US business tax deadlines run on a recurring annual cycle keyed to your entity type and financial year end, not to fixed dates that change each year. Once you know your entity type, the pattern holds.
This guide sets out the return each entity files, when it is due, and the supporting forms that travel with it. Dates are given as the recurring rule, with the calendar-year equivalent in brackets.
A due date landing on a weekend or public holiday generally moves to the next business day.
The annual cycle by entity type
C Corporation
- Form: Form 1120, US Corporation Income Tax Return
- Purpose: report income, deductions, and credits, and compute the tax liability
- Taxability: tax is levied at entity level, with shareholders taxed again on dividend distributions
- Due: the 15th day of the fourth month after the year end (April 15 for calendar-year corporations)
- Extended: six months later (October 15 for calendar-year corporations)
S Corporation
- Form: Form 1120-S
- Purpose: report income, deductions, and credits, and pass through information to shareholders
- Taxability: no tax at entity level; shareholders pay
- Due: the 15th day of the third month after the year end (March 15 for calendar-year filers)
Partnership
- Form: Form 1065
- Purpose: report income, deductions, and credits, and furnish partner details
- Taxability: no tax at entity level; partners pay
- Due: the 15th day of the third month after the year end (March 15 for calendar-year filers)
Sole proprietor
- Form: Form 1040, Schedule C
- Purpose: report business income and expenses within the individual return
- Due: aligned with the individual return deadline (generally April 15)
Tax-exempt organization
- Forms: vary by size and activity, including Form 990-N, Form 990-EZ, and Form 990
- Purpose: report financial information and activities
- Due: Form 990 is generally due the 15th day of the fifth month after the fiscal year end
- Penalties: late filing penalties scale with gross receipts
Late filing or underpayment attracts penalties for every entity type above. Filing an extension extends the time to file, not the time to pay, so estimate and pay by the original due date.
Estimated tax through the year
Most businesses do not settle up once a year. Corporations and pass-through owners generally make quarterly estimated payments, due the 15th day of the fourth, sixth, and ninth months of the tax year and the first month after it ends.
For calendar-year filers that means April, June, and September, then January. Underpaying installments attracts an interest-based penalty even if the annual return is filed on time.
Information returns and the January cycle
Separately from your income tax return, information returns fall due early in the calendar year regardless of your fiscal year end.
- Form W-2, to employees and the Social Security Administration, due January 31
- Form 1099-NEC, to contractors and the IRS, due January 31
- Form 941, the quarterly payroll tax return, due the month after each quarter ends
- Form 940, annual federal unemployment tax, due January 31
Our US payroll guide for employers covers the deposit schedules that sit behind these returns.
Corporate forms that travel with Form 1120
C corporations rarely file Form 1120 alone. Which additional forms apply depends on what the business did during the year.
Income, gains, and asset disposals
- Form 4797: gains or losses on the sale or exchange of business property such as real estate or machinery, taxed differently from ordinary income
- Form 8949: sales and dispositions of capital assets such as stocks, bonds, or real estate, feeding into Schedule D
- Form 6252: installment sale income, letting you report gain across the life of the installment rather than all in one year
Credits and deductions
- Form 3800: general business credits
- Form 6765: credit for increasing research activities, the R&D credit
- Form 8993: the section 250 deduction for FDII and GILTI
Foreign operations and cross-border reporting
- Form 1118: foreign tax credit for corporations, offsetting foreign tax against US liability to avoid double taxation
- Form 5471: required where a US shareholder owns or controls a foreign corporation, disclosing ownership, income, and transactions under the CFC rules
- Form 5472: required where a US company is 25% or more foreign-owned or transacts with a foreign affiliate. The penalty is $25,000 per missed or incomplete form, with further penalties for failing to respond to IRS notices
- Form 8992: GILTI calculation
- Form 8833: treaty-based return position disclosure, where the corporation claims US tax treaty benefits
- Form 1120-F: return of a foreign corporation with US-source income
- Form 8938: reporting of specified foreign financial assets
The foreign reporting forms carry the steepest penalties on this list, and they apply whether or not any tax is owed. Failure to file is penalized on its own terms.
Changing your tax year
If your fiscal year end changes, every deadline above shifts with it. The mechanics are covered in our guide to Form 1128 and changing your business tax year.
Building your own filing calendar
Two things determine your entire calendar: your entity type and your financial year end. Fix those, apply the recurring rules above, then layer on the information returns and any state obligations.
State deadlines often mirror the federal ones but not always, and franchise tax filings such as Delaware franchise tax and Texas franchise tax run on their own dates entirely.
How FinStackk keeps you on schedule
FinStackk prepares and files corporate, pass-through, and information returns, handles foreign reporting forms, and tracks the deposit and estimated payment schedule alongside your books.
Talk to our team if you want your filing calendar mapped for the year ahead.
*The information provided on this article does not, and is not intended to, constitute legal advice; instead, all information and content provided here is for general informational purposes only. Confirm current-year dates with the IRS or your advisor, since deadlines shift for weekends, holidays, and relief measures.