Hemant Sood, MD of Findoc, recommends the top investment instruments for senior citizens as NPS, Atal Pension Yojana, and Pradhan Mantri Vaya Vandana Yojana. These schemes offer low-risk or zero-risk investments backed by the government of India. The returns range from 6-7%, with regular interest payments. However, the regular monthly income from these schemes is taxable. Senior citizens should consider tax-efficient investment instruments, such as those linked with insurance, for long-term schemes.