My ex n I have been separated tor 4 years now, we have not file for divorce yet because of financial problems. We bouth decided that kids will live with me n see him on weekends. Now he is asking for my dagters ss# to get her a sycologist, because he things all this has affected my child. I see my child okey " normal 7 year old", she lives with me, I know better than him because I see her everyday, at school she is doing great. Do I have to give him the ss#? Or can I refuse?

I have no idea why he would need a SS# to get her a psychologist. There is no law that would require you to give him the number

Of course he can get it as the legal father ( no divorce so he has equal rights as you)
He can get it from the SS office if he wants it bad enough. I would assume he can also get it off past tax forms that he can access.

Also since there does not appear to be any written or court ordered child custody paper work, he may be preparing for a child custody case, showing he asked for her to see a psychologist and you refused treatment and would not provide him ss number and so on.

My daughters father has her SSN. I see no reason why he shouldn't. He needs it for taxes, for the doctr, and any other number of things.

Is there a reason you don't want him to have it?

I don't understand why you won't give it to him - is this worth the argument?

Who claims her on income taxes?

I note that you are intending to take this child (and apparently other children) out of State without notifying the father - https://www.askmehelpdesk.com/family-law/can-take-kids-out-state-vacations-out-fathers-consent-651672.html. Why is thiis becoming so confrontational? Are there other issues?

Your children are going to suffer if the bickering over non-issues continues.

And, yes, if the father pays for health insurance for the child he needs (and is entitled) to her SS information.