Sudheer-You have to invest in debt product according to your ease, either monthly or lump sum (if you have money available). There is no hard rule to it. Don’t use debt funds if your time horizon is less than 3 years. They will not give you fixed return and taxed as like Bank FDs or RDs. Hence, suggest you to go for RDs, if your time horizon is less than 3 years. However, if time horizon is more than 3 years, then go for short term debt funds.