Hi Rufus99
Any costs claimed against capital gains must meet the definitions at CG15150P onwards, in particular
CG15180 - Expenditure: enhancement expenditure - HMRC internal manual - GOV.UK (www.gov.uk)
for the type of costs being described.
If the fees were purely the owners contribution to general maintenance/upkeep of the building/property then would not qualify as enhancement expenditure for capital gains purposes.
It would usually have been allowable as a revenue cost against any rental income. General maintenance costs are not allowable costs against capital gains.
If any part of the fees were for improvements such as upgrading parts or the building to a higher standard or adding things that were not there before then this element may be allowable against any capital gain.
Please see the attached link
CG15180.
Thank you