Capital gain tax on joint tenant removed from title deed of a property

My wife and I jointly owned the house since 1988, value say £1,000 and included my son's name in the title deed in 2012, value say £3,500 as joint owner. He was living with us until he moved out sometime in 2003 and stayed at various hospital accommodations being NHS worker. Since then, he would stay with us from time to time. He bought a house in 2016 and paid an additional stamp duty. He now asked me to remove his name from the title deed. Is there any tax payable and if so what relevant information is required, any tax relief and how the tax is calculated base on current value say £4,500?

Hi Deal Cai,
As he is on the title deed, he would be seen as an owner of the property and as such is now 'selling' his share so Capital Gains Tax would apply. further guidance is available here:
Capital Gains Tax: what you pay it on, rates and allowances
Thank you.