Form 1120 is the federal income tax return for C corporations, which pay tax on their own profits at a flat 21% rate. Form 1065 is the information return for partnerships and most multi-member LLCs, which pay no federal income tax themselves and instead pass income and losses through to their owners’ personal returns. The choice between Form 1120 vs. Form 1065 isn’t really a choice at all in most cases: it’s dictated by how your business is legally organized, and that single fact drives almost every other tax difference you’ll encounter.
Which Form Your Business Files
Any domestic C corporation files Form 1120. The corporation reports its income, gains, losses, deductions, and credits on the form, then calculates and pays its own federal income tax.1Internal Revenue Service. About Form 1120, U.S. Corporation Income Tax Return
Partnerships file Form 1065. That includes general partnerships, limited partnerships, and limited liability partnerships. Form 1065 is also the default return for any LLC with two or more members that hasn’t elected corporate tax treatment.2Internal Revenue Service. About Form 1065, U.S. Return of Partnership Income The partnership uses the form to report its financial results, then issues each partner a Schedule K-1 showing that partner’s share of income, deductions, and credits.
A multi-member LLC lands in Form 1065 territory automatically. Unless the LLC files Form 8832 to elect corporate treatment, the IRS classifies it as a partnership under the default entity classification rules.3Internal Revenue Service. Limited Liability Company – Possible Repercussions4Internal Revenue Service. About Form 8832, Entity Classification Election
One boundary worth naming: S corporations file neither of these. They use Form 1120-S, a separate return with pass-through mechanics closer to Form 1065 than to Form 1120.5Internal Revenue Service. About Form 1120-S, U.S. Income Tax Return for an S Corporation If your business is an S corp, neither 1120 nor 1065 applies.
Who Actually Pays the Tax
The most consequential difference between the two forms is whether the business itself owes federal income tax. A C corporation filing Form 1120 is a taxpayer in its own right. It calculates net taxable income, applies credits, and pays tax directly to the IRS. Under IRC Section 11, that tax is a flat 21% of taxable income, regardless of how much the corporation earns.6GovInfo. 26 USC 11 – Tax Imposed
A partnership or multi-member LLC filing Form 1065 pays zero federal income tax at the entity level. The form is purely informational. The partnership calculates its net income or loss, allocates the results among the partners according to the partnership agreement, and each partner’s allocated share (the “distributive share”) flows onto that partner’s personal return, taxed at the partner’s individual rate.2Internal Revenue Service. About Form 1065, U.S. Return of Partnership Income
One practical consequence catches first-time partners off guard: you owe tax on your distributive share whether or not the partnership actually distributes cash. If the partnership earns $200,000 and reinvests every dollar, the partners still report $200,000 of income and owe tax on it. This is often called phantom income.
Double Taxation Versus the 199A Deduction
The 21% corporate rate looks attractive next to the top individual rate of 37%, but there’s a catch. When a C corporation distributes after-tax profits to shareholders as dividends, those dividends get taxed again on the shareholders’ personal returns. This is the classic double taxation problem.
Qualified dividends receive preferential rates: 0%, 15%, or 20%, depending on the shareholder’s taxable income.7Internal Revenue Service. Topic No. 404, Dividends and Other Corporate Distributions For 2026, the 20% rate applies to taxable income above $545,500 for single filers and $613,700 for married couples filing jointly. High-income shareholders may also owe the 3.8% net investment income tax on dividends when modified adjusted gross income exceeds $200,000 (single) or $250,000 (joint).8Internal Revenue Service. Topic No. 559, Net Investment Income Tax In the worst case, a dollar of corporate profit gets hit with 21% at the corporate level, then up to 23.8% when it reaches the shareholder. The combined effective rate approaches 40%.
Partners and LLC members avoid double taxation entirely. They also get an advantage C corporation shareholders don’t share: Section 199A of the tax code lets owners of pass-through businesses deduct up to 20% of their qualified business income before calculating their personal income tax. A partner with $100,000 of qualified business income could deduct $20,000 and pay tax on only $80,000.9Office of the Law Revision Counsel. 26 USC 199A – Qualified Business Income The deduction was set to expire after 2025, but the One Big Beautiful Bill Act, signed into law on July 4, 2025, made it permanent.
The 199A deduction has limits. Above certain inflation-adjusted income thresholds, it phases down for owners of specified service businesses like law firms, medical practices, and consulting firms, and can be further limited based on wages paid or depreciable property held by the business.
How Owners Get Paid
C corporation owners who work in the business receive W-2 wages, just like any other employee. The corporation deducts those wages as a business expense, and both the corporation and the owner-employee pay their respective halves of FICA taxes: 7.65% each (6.2% Social Security plus 1.45% Medicare). Whatever profit remains after wages and other expenses gets taxed at 21%.
