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Official form guide
Form 1120-SO: 1120 (Schedule O)
IRS Form 1120 Schedule O is the Consent Plan and Apportionment Schedule for a Controlled Group. It is used by component members of a controlled group to apportion the single 21% corporate tax rate benefit and other tax items. The form must be filed by each component member unless consolidated group rules apply.
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IRS Form 1120-SO - 1120 (Schedule O)
IRS Form 1120 Schedule O is the Consent Plan and Apportionment Schedule for a Controlled Group. It is used by component members of a controlled group to apportion the single 21% corporate tax rate benefit and other tax items. The form must be filed by each component member unless consolidated group rules apply.
Risk Radar
Scan points- 1Failing to file Schedule O when required can invalidate the apportionment plan and increase tax liability.
- 2Checking more than one box on line 3 (not allowed).
- 3Entering '0' in columns for an excluded member without notation '(E)'.
- 4Failing to include all component members in Part II.
- 5Using an outdated revision (pre-2018) that does not reflect the flat 21% rate.
Plain English
This form is used by corporations that are part of a controlled group to decide how to split the tax benefits among themselves. It helps them agree on how to use the flat 21% corporate tax rate. The form also records the apportionment plan and any changes to it.
Submission Date
- Filing date: 2018-12-10 22:00:09
- Preparation window: collect IDs, supporting records, and signatures in advance.
- Final review: verify names, dates, and required fields before submission.
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What this form is for
- Use this form when you are a component member of a controlled group and need to file a consent plan and apportionment schedule for apportioning tax-benefit items, attached to Form 1120, 1120-C, 1120-F, 1120-FSC, 1120-L, 1120-PC, 1120-REIT, or 1120-RIC.
- Do not use it when you are a subsidiary of a consolidated group that files a consolidated return; the common parent files one Schedule O on behalf of all members. Also do not use it if you are not a component member of a controlled group.
Form selector
Use this form or another form?
Situation: You are a component member of a controlled group filing Form 1120.
Why it matters: Schedule O must be attached to Form 1120 for controlled group apportionment.
✓ Check before you continue: Confirm you are not part of a consolidated group that files a single Schedule O.
Situation: You are a life insurance company in a controlled group.
Why it matters: Life insurance companies file Form 1120-L and attach Schedule O if applicable.
✓ Check before you continue: See instructions for life insurance controlled group rules.
Situation: You are amending an apportionment plan for a tax year beginning before 2018.
Why it matters: Use the 2012 revision of Schedule O for amendments of pre-2018 plans.
✓ Check before you continue: Ensure the tax year begins before January 1, 2018.
Situation: You are the common parent of a consolidated group.
Why it matters: File one Schedule O on behalf of all consolidated members.
✓ Check before you continue: No subsidiary should file its own Schedule O.
Likely form: Form 1120 (consolidated)
Situation: You are a foreign corporation filing Form 1120-F.
Why it matters: Schedule O attaches to Form 1120-F for controlled group members.
✓ Check before you continue: Verify you are a component member.
Deadline or filing window
Schedule O is filed with the corporation's income tax return. The due date is the same as Form 1120, generally the 15th day of the 4th month after the end of the tax year. Extensions for Form 1120 apply.
Checklist
What you need before filling it out
Field or section: Name of corporation
Document or info needed: Legal name as on tax return · Usually found in: Form 1120
Field or section: Employer identification number
Document or info needed: EIN · Usually found in: IRS correspondence
Field or section: Part I, line 1: Type of controlled group
Document or info needed: Check appropriate box (parent-subsidiary, brother-sister, combined, life insurance only) · Usually found in: Instructions for controlled group definitions
Field or section: Part I, line 2: Membership period
Document or info needed: Dates of membership during tax year · Usually found in: Corporate records
Field or section: Part I, line 3: Consent to adopt apportionment plan
Document or info needed: Effective date and signatures of all members · Usually found in: Signed agreement kept in records
Field or section: Apportionment methodology
Document or info needed: Description of percentages or method for each tax-benefit item · Usually found in: Apportionment plan document
Before you submit
- 1Verify the revision date on Schedule O is December 2018.
