Per the IRS Offers Tips for Taxpayers Who Missed the Tax Deadline webpage:

• File as soon as possible. If you owe federal income tax, you should file and pay as soon as you can to minimize any penalty and interest charges. There is no penalty for filing a late return if you are due a refund.
• Penalties and interest may be due. If you missed the federal filing deadline, you may have to pay penalties and interest. The IRS may charge penalties for late filing and for late payment. The law generally does not allow a waiver of interest charges. However, the IRS will consider a reduction of these penalties if you can show a reasonable cause for being late.
• E-file is your best option. IRS e-file programs are available through Oct. 15. E-file is the easiest, safest and most accurate way to file. With e-file, you will receive confirmation that the IRS has received your tax return. If you e-file and are due a refund, the IRS will normally issue it within 21 days.
• Pay as much as you can. If you owe tax but can’t pay it all at once, you should pay as much as you can when you file your tax return. Pay the remaining balance due as soon as possible to minimize penalties and interest charges.
• Installment Agreements are available. If you need more time to pay your federal income taxes, you can request a payment agreement with the IRS. Apply online using the IRS Online Payment Agreement Application tool or file Form 9465 Installment Agreement Request.
• Refunds may be waiting. If you’re due a refund, you should file as soon as possible to get it. Even if you aren't required to file, you may be entitled to a refund. This could apply if you had taxes withheld from your wages, or you qualify for certain tax credits. If you don’t file your return within three years, you could forfeit your right to the refund.

Related Links

• Installment Agreement Request - Form 9465 (After Filing Return)
• Installment Agreement Request - Form 9465 (Before Filing Return)
• IRS First-Time Penalty Relief

Note that any link in the information above is updated each year automatically and will take you to the most recent version of the webpage or document at the time it is accessed.