This guide covers who files, what the form contains, how to prepare it, the deadlines, and the cross-border points that matter for Australian-owned businesses. It is educational only and not individual tax advice.
Key Takeaways
- Form 1120 is the federal return for U.S. C corporations.
- Domestic corporations generally file even with no income or activity.
- Schedules C, J, K, L, M-1 and M-2 support the main form.
- A Form 7004 extension moves the filing date, not the payment date.
- A U.S. subsidiary and an Australian company trading directly in the U.S. face different filings.
What Is Form 1120, and Who Must File It?
What Form 1120 is used for
Form 1120 is the U.S. Corporation Income Tax Return. Corporations report income, gains, losses, deductions and credits on it, then calculate their federal income tax.
A C corporation pays tax at the corporate level. Pass-through entities work differently: income is generally reported by the owners or partners.
Who generally files Form 1120
Under the 2025 Form 1120 instructions, domestic corporations file whether or not they have taxable income, unless they are exempt under section 501. That includes newly formed corporations and those with a loss or little activity.
An LLC's legal form doesn't decide its tax treatment. Its federal classification does:
- A multi-member LLC defaults to partnership treatment (Form 1065).
- A single-member LLC defaults to disregarded status, reported on the owner's return.
- An LLC that elects corporate treatment on Form 8832 files Form 1120.
- An LLC that elects S status files Form 1120-S.
Confirm the entity's election before anything else.
Which businesses file a different return
- Form 1120-S: S corporations
- Form 1065: partnerships
- Form 1040 with Schedule C: many sole proprietors
- Form 990: qualifying tax-exempt organisations
Ownership structure matters for Australian groups. A U.S.-incorporated subsidiary of an Australian parent is a domestic corporation and generally files Form 1120.
An Australian company operating directly in the U.S. may need Form 1120-F. That return is generally required for U.S. trade or business activity, even without U.S.-source income or where a treaty exempts the income.
Filing the wrong return creates problems with filing, payment and disclosure, even when no tax is due. Check the latest IRS instructions for your tax year, and get advice if classification is unclear.
What Information and Schedules Are Included?
Page 1
The final 2025 form runs six pages before attachments. Page 1 covers:
- Corporation identification and tax year
- Total assets
- Income and deductions
- Taxable income, tax, refundable credits and payments
- Balance due or overpayment
- Signature and paid-preparer fields
Line numbers change between years, so always check them against the version for your tax year.
How income and deductions flow through
Income typically includes:
- Sales, returns and cost of goods sold
- Interest, dividends, rents and royalties
- Capital gains and other income
Deductions typically include:
- Compensation, wages and benefits
- Rent, professional fees and advertising
- Interest, depreciation and other allowable costs
Each figure should trace back to the ledger and to supporting invoices or payroll records.
Core schedules
| Schedule | Purpose |
|---|---|
| C | Dividends, inclusions and special deductions |
| J | Tax computation and payment |
| K | Other information |
| L | Balance sheets per books |
| M-1 | Book income reconciled with income per return |
| M-2 | Unappropriated retained earnings per books |
Balance sheet and reconciliation thresholds
Schedules L, M-1 and M-2 may be omitted only when both total receipts and year-end assets are below US$250,000 and Schedule K question 13 is answered Yes. Assets alone aren't enough.
Corporations with year-end assets of US$10 million or more generally file Schedule M-3 instead of M-1. Check the current instructions for the exceptions.
Additional forms and attachments
Attachments depend on the corporation's transactions, ownership and assets. No two returns necessarily carry the same set. Examples:
- Form 1125-A for cost of goods sold
- Form 1125-E for officer compensation, where total receipts are US$500,000 or more
- Form 4562 for depreciation and amortisation
- Form 8949, Schedule D and Form 4797 for capital and business property gains
- Form 8990 for business-interest limitation
- Form 5472 for foreign-owned corporations' related-party transactions
How to Prepare and File Form 1120
Gather the records
Start with this checklist:
- EIN confirmation, legal name, address and incorporation date
- Accounting method and the prior-year return
- Trial balance, profit and loss statement, balance sheet and general ledger
- Payroll records, invoices and receipts
- Loan records and fixed-asset schedules
- Estimated tax payment confirmations
- Shareholder, ownership and related-party details, including the Australian parent and any capitalisation or intercompany loans
Complete the return from the books
- Close the books for the tax year.
- Classify income and expenses.
- Calculate cost of goods sold where relevant.
- Identify book-to-tax adjustments.
- Review carryovers, losses and credits.
- Transfer supported totals to the form and schedules.
Then reconcile. Schedule L should agree with the general ledger, and retained earnings should tie to the financial statements.
Review common risk areas
- Wrong entity return or wrong tax year
- Missing initial or final return indicators
- Omitted schedules
- Misclassified expenses
- Unreported estimated payments
- Inconsistent balance-sheet figures
- Unreviewed officer compensation, related-party dealings, foreign ownership, credits and net operating losses
- Unreported changes in name, address, ownership or activity
Filing method and authorisation
E-filing is generally mandatory for corporations filing 10 or more returns of any type during the calendar year. That count aggregates income, employment, excise and information returns, not just corporate returns.
