Form 1120 Instructions 2026: Line by Line for C Corporations, the $250,000 Schedule K Test, the 21% Rate, and What OBBBA Changed

Form 1120, U.S. Corporation Income Tax Return, is the annual federal return every domestic C corporation files to report its income, deductions, and credits and to compute its tax at a flat 21%, whether or not it made money; it is due the 15th day of the 4th month after the tax year ends. For calendar-year corporations the 2025 return was due April 15, 2026, and extended returns are due Thursday, October 15, 2026. The 2026 return is due April 15, 2027. This guide maps the 2025 revision line by line, checked against the 2025 Instructions for Form 1120 and the form PDF on irs.gov in September 2026, from gross receipts on line 1a to the direct deposit fields new on line 37.

Key numbers (2025 Form 1120, filed in 2026):

Item	Figure	Source
Due date, calendar-year corporation	April 15, 2026; October 15, 2026 with Form 7004	IRC §6072(a); Instructions, When To File
June 30 fiscal year	15th day of the 3rd month (September 15) for years beginning before January 1, 2026	Instructions; T.D. 9821
Tax rate	21% of taxable income, Schedule J, line 1a	IRC §11(b)
Skip Schedules L, M-1, M-2	Schedule K, question 13: total receipts AND year-end total assets under $250,000	Form 1120, page 5
Schedule M-3 instead of M-1	Total assets of $10 million or more at year end	Instructions, Schedule M-3
Form 1125-E (officer pay detail)	Total receipts of $500,000 or more	Instructions, line 12
Estimated tax	Required when tax is $500 or more; due the 15th day of months 4, 6, 9, and 12; electronic funds transfer only	IRC §6655
Late-filing penalty	5% of unpaid tax per month, up to 25%; minimum is the smaller of the tax due or $525 once more than 60 days late (returns due in 2026)	IRC §6651
E-file mandate	10 or more returns of any type in the calendar year	Treasury Reg. §301.6011-5

Form 1120 reference card 2026: April 15 and October 15, 2026 due dates, 21% rate, $250,000 Schedule K question 13 test, $10 million Schedule M-3 threshold, $500,000 Form 1125-E threshold, $500 estimated tax trigger, $525 minimum late-filing penalty

Save this cheat sheet — key numbers in one image.

When Is Form 1120 Due?

Form 1120 is due by the 15th day of the 4th month after the corporation's tax year ends: April 15 for a calendar year, July 15 for a March 31 year end, January 15 for a September 30 year end. A Form 7004 filed by that date extends the return six months, to October 15 for calendar-year corporations, but it does not extend the time to pay. Tax still owed after April 15 accrues interest and the 0.5%-per-month failure-to-pay penalty.

One exception survives in the 2025 instructions: a June 30 year end files by September 15 (the 15th day of the 3rd month) with a seven-month extension to April 15. Under T.D. 9821 that ends for tax years beginning after December 31, 2025, so the year starting July 1, 2026 moves to the normal 4th-month date. The full calendar is in our C corporation tax deadlines guide.

Who Must File Form 1120?

Every domestic corporation that is not exempt under section 501 must file Form 1120 each year, including corporations in bankruptcy and corporations with no income, unless a special return applies. Three groups get here by different routes:

State-law corporations are C corporations by default, with no federal election needed
LLCs that filed Form 8832 to be taxed as a corporation file Form 1120 and attach a copy of the Form 8832 election for the year it takes effect
Former S corporations whose election was revoked or terminated file Form 1120 from the first C year onward

Special returns replace Form 1120 entirely: Form 1120-S after an accepted S election (see our Form 1120-S guide), 1120-F for foreign corporations, and separate forms for REITs, RICs, and homeowners associations. A corporation at least 25% foreign-owned answers "Yes" to Schedule K, question 7 and may owe a Form 5472 per related foreign party. A personal service corporation (health, law, accounting, consulting) checks item A, box 3, generally must use a calendar year, and pays the same flat 21%.

Which Schedules You Must Complete: Schedule K, Question 13

Schedule K, question 13 of the 2025 Form 1120 asks whether the corporation's total receipts and its total assets at the end of the year are both less than $250,000. "Total receipts" means page 1, line 1a plus lines 4 through 10. Answer "Yes" and the corporation does not complete Schedules L, M-1, or M-2; instead it enters the total cash distributions and the book value of property distributions made during the year on the question 13 line.

