With other kinds of transfer like Bank Transfer or UPI, you transfer the money from your bank account to the Demat account. But with "Smart Transfer", the amount you want to transfer from your bank account to your Demat account get credit in the Linen Amount. So in case you don't use the money for Trading or Investing, with bank transfer or UPI or any other transfer, the money sits in the Demat account and does not earn any interest. But with "Smart Transfer" you still earn interest while having the option to use the money for Trading or Investing. And with "Smart Transfer", adding money to your Trading account is just an OTP away.