One rule that somehow slipped in with self-assessment, back in the late 1990s, was that you have to claim capital gains tax losses within a little less than a six-year period, or you lose the benefit of them.

Before that, there was no time limit, so that if, say, you had held a valuable shareholding in 1982 which then collapsed, you could go back at any time and establish the loss and claim it against current or future gains.

One purpose of this short piece is to point out that this still applies: to losses incurred before self-assessment came in 1996.

For losses which have arisen since that date, though, the message is clear: claim these losses as soon as possible so that any necessary argument or negotiation with the Revenue can be got out of the way, and, most importantly, the chance of forgetting about the loss and missing the time limit is minimised.

Remember that losses can arise, for capital gains tax purposes, not just on sales of assets for less than you originally paid for them but also in cases where you have made investments that have gone bad, even though you haven't actually sold them. If such an investment goes down to being worth less than 5% of its cost, you can (and should) put in a 'negligible value' claim, treating the asset as if it had been disposed of at its market value at the time of the claim.