Independent form guide. BrieflyGo is not affiliated with or endorsed by IRS, USCIS, SSA, DOL, or any U.S. government agency. Official forms are sourced from public government websites.

IRSCorporate Tax (1120 Series)

Official form guide

Form 1120S23: IRS Form 1120S23

Form 1120S‑23 is the U.S. Income Tax Return for S corporations that have built‑in gains or excess passive income subject to the built‑in gains tax. File it with the IRS for the tax year in which the corporation meets those thresholds.

Fillable formOpen in Editor->

Need help with Form 1120S23?

Open it in the AI Editor for field guidance, checks, and PDF export.

Fillable formOpen in Editor->

Form Overview

IRS Form 1120S23 - 1120S23

Form 1120S‑23 is the U.S. Income Tax Return for S corporations that have built‑in gains or excess passive income subject to the built‑in gains tax. File it with the IRS for the tax year in which the corporation meets those thresholds.

The form captures total built‑in gains, passive income, tax credits, and the calculated built‑in gains tax.

Risk Radar

Scan points
  • 1A single mis‑calculated built‑in gain can generate a large penalty.
  • 2Mis‑identifying assets that trigger built‑in gains
  • 3Using incorrect fair‑market values
  • 4Omitting required Schedule K‑1 information
  • 5Failing to attach the Section 1374 worksheet

Plain English

If your S corporation owns assets that appreciated before you elected S status, the IRS may tax the built‑in gains. This form reports those gains and calculates the tax due. It’s only needed when the corporation triggers the built‑in gains rules.

Submission Date

  • Filing date: 2026-01-12 11:10:42
  • Preparation window: collect IDs, supporting records, and signatures in advance.
  • Final review: verify names, dates, and required fields before submission.

AI co-pilot

Fill it faster. Catch mistakes before you file.

Explains confusing fields in plain English
Flags missing signatures, dates, IDs, and attachments
Keeps the PDF ready for editor, send, and proof flows
Open AI workspace->

Glossary Terms

income taxincome

Hover a term to preview the meaning.

What this form is for

  • Use when the S corporation has built‑in gains or excess passive income.
  • Do not use for a regular S‑corp return without built‑in gains.
  • Check Form 1120S if the corporation has no built‑in gains.

Form selector

Use this form or another form?

No built‑in gains

Standard S‑corp return

✓ Verify no assets meet Section 1374 criteria

Form 1120S

Corporation dissolved during year

Close‑out filing

✓ Confirm dissolution date before using 1120S‑23

Final Form 1120S

Deadline or filing window

The return is due by the 15th day of the third month after the tax year ends (typically March 15 for calendar‑year filers). An automatic six‑month extension moves the deadline to September 15, but the extension must be filed using Form 7004 before the original due date.

  • —Total built‑in gains | Sum of asset appreciation | Taxable gain | Verify asset dates
  • —Excess passive income | Passive income – 25% of gross receipts | Taxable passive amount | Check for rounding errors

Checklist

What you need before filling it out

1

Built‑in gains amount

Asset acquisition records · Purchase invoices, prior tax returns

⚠ Often rounded incorrectly✕ High
2

Passive income total

Corporate income statement · Profit & loss statement

⚠ May double‑count dividends✕ Medium
3

Section 1374 worksheet

Completed worksheet · Internal calculations

⚠ Missing worksheet attachment✕ High
4

Signature authority

Officer’s appointment documents · Corporate bylaws

⚠ Unauthorized signer✕ High

Before you submit

  1. 1Use the 2024 edition of Form 1120S‑23
  2. 2All required schedules and worksheets attached
  3. 3Numbers match the corporation’s books
  4. 4Signature of an authorized officer present
  5. 5Taxpayer Identification Number (EIN) entered correctly
  6. 6Mailing address matches IRS instructions
  7. 7Electronic filing format approved if using MeF
  8. 8Payment (if any) included or EFTPS authorization submitted
  9. 9Copy retained for corporate records
  10. 10Confirmation of receipt (mail tracking or e‑file acknowledgment)

How to file this form

  1. 1Log in to the IRS e‑file portal and select Form 1120S‑23
  2. 2Enter corporate information and EIN
  3. 3Upload the completed Section 1374 worksheet
  4. 4Enter built‑in gains and passive income figures
  5. 5Review calculated tax and any credits
  6. 6Attach required schedules (K‑1, etc.)
  7. 7Sign electronically or print, sign, and mail

Known limitations

  1. 1IRS instructions do not provide a built‑in gains calculator; manual computation required
  2. 2Electronic filing is limited to corporations with a valid e‑file PIN
  3. 3The form does not accept extensions for built‑in gains tax alone; the entire return must be extended
  4. 4No automatic error checking for asset valuation mismatches

Field map

Compact field-by-field guide

9 fields

Entity Info

2 items

Corporation Name and EIN

Full legal name of the corporation and its Employer Identification Number.

Requiredtext
Address and Date Incorporated

Current mailing address and date of incorporation.

Requiredtext

Income

3 items

Gross Receipts or Sales

Total revenue from business operations before deducting costs.

