Readers' forum : Bargain basement

My client acquired a four-floor property in central London. To assist with the mortgage the basement was let out as a separate unit with its own entrance but it was never self-contained as regards the electrics and utilities so that 25% of the shared costs were made against the rental income. This arrangement has now ceased and the basement has been reincorporated into the main house with the requisite redecoration works.

Although at present there are no plans to sell in the near future I am conscious of advising the client on the potential capital gains tax were the whole property to be sold. I have advised the client to obtain a valuation of the house with and without the basement area at the date the rental ceased. However I still have an issue because the flat was not capable of being sold as a separate unit...