IRS webpage "When to File" says that April 18, 2023 is the last day for me to file taxes for the 2022 calendar year. From my understanding, this means that I won't be considered late as long as I mail or fax the tax forms to the IRS anytime before 2023-04-19 00:00. But what is the time zone used for the IRS deadline? Is it Eastern Time? If so, where is it mentioned?

Note: I am a non-resident alien who has to file Form 1120 and Form 5472 this year, either by physical mail or by fax.

  • 1
    For mailing tax returns, it's always local time zone.
    – RonJohn
    Apr 18, 2023 at 1:29
  • For deadlines, I always assume worst possible case. If necessary, file a preliminary return with your best estimate of what you owe, and then file an amended return later to either get back what you overpaid or pay what you forgot to include in the estimate. (Personally, I try to submit my taxes by March 15th, or at least have them ready to go pending the one piece of data that's delayed, so I'm never mailing them at the last minute.)
    – keshlam
    Apr 23, 2023 at 0:31

1 Answer 1


According to the IRS:

Topic No. 301, When, How, and Where to File

Your return is considered filed on time if the envelope is properly addressed, has enough postage, is postmarked, and is deposited in the mail by the due date. If you file electronically, the date and time in your time zone when your return is transmitted controls whether your return is filed timely. You will later receive an electronic acknowledgement that the IRS has accepted your electronically filed return.

Now how they determine that, I don't know. Is it based on your IP address or the home address you included on your 1040 form.

If you are trying to make the deposit into a IRA before the deadline don't cut it too close because the server could be busy.

  • What if I am sending by fax instead physical mail?
    – Flux
    Apr 18, 2023 at 0:27
  • 1
    @Flux I don't think you can file via fax
    – littleadv
    Apr 18, 2023 at 0:29
  • @littleadv I am filing Form 1120 and Form 5472, both of which have to be filed by fax or physical mail in my case. I have updated the question with this information.
    – Flux
    Apr 18, 2023 at 0:30
  • 1
    For e-file, the ERO will timestamp the return.
    – littleadv
    Apr 18, 2023 at 0:31
  • 2
    @littleadv It is personal finance because as owner of a US "disregarded entity", I have to file Form 5472. Form 1120 will mostly be blank in my case. It's just that the IRS requires Form 5472 to be attached to a Form 1120 in my case.
    – Flux
    Apr 18, 2023 at 0:35

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