Expenditure for capital gains and self assessment

Hi Can expenditure for a capital improvement such as new bathroom be utilised in the capital gains return upon sale of property but also before sale can it also be used for self assessment while renting that property out prior to sale

Hi,
Please have a look at the guidance at CG15180 onwards:
CG15180 - Expenditure: enhancement expenditure as some improvement are regarded as 'like for like' and are considered general repairs and maintenance, which cannot be set against capital gains.
Thankyou.