Daughter and father opening a joint brokerage account. Who pays taxes? It is entirely h er money going into the account. Thanks

You're going to have to identify who the primary owner is, and use that persons SSN on the account. That way the investment house will issue 1099 forms using that one SSN, and the right person ends up reporting the income on his/her taxes. So I would suggest you use the daughter's SSN on the account, since it's her money that's funding it, and I would strongly advise that the father NOT mix any of his own money with it, as then the paperwork needed to allocate the earnings to the rightful investor would get very complicated.

Agreed! I manage my daughter's IRA and stock portfolio while she is deployed to Iraq, but the stock and IRA accounts are in HER name, with HER SSN on the account. It is a LOT simpler that way.