**File the S-corp return as soon as you can, and check whether you qualify for penalty relief.** You can still file after the deadline.

You haven’t specified the tax year. The example below assumes a **2025 calendar-year return filed in 2026**, with one shareholder.

1. **Check whether an extension was filed.** The regular federal deadline was March 16, 2026. A timely Form 7004 extended filing to September 15, 2026, so a June filing would be timely. An extension for your personal taxes does not extend the corporation’s return. Generally, you cannot obtain a retroactive extension after the deadline. [IRS tax calendar](https://www.irs.gov/publications/p509), [extension instructions](https://www.irs.gov/instructions/i7004).

2. **Prepare Form 1120-S and your Schedule K-1.** TurboTax Business supports S-corp returns; choose a product that explicitly supports Form 1120-S. TurboTax Home & Business is designed for personal returns and sole proprietors. Using software is reasonable if your books are complete and you understand the corporate reporting. My recommendation is to use a CPA or enrolled agent familiar with S-corps if this is your first corporate return or your payroll and bookkeeping need work. [Intuit’s filing guidance](https://turbotax.intuit.com/tax-tips/small-business-taxes/how-to-file-federal-income-taxes-for-small-businesses/L8ghn14sF).

3. **Expect a monthly federal filing penalty unless relief applies.** For returns due in 2026, the base penalty is **$255 per shareholder for each month or partial month late, up to 12 months**. It applies even when the corporation owes no federal income tax. For example, filing June 20, 2026, after a March 16 deadline with no extension would mean four partial/full penalty months: **$1,020** for one shareholder. The maximum base penalty would be $3,060. Returns due in 2025 used $245 per month. [IRS penalty rates](https://www.irs.gov/payments/failure-to-file-penalty).

4. **Pursue penalty relief after filing.** Serious illness or a death in the family can support “reasonable cause,” depending on how it prevented filing. Keep records of what happened, the dates, and your efforts to catch up. If a penalty notice arrives, follow its instructions to request relief; the IRS says to submit the explanation after receiving the notice. A clean compliance history may also qualify you for first-time or automatic relief, depending on the return and processing date. Approval depends on eligibility. [Reasonable-cause guidance](https://www.irs.gov/payments/penalty-relief-for-reasonable-cause), [automatic relief guidance](https://www.irs.gov/pub/irs-access/p6171_accessible.pdf).

Also address your **personal return**, which reports the K-1 income, and check state filing requirements. Personal unpaid taxes, state obligations, and payroll issues can create separate charges.

**Which tax year and state are involved, and did you or a preparer file Form 7004?** Those details determine your actual deadline and likely penalty.