There are now two rates of CGT, 18% and 28%.
There are various exemptions. Cars, corporate bonds, and currency for personal use are exempt. So too are all sorts of ways of lending to the government. Gilts are CGT exempt, as are some National Savings. ISA savings schemes also escape. It shows that the government is not against capital gains per se, but wishes to channel investment into preferred areas, especially into loans to the state. Entrepreneurship is less valued than lending to the government, but can attract a preferential rate of 10%.
There are some strange rules. You can carry forward losses, but you have to offset losses against gains in any given year even where you have not used up your tax free allowance on the gains. On death losses can be carried back 3 years to get a rebate for the estate.
CGT is the most voluntary of taxes. People can and do delay taking profits if they think the rate is too high. They can buy assets which are exempt, as there is plenty of variety, and there are tax free wrappers. CGT in a way began as a Treasury device to stop people owning bonds and selling them just before they paid the interest to capture the income as a tax free capital gain. They stopped that sometime ago by making people buy gilts with adjustment of accrued income, so people do have to pay income tax. Yet the tax remains.
Should gains be taxed? Should gains on so many things be exempt? What rate is likely to maximise the tax take if you wish to keep a CGT? In the US and the UK over the last thirty years rates under 20% have collected more tax than higher rates. Could it be that we are well above the best rate to optimise the take? Is the 28% rate the reason the Treasury is forecasting lower receipts this year?
(This site does not offer tax advice and I am not a qualified tax adviser).