Is It Illegal If My Daughters Grandmother Asks For Her Social To Open A Savings Account For Her And Uses It For Something Else Without My Permission

Hello, I have a question about a situation and I am hoping someone has the answer for it.

Location: North Carolina

I have a daughter and her father and I are no longer together.

So long story short, she’s with me most of the time, she goes to see him every other weekend.

I was very clear that I am claiming her on my taxes, her dad was upset about that saying he wants to claim her but I was very clear that I am claiming her.

A little back story, she is on my insurance policy, I make and take her to doctors and dentists appointments, I was in charge of her daycare and paid for all of it, he didn’t help at all. He barely pays child support, he lied to our case worker about his income so he didn’t have to pay as much.

The other day, her dads mother asked for her social to open up a savings account for her, which is fine I have no problem with that but I think it’s odd timing, all the sudden she wants to made her a savings account? After her dad and I just had a disagreement about who’s claiming her on their taxes? I have a deep feeling that the real reason she wants the social is so her dad can use it to claim her on his taxes.

So my question,

If I give her my daughters social for her to use it for the savings account which is why she says she needs it and she goes behind my back and gives it to her dad so he can claim her on his taxes, is that illegal? I know it’s morally wrong since it’s deception, but I want to know if it’s illegal and what the repercussions would be if it does happen and if I report it?

Also, If her dad had just asked me for her social I would have no problem giving him a copy or the number but it’s the lying about why they need it that bothers me..