S-Corp Tax Deadlines: What to File and When

S-Corporations offer powerful tax advantages, but they come with a long list of filing obligations. Miss one deadline and the penalties stack up fast. This guide walks through every S-Corp tax deadline for 2026, from the corporate return to payroll filings to personal estimated payments.

The Core S-Corp Filing: Form 1120-S

Form 1120-S is the S-Corporation income tax return. It reports the company's income, deductions, credits, and each shareholder's share of those items. The S-Corp itself does not pay income tax — it is a pass-through entity. Instead, income flows through to shareholders via Schedule K-1.

Due date: March 15, 2026 (for calendar-year S-Corps). If you need more time, file Form 7004 by March 15 for an automatic 6-month extension to September 15. However, any estimated taxes owed must still be paid by the original deadline.

The penalty for filing a late 1120-S is $220 per shareholder per month (or partial month), up to 12 months. For a two-shareholder S-Corp, that means up to $5,280 in penalties alone. See our full breakdown of IRS late filing penalties to understand how these costs compound.

Schedule K-1 Distribution

Every S-Corp must distribute Schedule K-1 to each shareholder by March 15. The K-1 reports each shareholder's pro-rata share of income, losses, deductions, and credits. Shareholders use this information to complete their personal Form 1040.

If you file an extension for the 1120-S, the K-1 deadline extends as well — but your shareholders will need the information to file their personal returns. Late K-1s create a chain reaction of personal filing delays and potential penalties.

Personal Tax Returns (Form 1040)

Each S-Corp shareholder must report their K-1 income on their personal Form 1040, due April 15, 2026. If you have not received your K-1 by this date, you may need to file a personal extension using Form 4868.

The K-1 income is reported on Schedule E, Part II. Unlike sole proprietors, S-Corp shareholders do not pay self-employment tax on K-1 income — only on their W-2 salary. This is the primary tax savings of S-Corp election.

The Reasonable Salary Requirement

The IRS requires every S-Corp shareholder-employee to take a reasonable salary before distributing additional profits. "Reasonable" means compensation comparable to what similar businesses pay for similar work in your area. There is no specific formula, but the IRS looks at:

• Training, education, and experience
• Duties and responsibilities
• Time and effort devoted to the business
• Comparable salaries in similar businesses
• Dividend history and company profitability

Paying yourself too little triggers IRS scrutiny. If the IRS reclassifies distributions as wages, you will owe back employment taxes plus penalties and interest. A common benchmark is paying yourself at least 40-60% of net business income as salary, though this varies by industry and revenue.

Payroll Tax Deadlines

Because S-Corp shareholder-employees receive a W-2 salary, the S-Corp must handle payroll tax filings. Here is the full payroll calendar:

Form 941 reports income taxes withheld from employee wages plus the employer and employee shares of Social Security and Medicare taxes. Federal tax deposits are due either monthly or semi-weekly depending on your deposit schedule — check IRS Publication 15 for your specific schedule.

Estimated Tax Payments (Form 1040-ES)

S-Corp shareholders often need to make personal estimated tax payments on their K-1 income, since the W-2 withholding may not cover their full tax liability. Estimated payments are due quarterly: April 15, June 15, September 15, and January 15. Use the safe harbor rule — pay at least 100% of last year's tax liability (110% if AGI exceeded $150,000) to avoid underpayment penalties. Our quarterly estimated tax payments guide covers the calculation in detail.

Complete S-Corp Deadline Calendar for 2026

Frequently Asked Questions

When is the S-Corp tax return due?

Form 1120-S is due March 15 for calendar-year S-Corps. You can file Form 7004 for an automatic 6-month extension to September 15, but any estimated taxes owed must still be paid by March 15.

What is the reasonable salary requirement for S-Corp owners?

The IRS requires S-Corp shareholder-employees to receive a reasonable salary before taking distributions. Reasonable means comparable to what similar businesses pay for similar work. Paying too little triggers audits and reclassification of distributions as wages, plus back taxes, penalties, and interest.

Do S-Corp shareholders pay self-employment tax?

No. S-Corp shareholders do not pay self-employment tax on distributions. They only pay employment taxes (Social Security and Medicare) on their W-2 salary. This is one of the primary tax advantages of S-Corp election, but it only works if you pay yourself a reasonable salary first.