Delaware Business Tax Extension 2026: 2025 Tax-Year Filing Guide
LLC & Partnership · S Corporation · C Corporation · Fiduciary
This guide explains how to file a Delaware (DE) business tax extension for each entity type. Requirements differ by entity, and a federal extension generally carries to Delaware. However, an extension of time to file does not extend payment time, so estimated tax remains due by the original deadline.
Need a pro? Connect with a U.S.-based CPA or EA to prepare and file your DE return.
Remember, payment is still due by the original deadline. In other words, extensions only extend filing time.
Delaware (DE) rules depend on entity type. First, confirm the entity’s classification. Then file the required extension or retain federal proof when applicable, and pay required tax by the original deadline.
Delaware LLC Tax Extension: Filing Details
A calendar-year partnership or LLC taxed as a partnership generally files Form PRT-RTN, as applicable, when a Delaware filing obligation applies. For the 2025 calendar-year return, the extended filing deadline is September 15, 2026.
In addition, the extension applies to filing time only. Accordingly, pay any Delaware tax due by the original deadline to limit penalties and interest.
As a result, the extension applies to filing time only. Paying any Delaware tax due by the original deadline helps limit penalties and interest.
Delaware S Corporation Tax Extension: Filing Details
Generally, an S corporation files Form SCT-RTN, as applicable, when a Delaware filing obligation applies. The extended filing deadline for a 2025 calendar-year return is September 15, 2026.
Delaware C Corporation Tax Extension: Filing Details
Likewise, a C corporation files Form CIT-TAX, as applicable, when a Delaware filing obligation applies. Accordingly, the 2025 calendar-year return has an extended filing deadline of October 15, 2026.
Similarly, the extension applies to filing time only. Any Delaware tax due remains payable by the original deadline to limit penalties and interest.
Finally, the extension applies to filing time only. To limit penalties and interest, pay any Delaware tax due by the original deadline.
Fiduciary, Estate, and Trust Filing Details
Finally, a calendar-year estate or trust generally files Form FID-TAX, as applicable, when a Delaware filing obligation applies. For fiduciary 2025 calendar-year returns, the extended filing deadline is October 15, 2026.
Quick Reference: Deadlines and Forms
The table below provides a quick reference to Delaware business tax extensions. See our business tax extension hub for federal filing guidance.
| Entity Type | DE Return Form | Extension Method | Extended Deadline |
|---|---|---|---|
| LLC / Partnership | PRT-RTN | Federal 5-month; PRT-EXT | Sept. 15, 2026 |
| S Corporation | SCT-RTN | SCT-EXT | Sept. 15, 2026 |
| C Corporation | CIT-TAX | CIT-EXT | Oct. 15, 2026 |
| Fiduciary / Estate / Trust | FID-TAX | FID-EXT | Oct. 15, 2026 |
Frequently Asked Questions
Quick answers about Delaware business tax extensions – but always confirm the current rules with the Delaware Division of Revenue.
Visit Delaware Division of RevenueYes. However, the applicable entity-specific requirements listed above must be satisfied. Delaware grants extensions to LLCs, partnerships, S corporations, C corporations, and fiduciaries, but the rules – including which form to file, how long the extension lasts, and the payment threshold – vary by entity type. If you need an individual rather than business extension, see our Delaware individual tax extension page.
Generally no. In other words, pay required tax by the original deadline and confirm the current state payment rules. An extension of time to file does not extend the time to pay – failing to pay by the original deadline can result in penalties and interest, even if the return is filed within the extended window.
No. In practice, partnerships, S corporations, C corporations, and fiduciaries can use different original dates, extension periods, or forms. For 2025 calendar-year returns filed in 2026, partnerships and LLCs taxed as partnerships get a five-month extension (Sept. 15), while the others generally get a six-month extension (Oct. 15).
Review the Delaware Division of Revenue guidance for the entity’s return. Additionally, the DOR publishes the most current forms (CIT-TAX, PRT-RTN, FID-TAX, etc.) and any changes to extension periods or payment thresholds.
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