What is IRS Tax Form 1120?

All domestic corporations are required to file Form 1120, even if they don't have any taxable income, unless they are eligible for exemption under IRS code Section 501. It includes:

• Farming corporations
• Corporations treated as such through Form 8832
• Domestic disregarded entities with foreign ownership (in some situations)
• Corporations with ownership interests in specific entities like FASITs. 

Several variations of Form 1120 apply to certain entities, like:

• 1120-C for cooperatives
• 1120-F for foreign corporations
• 1120-H, 1120-L, 1120-POL, and 1120-S for HOAs, life insurance companies, political organizations, and S corporations, respectively.