Updated October 17, 2026. Quick answer: Form 1040 is the individual income tax return, and the deadline for a calendar year return is April 15 after the year ends. Applying the printed rule, a 2026 return is due Thursday, April 15, 2027, a date computed here and not published by the IRS. Form 4868 gives an automatic 6 months to file, which runs to Friday, October 15, 2027, but the instructions say it does not extend the time to pay.
Form 1040 for 2025, lines 12 to 38 read line by line: Form 1040 line 27, Form 1040 line 37 and Form 1040 line 38.
The dates at a glance
The editions read are written for the 2025 return, so they print 2026 dates. The table pairs each printed date with the same rule applied one year later.
| Date | As printed for the 2025 return | Same rule for the 2026 return |
|---|---|---|
| Original due date | “For a 2025 calendar year return, this is April 15, 2026, for most people.” | April 15, 2027, a Thursday (computed here, not published by the IRS) |
| End of the automatic extension | “Generally, we can’t extend the due date of your return for more than 6 months (October 15, 2026, for most calendar year taxpayers).” | October 15, 2027, a Friday (computed here, not published by the IRS) |
| Out of the country, extra time without a request | “you can pay the tax and file your return or this form by June 15, 2026.” | June 15, 2027, a Tuesday (computed here, not published by the IRS) |
Publication 509 repeats the April rule in its calendar: “File a 2025 Form 1040 or Form 1040-SR and pay any tax due.”
When Form 1040 is due
The Form 4868 instructions state the deadline for a calendar year return: “File Form 4868 by the due date of your Form 1040, 1040-SR, 1040-NR, or 1040-SS.” “For a 2025 calendar year return, this is April 15, 2026, for most people.”
Applying the same April 15 rule one year later, the return for tax year 2026 is due April 15, 2027. April 15, 2027 falls on a Thursday, so the weekend rule does not move it. This date is computed here, not published by the IRS. Publication 509 states the weekend rule: “if a due date for performing any act for tax purposes falls on a Saturday, Sunday, or legal holiday, the act is considered to be performed timely if it is performed no later than the next day that isn’t a Saturday, Sunday, or legal holiday.”
A fiscal year filer uses a different date. Publication 509 says “This form is due on the 15th day of the 4th month after the end of your tax year.”
For the form itself, see the Form 1040 page.
The automatic extension on Form 4868
The Form 1040 instructions describe the extension under the heading What if You Can’t File on Time: “You can get an automatic 6-month extension if, no later than the date your return is due, you file Form 4868.”
Form 4868 says what it is for: to apply for 6 more months to file Form 1040, 1040-SR, 1040-NR, or 1040-SS, or 4 more months if you are out of the country and a U.S. citizen or resident. It also lists what you must do: “File Form 4868 by the due date of your return.”
There is no need to explain the request. The form says “You don’t have to explain why you’re asking for the extension.” “We’ll contact you only if your request is denied.”
Paying electronically can serve as the request. The form says “The IRS will automatically process an extension of time to file when you pay part or all of your estimated income tax electronically.”
Once the extension is in place, the return itself is due on the later date. Publication 509 lists it under October 15: “If you have an automatic 6-month extension to file your income tax” return for 2025, the calendar tells the individual to file Form 1040 or Form 1040-SR and pay any tax, plus any interest and penalties due.
What the extension does not extend
The Form 1040 instructions are blunt about payment: “An automatic 6-month extension to file doesn’t extend the time to pay your tax.” “If you don’t pay your tax by the original due date of your return, you will owe interest on the unpaid tax and may owe penalties.”
Form 4868 says the same: “Form 4868 doesn’t extend the time to pay taxes.” “Although you aren’t required to make a payment of the tax you estimate as due”, the form warns that interest will follow if the tax is unpaid. Its interest paragraph reads “Even if you had a good reason for not paying on time, you will still owe interest.”
The form also sets a ceiling on the extra time: “Generally, we can’t extend the due date of your return for more than 6 months”. For a 2026 return that is October 15, 2027, computed here, not published by the IRS.
