# What is Form 1120 (C-Corp Annual Return)?

Country: United States

Form 1120 is the annual federal income tax return for US C-corporations, due 15 April for calendar-year filers (15th day of the 4th month after fiscal year-end for fiscal-year filers). Six-month automatic extension available via Form 7004.

## Current rate (Annual, calendar year default)

N/A: return only

## Example

Acme Inc. (calendar year C-corp) files Form 1120 by 15 April 2025 reporting 2024 taxable income, federal corporate income tax, and any tax credits (R&D, foreign tax credit, etc.).

## How Form 1120 (C-Corp Annual Return) works in United States

Form 1120 is the C-corporation's annual tax return to the IRS. It reports gross income, deductions, taxable income, and federal income tax owed. It is not a simple short form: a fully-completed 1120 for a complex C-corp can run dozens of pages.

**Filing deadlines**

- Calendar-year C-corps: 15 April (the 15th day of the 4th month after year-end)
- Fiscal-year C-corps: 15th day of the 4th month after fiscal year-end
- 6-month automatic extension via Form 7004 (to 15 October for calendar year corps)

The extension is for filing only: any tax owed is still due by the original deadline. Paying late triggers interest and failure-to-pay penalties.

**Estimated tax payments**

C-corps with a tax liability of $500 or more must pay estimated taxes quarterly:
- 15 April, 15 June, 15 September, 15 December (for calendar-year corps)

Safe harbor: pay 100% of prior year tax OR 100% of annualised current year tax. Large corporations ($1m+ in tax in any of the prior 3 years) must use current-year annualisation: prior year safe harbor is not available.

**Key schedules**

- Schedule C: dividends and special deductions
- Schedule J: tax computation and payments
- Schedule K: other information (stock ownership, foreign activities)
- Schedule L: balance sheet per books
- Schedule M-1: reconciliation of book income to taxable income
- Schedule M-2: analysis of unappropriated retained earnings
- Schedule M-3 (for corps with $10m+ assets): detailed book-tax reconciliation

**Late filing penalty**

5% of unpaid tax per month (or partial month), up to 25% maximum. Minimum penalty applies if the return is more than 60 days late: the lesser of $435 or 100% of unpaid tax.

Source: https://www.irs.gov/forms-pubs/about-form-1120

## Related terms

- [C-Corporation](https://accounts-os.com/us/glossary/c-corp)
- [Form 1120-S (S-Corp Annual Return)](https://accounts-os.com/us/glossary/form-1120s)
- [Form 1065 (Partnership Return)](https://accounts-os.com/us/glossary/form-1065)