Introduction
Form 1120 is the U.S. federal income tax return for domestic C corporations. The corporation reports its income, deductions, credits and tax liability to the IRS.
The requirement turns on how an entity is classified for tax, not on size, profit or trading activity. Many Australian owners of U.S. companies get caught here. They assume a dormant or loss-making company has nothing to file.
This guide covers who files, what the form reports, how it differs from other returns, how to prepare it, and what Australian owners should check across both jurisdictions.
Key Takeaways
- Domestic C corporations generally file Form 1120 every year, even with no taxable income.
- An LLC files Form 1120 only if it is classified or elects to be taxed as a corporation.
- Form 1120 covers the corporation; Form 1040 covers an individual.
- Confirm deadlines, penalties and filing methods against the current IRS instructions.
Who Files Form 1120?
The standard filer: a domestic C corporation
A domestic corporation taxed as a C corporation files Form 1120 as its own taxpayer. Shareholders do not file it individually. Under the IRS Form 1120 instructions, a domestic corporation must file whether or not it has taxable income, unless it is exempt under section 501 or must use a special return.
That covers newly formed, inactive and loss-making corporations. Having no income does not remove the obligation. Confirm the rule for your corporation's status and tax year.
LLCs and elections
The "LLC" label does not decide the return. Federal classification does:
- A single-member LLC is disregarded for income tax by default.
- A multi-member LLC is a partnership by default.
- Either can elect corporate treatment by filing Form 8832.
Only a corporate-classified LLC files Form 1120. Verify the election, its effective date and the IRS acceptance before relying on it.
Entities that usually file something else
| Entity | Usual return |
|---|---|
| S corporation | Form 1120-S |
| Partnership (including partnership-classified LLCs) | Form 1065 |
| Foreign corporation with U.S. business activity | Form 1120-F |
| Eligible homeowners association (section 528) | Form 1120-H |
| Most tax-exempt organisations | Form 990 series |
One caveat: a foreign-owned disregarded entity may file a pro forma Form 1120 attached to Form 5472. That is limited information reporting, not an ordinary corporate income tax return.
What Is Form 1120 Used For?
Form 1120 reports a corporation's income, gains, losses, deductions and credits, and calculates its federal income tax. The regular federal rate is 21% of taxable income. That is not the same as saying every corporation's effective rate is 21%.
Information you will need
- Gross receipts and cost of goods sold, where applicable
- Operating expenses and officer compensation
- Interest, dividends, rents and depreciation
- Capital transactions
- Estimated tax payments and credits
The form ties the accounting records to the tax position. Where required, you reconcile book income to taxable income and keep documents that support each deduction and credit.
Common schedules
| Schedule | Purpose |
|---|---|
| C | Dividends and special deductions |
| J | Tax computation and payment |
| K | Other information |
| L | Balance sheets per books |
| M-1 | Book-to-tax reconciliation |
| M-2 | Retained earnings analysis |
| M-3 | Required at year-end assets of $10 million or more |
| 1125-A | Cost of goods sold |
| 4562 | Depreciation and section 179 |
| D | Capital gains and losses |
A corporation with both receipts and year-end assets below $250,000 may skip Schedules L, M-1 and M-2 under Schedule K question 13.
Records checklist
- EIN, incorporation details and tax-year information
- Trial balance or financial statements
- Payroll and officer compensation records
- Asset register
- Loan details
- Shareholder and related-party transactions
- Estimated tax payments
- Prior-year returns
Keep records generally for 3 years. Some situations require longer, and unfiled or fraudulent returns require indefinite retention.
Form 1120 Compared With Other Tax Returns
Form 1120 vs Form 1040
Form 1120 is a U.S. corporation's return. Form 1040 is a U.S. individual's return.
Owners who are officers are generally employees, so their wages appear on a W-2 and then on their own Form 1040. Distributions from earnings and profits are generally dividends, also reported personally.
These are U.S. individual return rules. They do not establish an Australian owner's personal obligations in Australia.
Form 1120 vs Form 1120-S
A C corporation pays tax at the corporate level. An S corporation generally passes income, losses, deductions and credits to shareholders, who receive Schedule K-1.
S eligibility is narrow:
- Domestic corporation
- No more than 100 shareholders
- One class of stock
- No partnerships, corporations or non-resident alien shareholders
Form 2553, signed by all shareholders, makes the election. The non-resident alien restriction matters for Australian owners, because it generally rules out S status.
