If I pay off a mortgage on a buy-to-let property with my savings and I later sell the property, what is my capital gains tax liability? For example, purchase price £100,000, mortgage £50,000. I pay off the mortgage and later sell for £150,000.

Arthur Weller replies:
The capital gain is the difference between the sale price (here £150,000) and the purchase price (here £100,000), i.e. £50,000. The mortgage is not relevant to a capital gains computation (unless the purchaser takes over responsibility for the mortgage; see www.gov.uk/hmrc- internal-manuals/capital-gains-manual/cg12706).