intra day trading

Guys,
Please briefly explain the process if I failed to buy/sell intraday shares on that very day, specially the charges/penalties for that....
Please suggest me...

if you do not sell shares which you bought intraday, they will automatically considered as delivery based buying.

and if you dont buy shares which you sell intraday, forthcoming 5 days average price is calculated and adjusted accordingly.

Thanks Nilesh for your valuable answer.
But I come to know something about the term settlement or auction.
Means if I fail to buy or sell intraday shares on that day,it will go for auction and I have to pay 20% higher price of that shares.
Is it true....
Do u know the SEBI rules on it...
Please suggest me.....