Form 1120 goes one schedule further than its S corporation sibling. On Form 1120-S, the $250,000 question (Schedule B, question 11) excuses only Schedules L and M-1, and M-2 still gets filled in. On Form 1120, a "Yes" also excuses M-2, the retained earnings analysis. Item D on page 1 (total assets from the books) is required either way.

The other size thresholds that decide your attachments:

Trigger	What it requires	Where the rule lives
Total receipts $500,000 or more	Form 1125-E, detailing each officer's pay, feeding line 12	Instructions, line 12
Total assets $10 million or more	Schedule M-3 instead of M-1; check item A, box 4	Instructions, Schedule M-3
$10 million of assets plus audited financial statements	Schedule UTP, uncertain tax positions (question 14)	Instructions, question 14
A person owns 20% directly or 50% of the vote	Schedule G (question 4)	Instructions, question 4
Member of a controlled group	Schedule O (question 28)	Form 1120, page 5
Any capital gain or loss	Schedule D (Form 1120), feeding line 8	Form 1120, line 8

Check Which Form 1120 Schedules Apply to Your Corporation

Interactive

Which Form 1120 schedules does your corporation need?

Enter total receipts, year-end total assets, and taxable income from line 30. The check answers Schedule K, question 13, picks Schedule M-1 or M-3, flags Form 1125-E, and applies the 21% rate.

Total receipts

Line 1a plus lines 4 through 10.

Total assets at year end

Item D, per the corporation's books.

Taxable income (line 30)

After the NOL and special deductions.

Schedule K, question 13

Schedules L, M-1, and M-2 required

Complete Schedules L, M-1, and M-2, and carry Schedule L, line 15, column (d) to item D.

(a) Total receipts under $250,000No ($1,208,000)

(b) Total assets under $250,000No ($650,000)

Book-to-tax reconciliationSchedule M-1

Form 1125-E for line 12 officer compensationRequired (receipts $500,000 or more)

Schedule J, line 1a income tax (21%)$16,800

2026 installments at this tax level (Apr 15, Jun 15, Sep 15, Dec 15)$4,200 each

A calendar-year corporation's fourth installment is due December 15, not January 15, and every installment must be paid by electronic funds transfer. Form 2220 figures the penalty for a short installment.

2025 Form 1120 and instructions, checked September 2026. Total receipts = page 1, line 1a plus lines 4 through 10. Tax shown is Schedule J, line 1a only (no credits, CAMT, or other taxes). Installments assume 2026 tax equals this amount; large corporations ($1 million or more of taxable income in any of the 3 prior years) cannot rely on the prior-year amount after the first installment.

See every 2026 C corporation deadline

Form 1120 Page 1: Income, Lines 1a Through 11

Line	What goes there	Notes from the 2025 instructions
1a / 1b / 1c	Gross receipts or sales, returns and allowances, balance	All business receipts, before cost of goods sold
2	Cost of goods sold	From Form 1125-A
3	Gross profit	Line 1c minus line 2
4	Dividends and inclusions	From Schedule C, line 23
5	Interest	Taxable interest; tax-exempt interest goes on Schedule K, question 9
6 / 7	Gross rents, gross royalties	Rental expenses are deducted on the deduction lines
8	Capital gain net income	From Schedule D (Form 1120); corporations pay 21% on gains too
9	Net gain or loss from Form 4797, Part II, line 17	Ordinary gains and losses on business property
10	Other income	Attach a statement; ordinary income from a partnership K-1 goes here
11	Total income	Add lines 3 through 10

