if you live in Maine or Massachusetts you have until 4/17 to file an extension or return. Any other extension done after 4/15 is invalid (unless filed on or before 4/15 and rejected then you have 5 business days to refile). if you are due a refund it does not matter. if you owe and didn't pay you now have a potential 5% penalty and interest for late filing and payment. the penalty increase and interest increase the later you file and pay
