Zerodha Expiry Margins

can u please clear if i have a short call option in stock and on wensday my margin gets increased and shows negative account balance by my call is still OTM and i feel like taking it till expiry withouth paying margin. Then what will happen if it expires OTM but considering -ve balance since that wednesday because of more exposure or span,

Even if your position is OTM, you will still require additional margins to hold your position till expiry. If you are in margin shortfall and don’t add funds after you get alert your position will be squared-off any time by RMS.

and what about penalty charges. Are there any for non fullfillment of margin?

There is margin shortfall penalty charges by the exchange, you can read more here.