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US Tax Planning Guide

C-Corporation Tax Overview and Compliance

1. FEDERAL CORPORATE TAX

Tax Type Rate Notes
Federal Corporate Income Tax 21% Flat rate since TCJA 2017
Alternative Minimum Tax (AMT) 15% For corps with avg. income >$1B
Accumulated Earnings Tax 20% On excessive retained earnings
Double Taxation: C-Corps pay tax at corporate level (21%), then shareholders pay tax on dividends (15-20% qualified dividend rate).

2. STATE TAXES

State Corporate Tax Rate Franchise Tax
Delaware 8.7% $175 - $200,000+
California 8.84% $800 minimum
Texas 0% Margin Tax 0.375-0.75%
Nevada 0% $500+

3. QUARTERLY ESTIMATED TAXES

Due Dates for Form 1120-W:

  • Q1: April 15
  • Q2: June 15
  • Q3: September 15
  • Q4: December 15

Penalty avoidance: Pay at least 100% of prior year tax or 100% of current year tax.

4. ANNUAL FILING REQUIREMENTS

Form 1120 - Corporate Income Tax Return (Due: April 15)
Form 1120-W - Quarterly Estimated Tax
Form 941 - Quarterly Payroll Tax
Form W-2 - Employee Wage Statements (Due: January 31)
Form 1099 - Contractor Payments (Due: January 31)
Delaware Annual Report (Due: March 1)
State Tax Returns (varies by state)

5. TAX DEDUCTIONS FOR SOFTWARE/AI COMPANIES

  • R&D Tax Credit (Section 41): Up to 20% of qualified research expenses
  • Section 174: R&D expenses must be amortized over 5 years (domestic)
  • Section 179: Immediate expensing of equipment up to $1.16M
  • Qualified Business Income (QBI): Not applicable to C-Corps
  • Software Development: Can capitalize or expense

6. INTERNATIONAL TAX (GILTI/FDII)

  • GILTI: 10.5% tax on Global Intangible Low-Taxed Income
  • FDII: 13.125% rate on Foreign-Derived Intangible Income (incentive for exports)
  • BEAT: Base Erosion and Anti-Abuse Tax (large multinationals)

7. KEY DEADLINES 2025

Date Deadline
January 31, 2025 W-2s and 1099s due
March 1, 2025 Delaware Annual Report
April 15, 2025 Form 1120 (or extension)
October 15, 2025 Extended Form 1120 due