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IRS Form 1120-S (S Corporation Return)

IRS Classification Code: 1120-S

Regulatory Mandate Analysis

Official IRS U.S. Income Tax Return for an S Corporation. S corporations use this form to report income, gains, losses, deductions, credits, and other items. The S corporation is a pass-through entity — each shareholder reports their share of corporate income on their individual returns.

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Execution Architecture Steps

IRS Form 1120-S – S Corporation Return Guide

S corporations must file Form 1120-S to report income, gains, losses, deductions, and credits for the tax year. The form includes Schedule K-1 for each shareholder.

Filing Deadline

Form 1120-S is due on the 15th day of the 3rd month after the end of the corporation's tax year (March 15 for calendar-year S corporations).

Key Requirements
  • Must have previously filed and received approval of Form 2553 (S Corp election).
  • Attach Schedule K-1 for each shareholder showing their pro-rata share of items.
  • Report built-in gains, passive investment income, and other required items on Schedule D.

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