This guide covers all Arizona state tax deadlines for Tax Year 2025, filed in 2026, for individuals, calendar-year and fiscal-year businesses, and special entity types. Arizona conforms to the federal calendar for individuals and C corporations but applies its own 7-month corporate extension.

Arizona Tax Deadlines at a Glance (2026)

Individuals

Form 140 is due April 15, 2026 for residents, part-year residents, and non-residents with Arizona-source income. A valid extension moves the filing deadline to October 15, 2026; the extension applies to filing only, not to payment.

Businesses

• C Corps (Form 120): Due April 15, 2026. Arizona grants a 7-month filing extension, moving the extended deadline to November 16, 2026 (November 15 falls on a Sunday).

• S Corps (Form 120S) & Partnerships (Form 165): Due the 15th day of the 3rd month; for 2026 that statutory March 15 date rolls to March 16, 2026 because March 15 is a Sunday. Extended deadline September 15, 2026.

• LLCs: Follow their federal tax classification for Arizona filing.

Pass-Through Entity (PTE) Tax

Arizona offers an elective entity-level tax (Form 165PTE / 120S with PTE election) with a corresponding credit to owners. The election and payment align with the entity's return due date.

Fiscal-Year Entities

Returns are due the 15th day of the 4th month after year-end (C corps) or the 15th day of the 3rd month (pass-throughs).

Estimated Taxes (Individuals & Corporations)

Common CPA Pitfalls

• Assuming the federal 6-month corporate extension applies — Arizona gives C corps a 7-month extension (to November 16, 2026).

• Treating a federal extension as covering Arizona without confirming the state extension.

• Missing the PTE election timing for owners seeking the SALT-cap workaround credit.

How a CPA firm handles this at scale

A firm running Arizona returns keys each entity's state due date into the engagement calendar at intake, so 120S/165 returns are queued ahead of the March 16 date and 120/140 returns ahead of April 15 — with the 7-month corporate extension flagged separately from the federal one. SignalsHQ layers on top of the firm's existing tax software to surface these state-specific dates during intake and review, so a non-conforming extension doesn't slip through QC. See how SignalsHQ fits your prep workflow.