Arizona conforms to the federal calendar for individuals and C corporations but applies its own 7-month corporate extension. It is a flat-tax state (2.5%) and offers an elective pass-through entity tax at that same rate. All dates below are confirmed for tax year 2025, filed in 2026.
Arizona Tax Deadlines at a Glance (2026)
Entity Type | Form | Return Due | Extended Due Date |
|---|---|---|---|
Individuals | Form 140 | April 15, 2026 | October 15, 2026 |
C Corporations | Form 120 | April 15, 2026 | November 16, 2026 (7-month) |
S Corporations | Form 120S | March 16, 2026 | September 15, 2026 |
Partnerships | Form 165 | March 16, 2026 | September 15, 2026 |
Two date mechanics worth stating explicitly. The C-corporation extended due date is November 16, 2026 — Arizona’s 7-month extension runs to November 15, which falls on a Sunday, so it rolls to Monday. Likewise, the S-corporation and partnership deadline is March 16, 2026 because March 15 is a Sunday; those returns follow the 15th-day-of-the-third-month rule and get a 6-month extension to September 15.
Arizona’s Flat Rate and PTE Tax
Arizona has a flat individual income tax rate of 2.5% (since 2023). The corporate income tax rate is 4.9%, with a $50 minimum. Arizona’s elective pass-through entity tax is assessed at 2.5% — the individual rate — on resident owners’ income plus nonresident owners’ Arizona-source income. The election is made no later than the return’s due date (or extended due date), and electronic payment is required if the PTE’s liability is $500 or more.
Estimates, TPT, and Penalties
Individual estimated payments (Form 140ES) are due April 15, June 15, September 15, 2026, and January 15, 2027, with a safe harbor of 90% current-year or 100% prior-year. Businesses collecting the Transaction Privilege Tax (TPT) file by the 20th of the following month, though electronic filers get a grace period to the last business day. Late-payment penalty is 0.5% per month (max 10%); late-filing is 4.5% per month (max 25%); interest is the federal short-term rate plus 3 points.
CPA Action Steps
Use the 7-month corporate extension to November 16, 2026
File Form 120S and 165 by March 16, 2026 (weekend roll from March 15)
Apply the flat 2.5% individual / 4.9% corporate rates
Consider the 2.5% PTE election; remember EFT is required at $500+
Verify current rates and dates against the Arizona Department of Revenue (azdor.gov) before filing.