Requiredamount
Cost of Goods Sold

Direct costs attributable to producing goods sold by the corporation.

amount
Total Income

Gross receipts minus cost of goods sold and returns/allowances.

Requiredamount

Deductions

1 items

Total Deductions

Sum of all business expenses including compensation, rent, interest, taxes, and depreciation.

Requiredamount

Tax

2 items

Taxable Income

Total income minus total deductions.

Requiredamount
Total Tax

Tax calculated on taxable income using the applicable corporate tax rate, minus any credits.

Requiredamount

Signatures

1 items

Officer Signature

An authorized corporate officer must sign and date the return.

Requiredsignature
This compact map shows typical fields for this form type. The AI Editor gives precise field guidance after you open the PDF.

Almost done reviewing the fields?

Fillable formOpen in Editor->
Current form status
IRS

Form 1120S‑23 is currently in its 2024 edition. The IRS has not announced any upcoming changes for the 2025 filing year.

What changed or needs a fresh check

  • Edition date – verify the form is the 2024 version
  • Fee – no filing fee for Form 1120S‑23
  • Mailing address – use the address in the 2024 instructions
  • Electronic filing eligibility – confirm MeF acceptance for the tax year
  • Signature line – ensure an authorized officer signs

Form Preview

Form 1120S23 page 1

Page 1

Form 1120S23 page 2

Page 2

Open in AI Editor →

Quick Facts

S corporations that have built‑in gains or excess passive income must file.
The form captures total built‑in gains, passive income, tax credits, and the calculated built‑in gains tax.
File by the original due date of the S‑corp return (generally March 15) or by the extended deadline if an extension was filed.
Mail the completed form to the IRS Service Center listed in the instructions, or file electronically through the IRS Modernized e‑File (MeF) system if approved.
Errors can cause underpayment penalties, interest, or a delayed refund, and may trigger an audit of the corporation’s built‑in gains calculations.
1. Gather the corporation’s balance sheet, asset acquisition dates, and fair‑market values. 2. Compute built‑in gains using Schedule K‑1 data and the Section 1374 worksheet. 3. Fill out Form 1120S‑23 line‑by‑line, attaching the worksheet and any credit forms. 4. Review totals, sign, and submit electronically or by mail.

Downloads

Blank Form 1120S23↗Instructions↗

Fill Form 1120S23

AI-powered guidance for every field

Fillable formOpen in Editor->

Free to start / No account required

After you file

  1. 1Save the acknowledgment receipt or certified mail proof
  2. 2Store the signed return and worksheets in corporate records for at least seven years
  3. 3Monitor the IRS account for any notices about the built‑in gains tax
  4. 4If tax is owed, confirm payment cleared via EFTPS
  5. 5Update the corporation’s asset schedule to reflect the built‑in gains reported
  6. 6Review next year’s asset holdings to determine if another Form 1120S‑23 will be needed

Sources

  • SRCIRS Instructions for Form 1120S‑232024 edition
  • SRCIRS Publication 542Corporations
  • SRCSection 1374 of the Internal Revenue Code
  • SRCIRS Modernized e‑File (MeF) eligibility list
  • SRCForm 7004 instructionsextension rules
  • SRCIRS Schedule K‑1 (Form 1120S) guidance
  • SRCEFTPS user manualpayment procedures

Common confusion points

Built‑in gains vs. ordinary gains

Many think all appreciation is taxed

→ Verify Section 1374 applicability

Passive income threshold

25% of gross receipts can be mis‑calculated

→ Re‑calculate using total gross receipts

Form number

Some users look for Form 1120‑S instead

→ Confirm the “‑23” suffix for built‑in gains

Electronic vs. paper filing

Not all corporations are MeF‑eligible

→ Check eligibility before e‑filing

Extension filing

Filing Form 7004 extends the whole return, not just the built‑in gains portion

→ File Form 7004 by original due date

Workflow map

Related forms and next steps

4 signals

Before

Form 7004 – Request for Extension of Time to File

Current

1120S23

After

Form 2210 – Underpayment of Estimated Tax (if tax due)

Often used with

Schedule K‑1 (Form 1120S) – Shareholder’s Share of Income

⚠ If something goes wrong

  • Form 843 – Claim for Refund or Credit

Ready to get started?

Upload the form or open it in the AI Editor for intelligent guidance

Fillable formOpen in Editor->

Source transparency

Copyright & Licensing - US Government Forms

Independent guide

BrieflyGo links to and explains official public form sources. We are not a government agency, and this page is for general form guidance, not legal advice.

Public DomainCreated by the U.S. federal government. Not subject to copyright (17 USC § 105). Freely copyable without restriction.
Public DomainCreated by the U.S. federal government. Not subject to copyright (17 USC § 105). Freely copyable without restriction.
Public DomainCreated by the U.S. federal government. Not subject to copyright (17 USC § 105). Freely copyable without restriction.
Public DomainCreated by the U.S. federal government. Not subject to copyright (17 USC § 105). Freely copyable without restriction.
Verify current license terms with the source agency before reuse outside this platform.

Never sign without understanding every clause.

BrieflyGo reviews your contracts in plain English — instantly.

Try for free →