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Delaware Business State Tax Extension I C Corporations Filing Guide

Form 1100-T-EXT | Delaware Corporate Income Tax Request For Extension  ·  C Corporations  ·  Business Filing Guide

Overview

Delaware C Corporations are subject to state corporate income tax requirements, administered by the Delaware Division of Revenue. Delaware grants an automatic extension tied to an approved IRS extension, making the process simple for businesses that have already filed IRS Form 7004.

Original Filing Deadline

• The original due date for the Delaware C Corporations return is April 15, 2026. File or remit full payment by this date to remain in good standing.
• Extension Period & Extended Deadline
• Delaware automatically grants an extension to file, provided you have obtained an approved federal extension from the IRS by filing IRS Form 7004. With a valid IRS extension, the Delaware extended deadline becomes October 15, 2026. No separate state extension form is required—the federal extension serves as your Delaware extension.

Payment Is Still Due by Original Deadline

The extension applies to filing only—it is not an extension to pay taxes owed. Any outstanding tax liability must be paid by the original due date of April 15, 2026 to avoid penalties and interest. Use the Delaware | Online Tax Extension Payment to pay electronically. For mail-in payments, use Form 1100-T-EXT | Delaware Corporate Income Tax Request For Extension and send to: Delaware Division of Revenue P.O. Box 830 Wilmington, DE 19899-0830

Late Filing and Payment Penalties

• Failure to File: 5% of outstanding tax liability per month, up to maximum of 50% of tax liability due.
• Failure to Pay: 1% of outstanding tax liability per month, not to exceed 25%.

Best Practices

• Estimate and pay your Delaware business tax by April 15, 2026 to avoid interest and penalties.
• File IRS Form 7004 with the IRS to secure your federal extension, which Delaware automatically honors.
• Use the state online payment portal for fast, convenient electronic payment.
• Set a reminder to file your completed Delaware C Corporations return by October 15, 2026.

Final Thoughts

• Delaware’s business tax extension is straightforward once your federal extension is approved. Pay 100% of any tax due by April 15, 2026 and file your C Corporations return by October 15, 2026.
• Quick Reference Table
• State Abbreviation
• DE
• State Name
• Delaware
• Business Entity Type
• C Corporations
• Extension Status
• Approved with Federal Extension
• Return Due Date
• April 15, 2026
• Extended Due Date
• October 15, 2026
• Other Information
• Delaware grants your business an automatic 6-month extension provided you have obtained an approved IRS extension.
• The extension is NOT an extension to pay any taxes you may have due.
• Tax payments are due by the original return due date.
• Online Payment
• Delaware | Online Tax Extension Payment
• Payment Voucher Form
• Form 1100-T-EXT | Delaware Corporate Income Tax Request For Extension
• State Payment Agency
• Delaware Division of Revenue
• Mailing Address with Payment
• Delaware Division of Revenue P.O. Box 830 Wilmington, DE 19899-0830
• Failure to File Penalties
• 5% of outstanding tax liability per month, up to maximum of 50% of tax liability due.
• Failure to Pay Penalties
• 1% of outstanding tax liability per month, not to exceed 25%.

Working with a Tax Professional

Business tax returns are complex—a licensed CPA or Enrolled Agent can maximize deductions, ensure accurate calculations, and handle filing on your behalf. Here's how working with a TaxPro typically goes:

1. 1Get matched with a verified U.S.-based CPA or Enrolled Agent
2. 2Upload your business documents via secure drag-and-drop
3. 3Review and approve your return with upfront, transparent fees
4. 4Your TaxPro files your Delaware return by October 15, 2026

Quick Reference Table

State Abbreviation	DE
State Name	Delaware
Business Entity Type	C Corporations
Extension Status	Approved with Federal Extension
Return Due Date	April 15, 2026
Extended Due Date	October 15, 2026
Other Information	Delaware grants your business an automatic 6-month extension provided you have obtained an approved IRS extension. The extension is NOT an extension to pay any taxes you may have due. Tax payments are due by the original return due date.
Online Payment	Delaware | Online Tax Extension Payment
Payment Voucher Form	Form 1100-T-EXT | Delaware Corporate Income Tax Request For Extension
State Payment Agency	Delaware Division of Revenue
Mailing Address with Payment	Delaware Division of Revenue P.O. Box 830 Wilmington, DE 19899-0830
Failure to File Penalties	5% of outstanding tax liability per month, up to maximum of 50% of tax liability due.
Failure to Pay Penalties	1% of outstanding tax liability per month, not to exceed 25%.