Just have more like academic question! Day trading means to me closing out the position within the day by opposite trade in the same scrip. therefore committing no fund for the trades except the margin the broker imposed on the volume. That means when trader sells first, it is essentially a short sale. My question is, is it possible that in a particular point of time total short position is higher than the total real supply of the scrip? Does the day trader continue the short position if the trader want to? How does settlement takes place then? Is there security lending borrowing facility available? So that the short delivery can be close out by borrowing the scrip?