No, you do not need to worry. You filed by April 15th midnight.
What if I e-filed before April 15, but my return got rejected after the deadline?
If you're expecting a refund on your 2018 return, there's no rush. You have until October 15 to file, either electronically or by paper.
On the other hand, if you owe taxes, you have a 5-day grace period to either successfully e-file or paper-file your return to avoid possible penalties. April 20 is the last day of this grace period unless you're a Maine or Massachusetts resident, in which case you have until April 22.
By this cutoff date, your return must either be retransmitted (and later accepted, regardless of date) or postmarked for it to not be considered late.
Some returns keep getting rejected through no fault of the taxpayer, such as wrong data on the government's end. If you're in this boat, file a paper return, as it can take weeks, sometimes months, for the government to make the correction.
Late filing penalties apply if you owe taxes and didn't file your return or extension by April 15, 2019.
That being said, the IRS applies late penalties and interest on a case-by-case basis and will send a separate bill if penalties apply.
