In normal scenario what we do to buy stocks of any company? Lets say we have 5000 rupees available on our account and we want to buy any stock with a price of Rs. 50 per stock. So with our capital of 5000 rupees we can buy 100 stocks of this company. Sometimes stock broking companies give their customers to buy stocks in margin amount. Lets say the stock broking company is giving a margin to buy stocks with total value of Rs. 10000 at Rs. 5000. Here the extra margin amount of Rs. 5000 is the excess debit which should should be either cleared within a specified time period or the stocks should be sold. If someone neither sale the sales nor pay the excess debit amount within the specified time period then we call it as debit over due. Here the stock broking company will either sell off the shares to recover the extra margin amount or they will charge interest on it.