Kels, the way I understand it is that your broker doesn't actually have the certs. They work through a MM and the MM keeps the books on the shares they are "supposed" to have. Your brokerage will know WHICH MM has your shares though and when time comes that you request such shares, the broker will then put in a call to the MM telling him he needs x number of the shares the MM has on the books. This is where the problem comes... if the MM doesn't actually have the shares they have to get them which is where the delay comes into play. If you hold a large position or the MM is VERY SHORT then it might take them a while to buy the "real" shares back in order to make the delivery to the brokerage/transfer agent.