Because a margin shortfall arose on an open position — the funds and collateral backing it fell below the margin the exchange requires. The exchange levies a penalty on the shortfall for every day it lasts, and that penalty is passed on to you. It's charged separately from any profit or loss on the trade itself, and it isn't a Rupeezy brokerage charge.
But I had enough margin when I placed the order — why the shortfall?
Margin keeps changing while a position is open, so a gap can open even after a valid order. The usual causes:
- Mark-to-market (MTM) losses shrink the cash cushion behind the position.
- The exchange raises the margin (SPAN/VaR), sometimes overnight, so more is due for the same position.
- A hedge breaks — a protective leg expires or is squared off, and the remaining leg needs its full margin.
- You withdrew or reused funds that were quietly backing an open position.
The full breakdown, the penalty slabs, and how to avoid it are in What is a margin shortfall, and what is the penalty?
What should I do now?
The penalty accrues per day, so act quickly — add funds to clear the shortfall, or reduce the position to lower the requirement. Meeting margin with shares you already own is also an option: see collateral margin from pledging.