Maryland Business Tax Extension 2026: 2025 Tax-Year Filing Guide
LLC & Partnership · S Corporation · C Corporation · Fiduciary
This guide explains how to file a Maryland (MD) business tax extension for each entity type. For example, CBT taxpayers generally receive six months, while partnerships generally receive five months. However, estimated tax remains due by the original deadline. For federal filing details, see our IRS Form 7004 business tax extension guide.
Need a pro? Connect with a U.S.-based CPA or EA to prepare and file your MD return.
Remember, payment is still due by the original deadline. In other words, extensions only extend filing time.
Maryland (MD) rules depend on entity type. Confirm the entity classification, file the required extension or retain federal proof when applicable, and pay required tax by the original deadline.
Maryland LLC / Partnership Tax Extension: Filing Details
Maryland pass-through entities generally file Form 510. A six-month extension is available using Form 510/511E when required. For the 2025 calendar-year return, the extended filing deadline is Oct. 15, 2026.
In addition, the extension applies to filing time only. Therefore, pay required Maryland tax by the original deadline to limit penalties and interest.
The extension applies to filing time only. Pay required Maryland tax by the original deadline to limit penalties and interest.
Maryland S Corporation Tax Extension: Filing Details
Maryland S corporations generally file Form 510. The Comptroller allows up to a seven-month extension when the extension requirements are met. For the 2025 calendar-year return, the extended filing deadline is Nov. 16, 2026.
Maryland C Corporation Tax Extension: Filing Details
Maryland corporations generally file Form 500. A seven-month extension is available when Form 500E or the online extension process is completed by the original due date. For the 2025 calendar-year return, the extended filing deadline is Nov. 16, 2026.
The extension applies to filing time only. Pay required Maryland tax by the original deadline to limit penalties and interest.
Maryland Fiduciary / Estate / Trust Tax Extension: Filing Details
Use the current Comptroller guidance for Maryland fiduciary and trust returns; the corporate extension forms do not apply to every fiduciary filing. For the 2025 calendar-year return, the extended filing deadline is See Maryland guidance.
Quick Reference: Deadlines and Forms
The table below provides a quick reference to Maryland business tax extensions. See our business tax extension resource for broader filing guidance.
| Entity Type | NJ Return Form | Extension Method | Extended Deadline |
|---|---|---|---|
| LLC / Partnership | Form 510 / Form 511 | Federal 5-month; PART-200-T / CBT-206 | Sept. 15, 2026 |
| S Corporation | Form 510 | Form 510/511E | Oct. 15, 2026 |
| C Corporation | Form 500 / Form 500 | Form 510/511E | Oct. 15, 2026 |
| Fiduciary / Estate / Trust | Form 504 | Form 504 extension | Oct. 15, 2026 |
Frequently Asked Questions
Quick answers about Maryland business tax extensions – but always confirm the current rules with the Maryland Division of Taxation.
Visit MD tax agencyYes. However, the applicable entity-specific requirements listed above must be satisfied. Maryland 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 Maryland 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 Maryland Division of Taxation guidance for the entity’s return. Additionally, the DOR publishes the most current forms (Form 510/511E, PART-200-T, Form 504 extension, etc.) and any changes to extension periods or payment thresholds.
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