2026 US Tax Due Dates & Deadlines: Guide for CPAs

The 2026 US tax season is approaching, and Certified Public Accountants (CPAs) must stay vigilant about key filing deadlines. Missing tax dates can result in significant penalties and interest charges. By maintaining a current list of all due dates, CPAs can help clients prepare early and avoid noncompliance risks.

The 2026 tax filing season is expected to officially start around January 24, 2026, when the IRS begins accepting tax returns, giving tax professionals and their clients a clear timeline for preparation. While the IRS has not announced an exact official date, this timeline aligns with historical patterns.

Key 2026 tax calendar overview

The IRS will officially open the 2026 tax filing season in late January (expected around January 27, 2026), marking the start of individual and business return submissions for the 2025 tax year.

January 2026 Deadlines

January 15, 2026 – Final Estimated Tax Payment

The fourth quarter estimated tax payment for 2025 is due. Individual taxpayers and businesses must pay on time to avoid underpayment penalties.

January 31, 2026 – Employment Tax Forms Due

Employers must issue and file wage and compensation forms by January 31, 2026, including:

• Form W-2: Wage and Tax Statement
• Form 1099-MISC and 1099-NEC
• Form 1099-K for payment settlement entities

Important business tax due dates 2026

Apart from the January deadlines, there are couple of other deadlines which needs to be kept in mind.

March 16, 2026 – Partnership and S Corporation Returns

Partnerships and S Corporations (calendar year entities) must file or request extensions by this date because March 15 falls on a Sunday in 2026.

This business tax return deadline applies to:

• Partnerships (Form 1065)
• S Corporations (Form 1120S)
• Multi-member LLCs taxed as partnerships

Important Note: March 16 is both the S Corp tax filing deadline AND the S Corp tax return extension request deadline.

April 15, 2026 – Individual and C Corporation Deadline

What day to file taxes for most taxpayers? April 15, 2026, is the deadline for taxpayers to file 2025 federal income tax returns (Form 1040 and 1040-SR). If April 15 falls on a weekend or public holiday, the deadline shifts to the next business day.

This tax due date 2026 covers:

• Individual tax returns (Form 1040)
• C Corporations (Form 1120)
• Sole proprietorships (Schedule C)
• Single-member LLCs

C corp tax due date specifics:
C corporations need to file Form 1120 by April 15, 2026, if they are a calendar year business. Any taxes owed must be paid by this date to avoid penalties and interest.

Additional Notes:

• April 15, 2026 falls on a Wednesday and is not a federal holiday, so deadlines remain as such.
• You can file for a six-month extension using Form 4868 for individuals or Form 7004 for corporations, extending filing deadline to October 15, 2026.
• Extensions only delay filing, not payment; taxes owed must be paid by April 15 to avoid penalties and interest.

LLC tax due date breakdown

LLC tax due date varies by election:

Single-Member LLC:

• Disregarded entity: April 15, 2026 (with owner’s 1040)
• S Corp election: March 17, 2026

Multi-Member LLC:

• Partnership taxation: March 17, 2026
• S Corp election: March 17, 2026
• C Corp election: April 15, 2026

Business tax extension deadline

Corporate tax extension deadline provides crucial relief for unprepared returns:

• Partnerships/S Corps: Must file extension by March 16, 2026
• C Corporations: Must file extension by April 15, 2026

The extension filing is done using Form 7004 for C Corporations and Form 8868 for Partnerships and S Corps.

If filing an extension, the extended due date typically moves to September 15, 2026, for Partnerships and S Corps, and October 15, 2026, for C Corporations.

Tax payments are still due by the original deadlines to avoid penalties and interest.

Tax extension deadline 2026 schedule

Note:

• Extensions grant time to file, not time to pay. Taxes owed must still be paid by the original due date to avoid penalties.
• Taxpayers must file the appropriate extension forms by the original due date: Form 4868 for individual 1040 filers and Form 7004 for business entities like partnerships and corporations.
• Payments should be made by the original due date to avoid interest and penalties, even if an extension is granted.
• Certain taxpayers such as military members abroad or those affected by disasters may qualify for additional filing and payment relief.

