A question that many professionals had after the IRS announced the formal extension of time to file calendar year Forms 1040 in Notice 2021-21 was the impact of that extension on using a Form 4868 to extend both the income tax and gift tax return for 2020. In an update to the What’s New page for estate and gift taxes on the IRS website, the IRS provided information on this issue.[1]

The IRS states that a six-month extension of time to file the Form 709 otherwise due on April 15, 2021 can be obtained by:

Filing Form 4868, Application for Automatic Extension of Time To File U.S. Individual Income Tax Return (or, in limited cases, Form 2350, Application for Extension of Time to File U.S. Income Tax Return) on or before April 15, 2021 which will extend the due date for both the income tax and gift tax return; or
Filing Form 8892, Application for Automatic Extension of Time to File Form 709 and/or Payment of Gift/Generation-Skipping Transfer Tax on or before April 15, 2021.[2]

However, if a taxpayer files the Form 4868 after April 15, 2021 but on or before May 17, 2021 it will only serve to extend the time to file the income tax return. There would be no extension of time granted to file the gift tax return.

The page reads as follows in discussing the two methods available to obtain an extension of time to file Form 709:

Method 1: Extending the time to file your income tax return. Generally, a request for an extension of time for filing your calendar year federal income tax return will also extend the time to file your federal gift tax return. Use Form 4868, Application for Automatic Extension of Time To File U.S. Individual Income Tax Return, and in certain limited circumstances, Form 2350, Application for Extension of Time To File U.S. Income Tax Return, and file on or before April 15, 2021, to extend the time for filing both the 2020 federal income tax return and 2020 federal gift tax return.

You may use these forms to extend the time for filing your gift tax return only if you are also requesting an extension of time to file your income tax return.
Filing Form 4868 or Form 2350 after April 15, 2021 and on or before May 17, 2021, will not extend the due date for filing your 2020 federal gift tax return – it only will extend the due date for filing your 2020 income tax return. See Notice 2021-21, Relief for Form 1040 Filers Affected by Ongoing Coronavirus Disease 2019 Pandemic.
Note: You may file Form 4868 or Form 2350 after April 15, 2021 and on or before May 17, 2021 to extend the time for filing your 2020 federal income tax return regardless of whether you previously filed Form 8892, and regardless of how you checked the box in Part II of Form 8892 regarding an extension of time to file your individual income tax return.

Method 2: Filing Form 8892. If you do not request an extension of time for filing your income tax return, use Form 8892, Application for Automatic Extension of Time To File Form 709 and/or Payment of Gift/Generation-Skipping Transfer Tax, and file on or before April 15, 2021, to request an automatic 6-month extension of time to file your 2020 federal gift tax return. Form 8892 also serves as a payment voucher (Form 8892-V) for a balance due on federal gift taxes for which you are extending the time to file. For more information, see Form 8892.[3]

[1] “What's New - Estate and Gift Tax,” IRS website, April 12, 2021, https://www.irs.gov/businesses/small-businesses-self-employed/whats-new-estate-and-gift-tax (retrieved April 14, 2021)

[2] “What’s New - Estate and Gift Tax,” IRS website, April 12, 2021

[3] “What’s New - Estate and Gift Tax,” IRS website, April 12, 2021