A Form 1120 return is mostly decided by a handful of answers: who owns the stock, what the books say at year end, what the officers were paid and what left the company as dividends. This list is grouped in the order the return needs them. It is written for tax year 2026 returns filed in 2027, although the current IRS instructions you will prepare against are still the 2025 edition until the 2026 ones appear.
Who sends itSent by the preparer to each C corporation client after year end, or in November for a calendar-year client when you want year-end planning answers early. Items marked optional apply only when the client has that activity.
Reviewed November 10, 2026 · 29 items
0 of 29 ticked
01Ownership, year end and filing facts
02Books and financial statements
03Officers, payroll and payments to others
04Assets, deductions and carryforwards
05Tax payments, extension and signature
What firms get wrong
Starting from a trial balance that was pulled before year-end adjustments, then discovering Schedule L does not agree with the books the client actually closed.
Skipping the 25% foreign-ownership question because the client looks domestic, which can leave Form 5472 unfiled on a company with a foreign investor.
Applying the $2,000 Form 1099-NEC threshold to payments made in 2025, or the old $600 threshold to payments made after December 31, 2025.
Treating Form 7004 as an extension to pay, so the balance goes unpaid and interest runs from the original due date.
Applying the 7-month extension for a June 30 year end to a fiscal year that begins in 2026, which gets 6 months.
Taking officer pay from the books alone instead of the payroll provider's year-end reports, so Form 1125-E disagrees with what was filed.
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Questions about this checklist
When is a calendar-year corporation's Form 1120 due?
Form 1120 is generally due by the 15th day of the 4th month after the tax year ends, which for calendar-year 2026 means April 2027. If that day falls on a weekend or legal holiday, the return can be filed the next business day. A fiscal year ending June 30 is due by the 15th day of the 3rd month.
How long is the extension for a June 30 fiscal-year corporation?
For tax years beginning before January 1, 2026, the automatic extension on Form 7004 is 7 months for a June 30 year end. For tax years beginning in 2026 it is 6 months, the same as for other corporations. Check the beginning date of the tax year, not the ending date.
Does the corporation still file if it had no income?
A corporation that exists generally has to file Form 1120 whether or not it had taxable income, so collect the same documents for a dormant client. Ask for the year-end bank statement, the stock ledger and the prior return, and get a yes or no on whether anything happened during the year.
Which Form 1099-NEC threshold applies on a tax year 2026 return?
The IRS states $600 for payments made through 2025 and $2,000 for payments made after December 31, 2025. A tax year 2025 return asks about 2025 payments at $600. For tax year 2026 payments the figure is $2,000, and the Form 1099-NEC filings for them are due in early 2027.
Can the client answer the ownership questions in the checklist?
Yes. In Usual, a yes or no answer can show or hide follow-up items, so a yes on foreign ownership can reveal the related-party payment request while a no hides it. The client opens a personal link without a password, and reminders stop when everything is in.