Any incidental costs incurred in disposing of the property (as follows) can be deducted from chargeable gain to calculate RPGT:
Legal fees, accounting fees, surveyor’s fee, etc.
Real estate fees (sales commission)
Administrative fees
Repair or renovation to maintain or upgrade the property such as interior design such as IKEA furniture to redecorate your house
Cost of preserving or defending one’s title to, or to a right over the asset
Cost of advertising to make the disposal