What IRS Form 1120 (2017) Is For

Form 1120 is the U.S. Corporation Income Tax Return that C corporations file annually to report income, deductions, gains, losses, and credits for federal tax purposes (IRS Instructions for Form 1120 (2017)). Unlike individuals, corporations pay tax directly, so the form is used to calculate and report corporate tax liability. All domestic corporations, including those in bankruptcy, must file unless they qualify for a special return (like Form 1120-S for S corporations) or are exempt under section 501.

When You’d Use Form 1120 for 2017 (Late or Amended Filing)

You would file a late 2017 Form 1120 if you missed the original due date of April 17, 2018 (for calendar-year filers) or if you received IRS notices regarding an unfiled return. Amended filings are required when errors are discovered in reported income, deductions, credits, or partner allocations.

For refund claims, you generally had until April 2021 (three years from the original due date) or two years from the date tax was paid, whichever is later. However, if no return was filed, the IRS can assess tax indefinitely, making late filing important even if refunds are no longer available.

Key Rules Specific to 2017

• Tax rates: The maximum corporate tax rate was 35% under graduated brackets for tax years beginning before 2018.
  
  
• Blended rate requirement: Fiscal-year corporations spanning 2017–2018 had to calculate tax using a blended rate—35% for the portion of the year before January 1, 2018, and 21% for the portion after.
  
  
• Net Operating Losses (NOLs): For 2017, NOLs could be carried back two years and forward twenty years. Later law changes eliminated carrybacks for most years.
  
  
• Penalty structure: The minimum late-filing penalty for returns filed more than 60 days late was $210 or the tax due, whichever was smaller.
  
  
• Schedules: Corporations with assets of $10 million or more had to file Schedule M-3; smaller corporations generally filed Schedule M-1 and Schedule M-2.
  
  

Step-by-Step (High Level)

1. Gather records and transcripts: Use Form 4506-T or IRS online services to obtain 2017 account transcripts.
   
   
2. Use the correct-year form: Complete the 2017 Form 1120—not current versions, as tax law and line items differ.
   
   
3. Attach required schedules: Include Schedule M-1, Schedule M-2, Schedule D (capital gains/losses), and any applicable supporting forms.
   
   
4. Amendments: Use Form 1120X for corrections to an already filed return and explain all changes.
   
   
5. Submit to IRS: Mail to the correct IRS service center based on your location (e-filing is generally not available for very late returns).
   
   
6. Keep records: Maintain copies of the filed return, proof of mailing, and supporting documents for at least three years.
   
   

Common Mistakes and How to Avoid Them

• Wrong-year forms: Always use the 2017 form and instructions, as tax rates and rules changed after the Tax Cuts and Jobs Act.
  
  
• Ignoring blended tax rates: Fiscal-year filers must prorate tax between pre-2018 (35%) and post-2017 (21%).
  
  
• Schedule M-1 errors: Many filers omit or misreport the reconciliation of book and tax income.
  
  
• NOL reporting issues: Ensure carrybacks and carryforwards are properly calculated and reflected on Schedule K.
  
  
• Unsigned returns: A corporate officer must sign the return; unsigned filings are invalid.
  
  
• Incomplete documentation: Missing schedules or attachments can delay processing and trigger IRS correspondence.
  
  

What Happens After You File

• Processing: Paper returns typically take 6–8 weeks, but late or amended returns may take longer.
  
  
• IRS notices: You may receive confirmation, balance due statements, or requests for clarification.
  
  
• Penalties: Failure-to-file (5% per month, up to 25%) and failure-to-pay (0.5% per month, up to 25%) penalties accrue from the original April 2018 due date.
  
  
• Payment options: Use Form 9465 to request an installment plan if you cannot pay in full.
  
  
• Appeal rights: If you disagree with IRS adjustments, you may appeal through the IRS Office of Appeals.
  
  

FAQs

Can I still file my 2017 Form 1120 if I never filed?

Yes. There is no statute of limitations on unfiled returns—the IRS can assess tax indefinitely until a return is filed.

What penalties apply to a late 2017 Form 1120?

Failure-to-file penalties are 5% of unpaid tax per month (up to 25%), plus 0.5% per month for failure to pay, plus interest (IRS Instructions for Form 1120 (2017)).

How do I get 2017 transcripts?

Request via IRS Form 4506-T, through IRS.gov, or by calling the IRS business line. Processing typically takes 2–6 weeks.

Can I still claim a refund for 2017?

Generally no—the refund deadline was April 2021. Exceptions may apply if tax was paid late or under special provisions.

Do I need to amend state corporate returns too?

Yes, most states require amended returns when federal changes affect state liabilities. Check your state’s specific rules.

What if I find errors after filing a late return?

File Form 1120X to correct errors. Refund claims are limited by statutes, but corrections still help align IRS records.

Should I file even if I can’t pay?

Yes. Filing reduces penalties and starts the statute of limitations. You can request a payment plan afterward.

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