Hi,
As the disposal will not be at arms length, because you are transferring a share of the asset to your son, you will need to obtain the market value for the property at the time of the transfer of 25% to your son. As the property is jointly owned, both you and your wife will need to perform separate calculations.
To do this, split the acquisition costs and the market value 50/50. Work out 25% of the acquisition cost and the market value, for example, £100000 split 50/50 is £50000 at 25% = £12500. £200000 split 50/50 is £100000 at 25% = £25000. Buying and selling costs should also be apportioned.
There is a calculator to help you work out the amount of gain and the tax payable.
Tax when you sell your home
Thank you.