You do not say why you want or need your grandchild's SSN. If you have claimed your grandchild as a dependent on a previous tax return, then the SSN will be on that past year Form 1040.
As Champ @Bsch4477 replied above, you would have to show Social Security some proof or a reason to share that information with you if your son/daughter will not tell you the child's SSN. Are you trying to claim the child as a dependent on your own tax return?
https://www.ssa.gov
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
