In case you could not or did not file your ITR, you will need to submit a corresponding response on the e-filing portal. This is done so that if ever a need arises regarding your taxation documents, you have sufficient and valid proofs of not submitting the ITR. There can be multiple reasons for not filing the ITR which can be chosen from the drop-down menu as provided on the website.
Follow these steps in order to do so;

Step 1: Go to the official e-filing website

Step 2: On the home page you will find ‘Compliance’ tab. Click on the tab which will flash two options: ‘View and Submit my Compliance’ and ‘View my submission’.
Under the first option, you will find information regarding the years when you did not file ITR as per income tax department records. The other case may be that the income tax department needs third party details.

Step 3: On the screen, you will see two options:
‘the return has been filed’ and ‘the return has not been filed’. Select any one.

Step 4: On selection ‘the return has not been filed’, the following options will be displayed:
Return under preparation
No taxable income
The business has been closed
Choose the most relevant option and click ‘Submit’.
Once you have submitted your response, it will stay in records of the Income Tax Department for future references.

How to file the ITR offline?
Even after the whole income tax process has gone online, there are still some cases wherein offline filing of ITR is eligible. Either of the following two cases is allowed for offline filing and submission of ITR:
In the case of super senior citizens (individuals who are of the age 80 years and above)
In case of an individual or HUF having income less than 5 lakh rupees in a year and are not entitled to receive a refund
If you fall under either of the above two cases, you are allowed to file ITR offline.
Following is a simple three step guide to filing ITR offline:
Step 1: Request for a form 16
Step 2: Fill in the form and submit your ITR returns to the Income Tax Department
Step 3: Upon successful submission, the income tax department will issue an acknowledgment slip in your name.