“However, if an investor suffers a net loss, then this can be registered with HMRC within four years and be used to reduce taxable profits indefinitely.” 

If an investor made gains of £10,000, but losses of £15,000, then they could register a £5,000 loss with the taxman.

Mr Moore added: “Say the investor made gains of £17,300 in a future tax year, they could use the registered loss to reduce their tax bill. In this case, it would reduce below the annual exemption meaning no CGT would be payable at all.

“Realised losses can be registered with a self-assessment return, or alternatively you can write to HMRC to register the losses if you don’t have to complete a self-assessment.”

Richard Harwood, of the wealth manager Brewin Dolphin, added: “A point worth noting is that a gain or loss is usually realised when an asset is disposed of. So giving an investment away can be useful in this exercise. Transfers of assets between spouses are generally exempt.

“With careful planning this can mean one spouse moving assets to another to realise a loss, enabling them to crystallise a gain in some of their assets without incurring a tax liability.”