Unfiled Form 1120: Penalties and How to Catch Up

The short answer: Every C corporation has to file Form 1120 every year, profit or not. A missing return draws penalties of up to 5% of the unpaid tax for each month or part of a month it’s late (with a minimum after 60 days), and the late-payment part and interest keep running until the tax is paid. The IRS’s time limit only starts once a return is filed, so an unfiled year never closes, and the IRS can write the return itself. The way out is to rebuild the books and file the missing years oldest first, with a Florida Form F-1120 for each.

Does a C corporation have to file if it made no money?

Yes. The Form 1120 instructions say every domestic corporation that isn’t tax-exempt must file, whether or not it has taxable income.

A loss year is worth filing anyway: the return records the loss, which can generally be carried forward to reduce taxable income in later years, within limits. And since the federal penalties are a percentage of unpaid tax, a year with no tax due usually draws no federal penalty. Florida’s penalty works differently (below).

What does an unfiled Form 1120 cost?

First, the tax itself: 21% of taxable income for tax years beginning in 2018 or later (earlier years used graduated rates). Then three charges build on any of it left unpaid:

Late filing. 5% of the unpaid tax for each month or part of a month after the due date (including extensions), capped at 25%.
Late payment. 0.5% of the unpaid tax for each month or part of a month, capped at 25%.
Interest. Charged on the unpaid tax from its due date, and on the late-filing penalty as well. The rate is the federal short-term rate plus 3 percentage points, reset every quarter and compounded daily. For October to December 2026 it’s 7% a year. Underpayments over $100,000 can draw a higher rate (plus 5 percentage points).

The penalties overlap: in a month when both apply, the late-filing penalty is cut by the late-payment one, so that month costs 5% in total. The late-filing penalty hits its cap after five months; the late-payment penalty keeps adding up until the tax is paid or it reaches its own cap, and its monthly rate doubles if the tax is still unpaid 10 days after the IRS sends a notice of intent to levy.

Once a return is more than 60 days late, the late-filing penalty is at least the smaller of the tax due or a set amount, based on when the return was originally due (before extensions):

$525 for returns due in 2026
$510 for returns due in 2025
$485 for returns due in 2024
$450 for returns due in 2023
$435 for returns due from 2020 to 2022
$210 for returns due from 2018 to 2019
$205 for returns due from 2016 to 2017

A calendar-year 2022 return, due in April 2023, has a floor of $450 (or the tax due, if less).

Tax not paid in estimated installments during the year can also draw an underpayment penalty (Form 2220).

Filing stops the late-filing penalty from growing; only paying stops the late-payment penalty and interest. A payment plan spreads the payments out, but both keep running on the unpaid balance until it’s paid in full.

How far back can the IRS go on an unfiled year?

As far as it wants, while the return is missing. The IRS normally has three years after a return is filed to assess more tax (26 U.S.C. 6501(a)). When no return is filed, the law says the tax may be assessed at any time (6501(c)(3)).

IRS policy normally limits enforcement of delinquent returns to six years, and going further needs a manager’s approval (Policy Statement 5-133). That’s a policy about IRS effort, not a limit in the law. Which years to file is worth settling with a tax professional, especially if an IRS letter names years.

Can the IRS file the return for the company?

Yes. Under 26 U.S.C. 6020(b), the IRS can make the return from its own knowledge and whatever information it can obtain, and that return is treated as valid on its face. It tends to work against the company:

Expenses can be left out. The Internal Revenue Manual says there’s no legal requirement to allow business expenses, including cost of goods sold, on a return it prepares under 6020(b). An examiner may consider records the company supplies.
It counts for the late-payment penalty. The IRS’s return is treated as the company’s own when that penalty is figured (6651(g)).
It doesn’t start the assessment clock. Only a return the company files does that (6501(b)(3)).

The company can still file its own return afterward to claim its deductions and credits; the IRS says that’s in the taxpayer’s best interest and will generally adjust the account.

What about the Florida return?

Each year that needs a Form 1120 also needs a Florida Form F-1120. Florida’s Department of Revenue says corporations must file it every year, even if no tax is due.

