1. S Corporation Income Tax Return Deadline
2. Quarterly Income Tax Return Deadlines
3. Unemployment Tax Filing Deadline
4. Late Filing Penalties
5. Missed Deadline? What to Do
6. Tax Deadlines for Other Entities
7. Filing an Extension

The S corp tax deadline is officially the 15th day of the third month after the end of the tax year; this typically falls on March 15. An S corporation is a pass-through entity, which means that each shareholder reports profits and losses on his or her individual tax return. These are not taxed at the corporate level. However, the S corporation must file an informational tax return along with other IRS forms to detail the taxes withheld from employee wages.

S Corporation Income Tax Return Deadline

By the March 15 deadline, the S corporation must file Form 1120S, which details all financial activity, along with a separate Schedule K-1 that details each shareholder's portion of taxable business income. When the deadline falls on a weekend or holiday, the corporation may file these forms by the next business day. If you need an extension, you can file Form 7004 to receive a six-month extension. Shareholders must file and pay their associated taxes by April 15 (the same deadline as for all individual taxpayers).

Quarterly Income Tax Return Deadlines

S corporations that pay employee wages must withhold federal income and FICA (Social Security and Medicare) taxes. If this applies to your business, you also must file IRS Form 941 to report and remit these withholdings every quarter. Due dates for Form 941 are:

  • January 31
  • April 30
  • July 31
  • October 31

Unemployment Tax Filing Deadline

If you pay more than $1,500 in wages in any single quarter or have at least one employee work at least a portion of one day in at least 20 separate weeks, you must file Form 940 (Federal Unemployment Tax Return) on an annual basis. This form indicates the amount of wages on which your firm owes unemployment taxes. While you must file by January 31 each year, you can file as late as February 10 if you pay the entire amount due with your filing.

Late Filing Penalties

S corporations who do not file Form 1120S by the deadline will receive a fine of $195 per month or partial month the return is late, multiplied by the number of shareholders. For late filings of Form 941, you may owe 5 percent of the unpaid tax balance each month the filing is late, up to a cap of 25 percent. Form 940 carries similar late penalties as Form 941.

Missed Deadline? What to Do

If you have an S corporation and have missed a tax filing deadline, don't panic. However, it is important to act quickly and file your return as soon as possible. You should also pay overdue taxes as soon as you are able to do so, though you may be subject to penalties and/or a finance charge.

You can avoid the delay of sending a check through postal mail by having the payment debited directly from your bank account through IRS Direct Pay. You can also e-file your return until October 15. If you cannot pay your outstanding tax bill, you should still file your return and apply for an installment agreement. This allows you to make arrangements to pay your taxes over time.

Tax Deadlines for Other Entities

Most pass-through tax entities like S corporations, such as LLCs, are subject to the same annual tax deadline. Individuals (sole proprietors) and corporations must file by the 15th day of the fourth month of the fiscal year, which is typically around Emancipation Day for companies that follow the calendar year. For 2018, this date is April 17, with an extended deadline of October 15.

Exempt organizations must file by May 15 if they use the calendar year. An exempt organization can only receive a three-month extension and must file late returns by August 15, 2018.

Filing an Extension

Filing an extension is recommended if you need more time to get your tax paperwork in order. Use Form 7004 to request a six-month extension if you own a partnership, C corporation, or S corporation. Form 8868 is used for exempt organizations. Keep in mind that even if you are granted an extension, you must pay the overdue taxes on time.

If you need help with filing taxes for your S corporation, you can post your legal need on UpCounsel's marketplace. UpCounsel accepts only the top 5 percent of lawyers to its site. Lawyers on UpCounsel come from law schools such as Harvard Law and Yale Law and average 14 years of legal experience, including work with or on behalf of companies like Google, Menlo Ventures, and Airbnb.