If you have filed Return for A/Y 2017-18, then you have still option for revision of same.

You can still Revise fir A/Y 2017-18.

Revision of Return From A.Y. 2017-18

As per section 139(5), if any person, having furnished a return under sub-section (1) or sub-section (4) , discovers any omission or any wrong statement therein, he may furnish a revised return at any time before the expiry of one year from the end of the relevant assessment year or before the completion of the assessment, whichever is earlier.

In simple words, assessee can revise its return even filed after due date mentioned above within 2 years from the end of the relevant financial year.

For Example:

Mr. A can revise its return upto 31st March, 2019 for the financial year 2016-17 even return was filed after due date or before due date.

any person who has filed the original tax return on or before the due date can file a revised tax return before the expiry of one year from the end of the relevant assessment year, or before the completion of assessment, whichever is earlier. For example, if a person has filed his original return for the financial year 2015-16 within the due date, then he can file a revised return before March 31, 2018 or before the completion of the assessment of the particular financial year, whichever is earlier. The Income Tax Department has allowed revision of belated returns (returns which are filed after the due date) as well from F.Y 2016-17