If Income Tax department of India sends a notice letter to you about "Non filing of Income Tax Return" that means the Income Tax Department wants you to explain why you haven’t e-Filed your return and may additionally ask you to explain some facts regarding your transactions.
Why did I get this notice? - Reasons
I was shocked as about 2 years ago (given a financial year in the notice) my income was below the taxable limit. So the same question got into my head Why? Why me?