I used to work for a political non-profit soliciting $$$ over the phone via CC or pledge. The organization is/was legit, but we were always told by management that we had to provide a copy of the most recent financial statement and our tax ID # if requested. I don't know if that was a fed or state law or not, but they were adamant we do so if asked.
Since that time, I request a financial from every charity asking for money. That seems to weed the good out from the bad. Ideally, admin costs should be 10% or less.