So what you are saying is that you want the software to calculate the penalty just for the first three quarters, except in seven counties?  The underpayment is normally figured until the April 15 due date. Now what date do you use, April 15 or October 15?  

Many contracts have an "act of God" or "force majeure" clause, excusing nonperformance due to unforeseen circumstances.  I'll defend Intuit on that one.  And if clients expect preparers to spin their wheels doing calculations so that they don't get a bill, let them go elsewhere.  No one forced them to live in California, and if they aren't actually making money from bad weather, their income is probably not affected.  Certain people take a certain glee in delaying tax payments as long as they can.  Remember the long line of cars at the Post Office, the evening of April 15 back in the old days?  Let them focus on something more important, like the potential collapse of democracy.  They should have paid on January 15 anyway, because they never know when their bank is going to collapse.