Are there corporations that file Forms 1120, 1120-S, or 1120-F that cannot file their tax returns electronically

Yes, there are certain corporations that file Forms 1120, 1120-S, or 1120-F that cannot file their tax returns electronically. Specifically, the Corporate e-file Program does not accept and process the following corporate returns:

1. Returns with tax periods ending prior to January 1, 2018.
2. Returns covering multiple tax periods.
3. Returns related to the Bank Holding Company Tax Act, including the election to make installment payments for a portion of the total tax attributable to the Bank Holding Company Tax Act.
4. Prompt Assessments.

Additionally, the following forms cannot be filed electronically as a return at the parent level but must be filed in XML format if they are part of a consolidated return. If these forms are stand-alone filings (not part of a consolidated return), they must be filed in paper format:

1. Form 1120-L (Life Insurance Company)
2. Form 1120-PC (Property and Casualty)

The following forms must be filed in paper if they are stand-alone filings but can be attached in PDF format to a consolidated return:

1. Form 1120-C (Farmer's Cooperative Association)
2. Form 1120-FSC (Foreign Sales Corporations)
3. Form 1120-H (Homeowners Association)
4. Form 1120-IC-DISC (Interest Charge Domestic International Sales)
5. Form 1120-ND (Nuclear Decommission Trusts)
6. Form 1120-REIT (Real Estate Investment Trust)
7. Form 1120-RIC (Regulated Investment Companies)
8. Form 1120-SF (Settlement Funds)

Furthermore, Form 1120-X (Amended Return) cannot be e-filed as a stand-alone return and can only be submitted as an attachment to an 1120 return.

Sources:
Publication 4163 (12/2023)
Publication 4164 (10/2023)
Instructions for Form 1120 (2023)
Instructions for Form 1120-S (2023)
Publication 4452
IRM Part 3. Submission Processing. Chapter 42. Electronic Tax Administration. Section 4. IRS e-file for Business Tax Returns