Form 1120-S: What It Is, Who Files It, and How to Get It Right

Form 1120-S is used by S corporations to report the corporation’s income, deductions, and credits to the IRS. It also outlines each shareholder’s tax obligations via Schedule K-1. Tax returns for S corporations with a calendar year-end must be filed by March 15th, along with the corresponding tax returns for the shareholders.

The IRS expects corporations that have elected S status to file Form 1120-S every year, regardless of whether the S corporation had any income or tax activity. The IRS does not accept “we didn’t earn anything” as an explanation for failing to file.

Form 1120-S is conceptually simple. Since S corporations are pass-through entities, they do not pay federal income tax. Form 1120-S is used to report the S corporation’s income, loss, and deductions, and to report S shareholders’ tax obligations, which are reported via Schedule K-1, a form that is, in effect, an attachment to Form 1120-S. The pass-through nature of S corporations is one of the primary reasons many elect S corporation status.

While Form 1120-S is simple to understand, the rules, deadlines, and due dates make filing it difficult for many. This gathers the most important information you need to file Form 1120-S.

Who Needs to File Form 1120-S

Every corporation or LLC that has an S election with the IRS must file Form 1120-S. The S election is filed by Form 2553. Once the S election is approved, the corporation or LLC is obligated to file Form 1120-S, even if it did not generate any income.

S corporations have strict shareholder requirements. Nonresidents cannot be shareholders. Shareholders must be U.S. citizens, residents, or affiliated with estates, certain trusts, or tax-exempt organizations. Corporations and partnerships cannot be shareholders.

This affects many of the founders we work with. Nonresident founders who create a U.S. LLC can elect to be federally taxed as a corporation under Form 8832, but they cannot elect S corporation status. As soon as a nonresident has any ownership of the LLC, the S election cannot be made.

Further, the corporation may have only one class of stock, although voting rights may be differentiated. There can be a maximum of 100 shareholders.

If your corporation does not satisfy all of the above criteria, any Form 2553 you filed is invalid, and the IRS will treat your corporation as a C corporation, which could result in retroactive double taxation and be a nasty surprise that you will be audited for.

Form 1120-S Deadlines and Extensions

An S corporation must file Form 1120-S by the 15th day of the third month of the S corporation’s tax year, with the deadline for a calendar year ending December 31 being due by March 15 and extended to the next business day when March 15 falls on a weekend.

File Form 7004 by the original deadline to request more time to file. An extension grants you until September 15 to file; however, you must estimate and pay your tax liability by the original deadline. A filing extension is not a payment extension.

Deadlines are final, and at that point, you will incur all consequences.

What Happens If You File Late

Late Form 1120-S filings incur penalties for each shareholder.

In the example of a two-shareholder S corporation that filed six months late, the filing alone would incur a $2,940 penalty.

The 2026 late-filing minimum penalty is $510, regardless of any other tax.

Missing or incorrect Schedule K-1s also incur penalties; each K-1 carries a $330 penalty that doubles for intentional disregard.

If you are incurring penalties for each missed year due to a higher shareholder count, you really should file your return. The IRS may consider a request to waive first-time penalties if you previously missed a filing and you request it in writing, but don’t count on it.

What Form 1120-S Actually Contains

The Form 1120-S has multiple components to it, including the following:

Schedule K-1 is the most complicated piece. Each shareholder is given a K-1, which shows their income, losses, and credits. This K-1 information is then transferred to that shareholder’s personal return, and the shareholder pays tax at their individual rate.

Shareholders who reside in high-income states, such as California or New York, may owe substantial state income tax on their K-1, even if the S corporation has minimal state income.

Schedule K-2 and K-3: When You Need Them

If any shareholder has foreign tax credits or foreign income, then Schedules K-2 and K-3 must be included with the return. These recent additions, beginning with the 2021 tax year, have created some confusion.

Fortunately, there is a domestic filing exception. If the S corporation has not received a request from any shareholder for Schedule K-3 information at least one month before the S corporation’s tax return due date, then Schedules K-2 and K-3 are not required.

For most S corporations with only U.S. shareholders and no foreign income, K-2 and K-3 schedules are typically not required. To be certain an exception applies, check if any shareholder is completing Form 1116 to claim foreign tax credits on their personal tax return. If so, K-3 will be required.

Common Mistakes on Form 1120-S

Missing the late election window: If you incorporated but forgot to submit Form 2553, you can still make a late S election using Revenue Procedure 2013-30. As long as you have a reasonable cause, the IRS allows late elections, and you would benefit from pursuing this option prior to assuming the election opportunity is lost.

Enrolling an ineligible shareholder: Non-residents and preferred stock trigger the automatic termination of S corporation status, and S status would be lost for all prior periods for tax purposes. You must check the eligibility of each prospective shareholder in your cap table prior to closing the transfer.

Improper basis: The basis for each shareholder determines if losses can be deducted and if distributions would be taxable. The basis for each share is adjusted based on the shareholder’s share of the income, losses, and distributions. Most founders fail to keep sufficient records until the IRS questions a loss deduction or distribution.

Ignoring state-specific requirements: The federal Form 1120-S does not include state filings. California makes no distinction between S corporations and other corporations and imposes a minimum annual franchise tax of $800 plus 1.5% of the corporation’s net income. Other states, such as New York and New Jersey, have parallel S corporation filings that are separate from the federal tax return.

Not filing because the business was inactive: If the S election is in effect and you have not taken steps to dissolve the corporation or revoke the election, the IRS expects a return. The filing requirement does not disappear simply because the business has no income.

FAQ

Does an S corporation pay federal income tax?

The short answer is no. The income passes through to shareholders and is taxed at the individual rates. In most other scenarios, S corporations pay no federal income tax, but some built-in gains and passive income can trigger taxes at the entity level.

Can a non-U.S. citizen own shares in an S corporation?

Only in the case of U.S. residents (green card holders or those who meet the substantial presence test). Nonresidents are prohibited from owning shares in an S corporation, and foreign nationals without U.S. residency need to consider other options.

What is the difference between Form 1120 and Form 1120-S?

Form 1120 is for C corporations, and corporate-level income is taxed. Form 1120-S is for S corporations, and, in most cases, there is no federal income tax at the corporate level.

Can an LLC file Form 1120-S?

Yes. An LLC can be treated as a corporation for tax purposes by filing Form 8832 and can subsequently file Form 2553 to elect S status. In a similar vein, a single-member LLC can retain the LLC status legally and elect S corporation status by filing both forms.

What is Schedule K-1, and when is it distributed?

Schedule K-1 is the IRS form that identifies each shareholder’s share of a corporation’s income, loss, and credits/deductions for the tax year. Shareholders will need a K-1 to complete their individual tax return. K-1s are to be distributed by March 15 or when the K-1 is available.

Ready to get your S corporation filings in order?

We assist founders and business owners with entity registration, compliance filings, IRS tax filings, and BOI reports. If you want us to help you get your Form 1120-S filed properly, or if you want us to help you fix your S corporation election that you missed, contact our EasyFiling team, and we will help you with what you need.