Harper Tax CPA

Filing an S Corporation Late: IRS & California Penalties Explained

Missing the S-corporation filing deadline can be an expensive mistake — especially if you operate in California.

In this guide, we’ll walk through:

  • What “filing an S-corporation late” actually means
  • IRS late-filing penalties for Form 1120-S
  • California Franchise Tax Board (FTB) penalties for late Form 100S
  • The difference between a late S-corp tax return and a late S-election
  • What you can do now if your S-corp is already late

Disclaimer: Penalty amounts change periodically due to law changes and inflation adjustments. Always confirm with the latest IRS/FTB instructions or work with a CPA for your specific situation.

1. What Does “Filing an S Corporation Late” Mean?

When people say they “filed an S-corp late,” they might be talking about several different issues:

Late S-corporation tax return

  • Federal: Form 1120-S filed after the due date (generally March 15 for calendar-year S-corps, or the 15th day of the 3rd month after year-end), or after the extended due date if you filed a valid extension.
  • California: Form 100S filed after the same general deadline (or after the extended due date if you filed an extension).

Late S-corporation election (Form 2553)

Form 2553 was not filed on time, so the IRS may not treat the company as an S-corporation for that year unless late-election relief is granted.

Late payment of tax

  • Federal: Less common at the S-corp level, because income typically passes through to shareholders — but it can arise from corporate-level items like built-in gains tax, LIFO recapture, or other special taxes.
  • California: Very common, because S-corporations owe entity-level tax (1.5% of net income) and, for most ongoing S-corps, a minimum franchise tax.

This article focuses mainly on late tax returns and late payments for IRS and California.

2. IRS Late Filing Penalties for S Corporations (Form 1120-S)

A. Per-Shareholder Late Filing Penalty (IRC §6699)

If your S-corporation files Form 1120-S late and the delay is not due to reasonable cause, the IRS charges a per-shareholder, per-month penalty under Internal Revenue Code §6699.

For 2024 tax year returns required to be filed in 2025, the Form 1120-S instructions provide that:

  • The penalty is $245 per shareholder per month or part of a month,
  • Capped at 12 months,
  • Based on the number of persons who were shareholders during any part of the tax year.

Important: This dollar amount is adjusted periodically for inflation. Always check the latest Form 1120-S instructions for the current rate.

Example (Federal):
Your S-corp has 3 shareholders and files its 1120-S 4 months late.

  • Penalty ≈ $245 × 3 shareholders × 4 months = $2,940,
  • Even if the S-corp itself doesn’t owe any corporate-level tax.

This per-shareholder penalty can apply whether or not there is tax due. If tax is due, additional percentage-based penalties can stack on top.

B. Additional Failure-to-File and Failure-to-Pay Penalties (If Tax Is Owed)

If your S-corporation has corporate-level tax due (for example, built-in gains tax), additional penalties may apply:

  • Failure-to-file (general): Typically 5% of the unpaid tax per month or part of a month, up to 25% of the unpaid tax.
  • Failure-to-pay: Generally 0.5% of the unpaid tax per month or part of a month, up to 25%.

These amounts are in addition to the per-shareholder penalty under IRC §6699 when there is tax due.

C. Interest on Unpaid Tax and Penalties

On top of penalties, the IRS charges interest on:

  • Any unpaid tax, and
  • Certain penalties

Interest compounds daily at a rate the IRS sets quarterly and continues until the balance is paid in full.

3. California S Corporation Late Filing Penalties (Form 100S)

If your S-corporation is doing business in California, you’re dealing with two layers of risk: IRS penalties and California Franchise Tax Board (FTB) penalties.

A. $18 Per Shareholder Per Month Late Filing Penalty

California imposes a specific late filing penalty for S-corporations that fail to timely file Form 100S or that file an incomplete return.

For returns with original due dates on or after January 1, 2011, FTB guidance states:

  • Penalty = $18 per shareholder per month or fraction of a month,
  • Up to a maximum of 12 months,
  • Based on the number of shareholders during any part of the taxable year.

Example (California):
Your California S-corp has 4 shareholders and files its Form 100S 5 months late.

  • Late filing penalty ≈ $18 × 4 shareholders × 5 months = $360,
  • Even if no additional California tax is due.

