is not applicable to the sale of UK residential properties until you are actually filing your tax return hence the reason it is not there for the 2023 to 2024 tax year. Any gain for residential property must be reported and paid within 60 days, link given in previous reply.
You can also contact our Income Tax team to have a paper version of the property disposal return issued to you.
Income Tax: general enquiries
Thank you.