Form 1120X Tax Year 2020 Filing Checklist
Year-Specific Context
Form 1120X for the tax year 2020 amends the previously filed Form 1120 or Form 1120-A for C corporations. The 2020 tax year incorporates provisions from the Tax Cuts and Jobs Act, including the flat 21 percent corporate tax rate, as well as significant CARES Act provisions enacted in March 2020.
Key CARES Act provisions include a temporary net operating loss carryback to the five preceding tax years for losses arising in 2018, 2019, and 2020 with suspension of the 80 percent taxable income limitation, temporary increase in business interest deduction limitation from 30 percent to 50 percent of adjusted taxable income, employee retention credit for eligible employers, temporary increase in charitable contribution deduction limit from 10 percent to 25 percent for qualified cash contributions, and Paycheck Protection Program loan forgiveness exclusion from income with deductibility of related expenses.
Form 1120X Filing Requirements
File within three years from the date the original return was filed or within two years from the tax payment date, whichever is later. For calendar year 2020 corporations filing on April 15, 2021, the deadline is April 15, 2024. The CARES Act temporarily reinstated the five-year carryback losses from 2018 and 2019. Generally paper-filed, though electronic options have expanded.
Ten-Step Filing Checklist
Step 1: Gather Original Return and Supporting Documentation
Collect complete original Form 1120 or Form 1120-A for 2020, including all schedules: Schedule C for dividends, Schedule D for capital gains, Schedule J for tax computation at 21 percent, Schedule K for other information, Schedule L for balance sheets, Schedule M-1 for income reconciliation, and Schedule M-2 for retained earnings.
Gather receipts, invoices, bank statements, depreciation schedules, Forms 1099, Schedule K-1 forms the corporation received from partnerships or S corporations, payroll records, Paycheck Protection Program loan and forgiveness documentation, employee retention credit calculations, and IRS correspondence.
Step 2: Identify CARES Act Provisions Affecting the Amendment
Determine applicable CARES Act provisions. Evaluate net operating loss carryback to the five preceding years for losses in 2018, 2019, or 2020. Determine if suspension of the 80 percent taxable income limitation results in additional deductions. Verify business interest deduction under the temporary 50 percent limitation. Confirm Paycheck Protection Program loan forgiveness exclusion from income and expense deductibility. Verify employee retention credit calculation. Check charitable contributions under the temporary 25 percent limitation for qualified cash contributions.
Step 3: Verify and Document All Changes
Identify items requiring correction and prepare supporting documentation, including revised depreciation schedules, corrected Forms 1099, amended Schedule K-1 forms received from partnerships or S corporations, corrected capital gains schedules, revised income documentation, net operating loss carryback calculations under the CARES Act, business interest deduction calculations under the 50 percent limitation, employee retention credit documentation, charitable contribution adjustments, Paycheck Protection Program documentation, and other substantiating documents.
For each change, determine the original amount, net increase or decrease, and corrected amount. Create a detailed schedule by line number, including explanations and documentation.
Step 4: Complete Part I Using the Three-Column Format
Complete Part I with original amounts in column (a), net changes in column (b) with parentheses for decreases, and corrected amounts in column (c).
Line 1: total income, including proper Paycheck Protection Program loan forgiveness exclusion.
Line 2: total deductions including business interest under 50 percent limitation, charitable contributions under 25 percent limitation for qualified cash contributions, and expenses paid with forgiven PPP proceeds.
Line 3: corrected taxable income before net operating loss deduction and special deductions, applying net operating losses considering the CARES Act suspension of the 80 percent limitation.
Line 4: corrected tax at 21 percent.
Line 5: payments and credits, including employee retention credit.
Complete lines 6 through 11 for overpayment or balance due.
Step 5: Attach All Required Supporting Schedules
Attach schedules supporting changes. Revised Schedule C if the dividend income or dividends received deduction changed. Revised Schedule D and Form 8949 if capital gains have changed. Revised Schedule M-1 and M-2 if reconciliation changed. Copies of amended Schedule K-1 forms received from partnerships or S corporations. Revised Form 4562 if depreciation changed.
Form 8990 if section 163(j) applies with a 50 percent limitation. Form 5884-A if claiming employee retention credit. Form 1139 or detailed calculations for net operating loss carrybacks under the CARES Act, with copies of carryback year returns. Documentation for the 25 percent charitable contribution limitation. All third-party documentation supports amendments.
Step 6: Calculate Net Operating Loss Carryback if Applicable
If the corporation incurred a net operating loss in 2018, 2019, or 2020, calculate the carryback under the CARES Act, which allows a five-year carryback. Determine the loss amount, identify carryback years in sequence, apply the loss starting with the earliest year, calculate tax benefit from each year, and determine total refund.
To receive a quick refund, file Form 1139 within 12 months after the end of the loss year. Alternatively, include detailed calculations with Form 1120X and attach copies of the original returns for the carryback years. Show all computations in Part II.
Step 7: Complete Part II With Detailed Explanations
Provide detailed explanations referencing applicable 2020 TCJA and CARES Act provisions. For each changed line, include the line number, a clear description, the reason, and supporting computations.