This is in addition to any other penalties and interest.

B. Delinquent and Underpayment Penalties

If your S-corp owes California tax — for example:

  • 1.5% tax on net income, and
  • The $800 minimum franchise tax (for most ongoing S-corps)

— then filing or paying late can trigger additional penalties.

Common California penalties include:

  • A delinquent (failure-to-file) penalty tied to unpaid tax, and
  • A failure-to-pay penalty, which can accrue monthly,
  • Together, these can reach up to about 25% of the unpaid tax in many situations.

Interest accrues daily on unpaid tax and certain penalties until the balance is paid.

C. Minimum Franchise Tax and First-Year Relief

For most ongoing S-corporations:

  • California requires the greater of 1.5% of net income or the $800 minimum franchise tax,
  • The $800 minimum is due even if the corporation has a loss.

However, there is an important nuance:

  • Newly formed or qualified corporations (including S-corps) are generally exempt from the $800 minimum franchise tax in their first taxable year,
  • But any first-year net income is still subject to the 1.5% S-corporation tax.

Filing late does not eliminate the underlying tax. It simply adds late-filing penalties, late-payment penalties, and interest on top of whatever tax is ultimately due.

D. Possible Suspension/Forfeiture

If California returns and taxes are not handled for a sustained period, the corporation can be:

  • Suspended or forfeited by the FTB or Secretary of State.

Consequences can include:

  • Loss of the right to legally transact business in California
  • Inability to sue or defend in California courts
  • Loss of the exclusive right to use the corporation’s name
  • Problems with financing, contracts, and licensing

Reinstating a suspended/forfeited corporation usually requires:

  • Filing all past-due returns
  • Paying all taxes, penalties, and interest
  • Filing revivor or related reinstatement paperwork with the FTB/Secretary of State

4. Late S Election vs. Late S-Corp Tax Return

Many owners confuse a late S-election with a late S-corporation tax return.

Late S-Election (Form 2553)

If your S-election (Form 2553) wasn’t filed on time, the IRS may treat your entity as:

  • A C-corporation, or
  • A partnership or disregarded entity (depending on your structure)

This can lead to:

  • Unexpected double taxation if treated as a C-corp
  • Mismatch between how owners have taken distributions and how the IRS views the entity
  • Need to rework prior-year filings

The IRS does have procedures to request relief for a late S-election if:

  • You can show you intended to be an S-corporation,
  • You met all eligibility requirements, and
  • You missed the deadline due to oversight or misunderstanding.

These rules are described in the Form 2553 instructions and related revenue procedures.

California generally conforms to federal S status for corporations, but you still must:

  • File the appropriate California entity returns (such as Form 100S), and
  • Pay any applicable franchise tax and fees.

Late S-Corp Tax Return (1120-S / 100S)

Even if your S-election is perfectly valid and timely, filing:

  • Form 1120-S (federal) or
  • Form 100S (California)

late can trigger the penalties described above.

In other words, you can have:

  • A valid S-election and
  • Significant IRS and FTB penalties for late returns.

They’re separate issues that both need to be addressed.

5. Practical Consequences Beyond the Dollar Penalties

The dollar penalties hurt, but there are broader side effects of filing late.

Delayed K-1s to Shareholders

Shareholders can’t file accurate personal returns until they receive their Schedule K-1s. Late K-1s often mean:

  • Late or amended individual returns
  • Additional prep fees
  • Frustrated owners and spouses

Cash-Flow Strain

Penalties and interest can quickly turn a manageable balance into a cash-flow problem, especially for small or newer S-corporations.

Audit and Compliance Risk

A pattern of:

  • Late filing
  • Non-filing
  • Unpaid balances

— especially combined with other issues (unfiled payroll returns, missing 1099s, etc.) — can draw unwanted attention from tax authorities.

Banking and Financing Issues

Lenders often ask for:

  • The last one to three years of business and personal tax returns.

If your returns are late:

  • Loan approvals can be delayed or denied, and
  • You may have to scramble to get caught up under pressure.

6. What To Do If Your S Corporation Is Already Late

If your S-corp is already late, the most important step is to take action quickly.

