Federal Tax Returns by Entity Type: Form 1120, 1120-S, 1065, and Schedule C

Which Return Your Entity Files

The federal tax return your business files depends on its FEDERAL TAX CLASSIFICATION, not on its state-law form. An LLC under state law can be taxed as a sole proprietorship (disregarded), partnership, S-corp, or C-corp. The classification determines the return.

Disregarded entity (single-member LLC default): files Schedule C as part of the owner's Form 1040. No separate entity-level return.

Partnership (multi-member LLC default): files Form 1065. Each partner receives a Schedule K-1 reporting their share of income.

S-corporation (entity that filed Form 2553): files Form 1120-S. Each shareholder receives a Schedule K-1.

C-corporation (corporation default; LLC that filed Form 8832 electing C-corp): files Form 1120. The entity pays corporate tax (21% federal). Distributions to shareholders are taxed again as dividends (double taxation).

Form 1120 (C-Corporation)

At a Glance

Item	Value
C-Corporation	Form 1120, April 15 deadline
S-Corporation	Form 1120-S, March 15 deadline
Partnership	Form 1065, March 15 deadline
Sole Proprietor	Schedule C (on Form 1040), April 15 deadline
Extension	Form 7004 (entities) or 4868 (individuals), 6 months

Form 1120 is the US Corporation Income Tax Return. Filed by C-corporations and by LLCs that elected C-corp treatment via Form 8832.

Deadline: April 15 for calendar-year entities (15th day of the 4th month after fiscal year end). Fiscal-year C-corps file by the 15th of the 4th month after their fiscal year ends.

Tax rate: 21% federal flat rate on net income.

Extensions: Form 7004 extends the filing deadline 6 months to October 15. The extension does NOT extend the time to PAY, estimated tax must be paid by April 15 to avoid late-payment penalties.

Key schedules: Schedule J (tax computation), Schedule K (other information), Schedule L (balance sheet), Schedule M-1 (reconciliation of income), Schedule M-2 (analysis of unappropriated retained earnings).

Foreign-owned C-corp considerations: Form 5472 is required if any 25%+ shareholder is a foreign person. This is in addition to Form 1120.

Form 1120-S (S-Corporation)

Form 1120-S is the US Income Tax Return for an S Corporation. Filed by S-corporations and by entities that elected S-corp treatment via Form 2553.

Deadline: March 15 for calendar-year entities (15th day of the 3rd month after fiscal year end). This is one month EARLIER than the C-corp 1120 deadline.

Tax flow: the S-corp itself generally does not pay federal income tax. Net income flows to shareholders via Schedule K-1, taxed on their personal returns.

Reasonable salary requirement: S-corp owners who work in the business must pay themselves a reasonable salary via W-2 payroll BEFORE taking distributions. The 1120-S reports wages and distributions separately.

Built-in gains tax: S-corps that were previously C-corps may owe built-in gains tax on appreciated assets held at the time of conversion.

Extensions: Form 7004 extends the filing deadline 6 months to September 15.

Late-filing penalty: $235 per shareholder per month (capped at 12 months), even with no tax owed. For a 4-shareholder S-corp filing 3 months late, the penalty is $235 × 4 × 3 = $2,820.

Form 1065 (Partnership)

Form 1065 is the US Return of Partnership Income. Filed by general partnerships, limited partnerships, limited liability partnerships, and multi-member LLCs taxed as partnerships.

Deadline: March 15 for calendar-year entities (same as 1120-S, one month earlier than 1120).

Tax flow: the partnership itself does not pay federal income tax. Net income flows to partners via Schedule K-1, taxed on their personal returns.

Schedule K-1 issuance: each partner receives a K-1 reporting their share of income, deductions, credits, and other items. K-1s must be furnished to partners by March 15 (along with the 1065 filing).

Extensions: Form 7004 extends the filing deadline 6 months to September 15.

Late-filing penalty: $235 per partner per month (capped at 12 months). Same structure as the S-corp penalty.

Self-employment tax: partnership income flowing to general partners is subject to self-employment tax (15.3%). This is one of the reasons many partnerships convert to S-corps once profitable.

Schedule C (Sole Proprietor / Disregarded SMLLC)

Schedule C is filed as part of the owner's personal Form 1040. It reports the income and expenses of a sole proprietorship or a disregarded single-member LLC.

Deadline: April 15 (the personal Form 1040 deadline) for calendar-year activity.

Tax flow: net Schedule C income is added to the owner's other personal income and taxed at personal rates. Net income is also subject to self-employment tax (15.3% on the first $176,100 in 2025, 2.9% Medicare-only above that).

Extensions: Form 4868 extends the personal return filing deadline 6 months to October 15.

Common Schedule C deductions: home office (Form 8829), vehicle expenses, depreciation (Form 4562), and the qualified business income deduction (Form 8995 or 8995-A).

