I have the same issue. My client has the 12 digit "File Number" issued to the LLC upon formation. but not the 7 digit "Corporation" number that ProSeries wants. Discussion with CA Sec of State who told me a Corporation number would not be issued to an LLC that filed for 2553 electing to be taxed as an S-Corporation. Next call is to CA Franchise Tax Board I guess or ProSeries or enter applied for which will allow E-Filing??