- 2Attach Schedule O to the correct income tax return (Form 1120, 1120-C, etc.).
- 3Check that you are a component member of a controlled group for the tax year.
- 4If part of a consolidated group, confirm the common parent is filing one Schedule O on behalf of all members.
- 5Ensure the apportionment plan agreement is signed and retained in records, not attached to the return.
- 6Complete Part I lines 1-3 accurately.
- 7Enter the correct EIN and name.
- 8If amending a pre-2018 plan, use the 2012 revision of Schedule O.
- 9Review the instructions for life insurance controlled group if applicable.
- 10Keep a copy of the filed Schedule O and the signed agreement for your records.
How to file this form
- 1Determine if you are a component member of a controlled group for the tax year.
- 2Obtain the current revision (December 2018) of Schedule O (Form 1120).
- 3Complete Part I: check the type of controlled group, indicate membership period, and consent to adopt or amend an apportionment plan.
- 4Ensure all other component members consent to the apportionment plan and sign the agreement (keep signed copy in records).
- 5Attach Schedule O to your income tax return (e.g., Form 1120) before filing.
- 6File the income tax return with the attached Schedule O by the due date (including extensions).
- 7Retain a copy of the filed return and the signed apportionment plan agreement as proof of filing.
Known limitations
- 1Exception: If all members of a parent-subsidiary controlled group join in filing the same consolidated tax return, the parent does not have to file Schedule O.
- 2Life insurance companies are treated as a separate controlled group; they are not included with non-life insurance companies in the same Schedule O.
- 3For tax years beginning before January 1, 2018, use the 2012 revision of Schedule O to amend an existing apportionment plan.
- 4If a corporation is sold during the year and is not a component member for the testing date, it should not be included in Schedule O (see example in instructions).
Field map
Compact field-by-field guide
Entity Info
2 items
Full legal name of the corporation and its Employer Identification Number.
Current mailing address and date of incorporation.
Income
3 items
Total revenue from business operations before deducting costs.
Direct costs attributable to producing goods sold by the corporation.
Gross receipts minus cost of goods sold and returns/allowances.
Deductions
1 items
Sum of all business expenses including compensation, rent, interest, taxes, and depreciation.
Tax
2 items
Total income minus total deductions.
Tax calculated on taxable income using the applicable corporate tax rate, minus any credits.
Signatures
1 items
An authorized corporate officer must sign and date the return.
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Fillable formOpen in Editor->The current edition is Revision December 2018. It was revised to reflect the flat 21% corporate tax rate and repeal of the corporate alternative minimum tax. For the latest information, see IRS.gov/Form1120.
What changed or needs a fresh check
- Edition date — confirm the revision is December 2018.
- Fee — not stated in the official source — verify on agency site.
- Mailing address — not stated in the official source — verify on agency site.
- Signature — confirm the apportionment plan agreement is signed and retained in records, not attached to the return.
- Attachments — confirm Schedule O is attached to the appropriate income tax return (e.g., Form 1120).
- Consolidated group — if part of a consolidated group, confirm the common parent files one Schedule O.
Quick Facts
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After you file
- 1Retain a copy of the filed Schedule O and the signed apportionment plan agreement.
- 2Keep the signed agreement as part of your records for at least as long as the statute of limitations for the tax year.
- 3If you need to amend the apportionment plan, use the appropriate revision of Schedule O (2012 for pre-2018 years, current revision for later years).
- 4If you discover an error in the filed Schedule O, file an amended return (e.g., Form 1120X) and attach a corrected Schedule O.
- 5Monitor IRS guidance for any changes to controlled group rules or Schedule O.
- 6If you are no longer a component member, ensure you do not file Schedule O in future years.
Sources
- SRCInstructions p.1 — Schedule O must be filed by each component member of a controlled group.
- SRCInstructions p.1 — Consolidated groups: common parent files one Schedule O on behalf of members.
