When opening an account using a mental health instution as a representative payee. XYZ mental health as Rep Payee for
John Doe. Who signs the deposit agreement? What other documentation would be required?

Assuming this is for a social security payment: The Social Security Administrations website is pretty helpful about account titling. I suggest you start there. I also had to call about an issue once, and actually got a real live, person who was actually helpful.

We open a lot of this type of account. We require the Rep Payee papers issued by Social Security naming the institution as the Rep Payee for the individual. We keep a copy attached to our signature cards. The only signers on the account are those from the institution. The tax reported owner is not granted transaction rights to the account and we place a warning flag on the account that states this.

Correct..SSA website has wealth of information. Search for publication 05-10076 " A Guide for Representative Payees."
The representative payee needs to provide information and signs the signature card in that capacity. I would also suggest obtaining the letter from SSA showing the appointment.

As the other posters stated the SSA site is helpful, but to answer your question. The person appointed as Rep Payee signs the account documents.

Compliance Geek,
I think you've just got the wrong labels on the players. In the example given, the title would be: John Doe by XYZ Mental Health, Representative Payee.

XYZ Mental Health is opening the account and its appointed personnel would sign any documents. John Doe, the person under the disability, would not sign anything.

I knew that's what I was trying to say . I guess I need a few thousand more posts under my belt. I will read more carefully next time.

Thanks for the correction.