Hallo Luis,
Tax is not payable on your main residence. Tax will be payable on the sale of an investment property unless you do some crafty tax planning. One I particularly like is leaving the UK in April to go traveling, selling all of your assets during this "window of opportunity" and taking up residence in your new country some time later after everything is sold. During the period after permanently leaving the UK but before taking up permanent residence in the new country you are without tax residence and the gains are tax free. If you return to UK within 5 years though, tax will be payable. Quite a few crafy emigrants use this method, especially where the gains are significant.
