IRS Form 1120-S

Form 1120-S is a tax document S corporations use to report their income, losses, and dividends to the IRS. Unlike traditional corporations (C corporations), S corporations don’t pay income tax at the corporate level. Instead, the profits or losses "pass through" to shareholders, who report them on their tax returns.

If you’re a small business owner who has elected to structure your business as an S corp, Form 1120-S is how you tell the IRS what your company earned during the tax year, and how much of that income goes to each shareholder.

You’re required to file Form 1120-S if your business:

Even if your S corporation didn’t earn income or operate during the tax year, you must file Form 1120-S annually to stay compliant.

Form 1120-S includes key financial details about your business operations:

Schedule K-1s are especially important: each shareholder uses theirs to complete their personal income tax return.

Form 1120-S is generally due by March 15 for businesses operating on a calendar year. If your business uses a different fiscal year, the form is due by the 15th day of the third month after your tax year ends.

You can file for an extension using Form 7004, which gives you an additional six months to file, though any taxes owed by shareholders are still due by the original deadline.

You can file Form 1120-S electronically or by mail. Since it includes technical financial data, many small businesses use a tax professional or accounting software to complete and submit the form.

To complete it, you’ll need:

Accurate recordkeeping is paramount; any errors can delay processing or cause issues for shareholders.

Failing to file Form 1120-S—or filing it late—can lead to IRS penalties. If you don’t issue Schedule K-1s to shareholders on time, they may be delayed in filing their own returns or face fines themselves.

That’s why it’s important to:

You can always use digital HR and compliance tools to simplify the back-office work that supports accurate filings with features like time tracking, payroll, and digital document storage.

Form 1120-S helps S corporations meet their annual tax obligations and ensure shareholders report their income correctly. Even though the form is focused on taxes, your day-to-day systems, like how you track employee time and run payroll, affect your ability to file accurately and on time.

Whether you're just starting as an S corp or have been running one for years, the key is to stay organized and ahead of deadlines.

Sign up for Homebase today to simplify compliance, support cleaner recordkeeping, and make tax season less stressful.