Any gain is liable to capital gains tax (CGT), but only when you sell the shares. Given that the tax-free CGT allowance has just risen to £11,000, most individuals should be able to release gains tax free by phasing encashment. If you transfer your shares into an Isa within 90 days of acquiring them they will also be free from tax. For 2014‑15 you can transfer up to £11,880 worth of shares, or £15,000 after July.