The California regulations are very confusingly written. But I think the difference between the feds and ca is that ca assesses the penalties based on the original due date(April 15), not the extension date. So for federal, the failure to file is from the due date with extension assuming there is one, whereas for ca it’s the original due date regardless of extension. So if you are late with an extension for a month(let’s say nov 15), for the feds it 5% of the unpaid tax, whereas for ca it’s 25%, since it’s more than 6 mo late. Is that correct?
