Can I offset share losses against share gains?

This is a lovely easy question to answer. Yes!

When you report a loss, the amount is deducted from the gains you made in the same tax year. Let’s say you have sold some shares and made a total gain of £5,000. If you are also holding some shares outside an ISA which have gone down in value since you bought them (for example they cost you £10,000 but they are now worth only £8,000) you could sell them, make a capital loss of £2,000, offset this against your £5,000 gain and come in at the total allowance of £3,000 gains for the year. And not pay tax.

If your total taxable gain is still above the current taxable allowance (as at Nov 24) of £3,000, you can deduct any unused losses from previous tax years.

If your losses in any one year are more than your gains, you can carry these forward to be relieved against future gains.