T20's17 Jun 2008 20:58
They are just trade that allows the buyer 20 days to settle i.e. pay for the trade. When you deal with online brokers like Barclays the usual way of buying is actually a T3. You buy on day 1 and settle 3 days later.
If you feel a share will do well, but feel it will take longer than 3 days, you can buy and then pay 5,10, 20 days later. So say you bought £1000 worth of shares on a T20, and within 15 days they rose 50% you could sell them and pocket £500 without even paying for the initial amount. e.g. You buy £1000 worth of shares and are given 20 days to pay ... so your account is in -£1000. In that time it increases to be worth £1500 and you sell your account is +£500.
If you buy £1000 worth of shares and it drops 50%, and you decide to sell as you worry it may drop further, you only get £500 back, but still have the -£1000 to be taken off that, so you have to pay £500 by the end of the 20 days.
Does that help ?