Form 1120
In accounting, form 1120 means the federal income tax return of a domestic C corporation, filed every year whether or not it has taxable income — due the 15th day of the 4th month after year end, April 15 for a calendar year, with tax at 21% of taxable income under IRC §11(b).
Authority: IRS — Instructions for Form 1120 (opens in a new tab). Sources
The lessons that teach this
From the free founder back-office course, taught on one company's books, with exercises to work it yourself.
- Form 1120: the federal return, the extension and the 21% rateThe C corporation's federal return: due Apr 15, 2027 for a calendar year, 21% of taxable income, filed even in a loss year, and extended for filing only.10 min
- Foreign owners and beneficial ownership: Form 5472 and BOIForm 5472 for a corporation with a 25% foreign owner, and why a company created in the US files no BOI report under FinCEN's 2026 final rule.8 min
For founders
The same idea written for a founder: what it costs a startup that ignores it, and what to do in a real month.
- Form 1120: what to give your tax preparer, and whenWhat a startup hands its tax preparer for Form 1120: closed books, a balance sheet that ties to Schedule L, book-to-tax items, ownership and 1099s.
- Startup tax deadlines by month for a C-corpFederal tax deadlines for a calendar-year C-corp, month by month: W-2s, 1099s, Form 941, Form 1120, estimated taxes and Delaware franchise tax.
- Cash vs accrual accounting for startups, and the IRS ruleCash or accrual for a startup: why investors and auditors read accrual, when the IRS lets a C-corp file on cash, and the 2026 gross receipts limit.
What it is not called
Each of these means something else. Use one here and an accountant reading the product notices.
- the tax return unqualified
- Form 1120-S (an S corporation's)
Nearby in the catalog
No component names this concept outright. These sit in the same part of the system.
12Close, controls & consolidation
Family specAlso in Tax
Defined in Lexicon. This page is generated from that document, so the two can't disagree.