Encashment on maturity: purchase date cohorts determine maturity, annual interest accrual and reinvestment treatment. Rule 15 sets encashment on maturity for National Savings Certificates (VIII Issue) by grouping certificates into purchase date cohorts that determine the maturity period (six or five years), the amount payable on encashment for a Rs.100 denomination, and annual interest accruals. Interest specified for each year accrues to holders and, up to the cohort's prescribed reinvestment year, is deemed reinvested and aggregated with face value. Interest for other denominations is proportionate. The payable amount on maturity may be rounded to the nearest rupee.