@Zerodha,
Why don't you have a tie up with big banks like SBI,Axis,Citi to make instant Fund transfer.
This will make life a lot easier for many of your customers.
you can't expect everyone to have HDFC a/c to make instant fund transfers.
Is there any issue to get this done. May be you can open a/c's in these big banks as well to do instant fund transfer.
This will also reduce your support tickets related to Fund transfer issues and a LOT LESS COMPLAINTS FROM YOUR CUSTOMERS.