If your business is a partnership or a multi-member LLC, you file Form 1065; if it’s a C-corporation, you file Form 1120. That’s the short answer to Form 1065 vs. Form 1120, and the split follows a single principle: a 1065 filer passes income through to its owners, who pay the tax on their personal returns, while a 1120 filer pays federal income tax itself, at a flat 21% rate, before any money reaches shareholders.1Internal Revenue Service. About Form 1120, U.S. Corporation Income Tax Return
Who Files Form 1065
Form 1065, the U.S. Return of Partnership Income, is required for any domestic partnership. That means any business with two or more owners that hasn’t elected to be taxed as a corporation.2Internal Revenue Service. About Form 1065, U.S. Return of Partnership Income General partnerships, limited partnerships, and limited liability partnerships all file here.
Multi-member LLCs file Form 1065 by default. Unless the LLC affirmatively files Form 8832 to elect corporate treatment, the IRS classifies any LLC with more than one member as a partnership.3Internal Revenue Service. Limited Liability Company – Possible Repercussions Single-member LLCs are different: they’re disregarded entities that report on the owner’s individual return and don’t file Form 1065 at all.
Form 1065 is an informational return. The partnership doesn’t owe federal income tax on it. The return reports the entity’s total income, deductions, gains, and losses, and those amounts flow through to each partner on a Schedule K-1, which the partner uses to complete their personal Form 1040.4Internal Revenue Service. Partnerships A partner is taxed on their full distributive share whether they actually took a distribution or left the money in the business, a detail that surprises new partners often.
Who Files Form 1120
Form 1120, the U.S. Corporation Income Tax Return, is for domestic corporations that haven’t elected S-corporation status. Any entity incorporated under state law that doesn’t file an S election is treated as a C-corporation by default.5Internal Revenue Service. Instructions for Form 1120 Entities that affirmatively elect corporate classification by filing Form 8832 also file Form 1120.6Internal Revenue Service. About Form 8832, Entity Classification Election
Form 1120 is not just informational. The corporation calculates its own taxable income and pays federal income tax directly to the IRS at a flat 21% rate on all taxable income, regardless of amount.1Internal Revenue Service. About Form 1120, U.S. Corporation Income Tax Return
Where the S-Corporation Fits
Neither 1065 nor 1120 is the right form for an S-corporation. S-corps file Form 1120-S. An S-corp is legally a corporation, but for tax purposes it behaves more like a partnership, passing income through to shareholders rather than paying corporate tax.7Internal Revenue Service. About Form 1120-S, U.S. Income Tax Return for an S Corporation
To elect S status, the entity must be domestic, have 100 or fewer shareholders (all individuals, certain trusts, or estates), have no nonresident alien shareholders, and issue only one class of stock. Certain banks, insurance companies, and international sales corporations can’t elect S status at all.8Internal Revenue Service. S Corporations The election is made by filing Form 2553 no later than two months and 15 days after the start of the tax year in which it takes effect. Miss that window or fail to qualify, and the corporation files Form 1120 as a C-corp until a valid election is made.
What the Choice Actually Costs You
The core difference between the two forms is who writes the check to the IRS, and that ripples through everything else.
With Form 1065, the entity reports income but pays no tax on it. Each owner’s allocated share of profit or loss flows to their personal Form 1040 through Schedule K-1, and they pay tax at their individual rate.4Internal Revenue Service. Partnerships For 2026, individual rates run from 10% up to a top rate of 37%, which applies above $640,600 for single filers and $768,700 for married couples filing jointly.9Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Pass-through owners may also claim the Section 199A qualified business income deduction, which reduces taxable income by up to 20% of qualified business income. The deduction was originally set to expire after 2025 and was extended by the One Big Beautiful Bill Act; it phases out for higher earners in certain service industries and is subject to wage and property limitations above specified thresholds.10Office of the Law Revision Counsel. 26 U.S. Code 199A – Qualified Business Income
Form 1120 flips the arrangement. The corporation pays 21% on its profits. When it distributes what’s left as dividends, shareholders pay tax again at the individual level. Qualified dividends are taxed at the long-term capital gains rates of 0%, 15%, or 20%, depending on the shareholder’s income.11Internal Revenue Service. Topic No. 404, Dividends and Other Corporate Distributions High-income shareholders also owe the 3.8% net investment income tax on top of the dividend rate.12Internal Revenue Service. Net Investment Income Tax For a top-bracket shareholder, the combined federal bite on a dollar of corporate profit reaches roughly 39.8%. That double taxation is the defining tradeoff of the C-corporation structure.
