Capital gains requirement for property that's been split.

I would like some advice on what the CGT requirements are when property is split and sold separately. Scenario, my family bought a public house in the 80s. We intend to split off a small section of the pub and sell this as a development plot with the pub remaining in family possession. I assume that as the development plot was originally part of the pub purchase it needs to be considered for CGT in relation to that purchase, and therefore i need to work out the gain from the sale in relation to its share of the original property value to find the capital. I guess the only way to do this would be work out a % split based on current values (sale price for plot + estimated market value for pub), i.e. Apportionment (%) to plot = Actual plot sale price / Total value of property, i.e. Actual Plot sale price + Estimated market value of pub Apportionment(£) of original pub buy price to plot = Apportionment (%) to plot x original purchase price. Capital gains apportioned to the plot = Plot sale price - Apportionment(£) of original pub buy price to plot CGT due for plot = capital gains apportioned to the plot x CGT rate Then when the pub is eventually sold in the future the CGT due is worked out using its apportioned % (what is remaining) = 1 - % apportioned to plot Can you please confirm if my thinking is correct? Many thanks

Hi,
Please refer to CG12731 (Capital Gains Manual CG12731 - Capital Gains Manual: Introduction and computation: occasions of charge: part-disposals: formula for apportioning expenditure) for part disposals.
You advised that it was bought in the 1980s. If it was prior to 31 March 1982 you would use the Market Value at 31/3/1982 rather than actual cost before that date.
Thank you.