US C-Corporation — Form 1120 Annual Return

Confirm the entity is a domestic C-corporation (or an LLC with a Form 8832 C-corp election in effect) required to file Form 1120. Determine the tax year (calendar vs. fiscal), identify whether a consolidated return election under §1501 is in force (which would take this out of scope), and flag any special entity types (personal service corporation, REIT, RIC, S-corp election) that route differently. Establish whether the corporation existed for the full year or only a portion.

Gather and classify all income items flowing to Form 1120 Lines 1–11: gross receipts or sales (Line 1a), cost of goods sold from Form 1125-A (Line 2), dividends and subpart F/GILTI inclusions for Schedule C (Line 4), interest (Line 5), rents, royalties, capital gains from Schedule D (Form 1120) (Line 8), and other income. Identify any §351 contributions or unusual income events during the year. Flag any foreign income that may trigger Schedule C GILTI inclusions or Form 5471 obligations.

Compute and document all deductions on Form 1120 Lines 12–29a: compensation (separating officer comp for Form 1125-E if gross receipts ≥ $500,000), repairs, bad debts, rents, taxes, depreciation and §168(k) bonus depreciation from Form 4562, depletion, advertising, pension/benefit contributions, and other deductions. Apply the §163(j) business interest limitation via Form 8990 (30% of ATI cap on net business interest expense). Capitalize and schedule §174 specified research and experimental expenditures (domestic SREs amortized over 5 years, foreign over 15 years). Flag any §162(m) $1M compensation cap issues for publicly held corporations.

Compute Line 29b special deductions: the dividends-received deduction (DRD) on Schedule C (50% for <20% ownership, 65% for 20–79%, 100% for 80%+ affiliated group), subject to the §246(b) taxable-income limitation. Track and apply net operating loss (NOL) carryforwards on Line 29a — post-2017 NOLs are limited to 80% of taxable income with indefinite carryforward, no carryback. Compute the §250 GILTI/FDII deduction on Form 8993 if the corporation has GILTI inclusions (50% deduction at 2025 rates, effective 10.5% GILTI rate) or foreign-derived intangible income (37.5% deduction at 2025 rates). Note: §250 rates drop for tax years beginning after December 31, 2025.

Compute regular federal income tax at the 21% flat rate on Schedule J (taxable income from Line 30 × 21%). Assess Corporate Alternative Minimum Tax (CAMT) applicability: CAMT is a 15% minimum tax on adjusted financial statement income (AFSI) imposed on 'applicable corporations' with average annual AFSI exceeding $1 billion (or $100M for foreign-parented groups). For corporations below the AFSI threshold, document the CAMT non-applicability conclusion and skip Form 4626. Apply any tax credits (§41 R&D credit from Form 6765, foreign tax credit from Form 1118, §48C clean energy credits, etc.) on Schedule J, Part III.

Prepare the Schedule M-1 book-to-tax reconciliation (required unless Schedule M-3 is required), or Schedule M-3 if total assets at year-end are $10 million or more. Common M-1 additions: federal income tax expense, 50% disallowed meals, executive comp over §162(m) $1M cap, fines and penalties, political contributions. Common M-1 subtractions: tax-exempt interest, life insurance proceeds, prior-year tax refunds. Prepare Schedule L (balance sheet — required if total receipts AND total assets are both $250,000 or more), Schedule B (additional information), and Schedule K (other information). Flag Schedule UTP filing obligation if total assets are $10 million or more and the corporation has uncertain tax positions reserved under ASC 740-10.

Reconcile estimated tax payments against the tax liability. For calendar-year corporations, installments were due April 15, June 16, September 15, and December 15, 2025. Compute any §6655 underpayment penalty on Form 2220 (required to be attached if a penalty applies — unlike individuals, corporations must self-compute). Confirm the due date: April 15, 2026 for calendar-year corps (Form 7004 extends to October 15, 2026 but does not extend payment). Apply the e-file mandate — required if total assets ≥ $10M or the corporation files 10+ returns of any kind during the year. Assemble the complete return package, obtain officer signature on Form 8879-CORP, and transmit via IRS Modernized e-File.