April presents a critical tax compliance window for closely held businesses, family offices, and fiduciaries. Navigating these deadlines ensures your wealth preservation strategies and entity structures remain compliant. Here are the essential April 2026 due dates you need to track to avoid unnecessary penalties.

April 15: Entity and Fiduciary Deadlines

C-Corporations (Form 1120): Calendar year C-corporations must file their 2025 income tax returns and pay any associated tax. If additional time is necessary, file Form 7004 to request an automatic six-month extension. Remember that an extension applies to filing, not payment. Estimate and deposit your tax liability using Form 7004 instructions to mitigate late payment penalties. Additionally, the first installment for 2026 estimated taxes is due on this date.

Fiduciary Returns (Form 1041): A cornerstone deadline for estates and trusts. Fiduciaries must timely file a 2025 calendar year U.S. Income Tax Return for Estates and Trusts (Form 1041) or submit a formal extension request.

Payroll and Non-Payroll Withholding: For entities subject to the monthly deposit rule, ensure Social Security, Medicare, and withheld income taxes from March payments are properly deposited.

April 30: Quarterly Employer Taxes

Form 941: File your first-quarter 2026 return. Pay any undeposited tax under the accuracy of deposit rules. If your tax liability sits below $2,500, it can be paid in full with a timely filed return. Entities that made full, on-time deposits have until May 11 to file.

Federal Unemployment Tax: Deposit taxes owed through March if the total exceeds $500.

Exceptions and Disaster Relief

Due dates falling on a weekend or legal holiday automatically shift to the next business day. Furthermore, geographic areas designated as disaster zones often receive extended deadlines. Verify disaster declarations and specific relief dates through the following official channels:

• FEMA: https://www.fema.gov/disaster/declarations
• IRS: https://www.irs.gov/newsroom/tax-relief-in-disaster-situations

Managing complex entity filings requires precision and foresight. At Sullivan & Company CPA INC. in Burlingame, CA, we deliver clear, defensible strategies for high-net-worth families, fiduciaries, and legal counsel. Contact our advisory team today to ensure your estate and business tax compliance aligns with your broader financial legacy.