These bonds are tax free, which means that interest income earned from these bonds would not be added to income and form part of the total income in computation of tax.
The coupon rates for retail investors at the time of subscription was pegged at 8.15% and 8.3% for primary retail subscribers for the 10 year and 15 year period. Interestingly, for those now purchasing these Bonds from the markets, the coupon rate will stand reduced to 8% and 8.10% for 10 and 15-year terms, respectively, for all categories of investors.
Now the 10 year bond was last traded on Friday on NSE at Rs 1006, so even if you purchase it at that rate and are in the 20% tax bracket the yield works out to 9.5% and for those in the 30% tax bracket the yield works to 10.4%.
What is more important is that you would be locking up amounts for a longer period and are thus hedging against any decline in interest rates. These bonds also offer liquidity which means you can sell them. And of course, IRFC being a government owned entity the bonds are secure.