If adjusting net operating losses or carrybacks, explain the calculation and the five-year carryback application. If adjusting business interest under the 50 percent limitation, explain the calculation and reference Form 8990. If claiming or amending employee retention credit, demonstrate eligibility and show computation. If adjusting charitable contributions under the 25 percent limitation, explain qualifying donations and show calculations. If excluding Paycheck Protection Program loan forgiveness and deducting related expenses, explain the treatment. If from an IRS audit, reference the correspondence and attach the relevant IRS documents. Attach additional sheets as needed.
Step 8: Recalculate Tax Liability and Verify Calculations
Recalculate tax by multiplying corrected taxable income from Part I, line 3, column (c) by 0.21. Verify this is correctly reflected on Part I, line 4, column (c).
Check that the calculations on lines 1 through 4 reflect amendments considering the 2020 CARES Act provisions, including temporary net operating loss rules, a temporary increase in the business interest deduction to 50 percent, and a temporary increase in the charitable contribution deduction to 25 percent for qualified cash contributions.
Compare the corrected tax amount to the original tax amount. If you are claiming net operating loss carrybacks, please calculate the refund from each carryback year. Ensure all calculations are accurate and consistent.
Step 9: Review Limitations and Eligibility Restrictions
Review applicable limitations. Qualified cash contributions are limited to 25 percent under temporary CARES Act rules, while other contributions are limited to 10 percent. Net operating losses from 2020 are carried back five years under the temporary CARES Act, with no 80 percent limitation during the carryback. Business interest expense is limited to 50 percent of adjusted taxable income under the temporary 2020 rules. Capital losses offset capital gains only, carried back three years and forward five years.
The Employee Retention Credit has eligibility requirements based on a decline in gross receipts or the suspension of operations. Verify foreign corporations and nonresident alien shareholders do not claim restricted credits or deductions. Confirm compliance with 2020 TCJA and CARES Act provisions with proper substantiation.
Step 10: Sign, Date, and File
An authorized corporate officer must sign and date Form 1120X, providing the title and the date of signature. Acceptable signers include the president, vice president, treasurer, assistant treasurer, chief accounting officer, or other authorized officer. If a paid preparer prepared the return, the preparer must sign and provide their tax identification number, firm name, address, and phone number.
Submit Form 1120X with all attachments and any required payment. If claiming a net operating loss carryback refund, indicate whether filing Form 1139 separately or including calculations with Form 1120X. Make checks payable to the United States Treasury, including the employer identification number, tax year, and form number. Refer to the “Where to File” section in the Instructions for Form 1120X for the correct mailing address, based on your principal business location. Retain complete copy and all supporting documentation.
Key 2020 Form 1120X CARES Act Provisions
The 2020 Form 1120X reflects significant CARES Act provisions enacted for coronavirus pandemic relief. The most important change is that businesses can now use their losses from 2018, 2019, and 2020 to offset profits from the previous five years without the usual 80 percent limit, which differs from the TCJA rules that removed carrybacks and capped current-year deductions at 80 percent.
A temporary increase in the business interest deduction from 30 percent to 50 percent of adjusted taxable income provides additional capacity. Temporary charitable contribution increase from 10 percent to 25 percent applies only to qualified cash contributions for coronavirus relief. The Employee Retention Credit provides a refundable payroll tax credit for eligible employers who retain employees. Paycheck Protection Program loan forgiveness is excluded from income, and expenses paid with forgiven proceeds are deductible.
Form-Specific Limitations for 2020
Corporations cannot use Form 1120X to change certain elections unless the IRS regulations specifically permit it. Elections regarding depreciation methods, accounting methods, and inventory valuation are generally irrevocable. Consolidated groups must file consolidated Form 1120X if the amendment affects consolidated taxable income or tax liability.
Foreign corporations and nonresident alien shareholders are restricted from claiming certain credits and deductions available only to U.S. persons. Generally paper-filed; verify current electronic filing availability. If claiming net operating loss carrybacks, file Form 1139 within 12 months for quick refund or include calculations with Form 1120X. Ensure required signatures and correct IRS service center filing.
Conclusion
Filing Form 1120X for tax year 2020 requires careful attention to TCJA provisions, including the flat 21 percent rate and significant CARES Act provisions, including the temporary net operating loss five-year carryback with no 80 percent limitation, temporary business interest deduction increase to 50 percent, employee retention credit, temporary charitable contribution increase to 25 percent for qualified cash contributions, and the Paycheck Protection Program loan forgiveness exclusion.
Accurately complete Part I in a three-column format, provide detailed Part II explanations referencing TCJA and CARES Act provisions, attach required schedules and forms, and ensure compliance with limitations. Following this ten-step checklist facilitates the accurate completion of Form 1120X for 2020.
Need Help With Your Tax Filing?
If you’re missing tax documents or want to ensure the numbers you enter match IRS records, we can help.
We offer:
- Full IRS transcript retrieval (Wage & Income + Account)
- Professional tax form review
- Preparation & filing support
- Tax relief options if you owe the IRS
Call now before filing: (888) 260-9441
Fast transcript pull available
This checklist is for educational purposes only and does not constitute tax or legal advice. Always review official IRS instructions and consult a qualified professional for guidance.
