INCOME TAX NSC CALCULATION

I HAVE PURCHASE NSC FY 2016-17. AND ITS MATURITY IS FY 2020-21. I HAVE NOT SHOWN INTEREST ACCURED IN 2016-17 TO 2019-2020. I HAVE RECEIVED MATURITY AMOUNT. NOW WHAT I CAN SHOW INCOME TAX RETURN FILING FOR A.Y.2020-21. WHEN I PURCHASE I HAVE DEDUCTION U/S 80C CLAIMED.

WHETHER FIVE YEAR INTEREST IS TAXABLE AND DEDUCTION  80C CLAIM FOR 4 YEARS.

REPLY URGENTLY FOR FILING INCOME TAX RETURN