Contribution in Sukannya Samriddhi yojna of my granddaughter

1) She must be less than 10 years of age.

2) Biologycal Parents ( Father and Mother)  or legal guardians appointed by the Court Can only open the Sukanya Samriddhi yojana for girl child. 

Take more Opinion on this. 

I think you Can pay to her parents, they will Open account , because of one the condition in the Yogana .

if the amount is more then gift it to your son , which is exempt under Income tax Act 1961 , he will deposit in yojana . 

Sill take more opinion on this. 

Sir, can I contribute as a gift to my granddaughter?

Yes , You Can Gift money to your granddaughter if amount is more , however, it's always better to prepare or must prepare" Gift deed" from ,"Notary Public" ( Notary Advocate) , as a  documentary evidence. 

Gift from Grandfather to Granddaughter is also exempt under section 56(2) of the income tax Act 1961. 

Contact  near by CA he will guide you.