Form 1120 Page 1: Deductions, Lines 12 Through 27

Line	Deduction	What to watch
12	Compensation of officers	From Form 1125-E when total receipts are $500,000 or more
13	Salaries and wages (less employment credits)	Non-officer employees; reduce by wage-based credits
14	Repairs and maintenance	Improvements are capitalized, not deducted
15	Bad debts	Only amounts previously included in income
16	Rents	Office, equipment, and vehicle leases
17	Taxes and licenses	Payroll taxes, state taxes, licenses; never federal income tax
18	Interest	Subject to the section 163(j) limit (Form 8990) above the small business threshold
19	Charitable contributions	Capped at 10% of taxable income, figured before this deduction; excess carries forward
20	Depreciation	From Form 4562, including any section 179 expense (unlike Form 1120-S, where section 179 passes through)
21 / 22	Depletion, advertising
23 / 24	Pension and profit-sharing plans; employee benefit programs	Health and welfare plans go on line 24
25	Energy efficient commercial buildings deduction	Attach Form 7205
26	Other deductions	Attach a statement: amortization, start-up costs, insurance, legal and professional fees, supplies, utilities, the deductible 50% of business meals
27	Total deductions	Add lines 12 through 26

Line 12 holds a founder's salary. Reasonable compensation is deductible and a dividend never is, so "salary" that is really a return on stock can be reclassified on audit. At Anna Money, where we served 60,000+ small businesses, the corporate balance sheet was the part owners dreaded most, usually because loans to and from founders had never been booked as loans; Schedule L, lines 7 and 19 are where those balances end up.

Lines 28 Through 37: NOL, Special Deductions, Tax, and Payments

Line	What goes there	Notes
28	Taxable income before NOL and special deductions	Line 11 minus line 27
29a	Net operating loss deduction	Post-2017 losses offset at most 80% of taxable income (IRC §172)
29b	Special deductions, Schedule C, line 24	Dividends-received deduction: 50% (under 20% owned), 65% (20% or more), 100% (affiliated group)
30	Taxable income	Line 28 minus line 29c
31	Total tax	Schedule J, line 12; line 1a there is line 30 × 21%
32	First installment of section 1062 tax	New for 2025: farmland sold to qualified farmers, tax paid over four years
33	Payments and credits	Schedule J, line 23: prior overpayment, estimates, Form 7004 deposit
34 / 35	Estimated tax penalty (Form 2220), amount owed	Pay through EFTPS or IRS.gov/Payments
36 / 37	Overpayment; credit to 2026 estimates (37a) or refund (37b)	Direct deposit fields on 37c–37e are new for 2025

Schedule J, line 3 is the corporate alternative minimum tax, which reaches only "applicable corporations" under section 59(k), a test built around $1 billion of average financial statement income. Credits, including the general business credit from Form 3800, sit on lines 5a through 5f.

Schedule K: The Yes/No Questions That Trigger Extra Forms

Schedule K runs 32 items across pages 4 and 5. These answers most often add a form:

Question	What it asks	Consequence of "Yes"
4a / 4b	An entity or individual owns 20% directly or 50% of the vote	Attach Schedule G
6	Dividends paid in excess of earnings and profits	File Form 5452
7	A foreign person owns 25% or more	Form 5472 for each reportable related party
13	Receipts and assets both under $250,000	Skip Schedules L, M-1, M-2
15a / 15b	Payments requiring Forms 1099, and were they filed	$600 threshold for 2025 payments; $2,000 for payments made after December 31, 2025
24	Pass-through excess interest, or average gross receipts over $31 million with business interest	Attach Form 8990
27	Received, sold, or exchanged a digital asset	Report the activity on the return
29	Corporate alternative minimum tax status	Form 4626 unless the safe harbor applies

What OBBBA Changed for Form 1120

The One Big Beautiful Bill Act (P.L. 119-21, signed July 4, 2025) changed several numbers that land on Form 1120, with different start dates:

Change	Effective for	Where it shows up
100% bonus depreciation made permanent	Property acquired after January 19, 2025	Line 20, through Form 4562
Domestic research and experimental costs deductible again under new section 174A	Tax years beginning after December 31, 2024; Rev. Proc. 2025-28 covers catch-up of 2022–2024 amounts	The lines where those costs sit (wages, supplies, contractors)
Section 163(j) adjusted taxable income adds back depreciation, amortization, and depletion	Tax years beginning after 2024	Line 18, through Form 8990
Corporate charitable deduction allowed only above 1% of taxable income, still capped at 10%	Tax years beginning after December 31, 2025	Line 19 of the 2026 return
Section 1062 installment election for farmland sales to farmers	Sales in tax years beginning after July 4, 2025	New line 32 and Schedule J, line 22b

The research change matters most to software companies: from 2022 through 2024, domestic research costs, engineer salaries included, were amortized over five years; for 2025 they are deductible currently, or over at least 60 months by election. OBBBA's larger QSBS exclusion never touches Form 1120, because the benefit belongs to the selling shareholder (QSBS guide).

