What Are the Key Income Tax Filing Dates for 2021

Few challenges can seem more daunting than trying to make sense of your tax obligations. But understanding IRS filing deadlines can help you or your business stay on track while avoiding potentially costly fees and penalties.
With 2020 coming to a close and the new year quickly approaching, this is the perfect time to review some of the key IRS income tax filing deadlines for 2021.

Personal Income Tax Filing Deadlines

Federal Tax Filing Deadlines (form W-2)

For individuals filing their personal taxes, the filing deadline for your federal tax return is April 15th of each year. If the 15th falls on a weekend, the tax deadline is typically moved to the next business day. In 2021, April 15 falls on a Thursday. See our Personal Tax Organizer to help prepare for your 2021 tax filing.

The IRS has also altered the personal filing deadline because of extreme national weather crises, as in 2010 when a severe spring storm made it difficult for millions to get to a post office. Such decisions are made on an as-needed basis.

So, when does the IRS begin accepting returns? Early filers should watch for an announcement which generally comes early in January.

Estimated Tax — Quarterly Filings (form 1099)

If you are a freelance contractor, self-employed, or file a 1099 form rather than a W-2 form, you may be required to file quarterly estimated taxes. Quarterly estimated tax payments must be made using the following schedule:

Payment Period Filing Date
Jan 1 – Mar 31 April 15
April 1 – May 31 June 15
June 1 – Aug 31 Sept 15
Sep 1 – Dec 31 Jan 15

If your estimated tax deadline falls on a weekend or holiday, your filing will be accepted on the next business day.

Business Income Tax Filing Deadlines

Partnership Returns (form 1065)

If you operate a business partnership and file form 1065, your return must be filed by March 15, 2021.

C-Corporation Returns (form 1120)

The filing deadline for a C-corp is on the 15th day of the 4th month following the end of the company’s fiscal year. C-corporations that operate on a calendar year basis are required to file IRS form 1120, by April 15, 2021.

S-Corporation Returns (form 1120-S)

S-corp returns are due March 15, 2021, for those operating on a calendar year basis. For S-corps operating on a fiscal year basis, your return is due on the 15th day of the 3rd month following the close of the fiscal year.


We’ve all experienced hardships that can make it difficult or impossible to meet certain obligations on time. If you believe you need more time to file your return but do not want to incur additional late fees, missed filing fees, or penalties, you may file IRS form 4868 and obtain a 6-month filing extension (to October 15, 2021) without penalty.

Getting an extension is always preferable to late filing or late payment. The failure to pay penalty is approximately 0.5% for each month, up to 25% of the amount of tax that remains unpaid, whereas the failure to file fee is 5% of the unpaid tax required to be reported charged each month for up to 5 months. If you miss the tax filing deadline, contact us immediately to set up a complimentary confidential consultation.

Payment Plans

If you still cannot meet your federal tax obligations, despite a filing extension, you may still be able to contact the IRS and set up a monthly payment plan that fits within your budget. Payment plans typically assess far lower interest and penalties compared with those for late or non-payment.

A Note for Military Families

If you or a family member is serving in active duty service in a combat zone, the IRS allows 180 days after return from service to file any pending tax forms.

Important Deadlines for California Residents

If you’re a California resident, there are a few more tax deadlines you should know about.
Quarterly Estimated Tax (Form ES44)
If you’re a California Resident making quarterly estimated tax payments, your deadlines for filing are:

1st Quarter: July 15, 2021
2nd Quarter: July 15, 2021
3rd Quarter: Sept 15, 2021
4th Quarter: Jan 15, 2022

Estates or Trusts

If you are filing a return for an estate or trust, you must pay by July 15, 2021 (calendar year filers) or the 15th day of the 10th month after the end of the tax year (for fiscal year filers).

US Residents Traveling or Living Outside the US

If you are traveling or living outside the US at the time of filing, you may pay your tax by July 15, 2021, with no penalty. Please write “Outside the US on April 15th” in red ink on your return.

This is not an inclusive list of all applicable tax filing requirements and deadlines. You should speak with your tax preparer to ensure that you meet your filing requirements.

We hope this article helps you get organized and prepared for tax season. At Moskowitz LLP, we’ve built our reputation for helping clients navigate the often-confusing landscape of tax preparation and tax law. Our goal is to reduce your tax obligation while sparing you needless fees and penalties. Our experienced tax attorneys and professionals are here to help with both personal and corporate tax issues. Contact us today!

Our attorneys and accountants spend each year, every year, cleaning up back tax and accounting messes and lowering our client’s tax burden through realistic and practical tax planning for individuals.

Moskowitz LLP is a tax law and accounting firm that has dedicated over 30 years to representing individuals and businesses with civil and criminal tax problems, cleaning up accounting and tax messes, providing estate planning, and tax and accounting advisory services.

We make it easy and affordable for you to set yourself up for lower taxes and success.
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