Please tell me.

Deduction under section 80CCD is available out of total income

and Rebate U/s. 87A is available on taxable income after allowing all deductions

hence after allowing deductions there is no remaining taxable income you will not be liable to tax hence question of rebate does not arise

YES,

Deduction u/s 80CCD IS AVAILABLE OUT OF GROSS TOTAL INCOME (NOT FROM TOTAL INCOME as stated above )

deduction u/s 80CCD (1B) - additional deduction upto rs 50,000 for an amount deposited in NPS by an individual (is ALLOWED FROM GTI)

-AFTRE ALL THE DEDUCTIONS WE FIND OUT - TOTAL INCOME

REBATE U/S 87A (for AY 2019-20)
ASSESSEE- RESIDENT INDIVIDUAL HAVING TOTAL INCOME UPTO RS 3,50,000
REBATE - rs 2,500 or income tax payable, whichever is less

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