A closing auction is held for equities and investment funds in order to determine the official daily closing prices. These auctions last 10 minutes and run from 17:20 until 17:30. No trading takes place during the closing auction and the exchange system functions in the same way as during the opening phase. The orders in the order book are fictitiously matched and a hypothetical closing price is calculated on a continuous basis; no actual transactions take place, however. Only at the end of the closing auction are the orders in the order book executed according to the largest best execution principle. This last paid price is the official closing price.
As no transactions are carried out during the closing auction, the indices remain unchanged for the last ten minutes and are recalculated using the official closing prices.