taxbigman is correct, Proseries is just completely lost on this issue after years of having the correct info laid out for them right here in this thread. The PIN is not a valid signature on the Form 8879, it is what is being validated BY THE signature that is required on the 8879. Read 2007-79 discussed to death above, it is not confusing and clearly states that a signature in one of the specified formats is required on every 8879. The PIN is not one of the allowed formats. Handwritten, typed, stamped, computer generated etc. are all acceptable, but blank is not.