Paper returns go to an address set by the corporation's principal business location and its assets, and private couriers can't deliver to IRS P.O. boxes. Confirm the address in the current instructions.
An authorised officer, such as the president, treasurer or chief accounting officer, signs and dates the return. A paid preparer signs too and supplies a PTIN.
Keep the return and attachments. Supporting records are usually kept three years from the later of the due date or filing date, and property-basis records may need longer.
When professional support helps
Consider a qualified tax professional when you have:
- Foreign ownership or intercompany transactions
- Multiple states or complex credits
- Large book-to-tax differences
- A first or final return
- Uncertain entity classification
VJM Global supports Australian businesses with accounting and U.S. corporate tax compliance. Its team includes U.S.-trained CPAs and Indian Chartered Accountants with cross-border experience, and it has served 250+ Australian businesses. No adviser can promise a specific filing result.
Deadlines, Extensions, Penalties, and Related Filings
The filing and payment timeline
Treat three tasks separately: preparing the return, submitting it, and paying the tax.
- Calendar year: the 2025 return is due 15 April 2026, and a timely extension runs to 15 October 2026.
- Other fiscal years: due the 15th day of the fourth month after year-end, moved to the next business day if it falls on a weekend or holiday.
- June 30 year-end: due the 15th day of the third month.
- Estimated tax: instalments are generally required when expected tax is US$500 or more, due in the fourth, sixth, ninth and twelfth months.
Extensions and late filing risks
Form 7004 generally gives an automatic six-month filing extension if requested by the normal due date. The Form 7004 instructions state that an extension does not extend time to pay. Interest still runs on late tax.
Penalties under the 2025 instructions:
- Failure to file: generally 5% of unpaid tax per month or part-month, up to 25%
- Failure to pay: generally 0.5% per month or part-month, up to 25%
- Returns more than 60 days late: a minimum penalty applies (the smaller of US$525 or the tax due for returns filed in 2026)
Reasonable-cause relief may apply. Confirm current figures before relying on them.
Other obligations
Form 1120 covers only the US federal corporate income tax return. It does not satisfy:
- State corporate income or franchise tax
- Payroll tax, sales tax or information returns
- Foreign reporting requirements
- Australian tax and corporate filing obligations
Keep a compliance calendar that lists each obligation, the responsible person, the filing and payment dates, and any extension.
Form 1120 Considerations for Australian-Owned Businesses
U.S. subsidiary versus Australian company in the U.S.
An Australian group with a separately incorporated U.S. C corporation must meet that entity's Form 1120 obligations. Under Article 5 of the U.S.-Australia treaty, controlling a subsidiary doesn't by itself make either company the other's permanent establishment.
An Australian company operating directly in the U.S. may need Form 1120-F for U.S. trade or business activity or effectively connected income. Treaty-exempt income doesn't necessarily remove a filing duty, and a protective return can preserve deductions.
Permanent establishment analysis and state registrations still apply. No single rule covers every structure.
Cross-border records and transactions
Align the U.S. financial statements with the Australian parent's records for:
- Intercompany services, cost allocations and loans
- Royalties and dividends
- Ownership changes
- Foreign exchange treatment
Other U.S. filings may apply. Form 5472 is generally required where foreign ownership is 25% or more of voting power or value and there are reportable related-party transactions. The penalty for failing to file is US$25,000 per form, rising further for continued non-compliance after IRS notice.
FBAR reporting applies to corporations with foreign accounts aggregating over US$10,000.
Treaty withholding caps (subject to conditions) include:
- 5% on qualifying dividends
- 10% on most interest
- 5% on royalties
Coordinating U.S. and Australian advice
Review the U.S. return alongside Australian company tax, transfer pricing, withholding, GST and financial reporting. A U.S. subsidiary's income tax generally doesn't qualify as a foreign income tax offset against the parent's dividend income, so the two systems can't be treated as one.
Use advisers who work across both jurisdictions and document who is responsible for each filing, payment, record and tax position.
Frequently Asked Questions
What does page 1 of a tax return look like?
Form 1120's first page holds corporation details, income, deductions, taxable income, tax, credits and payments, plus signature fields. Use the current IRS form for exact lines.
How many pages are in Form 1120?
The final 2025 form has six pages before attachments and schedules. Check the count against your tax-year version.
Who is required to file Form 1120?
Domestic corporations, including LLCs electing corporate treatment, generally file unless exempt. Foreign corporations should assess Form 1120-F or another return.
Does a corporation have to file Form 1120 if it had no income or activity?
Generally yes. Domestic corporations file even without taxable income unless exempt or subject to a special-return rule.
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 that pass income and loss through to shareholders.
When is Form 1120 due and can the deadline be extended?
A calendar-year return is due 15 April, and fiscal years follow the IRS rules. Form 7004 may extend filing time by six months but not the time to pay.
This article is general information, not tax advice. Consult a qualified professional about your corporation's circumstances.
