Hi,
If the property was willed to the beneficiaries, then each of the beneficiaries, will need to work out if they have a capital gain. If they do, they will need to each report their gain individually. If there was no will, then the estate only has one annual exempt allowance and the estate pays the capital gains.
The online services helpdesk may be able to help you. You can contact them with the link below.
Technical support with HMRC online services
Alternatively, you could download a paper capital gains return.
Report Capital Gains Tax on UK property
If you do not have access to a the internet, you will need to contact HMRC and request a paper return.
Income Tax: general enquiries
Thank you.