Unable to correct my income tax return

You have to revise the return u/s. 139(5). You cannot rectify it till any assessment.

i.e. upload revised return (.XML file) with required changes.

How do upload the revised return?

Should I wait till the assessment for 2018-19 is completed?

No, the procedure is just same as filling original return.....

Just the change is it is filled u/s. 139(5) and not u/s. 139(1) ........

Thank you  for all the replies.

My Pleasure ............