Taxpayers who are out of the country
A separate rule gives some filers two extra months without a request. Form 4868 says “you’re allowed 2 extra months to file your return and pay any amount due without requesting an extension.” “Interest will still be charged, however, on payments made after the due date, without regard to the extension.”
The form limits the rule to a U.S. citizen or resident who is out of the country on the due date of the return, and it defines out of the country this way: “You live outside the United States and Puerto Rico and your main place of work is outside the United States and Puerto Rico” or “You’re in military or naval service on duty outside the United States and Puerto Rico.”
For a 2026 return the two extra months run from April 15, 2027 to June 15, 2027, a Tuesday, computed here, not published by the IRS. The form says a further extension needs a request: “File this form and be sure to check the box on line 8 if you need an additional 4 months to file your return.”
Penalties and interest as printed
The Form 1040 instructions print the penalties in a short list.
| Item | As printed in the 2025 Form 1040 instructions |
|---|---|
| Late filing | “the penalty is usually 5% of the amount due for each month or part of a month your return is late, unless you have a reasonable explanation.” |
| Late filing, ceiling | “The penalty can be as much as 25% of the tax due.” |
| Late filing, more than 60 days | “If your return is more than 60 days late, the minimum penalty will be $525 or the amount of any tax you owe, whichever is smaller.” |
| Late payment | “the penalty is usually 1/2 of 1% of the unpaid amount for each month or part of a month the tax isn’t paid.” |
| Late payment, ceiling | “The penalty can be as much as 25% of the unpaid amount.” |
Interest is separate: “We will charge you interest on taxes not paid by their due date, even if an extension of time to file is granted.”
Form 4868 prints both penalties. For late filing, “The penalty is usually 5% of the amount due for each month or part of a month your return is late. The maximum penalty is 25%.” “If your return is more than 60 days late, the minimum penalty is $525 (adjusted for inflation) or the balance of the tax due on your return, whichever is smaller.”
For late payment, “The late payment penalty is usually ½ of 1% of any tax (other than estimated tax) not paid by the due date of your return” and “The maximum penalty is 25%.”
Reasonable cause can relieve the late payment penalty: “You’re considered to have reasonable cause for the period covered by this automatic extension if both of the following requirements have been met.” “At least 90% of the total tax on your 2025 return is paid on or before the due date of your return through withholding, estimated tax payments, or payments made with Form 4868.” “The remaining balance is paid with your return.”
Estimated tax and other dates on the same calendar
The first installment of estimated tax falls on the same April date. Publication 509 says “pay the first installment of your 2026 estimated tax.” The installments are covered on the Form 1040-ES page, and the safe harbor page explains how retirees avoid an underpayment penalty.
The editions read for this page are the Instructions for Form 1040 (2025), Form 4868 (2025) and IRS Publication 509, Tax Calendars (2026), which are the revisions irs.gov served when they were read on 2026-10-17. They are written for the 2025 return filed in 2026, so every 2027 date on this page is computed here by applying the printed rules and is not published by the IRS. Check the revision printed on the form you are filing, because a later revision can change the dates and the penalty amounts.
Common mistakes
- Treating Form 4868 as more time to pay. The Form 1040 instructions say the automatic 6-month extension to file does not extend the time to pay, and interest is owed on unpaid tax from the original due date.
- Missing the Form 4868 deadline. The form must be filed by the due date of the return, and the form says the IRS generally cannot extend the due date for more than 6 months.
- Assuming the 2 extra months for filers out of the country stops interest. Form 4868 says interest will still be charged on payments made after the original due date.
Related: Form 1040, Form 1040-ES estimated tax, safe harbor estimated taxes, Form 1040-SR, and Form 709 due date and extension.
Sources
- Instructions for Form 1040 (2025): https://www.irs.gov/pub/irs-pdf/i1040gi.pdf
- Form 4868 (2025), Application for Automatic Extension of Time To File U.S. Individual Income Tax Return: https://www.irs.gov/pub/irs-pdf/f4868.pdf
- IRS Publication 509, Tax Calendars (2026): https://www.irs.gov/pub/irs-pdf/p509.pdf
Read from the IRS documents linked above on October 17, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.