Hi,
You would pay capital gains tax on the whole property. There would be two calculations needed, one based on your percentage of ownership and the other based on the percetage inherited.
To work out the gain, you will need to obtain the market value of the property at the time you first became joint owner. You would also need the probate value of the property at the time you inherited it, to work out the gain on the inherited proportion.
There is a capital gains calculator below to help you work this out.
Tax when you sell property
As the property was never your main residence, while you were joint owner, you do not qualify for private residence relief.
Thank you.