BUYING IN  , on the

English stock exchange, a transaction by which, if a member has sold securities which he fails to deliver on settling day, or any of the succeeding ten days following the settlement, the buyer may give instructions to a stock exchange official to " buy in " the stock required . The official announces the quantity of stock, and the purpose for which he requires it, and whoever sells the stock must be prepared to deliver it immediately . The original seller has to pay the difference between the two prices, if the latter is higher than the original contract price . A similar practice, termed " selling out," prevails when a purchaser fails to take up his securities .