@MichaelJPom "IRS notices of liability much greater."

So now it's not IRS, but just CA?  I wonder where they got their numbers.  Does FTB have its own "substitute for return" program?  But I would think they then share with IRS.  The data exchange is a two-way street.  Maybe IRS doesn't have a current address.  Or maybe federal returns were being filed, but not state.  You can't always believe what clients tell you.  But you can always make sure you get payment in advance.