Considering the retirement age to be 60, a person aged 40 should invest ₹55,000 in a monthly SIP for 20 years at 12% expected rate of return to build a retirement corpus of ₹5 crore, NDTV Profit reported. To build a retirement corpus of ₹6 crore, a person would need to invest ₹65,000 monthly in SIP at 12% return.