about NSC Maturity amount

Yes. Include it under interest income and deduction is available u/s 80C.

NSC (VIII Issue) Rules, 1989

Rule 24, “Interest on these certificates shall be liable to tax under the Income-tax Act, 1961 (43 of 1961), on the basis of the annual accrual specified in rule 15, but no tax shall be deducted at the time of payment of discharge value.”

As per Rule-15, interest accrued at the end of each year upto the end of the fourth year (i.e. except last year interest) shall be deemed to have been reinvested.

Further, accrued interest, which is deemed as reinvested, is deductible u/s 80C.