Capital Gains Tax is paid on any gains you make, other than your principle private residence. There is an annual allowance on which you pay nothing, currently �8200.00, so unless you have made other gains elsewhere then the house would have had to increase in value by �820,000 since you acquired your interest for you to pay any tax. Since last year the Inland Revenue have been gathering detailed information on land transactions by the Stamp Duty Land Tax from that everyone has to fill in.