Income

Yes, the assessee must file the income tax return.

One thing you should know is that when huge sums of money comes and go out of your bank account (you would have quoted your PAN while opening the Bank a/c), the banks are bound to submit details of the sums involved and  PAN to RBI every month, which will in turn reach the Income tax authorities. So there is a system in place which can track all the major transactions happening in all banks.

Unless you made the transaction in Cash, you not filing the return will be found out subsequently and huge penalties will be levied.