Worked Example: A Calendar-Year Startup's 2025 Form 1120

Teodora owns most of Kestrel Analytics, Inc., a Delaware C corporation with calendar-year books, three shareholders, and a $40,000 NOL carryforward from its first two years. Its 2025 return, rounded:

Form 1120 line	Item	Amount
1a / 1c	Gross receipts	$1,200,000
2	Cost of goods sold (hosting and data costs, Form 1125-A)	$180,000
3	Gross profit	$1,020,000
5	Interest income	$8,000
11	Total income	$1,028,000
12	Compensation of officers (Form 1125-E attached)	$180,000
13	Salaries and wages	$420,000
16	Rents	$48,000
17	Taxes and licenses	$52,000
19	Charitable contributions	$5,000
20	Depreciation (laptops and servers at 100% bonus)	$30,000
22	Advertising	$40,000
24	Employee benefit programs	$36,000
26	Other deductions (software, insurance, legal, deductible meals)	$97,000
27	Total deductions	$908,000
28	Taxable income before NOL and special deductions	$120,000
29a	NOL deduction (under the 80% cap of $96,000)	$40,000
30	Taxable income	$80,000
31	Total tax (Schedule J, line 1a: $80,000 × 21%)	$16,800
33	Estimated tax payments (4 × $4,500)	$18,000
36 / 37a	Overpayment, credited to 2026 estimated tax	$1,200

The 2024 return showed no tax, so the prior-year exception was unavailable for 2025; $4,500 a quarter covered 100% of the $16,800 owed. The charitable deduction clears its cap: 10% of taxable income figured before the contribution ($120,000 + $5,000 − $40,000 NOL = $85,000) is $8,500. Under the 2026 rule, the same gift would be deductible only above 1% of that base, roughly $850.

Schedule K, question 13: total receipts of $1,208,000 (line 1a plus line 5) fail the $250,000 test, so Schedules L, M-1, and M-2 are required, and $650,000 of assets keeps it on M-1 rather than M-3. Question 4b is "Yes" (Teodora owns more than 20%), so Schedule G is attached.

Schedule M-1	Amount
1. Net income per books	$118,200
2. Federal income tax per books	$16,800
5c. Nondeductible half of meals	$3,000
8a. Tax depreciation above book depreciation ($30,000 − $12,000)	−$18,000
10. Income per return (must equal line 28)	$120,000

Schedule M-2 runs from a $60,000 accumulated deficit, plus $118,200 of book income, to $58,200, the figure on Schedule L, line 25. For 2026, the $16,800 of 2025 tax sets Kestrel's prior-year safe harbor: $4,200 on April 15, June 15, September 15, and December 15, 2026, with the $1,200 credit counted toward the first.

Extensions, Estimated Tax, E-Filing, and Penalties

Form 7004, filed by the original due date, extends the return six months (seven under the June 30 exception) but not the payment.

Estimated tax is required once the corporation expects $500 or more of tax, paid by electronic funds transfer on the 15th day of the 4th, 6th, 9th, and 12th months; a calendar-year corporation's fourth installment is due December 15. Under IRC §6655, paying the smaller of 100% of this year's tax or 100% of last year's (from a 12-month return that showed tax) avoids the Form 2220 penalty, but a large corporation, with $1 million or more of taxable income in any of the three prior years, may use last year's tax only for the first installment. Form 1120-W is the worksheet for figuring the installments and is never filed; the penalty runs at the IRS underpayment rate, 7% for the fourth quarter of 2026.

E-filing is mandatory once the corporation files 10 or more returns of any type in the calendar year, counting W-2s, 1099s, and Forms 941 and 940.