Forms 1065, 1120-F and 990
- 1065: partnerships report as an information return, with profits and losses passing to partners.
- 1120-F: foreign corporations report their own U.S. tax position. It is not the return of a separately incorporated U.S. subsidiary.
- 990: most tax-exempt organisations, with 990-EZ or 990-N for smaller ones.
Classification, foreign status and activity can change the right form.
How to Prepare and File Form 1120
Preparation sequence
- Confirm entity classification and tax year.
- Gather complete accounting records.
- Reconcile the books.
- Identify the schedules and attachments that apply.
- Review prior-year carryovers.
- Check the return for consistency before signing.
Deadlines and extensions
The ordinary deadline is the 15th day of the 4th month after year-end, which is 15 April for calendar-year corporations. A weekend or legal holiday moves it to the next business day. June year-end corporations with years beginning before 2026 use the 3rd-month rule.
Form 7004 generally gives 6 months to file. It does not extend the time to pay.
Where and how to file
Corporations required to file 10 or more returns of any type in a calendar year must e-file Form 1120. Hardship waivers exist. For paper filing, use the IRS's official where-to-file page rather than a static address.
Signing, paying and penalties
- Signers: the president, vice-president, treasurer, assistant treasurer, chief accounting officer or another authorised officer.
- Payment: EFTPS or IRS Business Direct Pay.
- Late filing: generally 5% of unpaid tax per month, up to 25%. For returns due in 2026 and over 60 days late, the minimum is the smaller of tax due or $525.
- Late payment: generally 0.5% per month, up to 25%.
- Interest: 7% ordinary and 9% for large corporate underpayments, for October to December 2026 only.
Reasonable-cause relief can apply to some penalties.
Cross-Border Considerations and When to Seek Professional Help
Layers that apply to an Australian owner
U.S. incorporation, foreign ownership and Australian residence are separate tests. One reporting layer does not replace another.
- U.S. side: Form 1120 reports the corporation's income. A U.S. corporation that is at least 25% foreign-owned with reportable related-party transactions also files Form 5472.
- Form 5472 penalty: the Form 5472 instructions set a $25,000 penalty for failure to file correctly, per related party.
- Australian side: An overseas subsidiary is generally a foreign resident. If it fails the active income test, CFC rules may tax the Australian owner on certain income.
- Australian reporting: Assessable foreign income must be declared in Australia.
Other review points
- Form 1118 if the corporation claims foreign tax credits
- Form 1120-F if a foreign corporation is itself doing U.S. business
- Withholding: the default is 30%, but Australia-U.S. treaty limits can reduce it (dividends 15%, 5% or 0%; interest 10%; royalties 5%), subject to eligibility conditions
- Transfer pricing: both IRC section 482 and Australia's Subdivision 815-B apply arm's length standards to related-party dealings
- State filings in the U.S.
- Beneficial ownership reporting: FinCEN states U.S. companies are exempt from BOI reporting
Getting help
VJM Global supports Australian businesses with accounting outsourcing, bookkeeping, tax compliance and financial reporting. CPAs and Chartered Accountants work to U.S.-compliant standards.
Clean year-end financials make corporate return preparation easier. Coordination across jurisdictions is where errors usually start, and every structure differs, so seek tailored advice before filing.
Frequently Asked Questions
Where is Form 1120 filed?
Filing may be electronic or by mail, depending on the corporation's circumstances. Check the IRS "Where to File" page or ask an authorised tax professional for the current method and address.
What is the difference between Form 1040 and Form 1120?
Form 1040 is an individual federal income tax return. Form 1120 is a corporation's. Owners may have separate personal reporting obligations.
Who is required to file Form 1120?
Domestic C corporations generally file it. S corporations, partnerships, tax-exempt organisations and foreign corporations may use different forms or fall under exceptions.
Does a corporation have to file Form 1120 if it had no income?
Often yes. A domestic corporation generally must file even with no taxable income. Confirm the rule for your status and tax year with the IRS or a tax professional.
Can an LLC file Form 1120?
Yes, when it is classified or elects to be taxed as a C corporation. Other LLC classifications generally use different forms.
What is the difference between Form 1120 and Form 1120-S?
Form 1120 is for C corporations taxed at the corporate level. Form 1120-S is for eligible S corporations whose income and losses generally pass through to shareholders.
