As stated in exchange notice 21/09 NASDAQ OMX Derivatives Markets will, as of June 15, 2009, change the reference price used at standard exercise of stock options from Volume Weighted Average Price (VWAP) to the official closing price (Last Paid) of the underlying share.
In connection to this change NASDAQ OMX will change the time of publication of the official closing price of the underlying share. At present the orderbook summary with the official closing price is published approximately 17.23 CET. After the change the official closing price will be published at the time of the trading state ”Post Trade” at approximately 17.31 CET.
For further information, please see the attached document.