Penalties under IRC §6651 run 5% of unpaid tax per month late, up to 25%, with a minimum of the smaller of the tax due or $525 for returns due in 2026 filed more than 60 days late; late payment adds 0.5% a month. A corporation that owes nothing pays no failure-to-file penalty, unlike an S corporation under §6699. Reasonable cause can remove either penalty.

What Form 1120 Does NOT Do

It does not tax the shareholders. Dividends are reported to shareholders on Form 1099-DIV and taxed on their own returns; that second layer is the "double taxation" in our S corp vs C corp comparison.
It does not make or fix an S election. That is Form 2553; a corporation filing Form 1120 for a year it meant to be an S corporation needs late-election relief first.
It does not cover payroll. Officer and employee wages on lines 12 and 13 must also run through Forms 941 and W-2.
It does not file the state return. Most states want their own corporate return, often with a minimum tax, such as California's $800 on Form 100.

Common Form 1120 Mistakes

Deducting federal income tax on line 17. Federal income tax is never deductible; it appears only on Schedule M-1, line 2, as a book expense added back.
Recording dividends as a deduction. Distributions to shareholders belong on Schedule M-2, line 5 (and question 13 if the schedules are skipped), never on page 1.
Taking the full NOL. Post-2017 losses offset only 80% of line 28 income; a $150,000 carryforward against $120,000 of income allows $96,000, not $120,000.
Skipping Form 1125-E at $500,000 of receipts. The threshold counts line 1a plus lines 4 through 10, so interest and other income can push a company over it.
Still capitalizing domestic research costs. For 2025 returns, section 174A lets those costs be deducted currently; keeping the five-year amortization out of habit overstates taxable income.

Books That Tie to Schedule L: How Jupid Helps

Form 1120 is easy to fill in when payroll, founder loans, equipment, and income are already separated in the books, and slow when they arrive as one year-end spreadsheet. Jupid connects to the corporation's bank accounts and categorizes each transaction automatically at 95.9% accuracy, so officer pay, wages, depreciation-worthy purchases, and shareholder loans land in separate categories all year. Ask the AI accountant in WhatsApp or iMessage "what's our taxable income so far?" before the December 15 installment and the answer comes from the live ledger. Jupid does not prepare or file Form 1120; it keeps the numbers behind it clean. Try Jupid.

Action Checklist

If the 2025 return is on extension, file Form 1120 by Thursday, October 15, 2026, and pay any remaining balance through EFTPS.
Total line 1a plus lines 4 through 10 and year-end assets, then answer Schedule K, question 13; attach Form 1125-E if receipts are $500,000 or more.
Reconcile Schedule L to the general ledger, with founder loans on lines 7 and 19, and tie Schedule M-1, line 10 to page 1, line 28.
Deduct 2025 domestic research costs under section 174A and bonus-depreciate equipment acquired after January 19, 2025 on Form 4562.
Schedule the December 15, 2026 estimated tax installment by electronic funds transfer.

Sources

IRS: 2025 Instructions for Form 1120 (PDF)
IRS: Form 1120, U.S. Corporation Income Tax Return (2025 revision, PDF)
IRS: About Form 1120
IRS: Instructions for Form 8990 (Rev. December 2025): section 163(j) add-back for tax years beginning after 2024
IRS Publication 542, Corporations
IRS Publication 538, Accounting Periods and Methods
T.D. 9821, Return Due Date and Extended Due Date Changes (Federal Register, 2017): June 30 year-end exception through tax years beginning before 2026
IRC §11, Tax imposed on corporations
IRC §170, Charitable contributions
IRC §172, Net operating loss deduction
IRC §6072, Time for filing income tax returns
IRC §6651, Failure to file or pay
IRC §6655, Failure by corporation to pay estimated income tax
Treasury Regulation §301.6011-5, Required use of electronic form for corporate income tax returns

This guide is for general educational purposes and does not constitute tax, legal, or accounting advice. It describes the 2025 revision of Form 1120 and its instructions as posted on irs.gov and reviewed on September 24, 2026; line numbers, thresholds, and penalty amounts change between revisions, so confirm them against the instructions for the year you are filing. Consolidated groups, foreign-owned corporations, and corporations with net operating losses or research credits call for a tax professional. For advice specific to your situation, consult a qualified tax professional.