I can tell you from first hand experience that not only are the institutions inconsistent, but various departments within the institution are inconsistent too. The discount brokerage at my bank uses the current day trading range and allows you to pick the price anywhere between the low and high of the day at the time of your call. However, the full service arm of the same bank uses a standard practice of the previous day's closing price. This astounds me given that if the stock price rips higher one morning you can make a contribution using your previous closing price for an easy, guaranteed gain. Not sure how the OSC hasn't said something about this and standardized the practice, but they haven't. You may just have to find out what their individual practice is and then work it to your advantage.