What is Form 1120-S (S-Corp Annual Return)?
Form 1120-S is the annual federal income tax return for US S-corporations, due 15 March for calendar-year filers. The corporation does not pay federal income tax; instead, each shareholder receives a Schedule K-1 reporting their share of income, deductions and credits.
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Current Rate (Annual, calendar year)
N/A — informational return only
Example
Acme S-corp files Form 1120-S by 15 March 2025 reporting 2024 results. Each shareholder receives a K-1 to include on their personal Form 1040.
How Form 1120-S (S-Corp Annual Return) works in United States
Form 1120-S is the annual information return for S-corporations. Unlike Form 1120 (which reports and pays corporate income tax), Form 1120-S is informational — the S-corp pays no federal income tax. Instead, each shareholder's share of income, deductions, and credits is reported on a Schedule K-1, and shareholders report these items on their personal Form 1040.
**Filing deadline**
- Calendar-year S-corps: 15 March (the 15th day of the 3rd month after year-end) - This is one month EARLIER than the C-corp deadline, to give shareholders time to receive their K-1s and prepare personal returns - 6-month automatic extension via Form 7004 (to 15 September)
The extension covers the return only. If the S-corp owes built-in gains tax (from converting from a C-corp) or LIFO recapture, those taxes are due by the original deadline.
**Schedule K-1 distribution**
The company must furnish each shareholder's K-1 by the due date of the return (including extension). Shareholders cannot accurately file their personal Form 1040 until they receive their K-1. Late K-1s cascade into late personal returns — a reason many S-corp owners request personal return extensions.
**Late filing penalty**
$235 per month (or partial month) per shareholder, up to 12 months. A 5-shareholder S-corp filed 2 months late faces: $235 × 5 × 2 = $2,350 penalty.
**S-corp election timing**
To be treated as an S-corp for a given tax year, Form 2553 must be filed: - By the 15th day of the 3rd month of that tax year (March 15 for calendar year), OR - At any point during the preceding tax year
Late elections can be granted by the IRS for reasonable cause. A new company must file within 2 months and 15 days of formation to be effective for the year of formation.
**Shareholder basis tracking**
Shareholders must track their 'basis' in S-corp stock (starting basis + income allocations - loss allocations - distributions). Losses can only be deducted to the extent of basis. Distributions in excess of basis trigger capital gain. Tracking basis is the shareholder's responsibility — the 1120-S does not compute it.
Related terms
An S-corporation is a US entity that elects pass-through taxation under Subchapter S. The corporation itself pays no federal income tax; profits flow to shareholders' personal returns. Limited to 100 shareholders, all US individuals (or certain trusts), and one class of stock. Owner-employees must pay 'reasonable compensation' as W-2 wages subject to FICA.
Form 1120 is the annual federal income tax return for US C-corporations, due 15 April for calendar-year filers (15th day of the 4th month after fiscal year-end for fiscal-year filers). Six-month automatic extension available via Form 7004.
Form 1065 is the annual return for US partnerships and multi-member LLCs taxed as partnerships, due 15 March for calendar-year filers. The partnership does not pay federal income tax; profits flow to partners via Schedule K-1.
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