1. Form 1120 - US Corporation Income Tax Return
Every C-Corporation must file Form 1120, which reports income, deductions, and the final tax owed to the IRS.
It’s essentially the corporate version of an individual tax return.
If your company has requested an extension, your Form 1120 filing deadline is October 15.
2. Form 1118 - Foreign Tax Credit (Corporations)
If your C-Corp earns income from outside the US, you can claim a foreign tax credit using Form 1118.
This form helps avoid double taxation by offsetting taxes paid to foreign governments against US tax liability.
3. Form 4797 - Sale of Business Property
Sold or exchanged any business property during the year?
Form 4797 is required to report gains or losses from the sale of real estate, machinery, or other assets.
These are taxed differently from ordinary income, so correct reporting is essential.
4. Form 5471 - US Persons With Foreign Corporations
If a US shareholder owns or controls a foreign corporation, they must file Form 5471.
It discloses ownership details, income, and transactions to ensure compliance with Controlled Foreign Corporation (CFC) rules.
Failure to file can trigger steep penalties, so ensure this form is part of your filing checklist if your business owns or invests in entities abroad.
5. Form 5472 - Reporting for Foreign-Owned Corporations
Form 5472 applies if your US company is 25% or more foreign-owned or has transactions with a foreign affiliate.
The IRS uses it to track cross-border transactions and prevent tax evasion.
Penalty: $25,000 per missed or incomplete form, and additional penalties if you fail to respond to IRS notices.
6. Form 6252 - Installment Sale Income
If you sold assets and are receiving payments over time, you’ll need to file Form 6252.
It allows you to report income over the life of the installment instead of recognizing the entire gain in one year.
This can help spread your tax liability over multiple years.
7. Form 8833 - Treaty-Based Return Disclosure
Use Form 8833 if your C-Corporation claims benefits under a US tax treaty that reduce or modify US tax liability.
This ensures transparency with the IRS when applying international tax treaties.
8. Form 8949 - Sales and Dispositions of Capital Assets
If your company sold stocks, bonds, or real estate, report all such capital gains or losses on Form 8949.
The details then flow into Schedule D, forming the basis for capital gains tax calculation.
Other Common Corporate Tax Forms
In addition to the above, C-Corps often file several other forms alongside Form 1120:
- Form 3800 – Business Tax Credits (e.g., R&D, energy credits)
- Form 6765 – Credit for Increasing Research Activities (R&D Credit)
- Form 8992 – GILTI Calculation (Global Intangible Low-Taxed Income)
- Form 8993 – FDII & GILTI Deduction Computation (Sec. 250 deduction)
These forms are crucial for corporations with foreign operations, R&D activities, or intellectual property deductions.
Deadline Reminder - October 15 (If Extended)
All these C-Corp tax forms must be filed alongside Form 1120 by the October 15 extended deadline.
Corporate tax compliance can feel overwhelming, especially with multiple forms and foreign disclosures.
From Form 1120 to Form 5472, filing correctly ensures you avoid IRS penalties and take advantage of every available deduction or credit.
FinStackk helps C-Corporations simplify filing, prepare foreign reporting forms, and stay compliant before deadlines, so you can focus on running your business.