80u tax ribet kese milati h

Deduction under section 80U of Income Tax act 1961 can be claimed by an Individual who is a resident in India for the financial year relevant to the assessment year in which the person is taking the benefit

While filling details with DDO, under form 16 is better option than claiming it under ITR without form 16 support.

Whether return for AY 2017-18 was filed?

Agar aapne IT return bhara ho to revise kar sakte ho, nahi to arrears ka benefit nahi mil sakta.

& For return of AY 2018-19, you can claim deduction u/s. 80U, subject to satisfying all the conditions as per the section.

You can only revise the ITR filed for AY 2017-18; not earlier years.....