Definition
What is IRS Form 1120?
Form 1120 is the US Corporate Income Tax Return. Filed annually by US C-Corporations to report income, deductions, gains, losses, and calculate corporate income tax (currently 21% federal). Foreign-owned US LLCs disregarded for US tax also file pro-forma Form 1120 + Form 5472.
Who files
Who must file?
- All US C-Corporations (active or inactive)
- S-Corporations file Form 1120-S
- Foreign-owned single-member LLCs file pro-forma Form 1120 + Form 5472
- Disregarded entities with foreign owners: pro-forma Form 1120
- Even entities with no income must file (zero return)
When due
When due.
- Calendar-year filers: 15 April
- Fiscal-year filers: 15th day of 4th month after FY end
- Extension: file Form 7004 for 6-month extension (still pay tax due by original deadline)
- Foreign-owned LLCs with no operations: same deadlines apply
What to report
What gets reported.
- Income (sales, services, rent, interest, royalties)
- Deductions (COGS, salaries, rent, depreciation, etc.)
- Taxable income → federal tax (21%)
- Tax credits (R&D, foreign tax credit, etc.)
- Estimated payments made (quarterly Form 1120-W)
- Schedule M-1/M-3 (book-tax reconciliation)
- Form 5472 attached if foreign-owned