Self-Employment and Payroll Taxes
Employment tax works differently under each form. General partners and members of multi-member LLCs taxed as partnerships owe self-employment tax of 15.3% on their share of ordinary business income: 12.4% for Social Security (on earnings up to $184,500 in 2026) and 2.9% for Medicare on all earnings.13Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes)14Social Security Administration. Contribution and Benefit Base Earnings above $200,000 for single filers ($250,000 for joint filers) face an additional 0.9% Medicare surtax. Partners owe SE tax on their distributive share even when they don’t take a guaranteed payment or a draw.
Limited partners get a break. Under IRC 1402(a)(13), a limited partner’s distributive share is excluded from self-employment tax, and only guaranteed payments for services the limited partner actually performed are subject to SE tax.15Internal Revenue Service. Self-Employment Tax and Partners
C-corporation shareholders don’t pay self-employment tax on dividends. They do pay standard FICA on any W-2 salary drawn as employees of the corporation.
How Owners Take Money Out
How you pay yourself depends on which form you file.
In a partnership, working partners are typically paid through guaranteed payments, which function like a salary but are technically a partnership expense. The partnership deducts these on Form 1065, and they appear on the partner’s K-1 as taxable income subject to self-employment tax.16Internal Revenue Service. Partners Instructions for Schedule K-1 (Form 1065) Partners can also take draws, but a draw itself isn’t a separate income event; the partner is already taxed on their full distributive share.
In a C-corporation, a shareholder who works in the business must receive a W-2 salary, and the IRS requires that salary to be reasonable for the services actually performed.17Internal Revenue Service. S Corporation Employees, Shareholders and Corporate Officers Salary is deductible by the corporation and reduces its taxable income on Form 1120.18Internal Revenue Service. About Form W-2, Wage and Tax Statement After-tax profits distributed to shareholders come out as dividends, reported on Form 1099-DIV, and dividends are not deductible by the corporation.19Internal Revenue Service. About Form 1099-DIV, Dividends and Distributions
Fringe benefits tilt toward the C-corp side. Health insurance, group-term life insurance, and similar benefits can be provided tax-free to a C-corp shareholder-employee. Partners and LLC members taxed as partnerships face stricter rules: health insurance premiums paid by the partnership are included in the partner’s taxable income as guaranteed payments, though the partner can usually claim an above-the-line deduction to offset it.
What Happens When the Business Loses Money
Losses land in different places under each form, and the difference matters most in early years.
Under Form 1065, losses pass through to each partner’s personal return on the K-1, just like income. But a partner can only deduct losses up to their outside basis in the partnership, essentially invested capital plus allocated income minus distributions and previously claimed losses. At-risk rules and passive activity loss rules can restrict use further. Unusable losses carry forward until the partner has enough basis, at-risk amount, or active participation to absorb them. For 2026, individuals also face the excess business loss limitation: business losses beyond $256,000 for single filers or $512,000 for joint filers become a net operating loss carried forward to future years.
Under Form 1120, losses stay at the corporate level. A C-corp can carry a net operating loss forward indefinitely, but the deduction in any given year is capped at 80% of taxable income, so the corporation is always exposed to tax on the remaining 20%.20Office of the Law Revision Counsel. 26 USC 172 – Net Operating Loss Deduction Corporate losses don’t flow to shareholders. That’s a real disadvantage for early-stage businesses expecting several loss years, because pass-through owners can use those losses against their personal income while C-corp owners cannot.
Deadlines and Late-Filing Penalties
Form 1065 is due March 15 for calendar-year partnerships. Form 1120 is due April 15 for calendar-year corporations. Either entity can request an automatic six-month extension by filing Form 7004 before the original due date, but an extension only extends the filing deadline, not the payment deadline; any tax owed must still be paid by the original date.21Internal Revenue Service. Instructions for Form 7004
The penalty structures are different too. For returns due after December 31, 2025, a late Form 1065 costs $255 per partner for each month or partial month the return is late, up to 12 months.22Internal Revenue Service. Failure to File Penalty A five-partner partnership six months late owes $7,650, even though the partnership itself owes no income tax.
A late Form 1120 triggers a penalty of 5% of the unpaid tax for each month the return is late, up to 25%. If the return is more than 60 days late, the minimum penalty for returns required to be filed in 2026 is the lesser of the tax due or $525. A separate failure-to-pay penalty of 0.5% per month runs alongside.
Partners drawing K-1 income typically need to make quarterly estimated tax payments, since no employer is withholding on their behalf. Estimated payments are required for 2026 if you expect to owe at least $1,000 after withholding and credits, and your withholding won’t cover the smaller of 90% of your 2026 tax or 100% of your 2025 tax (110% if your 2025 AGI exceeded $150,000).23Internal Revenue Service. Estimated Tax for Individuals (Form 1040-ES) C-corporations have their own estimated tax obligations and generally must make quarterly deposits if they expect to owe $500 or more for the year.