- SRCInstructions p.1 — No member should attach the agreement to their return; keep signed copy in records.
- SRCInstructions p.1 — Use 2012 revision to amend pre-2018 apportionment plans.
- SRCForm p.1 — Schedule O attaches to Form 1120, 1120-C, 1120-F, 1120-FSC, 1120-L, 1120-PC, 1120-REIT, or 1120-RIC.
- SRCInstructions p.2 — Life insurance companies treated as separate controlled group.
- SRCInstructions p.3 — Example of corporation sold during year not included in Schedule O.
- SRCInstructions p.1 — Revision reflects flat 21% corporate tax rate and repeal of AMT.
- SRCNot stated in the official source — verify on the agency site: specific mailing address for filing Schedule O.
- SRCNot stated in the official source — verify on the agency site: fee for filing Schedule O.
Common confusion points
Confusion: Am I a component member?
Why it happens: Definitions of controlled groups can be complex.
→ Safe check: Review the definitions of parent-subsidiary, brother-sister, and combined controlled groups in the instructions.
Confusion: Can I attach the apportionment plan agreement to my return?
Why it happens: Some filers think the agreement must be filed.
→ Safe check: Instructions explicitly say no member should attach the agreement; keep it in records.
Confusion: Do I need to file a separate Schedule O for each subsidiary in a consolidated group?
Why it happens: Misunderstanding of consolidated filing rules.
→ Safe check: The common parent files one Schedule O on behalf of all members; subsidiaries do not file.
Confusion: What revision of Schedule O should I use for amending a plan from 2017?
Why it happens: Multiple revisions exist.
→ Safe check: Use the 2012 revision for tax years beginning before January 1, 2018.
Confusion: What if my controlled group has life insurance and non-life insurance companies?
Why it happens: Mixed groups are not treated as one.
→ Safe check: Life insurance companies are a separate controlled group; file separate Schedule O.
Confusion: Do I need to file Schedule O if the apportionment amounts haven't changed?
Why it happens: Assumption that no change means no filing.
→ Safe check: You must file every year you are a component member, even if unchanged.
Workflow map
Related forms and next steps
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Questions about IRS Form 1120-SO
What is IRS Form 1120-SO used for?
This form is used by corporations that are part of a controlled group to decide how to split the tax benefits among themselves. It helps them agree on how to use the flat 21% corporate tax rate. The form also records the apportionment plan and any changes to it.
Who must file IRS Form 1120-SO?
Any component member of a controlled group that is required to file a U.S. tax return must file Schedule O, unless all members join in filing a consolidated return. The common parent of a consolidated group files one Schedule O on behalf of all members.
What information does IRS Form 1120-SO require?
Part I collects information on the type of controlled group, member status, and any apportionment plan adoption, amendment, or termination. Part II reports the apportionment of tax benefits among component members, including EINs and tax year ending dates.
How do I complete IRS Form 1120-SO?
Complete Part I by checking the applicable box for type of controlled group and member status. If adopting, amending, or terminating a plan, complete line 3 and line 4. In Part II, enter the EIN and tax year ending date for the member filing and for other component members. Attach additional sheets if needed. Sign and file with the income tax return.
What happens if IRS Form 1120-SO is filed incorrectly?
Failure to properly file or adopt an apportionment plan may result in the inability to apportion tax benefits, potentially increasing tax liability. An apportionment plan cannot be adopted or amended unless at least one year remains in the statutory period for assessing a deficiency.
Confusion: Am I a component member?
Why it happens: Definitions of controlled groups can be complex. Safe check: Review the definitions of parent-subsidiary, brother-sister, and combined controlled groups in the instructions.
Confusion: Can I attach the apportionment plan agreement to my return?
Why it happens: Some filers think the agreement must be filed. Safe check: Instructions explicitly say no member should attach the agreement; keep it in records.
Confusion: Do I need to file a separate Schedule O for each subsidiary in a consolidated group?
Why it happens: Misunderstanding of consolidated filing rules. Safe check: The common parent files one Schedule O on behalf of all members; subsidiaries do not file.
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