this thread is great, thanks so much for posting!  i just about gave up.  called Proseries support last week, got nowhere with tech support, a total waste of time. 

figured i would google one more time to see if anyone came up with a solution.  lo and behold, 8 hours ago someone posted here, thank you!!

very glad there is a workaround from IRS. last thing i need is an audit letter saying there is no such registration number in their system.  now if only Proseries would add a check box for "N/a" and insert that code if you aren't trying to transfer the investment credit.