If you're expecting a refund, you have until October 15, 2013 to resubmit your 2012 return electronically. Should you miss that date, you have until April 15, 2016 (October 15, 2016 if you filed an extension) to file a paper return and claim your 2012 refund.
With a tax refund, there's no need to worry about late filing penalties, but the sooner you file, the sooner you'll get your money.
Now, if you owe taxes but you didn't file an extension, you have until April 19, 2013 to resubmit your rejected return and avoid the late filing penalty.
Should you miss the April 19 deadline, or you decide not to e-file, file a conventional paper return as soon as you are able, to minimize or prevent penalties and interest. Don't forget to submit proof that you e-filed your return on time. The late filing penalty is 5% of your owed taxes for every month (or fraction thereof) that your return is late, up to a maximum of 25%.
Important: To avoid a possible failure-to-pay penalty, any additional taxes you owe must be paid by April 15, 2013, regardless of whether or not you filed an extension. The failure-to-pay penalty is 0.5% (1/2 of 1 percent) of your owed taxes for every month (or fraction thereof) that the owed tax amount remains unpaid, up to a maximum of 25%.