Hi,
If you disposed of a property for less than or equal to the cost it was acquired, there is no gain and no requirement to report it using the private property disposal capital gains service (PPDCGT). However, if you have to complete a tax return for any other reason and the disposal value exceeds £50000, then you must declare the disposal in your tax return. You can see relevant boxes at section 1 of SA108 here:
Capital Gains summary (2024)
You will need to complete boxes 3 to 8. as appropriate. These boxes are on the online return in the capital gains section under residential property.
Thank you.