Looking for an answer to what is the deadline for filing the 2016 US individual tax returns after obtaining the automatic extension, I found multiple references with varying answers. Of course, the ultimate answer is what the IRS considers as last day to file.

Going to the IRS website, I found this page, stating that the last day is October 16, 2017.

However, in the instructions for the Form 1040, it says in page 7 that:

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.

The 2016 due date was April 18, 2017. According to my understanding of the regular manner in which people communicate time intervals, then a 6-months extension should bring us to an October 18 deadline, rather than October 16.

This is actually a crucial piece of information, because if someone only reads the (official) instructions, he may be late in getting his returns filed. Nowhere in the instructions could I find an explicit mention of the October 16 date.

Why is there a difference between the website and the document?

What happens if I file on the 17th or the 18th?

1 Answer 1


Those small slips in due date from April 15 to 16, 17 or even 18 are because of weekends and DC holidays, they are covered in the law. Even the 15 October due date is slipped by a day because the 15th is a Sunday.

from the [ instructions for form 4868 for 2016] are the lines:

Total Time Allowed Generally, we can’t extend the due date of your return for more than 6 months (October 16, 2017, for most calendar year taxpayers). However, there may be an exception if you’re living out of the country. See Pub. 54 for more information.

When filing 1040 forms for taxes, the deadline becomes very important for those that owe money. That deadline starts the clock for interest and penalties. For those that are due a refund that deadline becomes less important.

When you filed for an extension in April you were obligated to pay what you owed, because that is when the clock started for potential interest and penalties. You should have over estimated the amount you owed to make sure that when October rolled around you would be getting a refund. Thus making missing the October deadline by a day or two less punishing.

But if you will be sending money with your October forms, and you file late then you can expect that the IRS will calculate the interest and penalties which might apply. They will send you a notice for those, because you can ask them to calculate it for you.

One note: because of the hurricanes and other disasters in late summer and early fall such as the California wildfires the IRS frequently extends deadlines for taxpayers who live in a geographic area, here is one for hurricane IRMA

  • Thanks. Yes, when I filed for the extension, like almost every year, I also paid an amount substantially greater to what I expected to be my final due. Now it looks like I will be receiving most of that money back as a refund.
    – ysap
    Commented Oct 14, 2017 at 13:27
  • But the thing is that even the quote you brought does not explain why 6-months from Apr. 18 is Oct. 16... Personally I think that the instructions are sloppy with this regard. I don't understand why doesn't the IRS add an explicit mention of the due date in the 1040 instructions, just as they do for the regular due date. Customers should not be looking around for such fundamental piece of information.
    – ysap
    Commented Oct 14, 2017 at 13:30
  • @ysap: the extension statement is a blanket statement based on the normally scheduled due date of April 15. The fact that the 15th was changed to the 18th due to weekends doesn't impact the original Oct 15th final due date. You can look up the actual dates on the IRS website. Further, the instructions on the extension request form have the correct dates. In short - everyone who went down the path of requesting an extension was made aware of the final date.
    – NotMe
    Commented Oct 15, 2017 at 17:43
  • @NotMe - thanks. Not saying that you are wrong. All my rant is that IRS should put an explicit date in the instructions for 1040. You can't expect filers to remember what they read when they filed the extension, 6 months later.
    – ysap
    Commented Oct 15, 2017 at 21:14

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