I have a new single member LLC that wants to file as an S Corp but I cannot overcome the diagnostics that ask for date of incorp, state of incorp etc. How have you successfully filed these
Most states require registration of corporations, including LLC that elects to be a Subchapter S Corporation.
If the client doesn't have this info, then go to the state's Secretary of State website. Most states make this info available. Just do a name search and you should be able to see all of the filings with the state.