A. File and Pay As Soon As Possible

Both the IRS and FTB calculate many penalties per month or part of a month. That means:

  • Being one day late can be treated like being 29 days late for that month’s penalty.

Even if you can’t pay everything immediately:

  • File the returns as soon as possible to stop or reduce failure-to-file penalties.
  • Pay as much as you can to reduce failure-to-pay penalties and interest.

Every month you wait typically increases the total cost.

B. Request IRS Penalty Relief (When Appropriate)

The IRS offers several types of penalty relief:

First-Time Abatement (FTA) / Administrative Relief

For taxpayers with a clean compliance history, the IRS may waive certain penalties one time for a given period.

Reasonable Cause Relief

If your failure to file or pay was due to reasonable cause and not willful neglect — for example:

  • Serious illness or death in the family
  • Natural disasters
  • Records destroyed by casualty
  • Reliance on incorrect professional advice

— you may qualify for penalty abatement.

These requests typically involve:

  • Explaining the facts in detail
  • Showing what you did to correct the issue
  • Providing documentation when available

C. Request California Penalty Relief

California also allows penalty relief in some circumstances:

  • The FTB may waive penalties based on reasonable cause.
  • For business entities, this is often done using Form FTB 2924 – Reasonable Cause – Business Entity Claim for Refund when seeking a refund of penalties already paid.

California also offers a one-time abatement program for certain timeliness penalties, but that relief is currently oriented toward individual taxpayers. For S-corporations, reasonable cause is usually the primary route.

If the IRS abates your penalties for a particular year based on a documented reasonable cause explanation, that can sometimes support a parallel request to California for the same period and facts.

D. Clean Up Multiple Years at Once

If you’re behind for several years:

  1. Work year-by-year in order (oldest first).
  2. Make sure shareholder basis, distributions, and PTET/AB 150 issues (if applicable) are handled correctly.
  3. Plan your cash flow so you can catch up with both IRS and California without crippling your operations.
  4. Consider a phased payment plan or installment agreement if balances are large.

7. How a CPA Can Help With Late S-Corp Filings

Because S-corporations involve:

  • Entity-level filings (1120-S, 100S)
  • Shareholder-level reporting (Schedule K-1s and personal returns)
  • State-specific rules like California’s per-shareholder late filing penalty and minimum franchise tax

…cleaning up late filings is rarely a simple DIY project.

A CPA who regularly works with S-corporations and California clients can:

  • Reconstruct books and records if needed
  • Prepare and file past-due 1120-S and 100S returns correctly
  • Evaluate whether reasonable cause or first-time abatement is realistic
  • Coordinate IRS and FTB penalty abatement requests
  • Create a compliance calendar or system so you don’t miss future deadlines

8. FAQs: Late S Corporation Filing (IRS & California)

What happens if my S-corp return is just one day late?

For both IRS and FTB, many penalties are calculated per “month or part of a month” the return is late. That means:

  • Being 1 day late can be treated the same as being 29 days late for purposes of that month’s penalty.

Does filing an extension avoid late filing penalties?

A valid extension:

  • Extends the time to file,
  • Does not extend the time to pay.

If you:

  • File by the extended due date, you generally avoid failure-to-file penalties (including the IRC §6699 and CA $18/shareholder late filing penalties).
  • Still owe tax as of the original due date, you can still face late-payment penalties and interest on the unpaid balance.

If my S-corp has no income, can I still get penalties?

Yes. The IRS and California can impose late filing penalties even if there is no income and no tax due, including:

  • The federal per-shareholder penalty under IRC §6699, and
  • California’s $18 per shareholder per month penalty.

The absence of tax due does not automatically protect you from late-filing penalties.

Is the California $800 minimum franchise tax still due if I file late?

For most ongoing S-corporations, yes:

  • The $800 minimum franchise tax is generally due each year, even if the corporation has a loss.
  • Filing late can stack late-filing penalties, late-payment penalties, and interest on top of that.

Important nuance:

  • Newly formed S-corps are generally exempt from the $800 minimum in their first taxable year, but:
    • Any net income in that first year is still subject to the 1.5% S-corporation tax.
    • Penalties and interest can still apply if that first-year return or tax is filed or paid late.

 

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