NTPC bonds are issued by National Thermal Power Corporation Limited, a public sector undertaking or PSU. The NTPC is involved in the generation and distribution of electricity. The NTPC is rated AAA which means it is among the safest bond issuers and investments in NTPC bonds carry lowest risk. Until a few years ago, NTPC’s bonds were tax-free, meaning no tax would have to be paid on capital gains accumulated from selling NTPC bonds.