If you obtained a filing extension for your personal 2018 income tax return (Form 1040) and have not yet filed, today is the deadline for getting it in; you can still e-file the return (unless extended because of a federally-declared disaster). If you fail to file by today, you will owe a late filing penalty; no additional extensions can be granted. Calendar-year C corporations on extension must file Form 1120 for 2018 by today (unless extended because of a federally-declared disaster). Note: Today is also Information Overload Day.
New blog post today! What to Know about the ABC Test