Here's one for the books:
Some years ago I owned 3 small corporations in California. Just getting started, they were not yet profitable. I paid the minimum corporate ESTIMATED tax for each of them ... $800 EACH. Estimated tax is paid in advance of tax due date so CA floated on our money. When tax time came, we neglected to file returns for the corporations ... we figured any penalty would be a percentage of tax due and anything times zero would be zero. Wrong ... Ca kept our money in the estimated tax account and would only move into the tax paid account when our returns were filed (ugh).