Paperwork for Medical Claim -- no provider Tax ID?

I'm preparing to submit claims to insurance for therapy. My therapist now is out-of-network, and he says he can't even sign up as an out-of-network provider. The insurer keeps rejecting his Tax ID, or so he says. So I've asked for all the invoices that he would submit in order to submit them myself. They're missing Procedure Code, Diagnosis Code, Tax ID (and maybe more) even though I specifically asked that they be included on the invoices.

I've looked online for the CPT code and diagnosis code. I'll use 90837 for 60 minutes of CBT and F33.1 for Major Depressive Disorder. I can (perhaps) edit the PDF to add that info.

I looked up his record and got his NPI number and EIN. Then when I searched for a tax ID with that info, it came up blank. Of course I can just ask for his Tax ID, but now I wonder if the problem with the Tax ID is that he doesn't have one and maybe he's using his SS number. I feel this might be a delicate situation -- or that I'm treading into dangerous water. I had another provider (for my daughter) who wanted nothing to do with insurance. She played the game for a while until she got a bigger client base and then couldn't accommodate us.

I've been in therapy for three years. Initially, T was in network, and he submitted claims and I got billed the patient responsibility. But in January my employer switched insurance providers. All was well before that. This doesn't fall under Continuity of Care BTW.

Comments?