No separate return for the SMLLC: a single-member LLC that has not elected corporate treatment files everything on the owner's Form 1040. The LLC has no federal filing requirement of its own.

Foreign-Owned SMLLC: Special Case

A US single-member LLC owned by a foreign person is a disregarded entity for federal tax purposes, but Form 5472 + proforma Form 1120 are still required EVERY YEAR. This is the rule that catches many foreign founders by surprise.

The proforma Form 1120 is NOT a tax return in the normal sense. All income lines are zero. It exists solely to serve as a vehicle for Form 5472, which reports related-party transactions with the foreign owner.

The foreign owner's actual income from the SMLLC is reported on the owner's home-country tax return (and possibly on Form 1040-NR if US tax obligations exist). The proforma 1120 does not report income, only the existence of the entity.

Penalties for missing Form 5472: $25,000 per form per year. We cover this in detail in our Form 5472 article.

How Extensions Work

Form 7004: extends the deadline for entity returns (1120, 1120-S, 1065) by 6 months. Filed by the original due date. No reason required.

Form 4868: extends the deadline for personal returns (Form 1040, including Schedule C) by 6 months. Filed by the original due date.

Critical: extensions extend TIME TO FILE, not TIME TO PAY. Estimated tax due must be paid by the original deadline. Late-payment penalties accrue from the original due date even with an extension.

Failure-to-file penalty: 5% of unpaid tax per month, up to 25%. Filing an extension avoids this.

Failure-to-pay penalty: 0.5% of unpaid tax per month, up to 25%. Cannot be avoided by extension, only by paying.

Common Federal Return Mistakes

Mistake 1: Missing the March 15 deadline for 1120-S and 1065. This is one month earlier than the April 15 1040 deadline that most people remember. Missing it triggers the $235-per-shareholder/partner-per-month penalty.

Mistake 2: Not issuing K-1s by the partnership/S-corp filing date. K-1s must be in partners' hands so they can complete their personal returns. Late K-1s force partners to extend their personal returns.

Mistake 3: Confusing extension to file with extension to pay. The IRS does not care about your filing extension if you owed tax and did not pay by the original deadline.

Mistake 4: Foreign-owned SMLLC owners filing nothing because "disregarded entity has no return." Wrong, Form 5472 + proforma 1120 are required every year.

Mistake 5: S-corp with $0 reasonable salary and large distributions. The IRS audits this pattern. Reasonable salary first, then distributions.

How File.Business Handles Federal Returns

File.Business partners with CPAs to handle federal tax return preparation for our entity-formation and ongoing-compliance clients. We coordinate the data collection (financial statements, expense receipts, K-1s from any entities the client owns), the CPA prepares the appropriate return (1120, 1120-S, 1065, or Schedule C), and we ensure timely filing with the IRS.

For foreign-owned SMLLCs: we handle Form 5472 + proforma Form 1120 directly (not delegated to a CPA partner), since these are entity-existence filings rather than income returns.

Pricing: federal tax return preparation is priced by complexity (number of K-1s, number of states, foreign income, etc.). Starting prices: $549 for Schedule C, $899 for 1065 or 1120-S, $1,299 for 1120. Foreign-owned SMLLC Form 5472 + proforma 1120: $399 (covered separately).

Frequently Asked Questions

What federal tax return does my LLC file?

Depends on the LLC's federal tax classification. Single-member LLC default: Schedule C on the owner's 1040. Multi-member LLC default: Form 1065. LLC that elected S-corp: Form 1120-S. LLC that elected C-corp: Form 1120.

When are Form 1065 and Form 1120-S due?

March 15 for calendar-year entities (one month earlier than the April 15 personal Form 1040 deadline). Extensions to September 15 are available via Form 7004.

When is Form 1120 due?

April 15 for calendar-year entities. Extensions to October 15 are available via Form 7004.

Does an extension also extend the time to pay tax?

No. Form 7004 and Form 4868 extend the time to FILE only. Estimated tax must be paid by the original deadline to avoid late-payment penalties. Late-payment penalty is 0.5% per month, up to 25%.

What is the penalty for late-filing Form 1120-S or 1065?

$235 per shareholder/partner per month, capped at 12 months. For a 4-shareholder S-corp filing 3 months late: $2,820 even if no tax is owed.

Does a foreign-owned single-member LLC have to file a federal return?

Yes. Form 5472 + proforma Form 1120 are required every year. This is true even if the LLC has no US source income or business activity. Penalty for missing: $25,000 per form per year.

Can File.Business prepare my federal tax return?

Yes. We partner with CPAs to prepare federal returns for our clients. Starting prices: $549 for Schedule C, $899 for 1065/1120-S, $1,299 for 1120. Foreign-owned SMLLC Form 5472 + proforma 1120: $399.