Implementation Shortfall when the DP or BP is not and end of day close

I have yet to see this in practice problems, has anyone else?

So far, DP has been previous close when the decision was made, and BP was when the market closed and the trade had yet to be completed. Schweser notes in one of the practice exam answers that:

“DP is the market price at the time the trade decision was made. Because the market was closed at the time of decision, it is used”

To be clear, I’m looking for something like :

“The market closed at $25. The next day it opened at $25.5, and then a decision was made to trade.”


I found IS calculating more straightforward in official testing material (past AMs, Portal test and Mocks) than in some 3rd parties like Schweser. Shortly, if they said something like the decision price was XY or trader decided to place an order to buy xxxx shares of stocks at XY, than XY is DP. If there is a delay, BP is usually closing price on 1st trading day and for buying order is usually a bit higher than DP.