The S corp tax due date is the deadline by which an S corporation must file its informational return and other required information with the Internal Revenue Service (IRS). An S corp is subject to pass-through taxation, which means that each shareholder reports profits and losses on his or her individual tax return. While the corporation does not pay income tax at the corporate level, it still must provide the IRS an information return and withholdings report each year at tax time.

S corporations must submit this information annually using IRS Form 1120S. They also submit schedule K-1 for each shareholder; this document indicates his or her share of the company's income, credits, deductions, and losses to be reported on the shareholder's individual tax return. S corporations must also report information about payroll taxes. Depending on the state, an S corporation may need to pay state taxes at the corporation level.

When Are S Corp Income Tax Returns Due?

After the tax year ends, an annual tax return for an S corporation must be filed by the 15th day of the third month. This is typically March 15 for companies that end the tax year with the calendar year (December 31). When the fiscal year ends on another date, the due date is adjusted accordingly. If the date in question falls on a weekend or holiday, it is moved automatically to the next business day. This guideline applies to both Form 1120S and Schedule K-1.

When an S corporation is unable to meet the deadline as described above, filing IRS Form 7004 provides you with a six-month extension. Shareholders of an S corporation must adhere to the individual IRS taxpayer guideline, typically on April 15.

Employment Taxes

S corporations that pay employee wages must withhold both federal income tax and FICA (Medicare and Social Security) taxes. These withholdings must also be reported to the IRS using Form 941. In addition to federal income tax and FICA withholdings, this form is used to report FICA tax adjustments and COBRA credits for health insurance for unemployed workers. The quarterly deadline for Form 941 submission falls on April 30, July 31, October 31, and January 31.

Unemployment Taxes

If your S corporation has employees, you'll likely need to annually file Form 940, a federal unemployment tax return. This form is required for companies that pay more than $1,500 wages in any quarter of the year or has one or more employee working at least part of the day in at least 20 separate weeks. Form 940 indicates the wages for which the corporation must pay unemployment taxes to the IRS.

Federal unemployment taxes (FUTA) are due when they exceed $500 in a quarter. Regardless of when these taxes are paid, Form 940 must be submitted by January 31 after the last day of the tax year in question, or in February for corporations that paid FUTA taxes during that year. The deadline is extended to February 10 if these taxes have been paid in full.

Excise Taxes

Businesses that sell certain items or services must pay excise taxes. Examples include gas, betting, and indoor tanning. Items subject to excise taxes are required to fill out different forms with different deadlines. For example, betting is reported using a monthly filing of Form 730, while foreign insurance is reported using Form 720 each quarter.

Making Federal Tax Payments

S corporations have these options when it comes to making federal tax payments:

  • The Electronic Federal Tax Payment System, which is free of charge
  • Same-day wire transfer from your business bank account, which is typically a fee-based service
  • Via your tax professional or payroll service, which may require a fee

Late Filing Penalties

If you do not file Form 1120S by either the due date or the extension date, you'll be charged a penalty of $195 per month or partial month late times the total number of shareholders. If you miss the Form 941 deadline and owe taxes, your bill will be subject to a 5 percent penalty every late month or partial month, up to a cap of 25 percent. Form 941 is also subject to this penalty.

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