Section 12(1)(b) in The National Small Savings Fund (Custody and Investment) Rules, 2001
(b)Savings Certificates under "Major Head - 8002 Savings Certificates - Minor Head 101 Post Office Certificates" for savings Certificates issued prior to the 1st April, 1999 and "Minor Head - 107 Post Office Certificates (new series) for Savings Certificates issued on or after the 1st April, 1999;