Fast is a feature. It is not a free pass.
01
The trade sets the price. Settlement makes you the owner. Two different clocks. When you tap buy, you have locked a price. The shares only land in your demat, and the money only leaves for good, once settlement clears.
02
Your cash is not spendable the second you sell. On the standard cycle a Monday sale is a Tuesday withdrawal, and a holiday pushes it further out. When a real bill is waiting on the other side, plan around the settlement date, not the trade date.
03
Same day settlement changes the speed, not the homework. T+0 gets your money back faster. It does not make the thing you bought any better or any safer. The wait got shorter. The decision did not get easier.
The screen shows you a price the instant you tap. The market still needs a day to actually make it yours. The gap between those two is the one piece of plumbing worth understanding.