IRS tax due dates – Complete 2026 timeline

Quarterly Estimated Payment Schedule

Extended return deadlines

Deadline to file tax return with extensions:

• September 15, 2026 – Deadline for extended partnership and S corporation returns
• October 15, 2026 – Deadline for extended C corporation returns

Payments for estimated taxes must be made by these dates to avoid penalties and interest. These deadlines apply for calendar year taxpayers unless otherwise specified.

Tax filing deadlines for businesses – Strategic planning

Corporate tax filing extension deadline strategy

Tax filing deadline for corporations requires careful planning:

1. Assess readiness by February 15th
2. File extensions before original due dates
3. Estimate tax liability accurately
4. Make required payments by original deadlines

Multi state business considerations

State tax deadlines for multi-state businesses often differ from federal dates:

• Some states require separate extensions
• Payment requirements may vary
• Conformity rules affect timing

Note:

• For 2026, corporate tax deadlines generally remain April 15 for calendar year corporations, with extensions available until October 15.
• Extensions must be filed by the original deadline using Form 7004 for corporations.
• Estimated tax payments for corporations are typically due quarterly (April 15, June 15, September 15, December 15).
• Each state may have its own deadlines and extension rules, so multi-state businesses should check individual state tax authorities for specific requirements.
• Failure to adhere to both federal and state deadlines can result in penalties and interest assessments.

Penalty avoidance for CPAs

Common tax penalties in 2026

Failure to File Penalty:

• 5% per month (maximum 25%)
• Applies when returns are late

Failure to Pay Penalty:

• 0.5% per month (maximum 25%)
• Charged on unpaid taxes

Estimated Tax Penalty:

• Applied when insufficient payments made
• Safe harbor: 100% of prior year tax (110% if AGI > $150,000)

For 2026, these penalty rates and safe harbor rules remain consistent with prior years as per IRS regulations.

The failure-to-file penalty is generally more severe than failure-to-pay, so timely filing even if payment is partial is critical.

Estimated tax penalties apply if quarterly payments do not meet safe harbor thresholds or actual tax liability, particularly for self-employed and certain business taxpayers.

CPAs should advise clients to maintain accurate records and make timely payments to minimize penalty risks.

IRS tax deadlines for CPAs 2026 – Best practices

Maximizing deductions before tax deadlines 2026:

• Review depreciation elections
• Consider Section 179 deductions
• Analyze retirement plan contributions
• Implement tax strategies before year-end

Note:

• For 2026, CPAs should also consider bonus depreciation rules and updated limits under Section 179 as per the latest tax law changes.
• Retirement plan contribution limits may increase, so clients should maximize allowable contributions by year-end.
• Year-end tax planning should include reviewing timing of income and deductions, especially for pass-through entities and individuals subject to AMT or phaseouts.
• Stay updated with IRS announcements on filing extensions and changes impacting deduction eligibility for the 2026 tax year.

Filing strategies for tax professionals

Advising clients on 2026 tax deadlines

Tax deadline management for accountants involves:

1. Early client communication about required documents
2. Systematic deadline tracking using tax calendar software
3. Extension strategy discussions for complex returns
4. Penalty mitigation planning for late filers

CPAs managing tax deadlines for clients

Tax compliance for accountants in 2026 requires:

• Automated reminder systems
• Document request templates
• Extension filing procedures
• Payment deadline tracking

2026 Tax filing due dates for businesses – Action items

January Priorities

• Collect year-end documents
• Issue employment tax forms
• Make final estimated payments

February Priorities

• Begin return preparation
• Assess extension needs
• Review prior year audits

March Priorities

• File partnership/S corp returns
• Submit business extensions if needed
• Prepare individual returns

IRS Filing dates for Partnerships and Corporations

Partnership filing requirements

Business tax filing deadline for partnerships:

• Form 1065 due March 17, 2026
• K-1s must be issued to partners
• Extension available until September 15, 2026

Corporation filing requirements

Corporate tax return due date schedule:

• C Corps: April 15, 2026 (Form 1120)
• S Corps: March 17, 2026 (Form 1120S)
• Extensions add six months

Note:

• CPAs should remind clients that payments remain due by the original deadlines to avoid penalties, even if extensions are filed.
• Filing extension forms: Form 7004 for corporations and partnerships, Form 4868 for individuals.
• Quarterly estimated tax payments must also be tracked to ensure compliance.

FAQs