AZ — Arizona

Arizona Business Tax Extension — LLC & Partnership, S Corporation, C Corporation, Fiduciary

Arizona will extend any business return, and it will accept your federal extension instead of its own form. What it will not do is give every entity the same amount of time — and the spread is wider here than in most states. A C corporation gets seven months. An S corporation or partnership gets six. An estate or trust gets five and a half.

That seven-month figure for C corporations is worth pausing on, because Arizona’s own website still says six. The seven-month period was enacted by S.B. 1350 in 2021 and sits in A.R.S. §42-1107(D), which also states in as many words that it does not reach S corporations. The statute and both current-year form instructions agree; the older web page has simply not been updated.

One rule cuts across all four entity types and catches more Arizona filers than anything else: you must pay at least 90% of what you owe by the original due date. Fall short and Arizona adds an extension underpayment penalty on top of the ordinary late-payment penalty.

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Arizona Business Tax Extension — LLC & Partnership

Arizona partnerships and multi-member LLCs file Form 165, due the 15th day of the third month. March 15, 2026 falls on a Sunday, so the deadline moves to Monday, March 16, 2026. The extension runs six months, to September 15, 2026.

You can get there two ways, and neither requires much. File Arizona’s Form 120/165EXT, or simply rely on the federal extension you already filed — Arizona’s instructions say a federal extension extends the Arizona due date by the same period. Most partnerships never touch the Arizona form.

A partnership rarely owes Arizona tax itself, so the 90% payment rule usually has nothing to bite on. It becomes real if you have made the elective pass-through entity election, which puts a 2.50% tax at the entity level — and that money is due March 16, not September.

LLC & Partnership — 2026 Extension Checklist

Two dates, six months apart.

Arizona Late Filing & Late Payment Penalties — LLC & Partnership

Arizona stacks three separate penalties but caps the total at 25%. The one filers trip over is the extension underpayment penalty, which applies even when you filed the extension correctly — it is triggered by paying too little, not by filing too late.

Arizona LLC & Partnership — Quick Reference

Arizona Business Tax Extension — S Corporation

Arizona S corporations file Form 120S on the same calendar as partnerships: due March 16, 2026 because March 15 is a Sunday, extended six months to September 15, 2026.

This is the entity most likely to be given the wrong deadline by a well-meaning source. Arizona’s seven-month corporate extension is written into A.R.S. §42-1107(D) with an explicit carve-out: it “does not include small business corporation returns filed under section 43-1126.” That is the S corporation provision. An Arizona S corporation gets six months, and September 15 is the date.

Use Arizona’s Form 120/165EXT or lean on your federal extension — either works. Pay 90% of any liability by March 16 regardless, including the 2.50% pass-through entity tax if you have elected it.

S Corporation — 2026 Extension Checklist

Two dates, six months apart.

Arizona Late Filing & Late Payment Penalties — S Corporation

The same three penalties apply as for every other Arizona entity, with the same 25% combined ceiling. Because an S corporation often owes little at the entity level, the failure-to-file penalty is usually the larger exposure.

Arizona S Corporation — Quick Reference

Arizona Business Tax Extension — C Corporation

Arizona C corporations file Form 120 (or the short Form 120A) by April 15, 2026, and this is the one entity type Arizona gives seven months rather than six. Seven months from April 15 is November 15, 2026, which is a Sunday — so the working deadline is Monday, November 16, 2026.

Arizona’s own guidance is inconsistent on this point, so it is worth knowing where the seven months comes from. A.R.S. §42-1107(A) caps extensions at six months “except as provided in subsection D”; subsection (D) then sets the due date for a corporate or exempt organization return at seven months after the initial due date. It was added by S.B. 1350 in 2021, retroactive to tax years beginning after December 31, 2020. AZDOR’s extensions web page still reflects the old six-month rule.

A federal extension gets you the full Arizona seven months — the instructions state that a federal extension extends the Arizona due date by the same period the Arizona extension would have. And the 90% payment rule still applies on April 15, along with Arizona’s $50 minimum tax, which a corporation owes even in a year with no taxable income.

C Corporation — 2026 Extension Checklist

Pay in April. File as late as November.

Arizona Late Filing & Late Payment Penalties — C Corporation

Seven months of filing time makes the payment rules the real exposure for a C corporation. Both the late-payment and extension underpayment penalties run from April 15, no matter how much filing time you have left.

Arizona C Corporation — Quick Reference

Arizona Business Tax Extension — Fiduciary / Estate / Trust

Arizona estates and trusts file Form 141AZ, due April 15, 2026 — the instructions put it as “no later than midnight, April 15, 2026.” The extension runs five and a half months, not six, landing on September 30, 2026. Arizona states that date explicitly, which is a welcome change from most states.

The extension form is Form 141AZ EXT. This is a common filing error worth calling out: Form 204 is for individuals only and will not extend a fiduciary return, notwithstanding how often the two get conflated. A valid federal extension works in place of the Arizona form.

One exception runs the other way. A Qualified Funeral Trust extending on federal Form 7004 gets the full six months, to October 15, 2026 — two weeks past the ordinary fiduciary date.

Fiduciary / Estate / Trust — 2026 Extension Checklist

Two dates, five and a half months apart.

Arizona Late Filing & Late Payment Penalties — Fiduciary / Estate / Trust

Fiduciary penalties are identical to Arizona’s business penalties, and so is the 25% combined cap. The shorter extension window simply means less room before the failure-to-file penalty starts.

Arizona Fiduciary / Estate / Trust — Quick Reference

Arizona Business Tax Extensions — Frequently Asked Questions

Ready to Extend Your Arizona Business Return?

Arizona accepts your federal extension for every entity type. File once and extend both returns together.

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