The tax. 5.5% of Florida net income (figured after a $50,000 exemption) for tax years beginning on or after January 1, 2022. Earlier rates: 3.535% for tax years beginning in 2021, 4.458% for 2019 or 2020, and 5.5% before 2019.
Late with tax due. 10% of the unpaid tax for each month or part of a month, up to 50%, plus interest.
Late with no tax due. $50 for each month or part of a month, up to $300. Unlike the federal penalty, this one reaches loss years.

Florida’s time limit works much the same way. Under s. 95.091(3)(a), Florida Statutes, the Department can assess at any time when a required return wasn’t filed, unless the company disclosed the liability in writing before the Department contacted it. Florida also runs a voluntary disclosure program for companies it hasn’t yet contacted, though not every late return qualifies. What a late F-1120 costs, and how Florida’s disclosure program works, or see how the Florida return fits a catch-up.

In what order should the missing years be caught up?

Pin down which years are missing. The company’s IRS account transcripts show which returns the IRS has on record. How to find every unfiled business return.
Put any deadline first. A reply date on an IRS or Florida letter comes before everything else.
Rebuild the books from the oldest year forward. Each year’s closing balance sheet is the next year’s opening one.
Prepare Form 1120, then F-1120, for each year. One set of books feeds both, so the federal and Florida figures agree.
File, then pay or arrange to pay. Pay what the company can when it files; for the rest, the IRS directs businesses to call the number on their notice or visit an IRS office.
Then look at penalty relief, year by year.

Can penalty relief cover more than one year?

Seldom every year in a run. Penalty relief can be requested by you or an authorized representative (one route is automatic), and none of these routes is certain:

First-time abatement usually covers one year and needs a clean prior three years. In a string of missed years, that’s normally only the first one, since every later year has a missed return among its prior three.
The Automatic Exemption from Penalty applies without a request to Form 1120 returns for 2025 and later, but only when the prior three years were filed and paid on time, so it rarely helps a company catching up several years.
Reasonable cause covers the rest: the IRS looks for ordinary care defeated by events such as a fire or disaster, serious illness, or being unable to get records. Lack of funds alone doesn’t excuse paying late, and the company generally stays responsible even when someone else handled its filings.

When a penalty is reduced or removed, the IRS also reduces or removes the interest charged on it.

When should someone else deal with the IRS for the company?

Filing the missing returns doesn’t by itself need a representative. One is needed when someone other than the company’s officers deals with the IRS for it, such as answering an examiner, a notice or a collection letter. If your company needs a professional to represent it before the IRS, that’s the job of an attorney, a CPA or an enrolled agent. We’ll tell you on the call if your situation needs one and arrange it; it may be a separate engagement.

Willfully failing to file a required return is a misdemeanor under 26 U.S.C. 7203. If the unfiled years involve anything beyond records that simply fell behind, talk to a tax attorney before any return goes in.

Cayde rebuilds the books and gets every missing Form 1120 and F-1120 filed, at a fixed price in writing first: how a C corporation catch-up works.

Quick answers

Can a Form 1120 from several years back still be e-filed?

Only recent ones. The IRS e-file system takes Form 1120 for the latest tax year and the two before it; during 2026 that’s 2023, 2024 and 2025. Older years go on paper.

Once a late 1120 is filed, how long can the IRS audit it?

Generally three years from the date it’s actually filed, not from the original due date. Longer limits apply in some cases, such as a substantial omission of income or a fraudulent return.

Is a late 1120 penalized the same way as a late 1120-S?

No. The C corporation penalties are percentages of unpaid tax. An S corporation’s late-filing penalty is a flat $255 per shareholder for each month late, up to 12 months, for a return required to be filed in 2026, whether or not any tax is owed.

Can the Florida returns go in before the federal ones?

Not usefully. Florida’s tax is computed from federal taxable income, so each year’s federal figures have to be final first. Florida’s voluntary disclosure program also asks for a copy of the federal 1120 with each F-1120.

Sources

General information, not advice for your situation. Updated October 31, 2026.

What happens when a C corporation doesn’t file Form 1120?