Partners and LLC members don’t receive W-2 wages for their share of the profits. The partnership reports each owner’s distributive share on Schedule K-1, and the owner reports that income on their personal Form 1040.10Internal Revenue Service. Topic No. 554, Self-Employment Tax General partners typically owe self-employment tax on their full share of ordinary partnership income, covering both halves of Social Security and Medicare themselves.11Social Security Administration. Contribution and Benefit Base Self-employment income above $200,000 (single) or $250,000 (joint) also triggers a 0.9% Additional Medicare Tax.12Internal Revenue Service. Topic No. 560, Additional Medicare Tax
Limited partners get a break. Under IRC Section 1402(a)(13), a limited partner’s distributive share is excluded from self-employment tax. Guaranteed payments for services are the exception: they’re always subject to self-employment tax, even for limited partners.13Internal Revenue Service. Self-Employment Tax and Partners
Guaranteed payments themselves deserve a word. Partnerships often pay them to partners who contribute regular services or capital. They function somewhat like a salary because they’re made regardless of whether the partnership turns a profit, and the partnership deducts them on Form 1065. But unlike W-2 wages, they appear on the partner’s Schedule K-1 (Box 4), are always ordinary income, and are always subject to self-employment tax. They don’t carry the character of the partnership’s underlying income, so a guaranteed payment is ordinary even if the partnership’s profits come entirely from capital gains.
What Happens With Losses
Loss treatment is one of the clearest practical differences. When a partnership reports a net loss, that loss flows through to the partners’ personal returns, where it can offset wages, investment income, and other taxable income. For a business burning cash in its early years, this can produce real tax savings immediately.
The deduction isn’t unlimited. A partner can only deduct losses up to the adjusted basis of their partnership interest. If your basis is $50,000 and your share of losses is $80,000, you use $50,000 this year and carry the remaining $30,000 forward until you have enough basis to absorb it.14Internal Revenue Service. New Limits on Partners Shares of Partnership Losses Frequently Asked Questions Passive activity rules and at-risk limitations can further restrict what you deduct if you’re not actively involved in the business.
C corporation losses stay trapped inside the corporation. A loss reduces the corporation’s taxable income for the current year or carries forward to offset future corporate profits under the net operating loss rules, but it never flows to shareholders. If you invest $100,000 in a C corporation and it loses money for three years, none of those losses appear on your personal return. You realize a loss for personal tax purposes only when you sell or abandon your stock.
Health Insurance and Fringe Benefits
C corporations have a meaningful advantage on fringe benefits, particularly health insurance. A C corporation can pay health insurance premiums for owner-employees and deduct 100% of the cost as a business expense. Under a formal health plan, the owner-employee receives the benefit tax-free: it’s not included in taxable wages.
Partners and LLC members don’t get the same treatment. Health insurance premiums paid by the partnership on behalf of a partner are treated as guaranteed payments and included in the partner’s taxable income on the K-1. The partner can claim an above-the-line deduction for health insurance premiums on their personal return, which offsets the income tax impact, but the premiums remain subject to self-employment tax. C corporation owner-employees save that self-employment tax on their health insurance premiums compared to partners receiving the same benefit.
Filing Deadlines and Penalties
The two forms have different due dates, and the reason is practical: partnerships file first so partners receive their K-1s in time to prepare their personal returns.
Form 1065 is due by the 15th day of the third month after the tax year ends. For calendar-year filers, that’s March 15. The partnership must furnish Schedule K-1s to all partners by the same date.15Internal Revenue Service. Instructions for Form 1065 – U.S. Return of Partnership Income The late-filing penalty is $220 per partner for each month (or partial month) the return is late, up to 12 months.16Internal Revenue Service. Information About Your Notice, Penalty and Interest For a five-partner LLC filing four months late, that’s $4,400, owed even though the partnership itself has no tax liability. Small partnerships get hit with this penalty regularly because the owners didn’t realize the information return had an earlier deadline than their personal returns.
Form 1120 is due by the 15th day of the fourth month after the tax year ends. For calendar-year corporations, that’s April 15. Corporations with fiscal years ending June 30 must file by the 15th day of the third month.17Internal Revenue Service. Instructions for Form 1120 The late-filing penalty is 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 is $525 or 100% of the unpaid tax, whichever is less.18Internal Revenue Service. Failure to File Penalty The Form 1120 penalty scales with tax owed; the Form 1065 penalty is a flat per-partner amount.
Both entities can request an automatic six-month extension by filing Form 7004, pushing the Form 1065 deadline to September 15 and the Form 1120 deadline to October 15 for calendar-year filers.19Internal Revenue Service. About Form 7004, Application for Automatic Extension of Time To File Certain Business Income Tax, Information, and Other Returns An extension gives you more time to file, not more time to pay. C corporations must still estimate and pay any tax owed by the original deadline to avoid interest and failure-to-pay charges, and corporations expecting to owe $500 or more must make quarterly estimated payments through the year.20Internal Revenue Service. Estimated Taxes Partnerships don’t make estimated payments at the entity level, but individual partners must cover the income tax and self-employment tax on their distributive shares through their own quarterly estimates.